Topics in nutrition and food science.

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Topics in nutrition and food science.

• Dr M. Altamimi

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Characteristics of Modern life

• Urbanisation
• Ready to eat food, fast food and processed food.
• High calories (fat and carbohydrate) low fibre.
• Low in vitamins and minerals.
• Packaging. Not natural preservation.
• Refrigeration and freezing.
• Less physical activity.

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• Office based jobs.
• Chronic diseases, obesity etc.
• Aging, people live longer.

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• Diet together with physical exercise plays a
  major role when we try to prevent or postpone the
  onset of chronic conditions such as the metabolic
  syndrome.
• The food industry has already reacted to this
  challenge and a large number of products have
  been either reformulated or re-positioned to meet
  the current need for healthier foods.

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WHO

• Chronic diseases are diseases of long duration
  and generally slow progression. Chronic diseases
  are by far the leading cause of mortality in the
  world, representing 63 of all deaths. 36 million
  people died from chronic disease in 2008.

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Noncommunicable diseases

• Cardiovascular diseases account for most NCD
  deaths, or 17 million people annually, followed
  by cancer (7.6 million), respiratory disease (4.2
  million), and diabetes (1.3 million). These four
  groups of diseases account for around 80 of all
  NCD deaths, and share four common risk factors
• tobacco use
• physical inactivity
• the harmful use of alcohol and
• poor diets.

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Bad habits
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Stages of life and R F

• In the uterus
• intrauterine growth retardation (IUGR)
• premature delivery of a normal growth for
  gestational age fetus
• over nutrition in utero
• Intergenerational factors.

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• Infancy
• Retarded growth in infancy can be a reflected in
  a failure to gain weight and a failure to gain
  height. Both retarded growth and excessive weight
  or height gain can be factors in later incidence
  of chronic disease. Such as CVD
• There is increasing evidence that among term and
  pre-term infants, breastfeeding is associated
  with significantly lower blood pressure levels in
  childhood.
• Consumption of formula instead of breast milk in
  infancy has also been shown to increase diastolic
  and mean arterial blood pressure in later life.
  Obesity

(type 1 diabetes, coeliac disease, some childhood
cancers, inflammatory bowel disease) have also
been associated with infant feeding on
breast-milk substitutes and short-term
breastfeeding
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• Childhood
• low growth in childhood and an increased risk of
  CHD has been described, irrespective of size at
  birth.
• Relative weight in adulthood and weight gain have
  been found to be associated with increased risk
  of cancer of the breast, colon, rectum, prostate
  and other sites.
• Higher blood pressure in childhood (in
  combination with other risk factors) causes
  target organ and anatomical changes that are
  associated with cardiovascular risk, including
  reduction in artery elasticity.
• High blood pressure in children is strongly
  associated with obesity,

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• Most chronic diseases are present at later period
  of life - the result of interactions between
  multiple disease processes as well as more
  general losses in physiological functions (due to
  risk factors)
• lack of oxygen and adapted metabolism.

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Angiogenesis

• Angiogenesis is a process of new blood vessel
  growth that occurs in the human body at specific
  times in development and growth.
• Although crucial for embryonic development and
  wound healing, angiogenesis also contributes to
  disease, such as in the growth of solid tumors,
  chronic inflammation, atherosclerosis, ischemia,
  and diabetic retinopathy.

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Inducers

• A number of inducers of angiogenesis have been
  identified, there is an emerging concept that
  reactive oxygen species (ROS such as )

superoxide anion O2- hydroxyl radical (OH-),
lipid radical (LOO-), peroxy radicals (XOO-)
and singlet oxygen (O-).
Free radicals
ROS are products of mitochondrial respiration
(energy production).
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Dietary sources of ROS

• High fat diet and deep fries
• High sucrose (or refined carbohydrates )diet
• Protein sugar in high temperature (glycation)
• Low fruit and veg. diet
• Low vitamin and mineral diet (antioxidant).

Life style stress, pollution, smoking and low
activity.
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Golden rule

• More free radicals chronic diseases faster
  aging.
• Less free radicals healthier body.

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How to slow down generation of Free radicals?

• Homework.

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Comparison
B
A
Distance 10,000 km Fuel consumption 50,000
liter
Distance 200, 000 km Fuel consumption 1000,000
liter
Waste? Maintenance? Type of fuel?
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The challenges for nutrition in the twenty-first
century

• 1. Application of new scientific knowledge in
  nutrition.
• 2. Improved scientific knowledge on dietdisease
  relationships.
• 3. Exponential increase of health-care costs.
• 4. Increase in life expectancy.
• 5. Consumer awareness of nutrition and health
  relationships.
• 6. Progress in food technology.

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Functional foods
History
Japan 1940-1950 economical food with minimal
nutrients. 1950-1970 safe and hygienic food with
better taste. 1970- 1980 convenient food. Easy
or precooked food. 1980- Food for specific
health use (foshu). 1990 - Functional food.
(project)
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• The project also proposed for the first time the
  new concept of functional food and defined food
  functions as primary (nutritional), secondary
  (sensory) and tertiary (physiological). Food with
  physiological functions was of particular
  interest, because such food would be useful for
  improving the health of the general public

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Definition

• no simple, universally accepted definition of
  functional food exists. Examples
• food and drink products derived from naturally
  occurring substances consumed as part of the
  daily diet and possessing particular
  physiological benefits when ingested.
• food derived from naturally occurring substances
  that can and should be consumed as part of the
  daily diet and that serve to regulate or
  otherwise affect a particular body process when
  ingested.
• food similar in appearance to conventional food,
  which is consumed as part of a usual diet and has
  demonstrated physiological benefit and/or reduces
  the risk of chronic disease beyond basic
  nutritional functions.

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The main aspects of this working definition are

• the food nature of functional food that is not a
  pill, a capsule or any form of dietary
  supplement
• the demonstration of the effects to the
  satisfaction of the scientific community
• the beneficial effects on body functions, beyond
  adequate nutritional effects, that are relevant
  to improved state of health and well-being and/or
  reduction of risk (not prevention) of disease
• the consumption as part of a normal food pattern.

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F F Science

• By reference to the new concepts in nutrition
  outlined above, it is the role of functional food
  science to stimulate research and development of
  functional foods

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Claim promise of improvement

• Disease reduction claims meaning
• consumers have difficulties to differentiate
  between the terms disease risk reduction and
  prevention of diseases.

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How to write a claim
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EFFECT OF FOOD PROCESSING ON FUNCTIONALITY OF
FOODS
In foods containing vastly different
phytochemicals, the physiological activity due to
food processing may be a result of more than one
mechanism. Consequently, there may be a
decrease, increase, or a slight change in the
content and functionality of phytochemicals.
No/slight effect carotenoids comprising of
b-carotene and lycopene are generally stable to
heat treatments encountered in blanching,
cooking, and pasteurization/sterilization.
Interactions between polyphenols and ascorbic
acid may slow the degradation of the latter
during storage.
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Decrease in content and activity of
phytochemicals a classic example is that of the
technological indicator, ascorbic acid, which
is by far the most sensitive nutrient, and can be
damaged during most treatments. Chemical and/or
enzymatic oxidations are reported to decrease the
antioxidant efficacy of polyphenolics, while
leaching into the cooking water is mainly
responsible for loss of folates.
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Heat processing of Brassica vegetables of the
Cruciferae family greatly reduces their
functionality . Manufacture of black tea causes
a higher degree of enzymatic aerobic oxidation of
flavonoids, resulting in lower antioxidant
activity. Some processing operations such as
peeling and juice clarification can remove the
polyphenolics .
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Increase in content and activity of
phytochemicals partially oxidized
polyphenolics that result during food processing,
have been recently shown to exhibit higher
antioxidant activity than the corresponding
non-oxidized forms, due to increased ability to
donate a hydrogen atom
A moderate increase in carotenoid bioavailability
and enhanced phytochemical nutrient function in
cereal processing
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Examples of functional ingredients
Vitamin antioxidant mineral premixes tomato
powder, garlic powder, onion powder, spice mixes
amino acids, chitosan Omega-3-fatty acids (fish
and flax seed) whey protein powder Guarana
extract, G. biloba extract, ginseng extract,
rosemary probiotics natural antioxidants (from
tea) shield liquid antioxidants vegetable
peptones
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essential fatty acids concentrates performance
proteins natural fruit based flowering
compounds natural colours total extracts of
medicinal plants antioxidants soy ingredient,
soy proteins, soy protein hydrolysate soya
protein isolate concentrate super critical
extracts of spices and herbs glutamine
peptides lactoferrin, milk calcium lycopene,
garcinia, raw herbs whey protein concentrate
wheat fiber, b-carotene A. vera gel powder.
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Risk factor or state Design a Functional Food
CVD
osteoporosis
diabetes
Irritable bowl syndrome (IBD)
Pregnant woman
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OXIDATIVE STRESS AND ROS

• Oxidative stress rusting of tissues.
• Oxidative stress is imposed on the body s cells
  when the level of ROS outweighs the reducing
  capacity of antioxidant and antioxidative stress
  mechanisms

ROS
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Sources of ROS

• Endogenous sources of ROS
• tissue injury
• via auto - oxidation reactions in the presence of
  transition metal ions. Fe 2 or Cu
• during cytochrome P450 cycling.
• at inflammatory sites by activated and
  phagocytes.

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• Exogenous sources of ROS
• Exposure to ultraviolet (UV) radiation.
• Overexercise.
• Extrinsic xenobiotics found in tobacco smoke.
• Heavy metals.
• Organic pesticides.
• Lipid hydroperoxides in particular are
  potentially toxic products of peroxidized
  polyunsaturated fatty acids (PUFAs) derived from
  dietary fats.
• Compounds present in foods such as transition
  metal ions, heme from meats, isoprostanes,
  additives, lipids,

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DEFENSE SYSTEMS
Endogenous antioxidants and antioxidative defenses

• Glutathione ( GSH )
• tripeptide of ? glutamylcysteinylglycine.
• directly scavenge free radicals or act as a
  substrate.
• GSH present in foods and secreted in the bile can
  contribute to GSH concentrations in the
  intestinal lumen.

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• Antioxidative stress enzymes
• glutathione peroxidase (GPx).
• glutathione S -transferase ( GST ).
• Catalase
• Additional antioxidants
• uric acid.
• bilirubin - bound albumin, and albumin itself.
• Histidine - containing peptides such as
  carnosine.
• Melatonin.
• Amino acids, peptides, and even proteins.
• Se, Zn, Cu, Mn and riboflavin can all have
  co-factor functions for one of the above enzymes.

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Phytochemicals with antioxidant activities

• Polyphenols
• 5000 polyphenols and over 2000 flavonoids having
  been identified.
• Phenolic acids, Flavonoids, Lignans

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• Amides
• strong antioxidants capsaicinoids in chili
  peppers.
• Carotenoids
• Lycopene, ß carotene, xanthophylls such as
  zeaxanthin.

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Mechanism of action

• direct radical scavenging
• (2) downregulation of radical production
• (3) elimination of radical precursors
• (4) metal chelation
• (5) Inhibition of xanthine oxidase
• (6) elevation of endogenous antioxidants.

Curcumin and flavonoids have been shown to
upregulate intracellular GSH synthesis and
increase antioxidant enzyme activities
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METABOLISM AND BIOAVAILABILITY OF FLAVONOIDS

• The extent of absorption of dietary polyphenols
  in the small intestine is relatively small.
• Bacterial enzymes may catalyze several reactions.
• Anthocyanins were found in the cerebellum,
  cortex, hippocampus. important for learning and
  memory.

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Antioxidant and C D

• CVD
• Antioxidant prevent LL oxidation.
• Cancer
• Block activation to carcinogens.
• DNA repair.
• Inhibit the formation and growth of tumors.

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Dietary Fiber

• Dietary fiber (DF) has been consumed for
  centuries and most food labels in the supermarket
  now list dietary fiber.
• Even though fiber is not considered a nutrient,
  health professionals and nutritionists agree that
  fiber is required in sufficient amounts for the
  proper functioning of the gastrointestinal tract.

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Definition

• DF is the edible parts of plants or analogous
  carbohydrates that are resistant to digestion and
  absorption in the human small intestine with
  complete or partial fermentation in the large
  intestine.

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Why ?

• DF consumption has established the basis for
  associating high-fiber diets in epidemiological
  studies with reduced risk of most of the major
  dietary problems in the U.S.A. namely, obesity,
  coronary disease, diabetes, gastrointestinal
  disorders, including constipation, inflammatory
  bowel diseases.

Chronic diseases
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Classification Of Dietary Fiber

• dietary fiber has been to differentiate dietary
  components on their solubility in a buffer at a
  defined pH, and/or their fermentability in an in
  vitro system using an aqueous enzyme solution
  representative of human alimentary enzymes.

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Solubility

• Soluble fiber dissolves in water
• This includes gums, mucilages, pectin and some
  hemicelluloses.
• found in all types of peas and beans like
  lentils, split peas, pinto beans, black beans,
  kidney beans, garbanzo beans, and lima beans, as
  well as oats, barley, and some fruits and
  vegetables like apples, oranges, and carrots.

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Benefits

• For people with diabetes, eating foods that
  contain soluble fiber can help control or lower
  the level of sugar in their blood and decrease
  insulin needs
• It may also help lower blood cholesterol levels,
  especially LDL-cholesterol or the bad
  cholesterol.

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• Insoluble fiber does not dissolve in water.
• Whole grains, wheat and corn fiber, and many
  vegetables like cauliflower, green beans, and
  whole potatoes are good sources of insoluble
  fiber.
• aids digestion by trapping water in the colon.
• helps prevent two kinds of intestinal diseases,
  diverticulosis and hemorrhoids.

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Fermentability

• Fibers that are well fermented include pectin,
  guar gum, acacia (gum arabic), inulin,
  polydextrose, and oligosaccharides.
• Generally, well fermented fibers are soluble in
  water, while partially or poorly fermented fibers
  are insoluble.

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Physiological Effects of D fiber

• major physiological effects of dietary fiber
  originate from the interactions with colonic
  content throughout its fermentation.
• It influences several metabolic processes,
  including the absorption of nutrients,
  carbohydrate and fat metabolism, and cholesterol
  metabolism.

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• influences the colonic structure and barrier
  function, and as the large intestine encompasses
  a significant body of the human immune system.
• Some form gels (pectins), while others have a
  high water holding capacity (WHC).
• its ability to adsorb or bind bile acids and its
  fermentability by microorganisms in the gut.

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Colonic Fermentation And Its Consequences

• The large intestine is the most heavily colonized
  region of the digestive tract, with up to 1011
  -1012 anaerobic bacteria /gram.
• end products produced from the fermentation,
  including gases (methane, hydrogen, carbon
  dioxide), short chain fatty acids (SCFA).
• Increases in microbial mass from fiber
  fermentation contribute directly to stool bulk

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• Gas production from colonic fermentation can also
  have some influence on stool bulk.
• Poorly fermented cellulose produces very little
  acid during its fermentation, most of which is
  only acetic acid by contrast, in the case of
  more fermentable fibers, large quantities of SCFA
  are formed.
• The metabolic end products of fermentation
  including the gases, SCFA, and increased
  microbiota, play a pivotal role in the
  physiological effects of fiber and implications
  for local effects in the colon and systemic
  effects

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PHYSIOLOGICAL FUNCTIONS OF DIETARY FIBER

• Dietary Fiber And Cancer
• Colon cancer is one of the leading causes of
  cancer morbidity and mortality among both men and
  women in the Western countries, including the
  U.S.A.
• Dietary Fiber And Carbohydrate Metabolism
• An association between insufficient dietary fiber
  intake and increased risk of diabetes has been
  postulated since 1970s.

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• Dietary Fiber, Lipid Metabolism, And
  Cardiovascular Disease
• bind bile acids increasing their excretion and
  decrease cholesterol in the liver.
• SCFA are absorbed from the colon to the liver.
• Dietary Fiber, Mineral Bioavailability And Bone
  Health.
• certain highly fermentable fibers have resulted
  in improved metabolic absorption of certain
  minerals, such as calcium, magnesium, and iron,

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• Dietary Fiber, Role In Gut Barrier Function And
  Gastrointestinal Disorders.
• SCFA stimulating repair in a damaged colon.
• barrier to prevent foreign materials from dietary
  or microbial origin from crossing into the
  internal body cavity. Prevent Intestinal
  permeability or leaky gut syndrome.

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Probiotics

• Intestinal tract is home to one hundred trillion
  (1014) microorganisms.
• called the intestinal microflora.
• over 400 different species of microbes.
• The 400 species of microbes living in your body
  are fighting for space. They want to live, thrive
  and reproduce in your intestinal tract, an
  environment that offers the ideal temperature,
  humidity and food sources.

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• Depending on the type of bacteria, there is a
  different effect on the body bacteria can have
  healthy, e.g.,
• immune-boosting benefits or cause harm to the
  body.
• A careful balance is necessary for health.

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• Bad microbes live in your intestines and normally
  do not cause any disease-like symptoms.
• Bad microbes flourish in an alkaline environment.
• Opportunistic and neutral the majority.
• Good microbes found in the body, called
  probiotics.
• Probiotics have a positive impact on the bodys
  health. They prefer a more acidic intestinal
  environment. Many of the probiotics are called
  lactic acid bacteria.

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They define the term probiotic as live
microorganisms which when administered in
adequate amounts confer a health benefit on the
host.
How do they work? What are these health
benefits? How can we get them? What species can
provide them? Whats the relationship with
Chronic diseases? How can we maintain them?
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Some history

• Pasture 1880,
• Eli Metchnikoff 1908,
• Tisser 1900,
• W W I Nissil
• Southeast Asia, Boulardi. Cholera.
• 1950, group of scientists, found out that mice
  that were given oral antibiotics, which kill all
  bacteria, including probiotics, were more
  susceptible to infection.

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• Yakult Company of Japan in the 1930s. Yakult
  Company introduced a fermented milk product that
  contained a probiotic culture.
• The term probiotic was not actually coined until
  the 1960s.
• In 1978, Dr. Tomotari Mitsuoka, illustrated how
  the composition of intestinal flora changes
  during a lifetime.
• Probiotics decrease with aging.
• WHY?

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How Do Probiotics Work?

• The intestinal microflora has the metabolic
  activity potential equal to that of the liver,
  the most active organ in the body!
• The exact mechanisms of action by which
  probiotics elicit their beneficial effects are
  not fully understood.

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Suggested mechanisms

• Probiotics Compete for Receptor Sites

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• Change secretion to mask receptors

mucus
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• Probiotics Affect the Immune System
• Gastrointestinal tract is equipped with effective
  immune system, the most number of lymphoid is
  around the gut.
• Immune system is the key element of what to enter
  your body or not to.
• By producing antibodies these are messengers for
  all tissues connected with immune system.
• Probiotics supplementation is useful in a wide
  variety of immune-based ailments including
  allergies, asthma, eczema and irritable bowel
  disease.

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• probiotics help balance good and bad messengers
  of the immune system by keeping the system in
  check.
• The result is healthy immune reactions and a
  healthier you. A careful balance of inflammation
  is required in the intestinal tract.
• Too much of an immune reaction can result in
  inflammation and damage to the intestines
  reducing their ability to digest and absorb
  nutrients I B D.

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• Too little immune reaction allows pathogens to
  grow in the intestines, causing infectious
  diarrhea, which can develop into a chronic
  illness such as allergies.
• All in all, it appears that probiotics
• reduce allergic reactions
• improve overall immunity
• promote proper immune reactions against pathogens.

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• Probiotics Consume Available Nutrients
• There are lots of nutrients available in the
  digestive tract that support the needs of lactic
  acid bacteria to grow. By consuming a large
  portion of the available nutrients suitable for
  microbes, lactic acid bacteria restrains the
  growth of bad microbes.
• Probiotics Create an Acidic Environment
• Many bad microbes do not like a low pH.

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• Probiotics Produce Beneficial Enzymes
• The enzyme activity of probiotics has been found
  to help fight infectious disease, lactose
  intolerance, immune system deficiencies, and
  urogenital and vaginal diseases.
• Probiotics Produce Antimicrobial Effects
• Many of the probiotic strains of bacteria are
  able to produce substances that kill bacteria,
  called bacteriocins

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• Probiotics Support Gut Barrier
• Lactobacilli and Bifidobacteria produce fats that
  encourage the growth of cells that line the
  intestinal tract. These fats are called short
  chain fatty acids. These fats also have
  nutritional effects on the intestinal cells,
  keeping them well nourished and healthy.
• Gut integrity.

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• Probiotics Encourage Healthy Microflora
• In clinical trials, the use of combinations of
  probiotic species has been found to offer greater
  health benefits than any one of the probiotic
  species alone.
• Example
• Lactobacillus reuteri produces protein to enhance
  the growth of other lactobacilli.

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Manufacture of ProbioticBacteria

• Lactic acid bacteria (LAB) have been used for
  many years as natural biopreservatives in
  fermented foods.
• Dried concentrated probiotic cultures are the
  most convenient form for incorporation into
  functional foods, given the ease of storage,
  handling and transport, especially for
  shelf-stable functional products.

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Probiotics are the main bioactive component of
these fermented FF and numerous economic
indicators show that probiotic-enriched products
are still on the forefront of innovation in the
FF sector

• The probiotic yogurt market in Latin America grew
  32 annually from 2005 to 2007
• In the overall USA FF market, in 2004, fresh
  dairy products grew by 910 compared to 2 for
  cheese.
• The European food and beverage probiotics is
  expected to rise from its 2006 position of 62
  million to 163 million by 2013

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Selection of Strains

• the microbes should have GRAS (Generally Regarded
  As Safe) status, have a long history of safe use
  in foods, be non-pathogenic
• acid and bile tolerant
• should be viable (debatable).
• the bacteria should tolerate different
  technological stresses, such as acid, osmotic,
  cold, heat and drying stress.

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• Selecting the appropriate strain for a particular
  food can be divided in four categories
• Performance in the gastrointestinal tract (GIT)
• Industrial production.
• Safety of the microorganisms.
• Health benefit.

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Question

• Who do you think the most group of people in the
  community need functional foods, and Why?

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Potential Protective Effectsof Probiotics
Against Colorectal Cancer

• Colorectal cancer (CRC) is the fourth most
  frequent cause of cancer related mortality in the
  world.
• Approximately 944,000 new cases were diagnosed
  globally in 2000 and this accounts for 9.2 of
  all new cancer cases.
• the developed world suffering the highest rates
  and India one of the lowest

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• Evidence suggests that diet plays an important
  role in the aetiology of colorectal cancer.
• associations between overweight/ obesity (waist
  circumference), processed meat, alcohol and
  increased risk of colorectal cancer.
• Fiber, garlic, milk and calcium are associated
  with decreased risk.

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Colon Carcinogenesis

• involves inactivation of various tumor
  suppressing genes.
• activation of mutations.
• loss of function in DNA repair genes
• Metabolic activity of microflora.

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Role of the Gut Flora in Cancer

• Once the microbiota is established, little
  qualitative variation in the composition occurs
  over time, although there is extensive evidence
  that the metabolic activity of the microbiota can
  be modulated by diet.
• Evidence from a wide range of sources supports
  the view that colonic microbiota is involved in
  the aetiology of cancer.

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• The main pieces of evidence are
• Human feces have been shown to be mutagenic and
  exert tumor promoting activity in vitro and
  genotoxic substances of bacterial origin have
  been isolated.
• 2. Intestinal bacteria can produce, from dietary
  components, substances with genotoxic,
  carcinogenic and tumor-promoting activity.
• 3. Gut bacteria can activate procarcinogens to
  DNA reactive agents.

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• 4. Germ-free rats treated with the carcinogen
  1,2-dimethylhydrazine have a lower incidence of
  colon tumors than similarly treated rats having a
  normal microbiota.
• 5. Germ-free rats fed human diets exhibit lower
  levels of DNA defect in tissues than conventional
  rats.

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Evidence that probioticscan influence
carcinogenesis is derived from a variety of
sources

• 1. Effects on bacterial enzyme activities.
• 2. Antigenotoxic effects in vitro and in vivo.
• 3. Effects on pre-cancerous lesions in laboratory
  animals.
• 4. Effects on tumor incidence in laboratory
  animals.
• 5. Epidemiological and experimental studies in
  humans.

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• Examples
• metabolism of the primary bile acids to secondary
  acids, which are thought to possess
  tumor-promoting activity.
• nitrite can be converted to N-nitroso compounds
  (mutagenic) by bacteria under neutral pH.
• In a conventional rat study, supplementation of a
  high meat diet (72 beef) with L. acidophilus
  (1091010 organisms/day) significantly decreased
  by 4050 the activity of fecal b-glucuronidase
  and nitroreductase

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• consuming milk supplemented with 109 viable
  lactobacilli per day decreased activity of feacal
  enzymes.
• LAB was able to bind the mutagens in vitro.
• Production of SCFA, Acetate is the major SCFA
  found in human feces. In the host, it may be
  absorbed and utilized by peripheral tissues
• SCFA, in particular butyrate, are potential
  anti-carcinogenic.

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• Apoptosis or programmed cell death is one of the
  primary mechanisms by which multi-cellular
  organisms control normal development. In cancer
  it is out of control.
• Probiotics are able to balance apoptosis.

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First Exam

• 7-10-2013

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Prebiotics

• Coined by G. Gibson, non-viable food component
  that beneficially affect the host by selectively
  stimulating the growth and/or activities of one
  or a limited number of bacteria in the colon,
• Prebiotics allow the selective growth of certain
  indigenous gut bacteria.
• such as bifidobacteria and lactobacilli which are
  already resident in the human colon

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To be an effective prebiotic a colonic food must

• neither be hydrolysed nor absorbed in the upper
  part of the gastrointestinal tract.
• have a selective fermentation such that the
  composition of the large intestinal microbiota is
  altered towards a healthier composition.

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Commercially available prebiotics

• fructose-containing oligosaccharides (FOSs).
• these prebiotics are the European market leaders.
• Bifidobacteria are able to breakdown and utilise
  fructo-oligosaccharides due to their possession
  of the ß- fructofuranosidase enzyme.
• FOSs have proven prebiotic effects in human trials

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• Galacto-oligosaccharides (GOSs) are another class
  of prebiotics that are manufactured and marketed
  in Europe as well as Japan.
• They have found application in infant formula
  foods as
• they are naturally present (low quantity) in
  human milk.
• Gluco-oligosaccharides can also act as
  prebiotics. or Isomalto-oligosaccharides (IMOs).
  Slowly metabolized and pass to colon.

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• Xylo-oligosaccharides (XOSs) are also used as
  prebiotics in Japan
• XOS are much more acid stable than other
  prebiotics. For this reason, they have found
  application in soft drinks which tend to be
  acidic.
• Lactulose.

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Are Dietary Fibres prebiotics?

• Dietary fibres (e.g. from wheat, maize, rice,
  soya) have always been considered to have a
  beneficial effect on gut function and colonic
  bacteria, but this is a generalised stimulatory
  effect and such polysaccharides are not
  selectively fermented in the colon.

107
Mechanisms of Prebiotic Impact on Health

• Local and Physiological Effects of Prebiotics

Mucosal Structure
1) increase in numbers of epithelial cells, and
the intensities of their secretory functions.
2) enlarged the available area of nutrient
absorption
possibly SCFA are responsible for these adaptive
changes.
108

• Intestinal Mucus

Made of mucin produced by goblet cells lining the
gut. Act as barrier.
Mucus is a source of nitrogen and carbon for
bacteria its continuous production by the host
makes the gut good environment for microorganisms,
1) Administration of dietary prebiotics appears
to thicken the mucus layer and increase its
secretion by goblet cells
109

• Mineral Bioavailability

there is a strong inverse relationship between
the amount of phytic acid in the diet and iron
Ca, and Zn absorption.
1) prebiotics are known to have stimulatory
effects on iron absorption in the large bowel.
2) Addition of FOS to the diet restores zinc
absorption by enhancing zinc bioavailability
3) prebiotic consumption is associated with
enhanced breakdown of phytic acid (60), low pH
decrease its solubility
110
Colonic environment
Zn
SCFA
Phytic acid
Undigested Food (prebiotic)
Ca
Phytase enzyme
Fe
hydrolysis
fermentation
Probiotic bacteria
Ca
Zn
Fe
pH
Mineral Solubility
111

• Modulation of the Gut Microbiota

In chronic diseases and Gastrointestinal tract
diseases it was found that decreased levels of
bifidobacteria and lactobacilli are associated
with the problem. 1) Prebiotic can increase
these levels and prevent from C D.
112

• Immune System

prebiotics, may be particularly useful in
inflammatory conditions, or in children and the
elderly.
FOS and lactulose to the diet has been shown to
increase 1) mucosal immunoglobulin production.
2) lymph nodes number. 3) altered
pro-inflammatory compounds in the spleen and
intestinal mucosa.
113

• Lipid Metabolism

Human studies have been small in scope, focused
on the relationship between the intake of
prebiotics and serum lipid levels. The results
have been inconsistent, and any mechanisms of
action unclear. Animal studies showed lowering
effect of prebiotics on LDL and cholesterol
(especially when fed high fat meal) May be due
to interference with hepatic lipogenesis.
114
General Mechanism
115
Prebiotics Applications

• Infants
• Oligosaccharides are prebiotic factors in human
  milk, causing increased levels of bifidobacteria
  in breast-fed babies compared to bottle-fed
  infants.
• Prebiotics have been used in infant formulas in
  Japan over the last 2 decades, and in Europe for
  the last 5 years.
• addition of 0.8 g/dl of a mixture of 10 short
  chain FOS and 90 long chain infant formulas was
  safe to add to infant formula.

116

• Atopic Disease (allergy).
• Allergic disease in infants is based on
  imbalanced response to food allergen and lower
  numbers of bifidobacteria are found in allergic
  infant feces.
• By increasing the number of bifidobacteria
  prebiotics rebalance the immune response.
• Prebiotic feeding studies in allergic infants
  have demonstrated significant reductions in the
  incidence of atopic dermatitis, and this was
  associated with increased numbers of fecal
  bifidobacteria.

117

• Enterocolitis
• In premature infants, bifidobacterial
  colonization is delayed in favor of high levels
  of enterobacteria and clostridia enterocolitis.
• Breast-feeding has always been thought to protect
  against enterocolitis.
• No human studies using prebiotics alone.

118

• Infection Prevention
• Studies in children aimed at prevention of
  infection have also had mixed results.
• The addition of 1.1 g of oligofructose daily to
  cereal of 123 infants (424 months) was
  associated with reduced episodes of fever and
  medical visits. The control group had more sick
  days, and a higher intake of antibiotics.

119

• 134 infants fed prebiotics (8 g/l GOS/FOS) for
  the first 6 months of life, principally looking
  at allergic disease, the subjects were followed
  up until they were 2 years of age.
• fewer episodes of physician diagnosed infections
  , fewer episodes of fever and fewer antibiotic
  prescriptions.

120

• 2. Gastrointestinal Effects
• Irritable bowel syndrome (IBS) has been linked to
  intestinal bacteria in a number of different
  trials.
• IBS is a difficult disease to investigate,
  because the symptoms are highly subjective and
  difficult to quantify.
• Gas production discomfort and flatulence are some
  of the symptoms associated with IBS.
• many patients have visceral hypersensitivity, so
  prebiotic fermentation and gas production may
  exacerbate their symptoms, and have adverse
  affects on health and wellbeing.

121

• Constipation
• Prebiotics may have Laxative effects. May be due
  to gas production and increased microbial mass.
• There is a good relation between intestinal
  motility and bacterial composition.
• With the exception of lactulose, the prebiotics
  studied so far in human trials have been shown to
  have little effect on managing constipation, and
  to have only mildly laxative properties.

122

• Diarrhea Antibiotic-Associated Diarrhea.
• travelers diarrhea (E. coli) , frequency of
  diarrhea in the prebiotic group (11.2), compared
  to the placebos (19.5).
• Clostridium difficile infections are
  antibiotic-associated diarrhea (AAD).
• Diarrhea associated with Clostridium difficile is
  a leading cause of hospital outbreaks of diarrhea
  and it considerably increases mortality and
  healthcare costs.
• Prebiotics reduce episodes of AAD and C.
  difficile diarrhea relapse.

123

• 3. The Elderly
• As people get older they often have a greater
  susceptibility to diseases and suffer from an
  increase in gastrointestinal infections,
  malnutrition, constipation and diarrhea.
• decrease in immune function and a reduction in
  numbers of beneficial bacteria such as
  bifidobacteria, along with an increase in
  potentially harmful microrganisms.
• few studies on the use of prebiotics in the
  elderly.

124

• 4. Other Areas.
• Diabetes
• Because prebiotics are non-digestible low energy
  bulking ingredients this makes them beneficial
  they in diabetic control.
• The proposed mechanisms of action in diabetic
  disease involve SCFA. Since High concentrations
  of free fatty acids (mainly from food) in plasma
  lower the use of glucose in tissues, and induce
  insulin resistance.

125

• Rheumatoid Arthritis.
• In animal studies prebiotics showed ability to
  decrease pro-inflammatory compounds by modulating
  the gut microbiota.
• Obesity
• Prebiotics are excellent potential to act as
  substitutes for sucrose, and to be used as
  sweeteners.
• GOS are stable at high temperatures and low
  metabolic value at 1.73 kcal/g, while FOS are
  similar at 1.5 kcal/g.

126

• they promoted satiety, and reduced food intake.

127
Resistant Starches

• Resistant starches are defined as the sum of
  starch and products of starch degradation not
  absorbed in the small intestine of healthy
  individuals.
• There are four main groups of resistant starches
  RS1- RS4.
• RS1 is physically inaccessible starch (i.e.,
  starch in whole grains), RS2 is granular starch
  i.e., starch in green bananas), RS3 is
  retrograded starch (i.e., starch in cooked and
  cooled potatoes) and RS4 is a chemically-modified
  starch (i.e., an esterified starch).

128

• RS has a calorific value of 1.70 kcal/g.
• The glycemic response for RS is approximately 10
  that of a maltodextrin control.
• Type 3 RS was shown to be well tolerated up to
  doses as high as 45 g/d.

129
Applications

• Applications for RS include puffed or sheeted
  snacks, chips, extruded breakfast cereals, pasta,
  muffins, cookies and biscuits, crackers, frozen
  dough, breads.
• it can also be used in low calorie products
  reducing both calories and carbohydrates when
  replacing flour or other cereal-based
  ingredients.
• Due to its low water holding property, it also
  does not affect height and spread management of
  biscuits, cookies or other baked goods.

130

• RS enhances crispiness of cookies and crackers.
• In fried snacks, fat uptake may be reduced by up
  to 25 when RS is used, helping to meet
  high/rich in fiber claims.
• RS3 thermal stable as high as 150 C, it will
  retain more fiber content and structure than
  other resistant starches, which start to
  breakdown below 120 C.
• RS act as prebiotics in the gut.
• Sugar derived from RS can be used as sweeteners.

131
Workshop design

• Functional foods
• in Palestine, What do we need to know?

132
Garlic and Onion as Functional Foods

• Historically garlic and onion were used to
  preserve food from microbial spoilage.
• Garlic has been eaten more than 4000 years and
  onion was cultivated in middle east before 5000
  years.
• They were used for their medicinal properties.
• Garlic on the top of vegetable-pyramid
  representing potency in cancer prevention (NIC).

133
GENERAL COMPOSITION AND SULFURCOMPOUNDS OF
GARLIC AND ONION
134
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135

• The general composition is, of course, important
  to the nourishment of both garlic or onion
  eaters, however, in respect to the food function,
  the extraordinary high content of sulfur
  compounds in these vegetables should be much more
  important.
• These compounds are present as a group of
  sulfur-containing amino acids.
• When injured or damaged by slicing, the
  sulfur-containing amino acids in these plants are
  transformed immediately into volatile
  organosulfur compounds.

136

• These compounds are called Alliins.
• Alliin is degraded by alliinase into pyruvic acid
  and ammonia.
• Alliinase is heat labile, and irreversibly
  inactivated at pH 3.8 or lower.
• Oxidation of Alliins produces Allicin which has
  bactericidal and fungicidal effect.
• in water it is active up to 40 days.
• at -70C up to 2 years.

137

• Organoselenium Compounds in Garlic and Onion.
• Allium plants, especially garlic and onion, is
  their strong potential to uptake inorganic
  selenium, either selenate or selenite, from the
  soil or water culture medium, and synthesize
  organoselenium compounds.
• Se-containing peptides, has been determined, and
  from this peptide a potent agent for cancer
  prevention was derived.

138
PHYSIOLOGICAL AND NUTRITIONAL FUNCTIONS OF GARLIC
AND ONION, AND THEIR HEALTH BENEFITS

• Garlic and onion use sulfur compounds to protect
  themselves, Even in our bodies, sulfur-containing
  compounds play a defensive mechanism.
• Onion has a lesser amount of sulfur compounds as
  compared with garlic. However, because people
  consume onion much more than garlic, the amount
  of sulfur compounds taken from onion per person
  may be comparable to or more than that from
  garlic.

139

• Antibiotic Effect.
• growth inhibition by an aqueous garlic extract.
  Which was diluted 100 times with water (about 10
  ng/ml allicin) showed a clear inhibition zone,
  and some fungus did not grow inside of the zone
  for up to 7 days.
• Alkyl thiosulfinates are recognized as the most
  effective compounds exhibiting antimicrobial
  activity.

140

• Antithrombotic Effect.
• Suppression of platelet aggregation is the most
  beneficial effect of garlic intake.
• vascular dilation have been observed primarily
  with garlic oil in human and animal studies.
• Thus, garlic may prevent thrombus formation
  through many mechanisms involving antithrombotic,
  vasodilative effects.

141

• Lipid-Lowering Effect.
• several garlic compounds have been reported to be
  effective.
• The lipid-lowering effects appear to be due to
  their degradation products, those that may be
  produced from the compounds soon after the
  absorption from the intestine.
• And from the reduced gene expression may be an
  important factor in the lipid-lowering effects of
  garlic.

142

• Hypoglycemic Effects.
• It has been proposed that garlic compounds
  stimulate insulin production and prolong insulin
  turnover.
• Especially, sulfur compounds from garlic were
  considered to protect insulin from its
  inactivation.
• alliin (200 mg/kg) is known to reduce the plasma
  glucose level in diabetics.

143

• ANTICANCER EFFECTS OF GARLIC AND ONION
• A number of epidemiological and experimental
  studies indicated that garlic and onion can be
  considered as important functional foods for
  cancer prevention.
• study in northeast China found that the
  consumption of onion was inversely related to the
  risk of developing brain cancer.
• Similar studies reported that garlic intake
  significantly reduced the risk of prostate and
  breast cancers, and increased protective power
  against stomach and colorectal cancers.

144

• 3. Site-specific case-control studies on stomach
  and colorectal cancers suggest a protective
  effect of high intake of raw and/or cooked
  garlic.
• 4. The overall anticancer effects that have been
  reported for garlic and onion by some hundreds of
  researchers can be collected largely into three
  groups
• Antimutagenic and anticarcinogenic effects.
• Antiproliferative effects.
• Differentiation effects involving the apoptotic
  effect.

145

• Other Effects.
• blood pressure-lowering.
• Diuretic.
• anti-inflammatory, immunomodulatory.
• Enhancing effect on vitamin B1 absorption.
• stimulate both noradrenaline secretion from
  nervous systems and testosterone from testis.

146
Garlic processing

• Cutting, slicing, crushing.
• Allicin from damaged garlic turned to sulfides.
• Allicin may collected when slicing garlic in
  water, but sulfides better collected in cooking
  oil.
• Boiling and heating
• If an intact bulb is heated, alliin stays
  unchanged inside the bulb.
• if the heating is not quite sufficient to
  denature the alliinase, a large amount of alliin
  is transformed into allicin and sulfides while
  cooking or eating the bulb.

147

• Heating the chopped garlic in cooking oils,
  allicin, sulfides as well as alliin must be
  present, in the oils or within the pieces. Hence,
  people prefer to cook garlic with cooking oils or
  fatty meats.
• Pickling
• The pickled clove in any medium loses alliinase
  activity more or less, depending on the period of
  its preservation. It takes at least a month to
  penetrate a medium into the clove with a gradual
  decrease in alliinase activity.

148

• Garlic Oil
• Garlic Powder
• Dehydrated Onion Pieces
• Onion Powder
• Onion Oil
• Onion Salt
• Pickled Onion

149
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150
Quiz

• Discuss briefly how probiotics and /or prebiotics
  may prevent from cancer?

151
Green and Black Tea

• Tea (Camellia sinensis) has been discovered and
  utilized for its unique flavor and medicinal
  properties by man for a long time, which may be
  traced back to 50006000 years ago in China.
• Tea beverages are now the second most popular
  drinks and only next to water in terms of
  worldwide consumption.
• Scientific research on the chemical components
  and functionalities of tea is relatively recent.

152

• Through research, tea has been linked with health
  benefits including protection of oxidative DNA
  damage, lowering the atherosclerotic index and
  improving blood flow, liver function, and oral
  health.
• Nowadays, the utilization of tea has been
  extended not only to pharmaceutical products but
  also to toiletry, cosmetic, and food products.

153

• Commercial tea leaf products can be classified
  into three major types green tea, black tea, and
  oolong tea.
• Green tea is nonfermented processed tea, in which
  polyphenols in fresh tea leaves are less
  oxidized.
• Black tea and oolong tea are enzymatically
  fermented tea, with black tea being the most
  fermented and oolong tea partially fermented (or
  so called semifermented).

154
Tea polyphenols

• The functional properties of tea are believed to
  be due to tea polyphenols. The principal tea
  polyphenols are tea catechins.
• Catechin has been accepted as a quality indicator
  of green tea products.
• There are some 830 of total catechins in dry
  green tea leaves.
• The estimated daily intake of tea catechins based
  on 3 cups (600 mL) of green tea (1 4 g), which
  is brewed traditionally (15 min in boiling
  water), is in the range of 5382594 mg of total
  catechins.

155

• the antioxidative activity/free radical
  scavenging ability of tea catechin varies with
  the type of radical species, ionization state,
  pH, polarity, and enzyme in the designated
  studies.

156
GREEN TEA ANTIOXIDANTS AND HEALTH BENEFITS

• Green Tea and Neurodegenerative Diseases
• Catechins chelate metal ions such as copper(II)
  and iron(III) to form inactive complexes and
  prevent the generation of potentially damaging
  free radicals.
• In the rat brain tissue, green tea and black tea
  extracts were shown to inhibit lipid peroxidation
  promoted by iron.
• As well decrease neurons death (Alzheimer's)

157

• Green Tea and Obesity
• Polyphenols interact to alter the energy balance.
• the redox status or potential.
• the activities of obesity-related cells.
• Green Tea and Cardiovascular Disease.
• cardiovascular diseases is multifactorial and
  comprises processes, which appear to be affected
  by tea ingredients
• endothelial dysfunction.
• inflammation. And thrombus formation

158

• Green Tea and Cancer
• inhibition of oxidative stress.
• inhibition of carcinogen.
• induction of apoptosis.
• Inhibition of angiogenesis.
• Type of cancers
• Skin cancer Studies have suggested that green
  tea polyphenols may afford protection against
  inflammatory responses and the risk of skin
  cancer.

159

• Lung Cancer Ingestion of green tea (2 of diet)
  decreased the number of lung induced tumors in
  mice.
• consumption of green tea was associated with a
  reduced risk of lung cancer among nonsmoking
  women and the risks decreased with increasing
  consumption.
• Liver Cancer In a study in China it was found
  that Green tea drinking decreased the risk for
  the development of liver cancer by 78 among
  alcohol drinkers and 43 among cigarette smokers.

160

• Breast Cancer green tea consumption was
  associated with a reduction in breast cancer
  risk.
• Prostrate Cancer Green tea
• inhibits the growth and progression of prostate
  cancer in model mice.
• ANTIBACTERIAL AND ANTIVIRAL ACTIVITY
• Antimicrobial activity against cariogenic and
  periodontal bacteria has been reported.
• Tea extracts inhibit enteric pathogens such as
  Staphylococcus aureus, Salmonella typhi,
  Shigella, V. cholerae, Cam. jejuni,

161

• Tea polyphenols also inhibit bacteria responsible
  for tooth decay.
• black and green tea extracts can kill
  Helicobacter pylori associated with gastric,
  peptic, and duodenal ulcer diseases.
• but are not effective against Escherichia coli,
  Pseudomonas aeruginosa.
• Some results indicate that tea catechins are
  potentially antiviral and antiprotozoiac agents

162
Polyphenols stability

• The stability of tea catechins is dependent on pH
  and temperature. In acidic systems (pH lt 4), tea
  catechins are fairly stable.
• in systems of pH gt 5, that is, near neutral or
  alkaline systems, they degrade rapidly.
• On the contrary, tea catechins become less stable
  when processing temperature increases, where
  thermal degradation, oxidation could occur.
• 82C was reported as a turning point in thermal
  reactions of tea catechins

163

• Ascorbic acid showed a significantly protective
  effect on the stability of tea catechins.
• Functional food containing Green tea.
• green tea beverage products.
• Sport beverages.
• cereal, confectionary, dairy, edible oil.
• ice cream and noodle products containing green
  tea.
• Green tea extracts have also been incorporated in
  chocolates and chewing gums.

164
Tea and iron

• Display Settings
• Abstract

Send to
Crit Rev Food Sci Nutr. 2000 Sep40(5)371-98. Eff
ect of tea and other dietary factors on iron
absorption. Zijp IM, Korver O, Tijburg
LB. Source Unilever Research Vlaardingen, The
Netherlands. Abstract Iron deficiency is a major
world health problem, that is, to a great extent,
caused by poor iron absorption from the diet.
Several dietary factors can influence this
absorption. Absorption enhancing factors are
ascorbic acid and meat, fish and poultry
inhibiting factors are plant components in
vegetables, tea and coffee (e.g., polyphenols,
phytates), and calcium. After identifying these
factors their individual impact on iron
absorption is described. Specific attention was
paid to the effects of tea on iron absorption. We
propose a calculation model that predicts iron
absorption from a meal. Using this model we
calculated the iron absorption from daily menus
with varying amounts of enhancers and inhibitors.
From these calculations we conclude that the
presence of sufficient amounts of iron absorption
enhancers (ascorbic acid, meat, fish, poultry, as
present in most industrialized countries)
overcomes inhibition of iron absorption from even
large amounts of tea. In individuals with low
intakes of heme iron, low intakes of enhancing
factors and/or high intakes of inhibitors, iron
absorption may be an issue. Depletion of iron
stores enhances iron absorption, but this effect
is not adequate to compensate for the inhibition
of iron absorption in such an inadequate dietary
situation. For subjects at risk of iron
deficiency, the following recommendations are
made. Increase heme-iron intake (this form of
dietary iron present in meat fish and poultry is
hardly influenced by other dietary factors with
respect to its absorption) increase meal-time
ascorbic acid intake fortify foods with iron.
Recommendations with respect to tea consumption
(when in a critical group) include consume tea
between meals instead of during the meal
simultaneously consume ascorbic acid and/or meat,
fish and poultry.

• Crit Rev Food Sci Nutr. 2000 Sep40(5)371-98.
• Effect of tea and other dietary factors on iron
  absorption.
• Zijp IM, Korver O, Tijburg LB.
• Abstract
• Iron deficiency is a major world health problem,
  that is, to a great extent, caused by poor iron
  absorption from the diet. Several dietary factors
  can influence this absorption.
• Absorption enhancing factors are ascorbic acid
  and meat, fish and poultry
• inhibiting factors are plant components in
  vegetables, tea and coffee (e.g., polyphenols,
  phytates), and calcium.
• For subjects at risk of iron deficiency, the
  following recommendations are made. Increase
  heme-iron intake (this form of dietary iron
  present in meat fish and poultry is hardly
  influenced by other dietary factors with respect
  to its absorption) increase meal-time ascorbic
  acid intake fortify foods with iron.
• Recommendations with respect to tea consumption
  (when in a critical group) include consume tea
  between meals instead of during the meal
  simultaneously consume ascorbic acid and/or meat,
  fish and poultry.

165

• Am J Clin Nutr. 2001 Mar73(3)607-12.
• Green tea or rosemary extract added to foods
  reduces nonheme-iron absorption.
• Samman S, Sandström B, Toft MB, Bukhave K, Jensen
  M, Sørensen SS, Hansen M.
• Abstract
• BACKGROUND
• Phenolic compounds act as food antioxidants. One
  of the postulated mechanisms of action is
  chelation of prooxidant metals, such as iron.
  Although the antioxidative effect is desirable,
  this mechanism may impair the utilization of
  dietary iron.
• Results
• The presence of the phenolic-rich extracts
  resulted in decreased nonheme-iron absorption.
  Mean (/-SD) iron absorption decreased from 12.1
  /- 4.5 to 8.9 /- 5.2 (P lt 0.01) in the
  presence of green tea extract and from 7.5 /-
  4.0 to 6.4 /- 4.7 (P lt 0.05) in the presence
  of rosemary extract.
• CONCLUSION
• Phenolic-rich extracts used as antioxidants in
  foods reduce the utilization of dietary iron.

166

• J Hum Nutr Diet. 2004 Feb17(1)43-54.
• Impact of tea drinking on iron status in the UK
  a review.
• Nelson M, Poulter J.
• Abstract
• BACKGROUND
• The aims of this review are (1) to evaluate the
  literature on the likely impact of tea drinking
  on the iron status of different groups within the
  UK population
• RESULTS
• There is clear evidence to show that tea drinking
  limits the absorption of nonhaem iron.
• CONCLUSION
• From the available evidence there is no need to
  advise any restriction on tea drinking in healthy
  people with no risk of iron deficiency. In groups
  at risk of iron deficiency the advice should be
  to drink tea between meals and to wait at least 1
  h after eating before drinking tea.

167
What will happen to gut microflora if there is
more iron in the gut?

• Good bacteria dont require iron for growth (this
  is the case in infants).
• Enterobacteria require iron for growth.

168

• Am J Clin Nutr