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CHAPTER 8 CONCEPTS
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Thiamin, riboﬂavin, niacin, biotin, and pantothenic acid are B vitamins needed to produce ATP from carbohydrate, fat, and protein. Vitamin B6 is important for amino acid metabolism as well as energy production. Folate is a coenzyme that is needed for cell division. Vitamin B12, only found in animal foods, is needed for nerve function and to activate folate. Vitamin C is needed to form connective tissue and acts as a watersoluble antioxidant. Vitamin A is essential for vision, and it regulates cell differentiation and growth. Vitamin D is necessary for bone health. Vitamin E is a fat-soluble antioxidant. Vitamin K is essential for blood clotting.
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Do vitamins give you extra energy? Should everyone take folate supplements? Does eating carrots improve your vision? Can vitamin E protect you from heart disease?
Vitamins Are Vital to Your Health Vitamins Provide Many Different Functions in the Body Vitamins Are Found in Almost Everything You Eat We Need Enough but Not Too Much of Each Vitamin Some Vitamins Are Soluble in Water and Others Are Soluble in Fat Many B Vitamins Are Essential for Energy Production Thiamin: Important for Nerve Function Riboﬂavin: A Bright Yellow Vitamin Niacin: Deﬁciency Caused an Epidemic of Mental Illness Biotin: Eggs Contain It but Can Block Its Use Pantothenic Acid: Widely Distributed in Food and Widely Used in the Body Vitamin B6 Is Important for Protein Metabolism Vitamin B6 Is Needed to Synthesize and Break Down Amino Acids Both Animal and Plant Foods Are Good Sources of Vitamin B6 Too Much Vitamin B6 Is Toxic Folate and Vitamin B12 Are Needed for Cell Division Folate: Important for Rapidly Dividing Cells Vitamin B12: Absorption Requires Intrinsic Factor Vitamin C Saved Sailors from Scurvy Vitamin C Is Needed to Maintain Connective Tissue Vitamin C Is a Water-Soluble Antioxidant Citrus Fruit Is One of the Best Sources of Vitamin C Vitamin C Is the Most Common Vitamin Supplement Choline: Is It a Vitamin? Vitamin A Is Needed for Healthy Eyes Vitamin A Comes in Preformed and Precursor Forms Vitamin A Requires Fat for Absorption and Protein for Transport Vitamin A Is Necessary for Vision Vitamin A Regulates Gene Expression -Carotene Is a Vitamin A Precursor and an Antioxidant Vitamin A Needs Can Be Met with Plant and Animal Sources Vitamin A Deﬁciency Is a World Health Problem Preformed Vitamin A Can Be Toxic Vitamin D Can Be Made in the Skin Vitamin D Is Needed to Maintain Normal Calcium Levels Vitamin D Deﬁciency Causes Weak Bones Only a Few Foods Are Natural Sources of Vitamin D Too Much Vitamin D Causes Calcium to Deposit in the Wrong Tissues Vitamin E Protects Membranes Vitamin E Is a Fat-Soluble Antioxidant Vitamin E Deﬁciency Damages Membranes Most of the Vitamin E in Our Diets Comes from Plant Oils Vitamin E Is Relatively Nontoxic Vitamin K Is Needed for Blood Clotting Vitamin K Deﬁciency Causes Bleeding Drugs That Inhibit Vitamin K Prevent Fatal Blood Clots The Requirement for Vitamin K Is Met by Bacterial Synthesis and Food Sources
Vitamin D Concerns on the Rise
By Karen Collins, R.D.
Dec. 5, 2003—A lack of vitamin D—thought to be a problem of a bygone era—is showing up in growing numbers of women, children, and the elderly, increasing the risk of bone disease and possibly other health problems. Exposing only the face, hands, and forearms to sunlight for 10 to 30 minutes, just two or three days a week, can usually produce all the vitamin D we need. Longer exposure doesn’t produce more of this vitamin. Yet today, many people’s lifestyles and locations do not allow them to produce enough, making dietary sources vital. For more information on vitamin D concerns go to www.msnbc.msn.com/id/3660416.
ren’t vitamin deﬁciency diseases a thing of the past? After all, the vitamins have been identiﬁed, characterized, and puriﬁed. We get them from...
17. Vitamin K is essential for blood clotting. Since vitamin K deﬁciency is a problem in newborns, they are routinely given vitamin K injections at birth. Dicumarol, a
substance that inhibits vitamin K activity, is used medically as an anticoagulant. Vitamin K is found in plants and is synthesized by bacteria in the gastrointestinal tract.
11. Why does vitamin C deﬁciency interfere with wound healing? 12. List two food sources of preformed vitamin A and two of provitamin A. 13. How does vitamin A help you see light? 14. Why does vitamin A deﬁciency cause the eye to become dry, cracked, and infected? 15. What are the risks of consuming too much vitamin A? too much -carotene? 16. Why is vitamin D called the sunshine vitamin? 17. What is the function of vitamin D? Name two food sources. 18. What is the function of vitamin E? Name two food sources. 19. What is the main function of vitamin K?
1. What is a vitamin? 2. List four factors that can affect how much of a vitamin is available to the body. 3. What do enrichment and fortiﬁcation mean? 4. Name a function common to all of the B vitamins. 5. Why is thiamin deﬁciency a concern in alcoholics? 6. Why should milk be packaged in opaque containers? 7. What is pellagra? 8. How is vitamin B6 involved in amino acid metabolism? 9. Why is low folate intake of particular concern for women of childbearing age? 10. Why are vegans at risk for vitamin B12 deﬁciency? the elderly?
1. American Dietetic Association. America’s Food and Nutrition Attitudes and Behaviors—Nutrition and You: Trends 2000. Available online at www.ﬁndarticles.com/cf_dls/m0822/ 6_100/63910607/p1/article.jhtml/ Accessed January 13, 2004. 2. Tanphaichitr, V. Thiamin. In Modern Nutrition in Health and Disease, 9th ed. Shils, M. E., Olson, J. A., Shike, M., and Ross, A. C., eds. Baltimore: Williams & Wilkins, 1999, 381–389. 3. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboﬂavin, Niacin, Vitamin B-6, Folate, Vitamin B-12, Pantothenic Acid, Biotin, and Choline. Washington, D.C.: National Academy Press, 1998. 4. Ford, E. S., Smith, S. J., Stroup, D. F., et al. Homocyst(e)ine and cardiovascular disease: a systematic review of the evidence with special emphasis on case-control studies and nested case-control studies. Int. J. Epidemiol. 31:59–70, 2002. 5. Rimm, E. B., Willett, W. C., Hu, F. B., et al. Folate and vitamin B6 from diet and supplements in relation to risk of coronary heart disease among women. JAMA 279:359–364, 1998. 6. USDA Agricultural Research Service. Results from USDA’s 1994–1996 Continuing Survey of Food Intakes by Individuals and 1994–1996 Health Knowledge Survey. ARS Food Surveys Research Group, 1997. Available online at www.barc.usda.gov/bhnrc/ foodsurvey/home/html/ Accessed March 6, 2004. 7. Schaumburg, H., Kaplan, J., Windebank, A., et al. Sensory neuropathy from pyridoxine abuse. N. Engl. J. Med. 309:445–448, 1983. 8. Keniston, R. C., Nathan, P A., Leklem, J. E., and Lockwood, R. S. . Vitamin B6, vitamin C, and carpal tunnel syndrome. A cross-sectional study of 441 adults. J. Occup. Environ. Med. 38:949–959, 1997. 9. Wyatt, K. M., Dimmock, P. W., Jones, P. W., and Shaughn O’Brien, P. M. Efﬁcacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review. BMJ 318:1375–1381,1999. 10. Lesourd, B. M., Mazari, L., and Ferry, M. The role of nutrition in immunity in the aged. Nutr. Rev. 56(II):S113–S125, 1998. 11. Prinz-Langenohl, R., Fohr, I., and Pietrzik, K. Beneﬁcial role for folate in the prevention of colorectal and breast cancer. Eur. J. Nutr. 40:98–105, 2001. 12. Mersereau, P., Kilker, K, Carter, H., et al. Spina biﬁda and anencephaly before and after folic acid mandate—United States, 1995–1996 and 1999–2000. MMWR 53:362–365, 2004. 13. Keohler, K. M., Pareo-Tubbeh, S. L., Romero, L. J., et al. Folate nutrition and older adults: challenges and opportunities. J. Am. Diet. Assoc. 97:167–173, 1997. 14. American Dietetic Association. Position of the American Dietetic Association: Vegetarian diets. J. Am. Diet. Assoc. 103:748–765, 2003. 15. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, D.C.: National Academy Press, 2000. 16. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes: Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National Academy Press, 2001. 17. Ross, D. A. Vitamin A and public health. Proc. Nutr. Soc. 57:159–165, 1998. 18. Michaelsson, K., Lithell, H., Vessby, B., and Melhus, H. Serum retinol levels and the risk of fracture. N. Engl. J. Med. 348:287–294, 2003. 19. Feskanich, D., Singh, V., Willett, W. C., and Colditz, G. A. Vitamin A intake and hip fractures among postmenopausal women. JAMA 287:47–54, 2002. 20. Pryor, W. A., Stahl, W., and Rock, C. L. Beta-carotene: from biochemistry to clinical trials. Nutr. Rev. 58(I):39–53, 2000. 21. Pugliese, M. T., Blumberg, D. L., Hludzinski, J., and Kay, S. Nutritional rickets in suburbia. J. Am. Coll. Nutr. 17:637–641, 1998. 22. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, D. C.: National Academy Press, 1997. 23. Kolleck, I., Sinha, P., and Rustow, B. Vitamin E as an antioxidant of the lung: mechanisms of vitamin E delivery to alveolar type II cells. Am. J. Respir. Crit. Care Med. 166:S62–66, 2002. 24. Iwamoto, J., Takeda, T., and Ichimura, S. Treatment with vitamin D3 and/or vitamin K2 for postmenopausal osteoporosis. Keio J. Med. 52:147–150, 2003. 25. Booth, S. L., Pennington, J. A. T., and Sadowski, J. A. Food sources and dietary intakes of vitamin K1 (phylloquinone) in the American diet: data from the FDA Total Diet Study. J. Am. Diet. Assoc. 96:149–154, 1996.
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