Chapter 7 Nutrition - Lecture notes 1 PDF

Preview

Summary

Kate Yerxa was the professor, and these are the notes I took during lecture. ...

Description

Chapter 7 Vitamins Definition and Classification of Vitamins ● Vitamin: an essential, non-caloric, organic nutrient in tiny amounts in the diet ● Vitamins help the body’s metabolic enzymes maximize energy yields from macronutrients as well as help maintain the health of the body’s cells, tissues, and organs ○ Some vitamins exist as precursors (or provitamins) ■ Provitamins need to be converted to active form in the body ● Two Classes of Vitamins: fat soluble and water soluble Fat Soluble Vitamins: A, D, E, and K ● Found in fats and oils of foods ● Require bile for absorption ● Storage ○ Stored in liver and fatty issues until needed ○ Not needed in the diet daily ○ Can reach toxic levels if too much is consumed ● Deficiencies ○ Deficiencies can occur when people experience fat malabsorption ○ Diets that are extraordinarily low in fat ● Roles ○ Vitamins A and D act like hormones and influence cellular activity ○ Vitamin E protects the tissue from oxidative stress Vitamin A Forms: 1. Beta-carotene– plant derived precursor 2. Retinol– active form stored in liver 3. Converted by cells into its other two active forms, retinal and retinoic acid, as needed Roles ● ● ● ● ● ●

Gene expression Vision Maintenance of body linings and skin Immune defense Growth of the body Normal cell development

Vitamins A Deficiency ● Second leading cause of blindness worldwide ○ Night blindness ○ Xerophthalmia

● ● ●

○ Macular degeneration Increase risk of infection Bone growth: Vitamin A assists in growth (via remodeling) of bone Decreased ability to reproduce

Toxicity of Vitamin A ● Can occur when excess vitamin A (preformed) is taken as supplements or in fortified foods ● Excessive vitamin A during pregnancy can cause birth defects ● Ordinary vitamin supplements in the context of today’s fortified food supply can add up to small daily excesses of Vitamin A ● Signs and Symptoms ○ Bone/Muscle pain, loss of appetite, skin disorders, headache, dry skin, hair loss, increased liver size, vomiting ○ Fetal malformation ○ Possible permanent damage ● Effects of high carotenoid intake- yellowing of skin ● Preformed ○ Retinoids ○ Found in animal products- fish, liver, fortified milk and yogurt, and eggs ● Proformed ○ Carotenoids ○ Found in plant products- dark green veggies, orange veggies, fruits, tomatoes ○ 3 carotenoids serve as provitamin A in humans: beta-carotene, lutein, and zeaxanthin Vitamin A DRI women: 700 Vitamin A DRI men: 900 Vitamin D ● Synthesized from sun exposure ● Insufficient sun exposure makes this a vitamin ● Activated by enzymes in liver and kidneys ● Food Sources ○ Fatty fish (salmon, herring) ○ Fortified milk, yogurt, margarine ○ Some fortified cereal, juice ○ Eggs Roles of Vitamin D ● Calcium Regulation ○ Vitamin D functions as a hormone to regulate blood calcium and phosphorus levels

○

●

To replenish blood calcium, vitamin D acts as three body locations to raise blood calcium levels: skeleton, digestive tract, and kidneys Vitamin D acts at the genetic level to affect how to grow cells, multiply, and specialize ○ Deficiency may be associated with cardiovascular disease and risk factors, some cancers, respiratory infections, inflammatory conditions, multiple sclerosis, and higher death risk

Deficiency of Vitamin D ● Rickets is the result of low vitamin D ○ Affects children - causes bowed legs, enlarged head, joints and rib cage ● Osteomalacia (soft bones) ○ Rickets-like disease in adults ○ Bones lose minerals and become porous Factors affecting Vitamin D synthesis 1. Advanced age- skin loses capacity to synthesize vitamin D 2. Clothing- remaining covered with no skin exposure to sun 3. Geography- north of Boston (above 40 degrees latitude) vitamin D synthesis is limited from November through March 4. Skin pigmentation- darker pigmented skin synthesizes less vitamin D 5. Sunscreen Vitamin D Toxicity ● Vitamin D can be very toxic, especially in infancy and childhood ● Results in ○ Over absorption of calcium (hypercalcemia), increase calcium excretion ○ Calcium deposits in organs and blood vessels ○ Growth retardation Vitamin D intake recommendations and food sources ● 15 micrograms/day for people ages 1-70 years ● 20 micrograms/day for adults over 70 years ● Fatty fish, liver oil, and egg yolks ● Butter, fortified margarine and milk ● Fortified soy products, cereals and infant formulas Vitamin E ● Vitamin E is an antioxidant ○ Oxidative damage can lead to inflammation that is associated with cardiovascular disease and some types of cancer ○ The lung tissue is susceptible to oxidative damage due to the high oxygen concentrations found there

Vitamin E Deficiency ● Deficiencies are almost never seen in healthy humans ● Vitamin E deficiency may occur in diseases with fat malabsorption or in premature babies born before the transfer of the vitamin from mother to the infant, which takes place in the last weeks of pregnancy ○ An infant’s RBCs rupture and infant becomes anemic Vitamin E Toxicity ● No adverse effects arise from consuming foods that naturally provide vitamin E ● Vitamin E supplements may increase the effects of anticoagulant medication ● Increased risk for brain hemorrhages, a form of stroke ● Vitamin E supplements should be used at low doses so that the UL of 1000mg/day is not exceeded Vitamin E: Recommendations ● 15 milligrams a day for adults ● On average, U.S. intakes of vitamin E fall substantially below the recommendation Food Sources ● Widely distributed in plant foods; fresh, oils, seeds ● Processing of foods and their associated vegetable oils can lead to the destruction of Vitamin E Vitamin K Roles of Vitamin K 1. Main function of vitamin K is to help synthesize proteins that help blood clots ● People with heart problems may need a blood thinner, warfarin, which interferes with the effects of vitamin K ● Such individuals may need vitamin K if they encounter excessive bleeding with warfarin use 2. Also necessary for the synthesis of key bone proteins Vitamin K Deficiency ● Vitamin K can be made by intestinal bacteria ○ Vitamin K deficiency is rare but can occur if a person is on antimicrobial medicine that destroys intestinal bacteria ● Newborn babies have a sterile intestine and it may take a couple of weeks for the intestinal bacteria to get established ○ Newborns are given a dose of vitamin K at birth Vitamin K Toxicity ● Toxicity is rare and there is no tolerable upper intake level

●

Toxicity causes jaundice and may occur if supplements of a synthetic version are oversonsumed

Vitamin K Requirements and Food Sources ● 20 micrograms/day for men ● 90 micrograms/day for women ● Food Sources ○ Green leafy veggies ○ Broccoli ○ Peas ○ Green beans ■ Resistant to cooking losses ■ Limited vitamin k stored in the body Overview of Water Soluble Vitamins B vitamins and vitamin C ● Dissolve in water ● Generally readily excreted from body ● Subject to cooking losses ● Function as coenzymes ● Participate in energy metabolism ● 50-90% of B vitamins are absorbed ● Marginal deficiency more common Vitamin C Roles of Vitamin C 1. Synthesis of collagen: collagen forms the base for all of the body’s connective tissues and for scar formation 2. Iron absorption: Vitamin C protects iron in the intestines from oxidation and enhances its absorption 3. Antioxidant: acts as an antioxidant, especially protecting the immune system cells from free radicals generated during their assault on invaders 4. Immune function? Vitamin C in large quantities does not prevent colds– but may reduce symptoms Vitamin C Deficiency ● Most scurvy symptoms are due to the breakdown of collagen in the absence of vitamin C ● Slow growth, tenderness when touched, bleeding gums, swollen ankles and wrists, red spots on skin, weakness, loose teeth, anemia Vitamin C Recommendations ● DRI= 90 mg for men, 75 mg for women ● Only 10 mg/day needed to prevent scurvy

● Recommendation for smokers: 125 mg/day for men, 110 mg/day for women Vitamin C Food Sources ● Fruits and veggies B Vitamins B-complex Thiamin (vitamin B1) ● Energy metabolism of all cells ● Nerve cell membranes ● Deficiency ○ beriberi ○ Alcohol abuse ● DRI Recommendation ○ 1.1 mg/day for women ○ 1.2 mg/day for men ○ Most exceed need through diet Food Sources of Thiamin ● Pork products ● Whole and enriched grains ● Legumes ● Milk ● Orange juice ● Seeds Riboflavin (vitamin B2) ● Riboflavin plays a role in energy metabolism ● Deficiency ○ When thiamin is deficient, riboflavin is usually deficient as well ○ Riboflavin deficiency may be seen in children or the elderly who do not consume milk and meats ○ Cheilosis, inflammation of mouth and tongue, dermatitis, sensitivity to sun ● DRI: ○ 1.1 mg/day for women ○ 1.3 mg/day for men ● Non-toxic Food Sources of Riboflavin ● Milk/milk products ● Enriched grains/cereals ● Eggs ● Spinach ● Oysters

●

Brewer’s yeast

Niacin (Vitamin B3) ● Coenzyme forms used in energy metabolism ● Deficiency ○ Pellagra ○ Late symptoms: 3 D’s– dementia, dermatitis, diarrhea ● DRI ○ 14 mg/day for women ○ 16 mg/day for men ● Toxicity ○ Upper level is 35 mg/day ○ Used in the past to improve blood lipids ○ “Niacin flush” Food Sources of Niacin ● Chicken/Turkey ● Enriched grains ● Beef ● Fish ● Niacin is heat stable; little cooking loss Pyridoxine (Vitamin B6) ● Participates in over 100 reactions in body tissues ● Activate enzymes needed for metabolism of carbs, fat, and protein ● Synthesize nonessential amino acids via transamination ● Synthesize neurotransmitters ● Synthesize hemoglobin and WBC ● Role in homocysteine metabolism DRI ● ● ●

1.3 mg/day for adults 1.7 mg/day for men over 50 1.5 mg/day for women over 50

Deficiency ● Show up as changes in skin, weakness, and depression ● Neurological symptoms seen in cases of extreme deficiency ● Vulnerable populations ○ Alcoholics Toxicity ● Difficulty walking due to the effects of excess vitamin B6 on the nerves ● Toxic effects are reversible

Food Sources ● Animal products ● Cereals ● Potatoes ● Milk ● Bananas ● Cantaloupes ● Broccoli ● Spinach Folate ● Coenzyme ○ DNA synthesis ○ Homocysteine metabolism ○ Neurotransmitter formation Food Sources ● Green leafy veggies, dried beans, orange juice, fortified cereals, fortified bread Folic Acid and Folate ● Folic Acid is the synthetic form added to food and present in supplements- more readily absorbed than natural folate ● Folate: the form found naturally in foods, contains extra units of glutamic acid that must be removed before absorption ○ Destroyed by heat and processing ○ Vitamin C protects folate from degradation DRI for Folate ● 400 micrograms/day for adults ● 600 micrograms/day for pregnant women ● Upper level 1 mg (synthetic form) ○ Folate in food has limited absorption ○ Maks symptoms of vitamin B12 deficiency (enlarged RBCs) Folate Deficiency ● Megaloblastic Anemia ● Neural tube defects (NTD)

Vitamin B12 ● Synthesized by bacteria and fungi ● Coenzyme

●

○ Role in folate metabolism ○ Maintenance of the myelin sheaths ○ Red blood cell (RBC) formation Deficiency ○ Pernicious anemia ○ Nerve degeneration and paralysis

B12 Absorption ● Requires a protein from salivary gland ● Requires stomach acid ● Requires intrinsic factor ● Absorbed in the last part of the small intestine ● About 50% of B12 is absorbed Food Sources ● Only found in animal products and fortified foods: ○ Meats, poultry, seafood, eggs, milk products, breakfast cereal ● DRI ○ 2.4 micrograms/day for adults Biotin and Pantothenic Acid ● Important for energy metabolism ● Biotin ○ Cofactor for enzymes ○ Gene expression ○ No Upper level ● Pantothenic Acid ○ Key coenzyme Vitamin Supplements: What are the benefits and risks? ● People prone to vitamin deficiencies ● Elderly people with diminished appetite ● People with wasting illnesses ● Malabsorptive diseases...