Chapter 7 - THE VITAMINS Outline Classification General...

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Unformatted text preview: THE VITAMINS Outline Classification General points about vitamins Individual vitamins Functions Food sources Selected deficiencies Potential for toxicity Supplements Classification Fat soluble vitamins Water soluble vitamins Water soluble vitamins Thiamin Riboflavin Niacin Vitamin B6 Vitamin B12 Folate Pantothenic acid Biotin Vitamin C Fat soluble vitamins A D E K General points about vitamins Needed in minute amounts May have precursors (provitamins) Differ in saturation points For example: vitamin C 1000-5000 mg. supplement advocates 2000 mg. UL 150 mg. aver. intake 110-125 mg. RDA smokers 100 mg. saturation pt. 75-90 mg. RDA 30 mg. tissue need 10-20 mg. prevent scurvy More general points about vitamins Most function in most cells Vitamins influence and are influenced by other nutrients Too much is as dangerous as too little Vitamin A Deficiency night blindness thickening of the cornea changes in epithelial cells infections death Toxicity skin redness fetal malformations dermatitis bone malformations uncontrolled bleeding bone fractures liver toxicity death . Vitamin A and beta-carotene Precursor: Carotene Active: Retinol Functions of vitamin A: vision: light perception vision: health of cornea health of epithelial cells bone & teeth growth Gene expression immunity Carotenes Functions: source for vitamin A antioxidant protective against cancers Macular degeneration? Vitamin A cont. Deficiency Toxicity Food sources: animal foods: liver, butter, egg yolk, cheese, whole or fortified milks plant foods: dark green & deep orange vegetables & fruits . Vitamin D Precursor: cholesterol Functions: blood Ca & P regulation mineralization of bones increased calcium absorption reduces calcium excretion by kidneys release of calcium from bones Cellular functioning Cell maturation Vitamin D cont. Deficiency: rickets, osteomalacia Toxicity Food sources: whole & fortified milk & margarine, egg yolks, liver, sardines, salmon with bones Sunlight synthesis of Vitamin D Factors that limit synthesis Pollution Urban environment Northern location Homebound Season Sunscreens Time of day Dark skin . Vitamin E Function: antioxidant- protection against free radicals Deficiency: rare hemorrhaging in premature infants Toxicity: rare Food sources: vegetable oils , peanuts and their products; whole and fortified grains; sunflower seeds Vitamin K Functions: blood clotting, bone formation Deficiency: newborns, people taking antibiotics, people who can't absorb fat Toxicity: possible Sources: food: dark green leafy vegetables, cabbage type vegetables, liver; bacterial synthesis Water Soluble Vitamins Vitamins as coenzymes . Niacin Precursor: tryptophan Function: co-enzyme in energy metabolism Toxicity: relatively non-toxic Food sources: animal proteins, whole & enriched grains, nuts, legumes . Thiamin Functions: co-enzyme in energy metabolism Toxicity: relatively non-toxic Food sources: pork, whole & enriched grains, liver, legumes . Riboflavin Functions: co-enzyme in energy metabolism Toxicity: relatively non-toxic Food sources: dairy products, whole & enriched grains, egg yolk, leafy green vegetables, liver . .Vitamin B6 Functions: co-enzyme in energy metabolism; red blood cell synthesis; synthesis of hemoglobin & neurotransmitters; immune function & steroid activity; nervous system development Toxicity: neurological damage Food sources: animal proteins, whole grains, leafy green vegetables, legumes . Folate (Folic Acid, Folacin) Functions: DNA synthesis; part of a coenzyme needed in cell synthesis; cell division & replication; prevent neural tube defects Deficiency: a type of anemia Toxicity: potentially toxic Food sources: green leafy vegetables, legumes, oranges, seeds, liver, enriched grains . Vitamin B-12 Functions: Part of a coenzyme used in new cell synthesis; helps maintain nerve cells; prevent neural tube defects Deficiency: pernicious anemia Toxicity: relatively non-toxic Food sources: animal products Heart disease; could it be more than just fat? Elevations in homocysteine Folate, vitamin B12, B6 . Pantothenic Acid Function: part of a coenzyme in energy metabolism Food sources: widespread in foods . Biotin Function: part of a coenzyme in energy metabolism Food sources: widespread in foods . Vitamin C Functions: collagen synthesis antioxidant amino acid metabolism resistance to infection enhances iron absorption thyroid hormone synthesis Vitamin C cont. Toxicity: at levels >2000 mg. Food sources: Citrus fruits, broccoli, cabbage-type vegetables, peppers, cantaloupe, strawberries Supplementation??? Who might benefit? Chronic dieters Elderly Chronic GI, liver, pancreas diseases, cancer Medications that interfere with body's use of nutrients Pregnant and lactating women Selecting supplements Ignore promotional information More is not better Avoid doses > 100% of RDA/AI Choose broad spectrum Check prices Avoid non-nutrients, tonics, time release, organic, natural, high potency, stress formulas Remember: Supplements are not nutritionally complete We don't know everything about nutrition Food has additional benefits Poor correlation between supplement need and usage More expensive What about non-nutrient supplements? Can you Explain differences between fat- & watersoluble vitamins Describe roles for each vitamin List good food sources Describe how vitamin deficiencies/toxicities might develop Describe how to select a supplement Describe when a supplement might be appropriate ...
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