Nutrition and Metabolism

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Nutrition and Metabolism

• Chapter 18

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Appetite

• Hypothalamus contains feeding center and satiety
  center
• If feeding center is damaged anorexia can result
• If satiety center is damaged hyperphagia
  (overeating) and obesity can result
• The satiety center has special neurons
  (glucostats) that rapidly absorb glucose after a
  meal and suppress appetite

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Appetite and hunger control

• Chewing and swallowing temporarily satisfies the
  appetite
• Hunger is stimulated by peristalsis
• Mild hunger contractions begin soon after
  emptying
• Increase over period of hours (painful)
• CCK from small intestine inhibits appetite
• Ghrelin from stomach-stimulates appetite

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Calories

• Amount of heat required to raise 1 g of water 1
  degree Centigrade
• 1000 calories is a Kcal
• Calories measure the ability to do work
• Most dietary calories come from carbohydrate,
  fat, and protein
• Carbs and proteins yield about 4 kcal/g
• Fats yield 9 kcal/g

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Nutrients

• Ingested chemical used for growth, repair, or
  maintenance
• 6 major classes water, carbohydrate, lipids,
  proteins, minerals, and vitamins
• Water, carbohydrate, lipid, and proteins are
  macronutrients because they must be consumed in
  large quantities
• Minerals and vitamins are micronutrients

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Recommended daily allowance

• Developed in 1943 by National Research Council
  and National Academy of Sciences
• Been revised many times
• Body cant make 8 amino acids, most minerals and
  vitamins, and some fatty acids
• These are essential nutrients (MUST eat them)

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Carbohydrate

• Hypoglycemia is low blood sugar, makes you weak
  and dizzy)
• Necessary to have balance for brain and
  erythrocytes.
• Many other cells can use carbohydrate and/or
  fatty acid
• Of 175 g suggested per day, the brain consumes
  120g !

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Forms of carbohydrate

• Monosaccharide-simple sugar
• Include glucose (blood sugar), galactose, and
  fructose
• Disaccharide -two monosaccharides together
• Include sucrose, lactose, and maltose
• Polysaccharides- complex carbs
• Only nutritional one is starch

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Lipids (are you an apple or pear?)

• Males average 15 body fat
• Females average 25 body fat
• Fat is better for storing energy and contains
  over 2 times the energy
• Reserves in a man gives him 119 hours of running
  time versus 1.6 for carbs
• Cholesterol and phospholipids are major
  structural components of cell membranes
• Cholesterol is an animal product ONLY and is
  needed for steroid hormones (200 mg/dL or less
  recommended)

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Requirements and info

• No more than 30 of daily intake
• 10 saturated (solid at room temp)
• Essential fatty acids- linoleic acid for sure,
  linolenic acid and arachidonic acid possibly
• HDL-high density lipoprotein-Good cholesterol
• LDL-low density lipoprotein-Bad cholesterol

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Proteins

• 12-15 of body mass (65 of this is in skeletal
  muscle)
• Necessary for muscle contraction, motility of
  cilia and flagella, and are major structural
  component
• Need 44-60 g (multiply your weight by 0.37 to
  give you your estimate)
• 20 amino acids available to make protein

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8 essential amino acids

• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine
• Infants need histidine too!

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Minerals

• 4 of body mass
• ¾ of this is calcium and phosphorus in bones and
  teeth
• Calcium-
• Phosphorus
• Sodium-
• Chloride
• Magnesium
• Potassium
• sulfur

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Vitamins

• Water soluble-excreted by kidneys and cant be
  stored
• C (ascorbic acid) and B vitamins (B1, B2, B 6,
  B 12, niacin, panthothenic acid, folic acid, and
  biotin)
• Fat soluble vitamins-incorporated into lipid
  micelles in small intestine and absorbed with
  dietary lipids
• Includes A, D, E, and K
• People who dont eat enough fat may have
  deficiency in fat soluble vitamins
• Hypervitaminosis-excess vitamins

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Terms

• Basal Metabolic rate-measures rate your body uses
  energy
• Glycogenesis- synthesis of glycogen (stimulated
  by insulin)
• Glycogenolysis- hydrolysis of glycogen (releases
  glucose between meals)
• Gluconeogenesis-synthesis of glucose from
  noncarbohydrates (fats, amino acids)
• Occurs mainly in liver
• Kidneys can also do this after weeks of fasting
  (starving)

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Disease/disorders

• Rickets- vitamin D deficiency in children causing
  bowing of legs etc
• Osteomalacia-vitamin D deficiency in adult causes
  weakened bones
• Vitamin K deficiency in newborns causes
  hemorrhagic disease of the newborn characterized
  by abnormal bleeding
• Beriberi- deficiency of thiamine (B 1)-GI upset,
  confusion, weakness, paralysis, and death
• Excess niacin-acute toxicity, flushing, wheezing,
  vasodilation, headache, diarrhea, vomiting
• Pellagra -deficiency in niacin- dermatitis,
  inflammation of GI, diarrhea, and mental disorders

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More diseases/disorders

• Scurvy- vitamin C deficiency (limeys)-bleeding
  gums, bruising, abnormal bone development in
  children
• Pica- eating ice chips, dirt, etc and is a sign
  of mineral deficiency
• Malnutrition -poor nutrition-not enough essential
  nutrients
• Starvation- no food! Can stay alive 50-70 days
  without food, but with lots of consequences!

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One more set

• Kwashiorkor-protein starvation-leaves bellies
  swollen
• Marasmus lack of nutrients causing people to
  look like living skeletons
• anorexia nervosa-self imposed starvation
• Bulimia-binge and purge

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Deficiency or excess

• Vitamin A deficiency-night blindness, dry skin,
  more infections (worlds most common deficiency)
• Vitamin A excess-anorexia, nausea, vomiting,
  headache, pain, frail bones, hair loss, enlarged
  liver and spleen, and birth defects