Nutrition
description
Transcript of Nutrition
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Nutrition
• Nutrition - Science of foods and nutrients– Nutrient – a component of food that performs a
physiological function• All body functions depend on proper nutrition• Food Guide– Guides food choices to fulfill nutritional needs– Guidelines change as nutritionists gain
information… not a pyramid anymore!
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Nutrition - Guidelines
• It’s just chemistry!– Balance energy taken in with energy used to maintain
your weight
• Eat a variety of foods– Our bodies require ALL the different types of nutrients
for different things!– A balanced diet provides all the nutrients and vitamins
you need!– Drink lots of water!
• All those enzyme reactions (hydrolytic) need water.
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Nutrition - Guidelines
• You still need fat!• A moderate total fat intake low in saturated fats and cholesterol
• Protein is a must!!!• Vegetarians need to be especially careful!• Sources include poultry, fish, plants
• Choose whole foods• Fresh fruits and veggies, whole grains, legumes,• Provides fiber and complex carbs
• Avoid Processed foods• “white” breads and pastas (refined carbs)• Canned goods – often higher in sodium
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Nutrients: Carbohydrates
• Primary energy source• Can be classified as simple carbohydrates or complex
carbohydrates.
• Simple carbohydrates are usually monosaccharides (single sugars) or disaccharides (two sugars linked together)
• Glucose– Most important monosaccharide.– Most readily available energy source– Brain cells ONLY use glucose for energy!
• Other cells can use fatty acids as well.
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Nutrients: Carbohydrates cont’d
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Nutrients: Carbohydrates cont’d
Complex carbohydrates• Include oligosaccharides (chains of up to 10
sugars) and polysaccharides ( >10 sugars linked together)– Eg: starch, glycogen, and cellulose.
• Get broken down to glucose• Contain fiber
• Insoluble fiber - may protect against cancer• Soluble fiber - combines with bile acids and
cholesterol
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Nutrients: Carbohydrates cont’d
• Simple sugars (mono- and disaccharides)– Elevate blood sugar
rapidly– Pancreas releases
overload of insulin– Sugar taken up
rapidly – hunger returns
– Could lead to insulin resistance
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Reducing high glycemic index carbohydrates
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Nutrients: Proteins
• Functions– Bodily growth and development– Regulate metabolism– Can be energy source (during starvation)
• Used to make structural proteins in the body– Muscle, hair, skin, nails
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Nutrients: Proteins cont’d
• Used for synthesis of other proteins, including:– Hemoglobin– Plasma proteins– Enzymes– Hormones
• Synthesizing proteins…– Requires all 20 amino acids (building blocks for protein)– 8 must be supplied in diet - essential amino acids– Remaining 12 can be synthesized by the body
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Nutrients: Proteins cont’d.
• “Complete” proteins– Contain all 20 amino acids– Eggs, meat, milk
• “Incomplete” proteins– Generally from plants– Lack at least one essential amino acid– Vegetarians must combine plant protein sources
• Complementary Proteins
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Complementary proteins
• Table 14.5
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Nutrients: Proteins cont’d.
• Amino acids are not stored in the body– Must take in daily supply
• Too much protein can be harmful– Processing of amino acids produces urea– Urea excretion requires water– Can lead to dehydration– Can also cause calcium loss
• Some protein-rich foods also are high in saturated fats (eg: red meat)– Can lead to cardiovascular disease
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Nutrients: Lipids
• Used as energy storage (stores MUCH more energy than carbs)
• Saturated fats– Solids at room temperature– Animal origin• Exceptions: palm oil, coconut oil
– Associated with cardiovascular disease
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Nutrition: Lipids cont’d
• Unsaturated fats (liquids at room temp.)– Oils contain mono- and polyunsaturated fats– Polyunsaturated oils contain essential fatty acids• Linoleic acid and alpha-linolenic acid
• Omega-3 fatty acids– Especially protective against heart disease– Cold water fish, flax seed oil
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Nutrition: Lipids cont’d.
Fats that cause disease:• Plaques- form in arteries
• Contain cholesterol and saturated fats
• Cholesterol• Carried in blood by low density lipoprotein (LDL) and high density
lipoprotein (HDL)• LDL-”bad” cholesterol - transports from liver to cells• HDL- “good” cholesterol - transports to liver to make bile salts
• Trans-fatty acids• May reduce ability to clear cholesterol• In commercially packaged foods• Linked to diabetes and heart disease
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Reducing certain lipids
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Nutrition: Vitamins
• Coenzymes– organic molecules that are required by certain enzymes
to carry out their reactions
• Cofactors – inorganic substances that are required for, or increase
the rate of, enzyme reactions
• 13 vitamins– Fat soluble - A,D,E,K– Water soluble – B vitamins (8) and vitamin C
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Nutrition: Vitamins cont’d
• Antioxidants– Vitamins C, E, and A– Defend against free radicals (eg: O2
-, OH-)• Molecules responsible for aging and tissue damage• Cell metabolism creates free radicals • Damages DNA – causes a variety of harmful effects in
cells.
– (Lack of vitamin C causes scurvy)
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Free Radicals
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Scurvy
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Nutrition: Vitamins cont’d
– Vitamin D• Converted in skin to active form by UV light• Further modified by kidneys and liver
– Becomes “calcitrol”– Promotes calcium absorption from intestines
• Deficiency causes rickets
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Fat-soluble vitamins
• Table 14.7
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Nutrition: Minerals
• Major minerals– Body contains more than 5 grams of these minerals– Found in components of cells– Also found in structural components (eg: teeth, bones)– Include magnesium, calcium, sodium, and potassium.
• Trace minerals– Body contains less than 5 grams of these– Components of larger molecules
• Iron - part of hemoglobin• Iodine - part of thyroxine (a thyroid hormone)• Zinc, copper, selenium - components of enzymes
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Minerals in the body
• Fig. 14.17
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Nutrition: Minerals cont’d.
Calcium• Deficiency causes osteoporosis
• Bones become porous and fracture easily.
• Calcium intake can slow bone loss• Requirements
• Men and premenopausal women-1000 mg/day• Postmenopausal women-1300 mg/day
• Vitamin D is essential in absorbing calcium!
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Nutrition: Minerals cont’d.
Sodium• Requirement is 500 mg/day• Average intake in US is 4000-5000 mg/day
• May be linked to hypertension
• Only is naturally occurring in diet• added in processing• added as table salt
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Reducing dietary sodium
• Table 14.10
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Nutrition: Eating Disorders
Obesity• Body weight 20% above normal• 28% women and 10% men in US are obese• Hormonal, metabolic, and social factors
• May be linked to lack of leptin- satiety hormone
• Behavioral therapy is usual treatment
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Nutrition: Eating Disorders cont’d
Bulimia Nervosa• Can coexist with obesity or anorexia• Binging and purging-damage from vomiting• Overly concerned about body shape and
weight• Can damage kidneys and cause fatal
arrhythmias• Psychotherapy and medication are treatments
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Recognizing Bulemia
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Nutrition: Eating Disorders cont’d
Anorexia Nervosa• Morbid fear of gaining weight• Athletes at risk• Distorted self-image• All symptoms of starvation
• Low blood pressure• Constant chilliness• Irregular heartbeat
• Can result in death• Force-feeding and psychotherapy are critical
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Recognizing anorexia nervosa
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