Energy Metabolism

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Energy Metabolism

• Utilization of energy-yielding nutrients for fuel

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Metabolism of Nutrients

• Once absorbed, energy-yielding nutrients are
  transported to cells
• Further metabolism (processing) occurs
• Metabolic pathways series of reactions that
  transform nutrients into final product that can
  be used by the body
• Catabolic pathways release energy trapped in
  chemical bonds
• Energy converted into ATP
• ATP is the energy currency of the cell

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ATP Adenosine triphosphate
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Elimination of Metabolic Wastes Body Organ
Systems
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The Carbohydrates Sugars, Starches, and Fibers

• Chapter 4

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Introduction

• Carbohydratesenergy fuel
• For the brain glucose
• For muscles glucose, glycogen, fat
• Sources of carbohydrates?
• Fattening overgeneralization

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Carbohydrate Family

• Abbreviation CHO
• Sugars (simple CHO)
• Monosaccharides
• Chemical shorthand C6H12O6
• Glucose, fructose, galactose
• Disaccharides
• Maltose, sucrose, lactose
• Polysaccharides (complex CHO)

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Chemists View of Monosaccharides
Fructose
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Monosaccharides

• Same numbers and kinds of atoms
• Differing structure and sweetness
• Glucose blood sugar
• Part of every disaccharide
• Fructose
• Sweetest of the sugars
• Galactose
• Only in a few foods

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Disaccharides

• Pairs of three monosaccharides
• Maltose two glucose units
• Sucrose glucose and fructose
• Lactose galactose and glucose
• Condensation
• Links two monosaccharides together
• Hydrolysis
• Breaks a disaccharide in two

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Polysaccharides

• Glycogen
• Storage form of energy in muscle and liver
• Glucose units
• Starch
• Storage form of energy in plants
• Glucose units
• Fibers
• Not digestible, but very beneficial

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Fibers

• Differ from starches
• Soluble fibers
• Mix with water - form a gel
• Slow transit time in colon
• Insoluble fibers
• Do not mix with water or form a gel
• Speed transit time in colon
• Both forms of fiber slow gastric emptying

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Whole Grains

• Bran layers good source of fiber and vitamins
• Germ good source of vegetable oils and vitamin E
• Endosperm contains starch and some protein

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Whole vs. Refined Foods

• Carbohydrates in whole foods, such as fresh
  fruit, dairy or whole grains, are in their
  natural state
• Refining CHO separates the CHO from vitamins,
  minerals, fiber, and phytochemicals
• Whole all edible parts present
• Refined some edible parts removed

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Digestion and Absorption of CHO
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Absorption of CHO
Monosaccharides, the end products of carbohydrate
digestion, enter the capillaries of the
intestinal villi.
In the liver, galactose and fructose are
converted to glucose.
Monosaccharides travel to the liver via the
portal vein.
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Fiber slows nutrient absorption
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More Health Benefits of Fiber

• Diets high in fiber, or indigestible
  carbohydrates, can relieve or prevent certain
  bowel disorders
• Hemorrhoids
• Diverticulosis
• Diverticulitis
• Constipation

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Epidemiological studies have shown that the
incidence of colon cancer is lower in populations
that consume diets high in fiber.
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Sources of Fiber
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Carbohydrate Metabolism

• Primary role of CHO glucose for energy
• Fuels most of bodys cells
• Preferred source for brain, nerve cells, and
  developing red blood cells
• We need a constant supply!

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The Constancy of Blood Glucose

• Steady supply in blood stream
• Intestines food
• Liver glycogen
• Blood glucose homeostasis
• Insulin
• Glucose from blood into cells
• Glucagon epinephrine
• Brings glucose out from storage

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Carbohydrate Stores

• We store glucose as glycogen in times of
  abundance
• Liver storage
• Condensation into glycogen
• Hydrolysis for release of glucose when needed
• Muscle
• Hoards glycogen stores for use during exercise
• Muscle glycogen not available to supplement blood
  glucose
• If diet is insufficient, body converts other
  compounds
• Making glucose from protein
• Amino acid conversion
• Gluconeogenesis

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CHO Intake and Ketogenesis

• When CHO is inadequate, fat metabolism shifts
• We make ketone bodies from fat fragments
• Ketone body formation starvation
• Dulls hunger
• Ketosis acid-base balance
• Acidifies blood
• Minimum carbohydrate needs for protein sparing
  and prevention of ketosis 50-100g/day
• Varies based on metabolic rate and activity
• In times of excess glucose used to make fat

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Availability of Carbohydrates Determines Fatty
Acid Metabolism
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The Constancy of Blood Glucose

• Glycemic response
• Speed of glucose absorption, level of blood
  glucose, and return to normal glucose levels
• Low glycemic response
• Desired
• High glycemic response
• Glycemic index and glycemic load
• Way of measuring effects on blood sugar of
  various foods

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The Constancy of Blood Glucose

• Balancing within the normal range
• Balanced meals at regular intervals
• Diabetes mellitus
• Insulin is either inadequate or ineffective
• Type 1 diabetes
• Type 2 diabetes
• Hypoglycemia
• Occurs most frequently in poorly managed diabetes

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Abnormal Blood Glucose Diabetes Mellitus

• Leading cause of blindness in the US
• Accounts for 44 of all new cases of kidney
  failure
• Gestational diabetes can occur in women during
  pregnancy
• May increased risk of developing type 2 diabetes
  later in life

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Diabetes Symptoms and Complications

• Immediate Symptoms excessive thirst, frequent
  urination, excessive hunger
• Long Term Complications damage to the heart,
  blood vessels, kidneys, eyes and nervous system.
• Infections are more common in patients with
  diabetes, and amputations may be necessary

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Diabetes Treatment

• Goal maintain blood glucose within normal range
• Treatment involves diet, exercise, and sometimes
  meds
• Refined CHO increasingly implicated in type 2 DM
  risk
• Best way to reduce risk for type 2 DM maintain
  healthy body weight

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Lactose Intolerance

• The enzyme lactase is needed to digest lactose,
  the sugar found in milk.
• If lactose is not digested in the small
  intestine, it passes through to the large
  intestine.
• Undigested lactose in the small intestine can
  cause cramping, abdominal distention and
  diarrhea.

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Lactose Intolerance

• Lactase activity
• Highest immediately after birth
• Declines with age
• Symptoms of intolerance
• Prevalence
• Genetically determined
• Worldwide 70
• US 25

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Lactose Intolerance

• Dietary adjustments
• Manage dairy consumption rather than restriction
  (for some people)
• Probiotic bacteria can ease symptoms, aid in
  digestion
• Fermented milk products often better tolerated
• Response is highly individual
• Potential nutrient deficiencies?
• Riboflavin, vitamin D, and calcium
• We can get these from other foods

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Health Effects of Sugars

• Pleasure in moderate amounts
• In excess potential nutrient deficiencies and
  increased risk of chronic disease
• Energy with few other nutrients
• Best limited to discretionary kcal
• Honey
• More energy per spoonful than table sugar, but
  twice as sweet
• Health benefits
• Sugar sources concentrated vs. dilute

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Recommended Intakes of Sugars

• Dietary Guidelines
• Choose and prepare foods with little added sugar
• DRI (from USDA)
• Added sugars
• No more than 25 of days total energy
• Impact on other food groups
• WHO recommendations no more than 10!

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Alternative Sweeteners

• Artificial sweeteners
• Non-nutritive sweeteners
• Large doses and adverse effects
• Stevia an herbal product
• Generally recognized as safe (GRAS)
• Sugar alcohols
• Provide kcalories
• Benefits and side effects

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Health Effects of CHO

• Heart disease
• Whole grains
• Slow release of sugars into blood
• Phytochemicals - antioxidant effects
• Soluble fibers
• Help to eliminate cholesterol
• Improving heart disease risk factors

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Health Effects of CHO

• Diabetes
• High-fiber foods
• Quantity and quality of CHO foods
• GI health
• High-fiber foods
• Ample fluids
• Weight management
• High-fiber foods and whole grains
• Feeling of fullness

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Health Effects of CHO

• Cancer
• Dietary fiber and colon cancer
• Fiber supplements vs. food sources
• Sources of dietary fiber - what are they?
• Phytochemicals
• Preventing colon cancer
• Diluting, binding, and removing cancer-causing
  agents
• Bacterial fermentationSCFA

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Health Effects of CHO

• Excessive fiber - usually due to supplementation
• Insufficient energy or nutrient needs (fullness)
• Abdominal discomfort, gas, diarrhea
• GI obstruction
• Impaired nutrient absorption
• Dietary goals for CHO
• Balance, moderation, variety

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From Guidelines to Groceries

• Read food labels
• Total carbohydrate
• Sugars
• Fiber
• Sugars
• Added vs. natural sugars - how can we tell?
• Grain products (bread, crackers, etc.)
• Hidden refined ingredients
• What to look for

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A sugar by any other name

• Agave nectar
• Brown sugar
• Cane crystals
• Cane sugar
• Corn sweetener
• Corn syrup
• Crystalline fructose
• Dextrose
• Evaporated cane juice
• Fructose
• Fruit juice concentrates
• Glucose

• High-fructose corn syrup
• Honey
• Invert sugar
• Lactose
• Maltose
• Malt syrup
• Molasses
• Raw sugar
• Sucrose
• Sugar
• Syrup