nutrition student

8/8/2019 Nutrition Student

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Nutrition and Metabolism

Body WeightStable with equal energy intake and output

around a homeostatic set pointDetermined by combination of environmental and hereditary factors

30-50% of variation between individuals due toheredity rest due to eating and exercise habits


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Gut-Brain Peptides

Short term appetite regulators (effectslast minutes to hours)

Ghrelin produces hunger From stomach cells (when empty)


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Gut-Brain Peptides

Long term appetite regulators (effectslast weeks to years)

Leptinsecreted by adipocytes in proportion to bodyfat stores

Insulinpancreatic beta cells


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Some Factors in Appetite Regulation

Appetite is briefly satisfied by chewing swallowing stomach filling

Neurotransmitters stimulate desire for different foods

norepinephrine carbohydrates galanin fats endorphins protein


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Calories

One calorie - amount of heat required toraise temperature of 1 g of water 1 C

1000 calories is a kilocalorie or Calorie

Fats contain about 9 kcal/gCarbohydrates & proteins, about 4 kcal/g

sugar and alcohol are empty calories -- fewnutrients

Substance used for fuel is oxidizedprimarily to make ATP


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Metabolic Rate

Amount of energy used in the body in a givenperiod of time (kcal/hr or kcal/day)

measured directly in calorimeter (water bath)

Basal metabolic rate (BMR) relaxed, awake, fasting, comfortable temperature adult male BMR is 2000 kcal/day (female slightly less)

Factors affecting total MR pregnancy, anxiety, fever, eating, thyroid hormones,

and depression


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Nutrients

Ingested chemical used for growth, repair or maintenanceRecommended daily allowances (RDA)

safe estimate of daily intake for standardneeds

Essential nutrients can not be synthesized

minerals, vitamins, 8 amino acids and 1-3fatty acids must be consumed in the diet


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Carbohydrates

Carbohydrates found in 3 places in body muscle and liver glycogen; blood glucose

Most carbohydrate serves as fuel neurons and RBCs depend on glucose

Blood glucose carefully regulated by

insulin and glucagon


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RDA and Dietary Sources of Carbs

Carbohydrates are rapidly oxidized, RDA greater than any other nutrient (175 g/day)

Complex vs. Simple carbohydrates Complex carbohydrates

Polysaccharides, mixed with vitamins & mineralsFruits, veggies and whole grains

Simple carbohydratesSimple sugarsProcessed foodsempty calories


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Dietary Fiber

Fibrous material that resists digestionFiber is important to diet (RDA is 30 g/day)

excess interferes with mineral absorption -iron

Water-soluble fiber (pectin) q blood cholesterol and LDL levels

Water-insoluble fiber (cellulose, lignin) absorbs water in intestines, softens stool,

gives it bulk, speeds transit time


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Lipids

Average adult male 15% fat; female 25%fat

bodys stored energyhydrophobic, contains 2X energy/g, compactstorageGlucose sparing (glycogen)

fat-soluble vitamins (A,D,E,K) absorbed withdietary fat

ingest less than 20 g/day risks deficiency


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Functions of Lipids

Diverse functions structural

phospholipids and cholesterol are components of

plasma membranesMyelin need for proper nerve function

chemical precursorscholesterol - a precursor of steroids, bile salts and

vitamin D


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Fat Requirements and Sources

Should be less than 30% of daily calorieintake

typical American gets 40-50%

Most fatty acids synthesized by body essential fatty acids must be consumed omega-3 & omega-6 fatty acids


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Fat Requirements and Sources

Saturated fats animal origin -- meat, egg yolks and dairy

products

Unsaturated fats found in nuts, seeds and most vegetable oils

Cholesterol found in egg yolks, cream, shellfish, organ

meats and other meats


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Total Cholesterol

Desirable to maintain total cholesterolconcentration of < 200 mg/dL

dietary restrictions lower blood cholesterol

levelsby 5% with restriction of dietary cholesterolby 15 to 20% with restriction of certain saturatedfats

vigorous exercise lowers blood cholesterol


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Desirable Lipoprotein Levels

High levels of HDL indicate cholesterol is being removed from arteries

Low levels LDL

high LDL correlates with cholesterol deposition inarteries

Recommendations exercise regularly avoid smoking, saturated fats, coffee and stress


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Proteins

12-15% of body mass mostly in skeletal muscles

Functions muscle contraction cell membranes (receptors, cell identity, pumps) fibrous proteins (collagen, keratin)

globular proteins (antibodies, myoglobin,enzymes) plasma proteins: blood osmolarity and viscosity


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Requirements for Protein

RDA - 44-60 g/dayNutritional value depends onproportions of amino acids

8 essential amino acids can not besynthesized

isoleucine, leucine, lysine, methionine,phenylalanine, threonine, tryptophan and

valineCells do not store surplus proteinComplete proteins (dietary)


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Dietary Sources

Animal proteins (meat, eggs and dairy)are complete proteins

closely match human proteins in amino

acid compositionPlant sources must be combined in theright proportions

beans and rice are a complementarychoice


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Functions of MineralsCalcium and phosphorus

bones and teeth

Phosphorus phospholipids, ATP, buffers, nucleic acids

Calcium, iron, magnesium and manganese cofactors for enzymes

Iron - essential for hemoglobin and myoglobin

Chlorine - component of stomach acid (HCl)Mineral salts

electrolytes; govern function of nerve and musclecells; regulate distribution of body water


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Vitamins

Body synthesizes some vitamins fromprecursors

niacin, vitamin A and D vitamin K, folic acid

produced by intestinal bacteria

Water-soluble vitamins (C, B)

absorbed with water in small intestine; notstored

Fat-soluble vitamins (A, D, E, K) absorbed with dietary lipids; stored

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