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Carbohydrates ch4
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Carbohydrates ch4






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Carbohydrates ch4 Carbohydrates ch4 Presentation Transcript

  • The Body’s Choice for Energy
    • Energy : 4 kcal/gram
    • Recommendations: 50-60% of total energy intake from CHO
      • Emphasis on whole grains, fruits and vegetables (<10% of total energy intake from simple sugars)
      • At LEAST 50-60 grams CHO/day to prevent KETOSIS
        • Low CHO intake  incomplete breakdown of fat  ketone bodies  ketosis (disturbs acid-base balance)
    • CHO has a “ protein-sparing ” effect
      • Long-term starvation  protein “wasting” in muscles, heart, liver, kidneys, other organs
    • Simple Sugars
      • Monosaccharides
      • Disaccharides
    Fig. 4.2 Fig. 4.3
    • Complex CHO
      • Polysaccharides
        • Starches = amylose (straight chain) and amylopectin (branched chain)
        • Glycogen = “animal starch”
      • Oligosaccharides
    Fig. 4.4
    • Human and animal storage form of glucose
    • Highly branched
    • Only synthesized and stored in muscle and liver
    • Liver glycogen supplies blood glucose
      • Exhausted in ~ 18 hours
    • Muscle glycogen used only for muscles
    • Non-digestible CHO (from plants)
    • Recommendation: 25 grams/day for women or 38 grams/day for men (from food best)
    • Two basic types:
      • Insoluble fiber (nonfermentable)
      • Soluble fiber (viscous)
    • Insoluble fiber
      • Sources: wheat products, brown rice, fruit and vegetable peels, fibrous plant foods (ex: celery)
      • Function: increases fecal bulk allowing easier waste elimination and regularity
    • Soluble fiber
      • Sources: insides of fruits and vegetables (apples, bananas, etc.), legumes, barley, oats, white rice
      • Function: slows gastric emptying, slows glucose absorption, decreases “bad” cholesterol
    • Non-caloric or lower caloric sweeteners
      • Sugar alcohols – sorbitol, xylitol
        • 1.3-3 kcal/gram
        • May cause diarrhea
        • Noncariogenic
      • Aspartame – Nutrasweet, Equal
        • Made from 2 amino acids (including phenylalanine)
        • 4 kcal/gram but is about 200 times sweeter than sucrose
        • Can be altered by cooking (protein-based) – not dangerous but does not taste sweet
        • No more than 50 mg/kg body wt (14 cans diet soft drink!)
        • PKU = phenylketonuria – cannot metabolize phenylalanine, so can’t have aspartame
    • Sucralose – Splenda
        • Sucrose derivative
        • 600 times sweeter than sucrose
        • Heat stable, good for baking
        • Not well-absorbed, rest excreted by kidneys
    • Stevia
      • Extract from South American shrub
      • 100 to 300 times sweeter than sucrose
      • GRAS classification by the FDA
    • Amylase = starch-digesting enzyme
      • Produced in mouth (salivary or alpha-amylase) and pancreas (pancreatic amylase)
    • Other enzymes produced by small intestine cells (sucrase, lactase, etc.)
    • Monosaccharides absorbed across small intestine absorptive cells into capillaries  portal vein
    • Soluble fiber fermented by bacteria in large intestine  gas, acids
    • Hyperglycemia = over 125 mg/dl
    • Normoglycemia = 70-100 mg/dl
    • Hypoglycemia = below 40 to 50 mg/dl
    • Diabetes - inability to handle glucose properly
      • Diabetes is characterized by chronic hyperglycemia with sometime dangerous episodes of hypoglycemia
    • Insulin
      • Produced by beta cells in pancreas in response to hyperglycemia
      • Binds to insulin receptors on cells, leading to an increase in glucose absorption by cells  return to normoglycemia
    • Glucagon
      • Produced by cells in pancreas in response to hypoglycemia blood glucose
      • Stimulates breakdown of glycogen in liver to glucose  return to normoglycemia
  • Fig. 4.9
    • Three main types:
      • Type 1 (insulin-dependent diabetes)
      • Type 2 (noninsulin-dependent diabetes)
      • Gestational diabetes
    • Related to morbidity and mortality with other problems (kidney failure, heart disease, hypertension, poor wound healing, poor blood circulation)
    • Insulin-dependent or “childhood onset” diabetes
      • Autoimmune disease – destruction of beta cells in pancreas  NO insulin made
        • All patients with type 1 diabetes require daily insulin injections
    • Noninsulin-dependent or “adult onset” diabetes
      • Genetic and lifestyle connection
      • Epidemic rise in incidence in US and other developed nations, including children
      • Characterized by insulin receptor insensitivity
        • Usually, insulin not needed because the pancreas makes plenty
        • Pancreas ramps up insulin production, may eventually “wear out”  need for insulin injections
        • May be controlled with diet, exercise, and medications
    • Health risks caused by long-term elevated insulin:
      • Increased blood TGs, smaller (more dangerous) LDL
      • Increased risk for heart disease
      • Increase fat deposits in adipose tissue and organs (including liver)
      • Increased blood clotting tendencies
      • Damage to kidneys
    • Affects 3-5% of pregnancies
    • Normal for slight insulin insensitivity during pregnancy, but too much  hyperglycemia/gestational diabetes
      • So very similar in symptoms to type 2 diabetes
    • Usually resolves after birth
    • Both mother and child at higher risk for type 2 diabetes later in life
    • “ Forms” of sugar
    • Note: “Low fat” and “Fat-free” foods tend to be high in simple sugars
    • Bone health
      • Soft drinks/sugary beverages may contribute to compromised bone health if replace milk
    • Dental health
      • Simple sugars are cariogenic
      • Sticky, gummy CHOs
      • Bacteria in mouth metabolize sugar  produce acids  dissolve tooth enamel
      • Fluoridated water and toothpaste help protect enamel, prevent dental caries
    Fig. 4.12
    • Humans produce few enzymes that can break beta bonds in CHOs, including lactose
    • Lactose intolerance is reduced or absent lactase  maldigestion of lactose  fermentation by colon bacteria  bloating, gas, acid production, discomfort, diarrhea
    • Normal as we age (less dependence on milk for nutrients)
    • 75% of world is lactose intolerant
      • Esp. Asian, African, Hispanic American populations
    • How to obtain calcium?
      • Small portions of lactose-containing foods
      • Low lactose dairy (cheese, yogurt)
      • Lactase-treated products, lactase pills
      • Non-dairy calcium sources:
        • Dark green, leafy vegetables (not spinach), including broccoli
        • Calcium-fortified OJ
        • Soy products, particularly calcium-fortified
        • Calcium-fortified cereals