Nutrition

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!

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.

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

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.

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


• 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

Reducing high glycemic index carbohydrates

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

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

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

Complementary proteins

• Table 14.5

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

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

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

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

Reducing certain lipids

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

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)

Free Radicals

Scurvy

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

Fat-soluble vitamins

• Table 14.7

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!

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

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

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

Recognizing anorexia nervosa

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Documents

Nutrition