Nutrition and Metabolism

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Nutrition and Metabolism
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Critical Thinking QuestionWhy does your body
need food?

• Answer
• Food has two main functions
• Food provides raw materials for cells to build
  new molecules for growth and reproduction
• Food provides energy

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Nutrients

• Many cells of the body (ex. liver cells) can
  convert one molecule into another based on what
  is needed
• Essential nutrients must be provided by the diet
  because they cant be created through conversions

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• Nutrition

• Nutrient substance used by the body for growth,
  maintenance, and repair
• Categories of nutrients
• Carbohydrates
• Lipids
• Proteins
• Vitamins
• Minerals
• Water

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Major Nutrients
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• Dietary Sources of Carbohydrates

• Most are derived from plants
• Sugars (fruits) and starches (vegetables)
• Exceptions lactose from milk and small amounts
  of glycogens from meats

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• Body Uses of Carbohydrates

• Preferred source (esp. glucose) to produce
  cellular energy (ATP)
• Examples neurons and red blood cells

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Dietary Requirements of Carbohydrates

• 125-175 grams/day (mainly complex carbohydrates)
• Complex carbohydrates bread, cereal, rice,
  potatoes
• Strive for Five servings of fruits and
  vegetables per day

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Dietary Requirements of Carbohydrates

• Excesses
• Obesity
• Nutritional deficits (empty calories)
• Gastrointestinal problems (constipation)

• Deficits
• Tissue wasting (muscle breakdown)
• Metabolic acidosis (fat breakdown)

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• Dietary Sources of Lipids

• Saturated fats from animal products (meat and
  dairy)
• Unsaturated fats from nuts, seeds, and vegetable
  oils
• Cholesterol from egg yolk, meats, and milk
  products

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Trans fats

• Healthy vegetable oils that have been
  hydrogenated to make them more solid
• Used in many snack and junk foods
• Increases shelf life of foods (they dont get
  rancid)
• Have the most negative effect on cholesterol
  raises the bad, lowers the good

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• Body Uses of Lipids

• Help body absorb fat-soluble vitamins
• Major energy fuel for liver cells and skeletal
  muscle
• Main component of ALL cell membranes
• Adipose tissue protects organs, provides
  insulation, and stores energy
• Cholesterol is necessary to make hormones and bile

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• Dietary Requirements of Lipids

• 30 or less of total caloric intake
• Saturated fats should be less than 10 of total
  calories
• Cholesterol should be less than 250 mg (ex. one
  egg yolk)

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Dietary Requirements of Lipids

• Deficits
• Weight loss
• Difficulty with temperature regulation
• Poor growth/repair

• Excesses
• Obesity
• Increased risk of cardiovascular disease

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Fat Substitutes

• Modified starches or proteins
• Some are metabolized, but some are not because
  they cannot be absorbed
• Drawbacks
• Typically dont stand up to heat for frying
• Dont taste the same as real fat
• May cause GI disturbances (ex. diarrhea)
• May interfere with the absorption of fat-soluble
  drugs and vitamins

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• Dietary Sources of Proteins

• Most complete proteins come from animal products
  (eggs, milk, meat)
• Complete proteins contain all essential amino
  acids
• Legumes (beans and peas), nuts, leafy greens also
  have proteins, but are incomplete
• Incomplete proteins missing or low in one or
  more of the essential amino acids

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• Body Uses of Proteins

• Major component of structural materials (skin,
  nails, muscles)
• Regulate chemical reactions (enzymes)

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• Dietary Requirements of Proteins

• Depends on age, size, and metabolic rate
• 0.8 grams per kilogram of body weight
• General conversion divide weight in pounds by 3
  to equal the number of grams needed

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Dietary Requirements of Proteins

• Excesses
• Obesity
• Aggravation of chronic disease

• Deficits
• Profound weight loss and tissue wasting
• Poor growth/repair
• Anemia

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• Vitamins

• Most vitamins are used as coenzymes, helping
  enzymes with their chemical reactions
• Most must be ingested the body can only make
  Vitamins A, B, D, and K

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• Vitamins

• Two main categories
• Water-soluble absorbed with water, not stored in
  the body, excreted in the urine if not used
• Fat-soluble absorbed with fats, stored in the
  body, excesses can lead to toxicity

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• Minerals

• Body requires moderate amounts of 7 minerals (Ca,
  P, K, S, Na, Cl, Mg) and trace amounts of about
  12 others
• Make up 4 of the body weight, mostly due to Ca
  and P in bones
• Provide strength to certain structures

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• Minerals

• Vital components to many biological compounds
  (ex. iron (Fe) in hemoglobin)
• Important electrolytes (sodium/chloride ions)
• Found in mostly vegetables, legumes, milk, and
  meats

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• Metabolism

• Definition all chemical reactions necessary to
  maintain life
• Catabolism substances are broken down to
  simpler substances
• Energy (ATP) is released from food during a
  catabolic process called cellular respiration

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• Metabolism

• 2) Anabolism larger molecules are built from
  smaller ones
• Tissue growth and repair
• Storage molecules (ex. glycogen)

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Three Major Stages of Metabolism

• Stage 1
• Occurs in the digestive tract
• Absorbed nutrients are transported to cells
  through the blood

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Three Major Stages of Metabolism

• Stage 2
• Occurs in the cytoplasm of body cells
• a) Nutrients are built into cellular molecules
  (anabolism)
• b) Nutrients are broken down into ATP without
  oxygen (catabolism) a.k.a. GLYCOLYSIS

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Three Major Stages of Metabolism

• Stage 3
• Occurs in the mitochondria of body cells
• Nutrients are broken down into ATP (catabolism)
  in the presence of oxygen a.k.a. CELLULAR
  RESPIRATION

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Cellular Respiration

• Series of reactions that breaks down food
  molecules to create ATP
• Must occur in a series of steps or else energy
  would be released as a blast of energy
• ATP is the ONLY energy cells can directly use
• Cells release carbon dioxide (CO2) and water
  (H2O) as a result of the reactions

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• General Equation for Cellular Respiration

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Cellular Respiration

• Two separate pathways, BOTH start with GLYCOLYSIS
  (NO OXYGEN NEEDED)
• Glycolysis is the first step, but only extracts
  10 of energy from glucose only 2 ATP per
  reaction!
• Remaining 90 of energy is still locked in an
  intermediate molecule (pyruvic acid) made from
  glucose

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Cellular Respiration

• Presence or lack of oxygen determines the next
  step
• 1) To continue WITHOUT OXYGEN (Anaerobic)
  Lactic Acid Fermentation
• 2) To continue WITH OXYGEN (Aerobic)
• Cellular Respiration

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Lactic Acid Fermentation

• Glycolysis can make ATP really fast, but if there
  is no oxygen, it proceeds to lactic acid
  fermentation
• In muscle cells, lactic acid builds up and then
  is removed by blood to the liver (i.e. muscle
  soreness after vigorous exercise)
• In the liver, it will be converted to a useable
  energy molecule when oxygen is available

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Cellular Respiration

• When oxygen is available, glucose is further
  broken down in the mitochondria to make ATP
• Slightly longer process, but yields almost 20x
  the amount of ATP as glycolysis
• Remaining 90 of energy is released by two steps
• 1) Krebs cycle
• 2) Electron Transport Chain (ETC)

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• Metabolic Pathways Involved in Cellular
  Respiration

Figure 14.17
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ATP The Totals

• Without oxygen the cell can produce only 2 ATP
  molecules during glycolysis
• With oxygen the cell can produce 36 more ATP in
  the Krebs cycle and ETC
• Final Total 38 ATP from 1 glucose
• Cellular respiration extracts 38 of energy from
  glucose the rest is lost as ???

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Why settle for only 38?

• Answer
• If glucose were burned
• directly in air, 100 of the
• energy would be in the form
• of heat and light, which the human body cannot
  use. So, 38 is actually pretty efficient!!

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Metabolism of Specific Nutrients
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Carbohydrate Metabolism

• Most carbohydrates are eventually transformed to
  glucose to create ATP through cellular
  respiration
• Too much glucose (supply gt demand) leads to
  glycogenesis
• Glycogenesis conversion of glucose to glycogen
  to be stored in the liver and skeletal muscles
• Too little glucose (supply lt demand) leads to
  glycogenolysis
• Glycogenolysis glycogen stored in the liver is
  converted back to glucose and released into the
  blood

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• Fat Metabolism

• Fats make up 78 of energy reserves
• Broken down into fatty acids and glycerol which
  go through various stages in cellular respiration
  to make ATP
• Body cells remove fat and cholesterol to build
  membranes and steroid hormones
• Excess fatty acids and glycerol are converted to
  triglycerides through lipogenesis

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• Fat Metabolism Cholesterol Transport

• Cholesterol and fatty acids cannot freely
  circulate in the bloodstream
• They are transported by lipoproteins
  (lipid-protein complexes) made by the liver
• Low-density lipoproteins (LDLs) transport from
  liver to body cells (bad cholesterol)
• High-density lipoproteins (HDLs) transport from
  body cells to the liver (good cholesterol)

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• FACT

You need very little cholesterol in your diet
because most of the cholesterol that your body
needs is made in the liver!
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• Protein Metabolism

• Ingested proteins are broken down to amino acids
• Cells remove amino acids to build proteins (cell
  structures and enzymes)
• Excess amino acids are used for energy or
  converted into fat for storage
• Amino acids are used to make ATP only when
  proteins are overabundant or there is a shortage
  of other sources

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• Protein Metabolism
• Production of ATP from Proteins

• Amine groups are removed from proteins as ammonia
• The rest of the protein molecule enters the Krebs
  cycle in mitochondria
• The liver converts harmful ammonia to urea which
  can be eliminated in urine

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Catabolic-Anabolic Steady State of the Body

• ABSORPTIVE STATE
• During and shortly after eating
• Focus is ANABOLISM and ENERGY STORAGE

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Catabolic-Anabolic Steady State of the Body

• POST-ABSORPTIVE STATE
• When the GI tract is empty
• Focus is CATABOLISM and FUEL REPLACEMENT IN BLOOD

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• Question What are the roles of the liver in
  metabolism?

• Answers
• Several roles in digestion (bile)
• Detoxifies drugs and alcohol
• Produce cholesterol, blood proteins (albumin and
  clotting proteins)
• Gluconeogenesis glucose is produced from fats
  and proteins

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• Critical Thinking Question How does the body
  increase blood glucose levels without ingesting
  additional food?
• Answer Glycogenolysis and gluconeogenesis!

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Energy and Exercise

• Quick energy
• Stored ATP 10 seconds of energy
• Lactic Acid Fermentation 90 seconds of energy
• This creates an oxygen debt - heavy breathing is
  required to get rid of lactic acid build up

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Energy and Exercise

• Long term energy
• Cellular Respiration - breaks down glycogen,
  which has enough stored for 15-20 minutes of
  constant activity
• After 20 minutes, when body runs out of glycogen,
  it breaks down fat
• Pacing is necessary because cell respiration
  releases energy more slowly than the other
  processes

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Amount of Energy in Food

• 1 gram of glucose 3811 calories of heat energy
• calorie the amount of energy needed to raise 1
  gram of water 1C
• Calorie (kilocalorie) food calorie 1000
  calories
• 1 gram of FAT 9 Calories
• 1 gram of CARBOHYDRATE or PROTEIN 4 Calories

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FACT

• One pound of fat equals 3500 Calories.

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• Regulation of Food Intake

1. Levels of nutrients in the blood
2. Hormones
3. Body temperature
4. Psychological factors

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• Basal Metabolic Rate

• Basic metabolic rate (BMR) amount of heat
  produced by the body per unit of time at rest
  (energy used to perform ESSENTIAL activities)
• Heat is energy out as a result of cellular
  activities

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• Factors that Affect BMR

1. Age children and adolescents have a higher BMR
2. More thyroxine produced means higher metabolic
   rate (most important control factor)
3. Surface area small body usually has higher BMR
4. Gender males tend to have higher BMR

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• Total Metabolic Rate (TMR)

• Total amount of kilocalories the body must
  consume to fuel ongoing activities
• TMR increases with an increase in body activity
• TMR must equal calories consumed to maintain
  homeostasis and maintain a constant weight
• Body weight is usually relatively stable if
  energy intake and output remain equal

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WHAT IS THE BEST WAY TO LOSE WEIGHT?

• Decrease energy in and/or increase energy out,
  which means lower calorie intake and increase
  activity level.
• BUT, IT IS STILL IMPORTANT TO MAINTAIN A BALANCED
  DIET THAT INCLUDES ALL NECESSARY NUTRIENTS!

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FACT

• Over the last 20 years, rate of obesity in teens
  has tripled to over 16.
• Center for Science in the Public Interest, 2005

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Cyclic Dieting

• Also known as yo-yo dieting
• Recent research shows that the risk of trying to
  lose weight over and over again is a myth
• It is actually better for your weight to be down
  half of the time than never at all

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Adolescent Nutrition
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FACT

• Only 2 of teens with a healthy weight eat a
  nutritious diet as defined by the USDA.
• Center for Science in the Public Interest, 2005

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Adolescent Nutrition

• Adolescence is a time of rapid physiologic,
  psychological, and social development influencing
  nutrient needs as well as the individuals
  ability to supply those needs. Disruptions in the
  balance between nutrient requirements and intake
  during adolescence impact on such major health
  problems as atherosclerosis, hypertension,
  obesity, anorexia nervosa, bulimia nervosa, and
  birth of suboptimal-weight infants. Dietary and
  exercise habits formed as the adolescent achieves
  increased independence have the potential to
  enhance or undermine health throughout life.
  Dietary indiscretion as another form of
  risk-taking behavior is a new concept worthy of
  scientific inquiry.
• Marc. S. Jacobson, MD, LIJ, Schneider,
  Childrens Hospital

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Reasons for Nutritional Deficiencies in Teens

• More responsibilities, ex. part-time job
• More freedom, ex. license, dating
• Increase in sedentary activities, ex. video
  games, IM
• Changes in traditional family (more responsible
  for own meals)
• Social pressures, ex. being thin, rebelling
  against parents, showing athletic prowess
• ALL OF THESE CAN RESULT IN
• POOR FOOD CHOICES!!

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FACT

• Children receive over 30 marketing messages for
  food EVERY DAY.
• Center for Science in the Public Interest, 2005

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Reasons Teens Have Increased Nutritional
Requirements

• Proper nutrition improves behavior, school
  performance, and cognitive development!
• Proper nutrition increases participation in
  school activities!
• Proper nutrition now will lead to good eating
  habits later in life!

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Reasons Teens Have Increased Nutritional
Requirements

• Adolescent growth spurts (peaks at puberty)
• Begins at 10/11 years old in girls, done at 15
• Begins at 12/13 years old in boys, done at 19
• Increase in height, so increase in skeletal mass
  (gain 45 of adult skeletal mass)
• Menstruation in females

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Reasons Teens Have Increased Nutritional
Requirements

• Lean body mass doubles in males
• Body fat content doubles in females (from 10 to
  20)
• Hormonal changes affecting different organs,
  including the BRAIN
• Sexual maturation

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Increased Nutrient Requirements in Adolescents

• Increased calories for girls 2,200 Cal/day and
  for boys 2,500 Cal/day
• Fiber 30-40 grams/day
• Needed for normal bowel function, preventing
  cancer, and coronary artery disease
• Vitamins A, C, E
• Vitamin A is needed for vision
• Vitamin C used quickly under emotional and
  physical stress
• Vitamin E is an antioxidant

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Increased Nutrient Requirements in Adolescents

• Protein 50-60 grams/day
• Calcium 1,300-1,500 mg/day
• Iron for girls 15 mg/day and for boys 12 mg/day
• Necessary for transporting oxygen
• Needed to make red blood cells (menstruation)
• Other minerals zinc, phosphorous, magnesium
• Zinc is necessary for protein formation and
  sexual maturation

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Nutritional Deficiencies in Adolescents

• Ca (only 600-800 mg/day consumed)
• Fe (iron-deficient anemia affects 2-10 of this
  age group)
• Excess sodium
• Dietary fat gt33 of calories
• French fries gt25 of all vegetables
• Simple sugars exceed complex carbs
• Fiber lt50 of RDA

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FACT

• 60 of overweight 5 to 10 year olds have at
  least 1 risk factor for heart disease.
• Examples increased BP and/or insulin levels
• This number is equal to approximately 25 of
  all 5 to 10 year olds.

Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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FACT

• TOP TEN SOURCES OF ENERGY FOR TEENS
• MILK
• BREAD
• CAKES/COOKIES/DONUTS
• BEEF
• CEREAL
• SODA
• CHEESE
• CHIPS
• SUGAR
• CHICKEN

Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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FACT

• Sweeteners and added sugars provide over 20 of
  a teenagers
• total calories per day.

Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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FACT

• Almost 10 of teenagers calories come from soda.

Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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FACT Teens who drink more than two cans of soda
per day demonstrate poor nutrition in many other
areas.
Nutrient Intake by Level of Soft Drink Consumption
Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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FACT

• Less than 25 of boys and less than 50 of girls
  consume the recommended servings of fruit per day.

Guidelines for Adolescent Nutrition Services,
2005 - J. Stang and M. Story, Editors.
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Nutritional Problems of Adolescents

• Eating disorders (includes crash dieting)
• Chronic disease obesity, diabetes, heart
  disease
• Delayed growth
• Delayed sexual maturation
• Why?

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Dietary Sources of Nutrients Needed by Adolescents

• Vitamin A
• Tomatoes, winter squash, cantaloupe, carrots,
  spinach, broccoli, sweet potato
• Vitamin B6
• Soybeans, bananas, meat, fish, beans, nuts, whole
  grains
• Vitamin E
• Oils (wheat germ, sunflower, safflower, corn),
  almonds, peanuts
• Vitamin D
• Sunlight, fortified milk
• Vitamin C
• Peppers, broccoli, citrus fruits, strawberries,
  melons, tomatoes, cabbage, green leafy
  vegetables, papaya, winter squash
• Folic acid
• Green leafy vegetables, beans, asparagus, orange
  juice

• Iron
• Fish, green vegetables, nuts, iron-fortified
  cereals, raisins.
• Calcium
• Dairy products, green leafy vegetables, salmon
• Zinc
• Red meat, oysters, crabmeat, beans, whole grains
• Magnesium
• Whole seeds, nuts, legumes, grains
• Fiber
• Peas, beans, whole grains, sweet potato, green
  leafy vegetables

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Easy Ways to Improve Your Nutrition

• Try leaner versions of foods like dairy products
  and meats
• Eat smaller portions more frequently
• Vary your diet so you dont get bored
• Dont overeat foods with added sweeteners
• Put color into your diet with fruits and
  vegetables
• Think ahead so that you have snacks available
  when you need energy
• Replace soda/lemonade/sports drinks with fruit
  juice
• EAT BREAKFAST
• Try whole grain or wheat bread instead of white
• Drink water, it helps to fill you up
• START MOVING!