Chapter
11 Water-Soluble Vitamins
The Water-Soluble Vitamins: Eight Bs and a C • Kidneys generally remove and excrete water-soluble vitamins • Should be part of your daily diet • More fragile than fat-soluble vitamins • Some destroyed with cooking
The B Vitamins • B vitamins act primarily as coenzymes • Work as catalysts • Function in energyproducing metabolic reactions
Thiamin • Functions • Dietary recommendations • Coenzyme in energy metabolism • Helps synthesize neurotransmitters
• Dietary recommendations • Food sources • Whole and enriched grains • Pork, legumes, nuts, liver
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Thiamin • Deficiency • Beriberi • Wernicke-Korsakoff Syndrome
• Toxicity
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Riboflavin • Functions • Coenzyme in energy metabolism • Supports antioxidants
• Dietary recommendations • Food sources • Milk and dairy products • Whole and enriched grains
• Deficiency • Ariboflavinosis
• Toxicity
Niacin • Functions • Coenzyme in energy metabolism • Supports fatty acid synthesis
• Dietary recommendations • Food sources • Whole and enriched grains • Meat, poultry, fish, nuts, and peanuts
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Niacin • Deficiency • Pellagra
• Toxicity and Medicinal Uses • High doses used to treat high blood cholesterol • Side effects: skin flushing, liver damage
Pantothenic Acid • Functions • Component of coenzyme A • Dietary recommendations • Food sources • Widespread in foods • Deficiency and toxicity are rare.
Biotin • Functions • Amino acid metabolism • Fatty acid synthesis • DNA synthesis
• Dietary recommendations • Food sources • Cauliflower, liver, peanuts, cheese
• Deficiency and toxicity are rare
• Functions • • • • •
Vitamin B6
Protein metabolism Blood cell synthesis Carbohydrate metabolism Neurotransmitter synthesis Vitamin B6, Folate and Heart Disease
• Dietary recommendations • Food sources • Meat, fish, poultry, liver • Potatoes, bananas, sunflower seeds
Vitamin B6 • Deficiency • Microcytic hypochromic anemia
• Toxicity and medicinal uses • Can cause permanent nerve damage in high doses
Folate • Functions • Coenzyme in DNA synthesis and cell division • Needed for normal red blood cell synthesis • Dietary recommendations • Food sources • Green leafy vegetables, orange juice, legumes • Fortified cereals, enriched grains
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Folate • Deficiency • Folate and heart disease • Megaloblastic anemia • Can contribute to neural tube defects • Women of childbearing age need 400 micrograms/day of folic acid • Folate and cancer
• Toxicity • Can mask vitamin B12 deficiency
Vitamin B12 • Functions • Needed for normal folate function • DNA and red blood cell synthesis • Maintains myelin sheath around nerves
• Absorption • Dietary recommendations
Vitamin B12 • Food sources • Only animal foods: meats, liver, milk, and eggs
• Deficiency • Symptoms • Pernicious anemia • Megaloblastic anemia + nerve damage
• Toxicity © Photodisc
Vitamin C • Functions • • • • •
Needed for collagen synthesis Antioxidant Iron absorption Synthesis of vital cell components Immune function
• Dietary recommendations
Vitamin C • Food sources • Fruits: citrus, strawberries, kiwi • Vegetables: broccoli, tomatoes, potatoes
• Deficiency • Scurvy
• Toxicity • May cause GI distress in high doses © Photodisc
Choline: Vitamin-Like Compounds • • • • • •
Can synthesize most of what you need Helps metabolize homocysteine Is a compound of other substances Opposes folate requirements Can be made from methionine Widespread in foods
Conditional Nutrients • • • • •
Inositol Carnitine Taurine Lipoic acid Bogus vitamins
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What Do You Believe? • Thirty-five percent of Americans surveyed in 1997 said that they believed vitamin supplements were necessary to ensure good health. • Women were more likely than men to believe they needed supplements.
Thiamin Pyrophosphate • Thiamin pyrophosphate (TPP) contains the B vitamin thiamin and two phosphate groups.
Symptoms of Vitamin B12 Deficiency 窶｢ The major outcome of impaired vitamin B12 absorption is vitamin B12窶電eficiency anemia. 窶｢ Neurological symptoms include tingling and numbness in the extremities, abnormal gait, and cognitive changes ranging from loss of concentration to memory loss, disorientation, and dementia.
Megaloblastic Anemia • When red blood cell precursors in the bone marrow cannot form new DNA, they cannot divide normally. • These precursor cells continue to grow and become large, fragile cells called megaloblasts. • Megaloblasts displace red blood cells, resulting in megaloblastic anemia.
Folate and Its Major Components • Folate is made up of pteridine, paraaminobenzoic acid (PABA), and least one molecule of glutamic acid (glutamate).
Pernicious Anemia • Pernicious anemia is the result of an autoimmune disorder in which the body destroys the parietal cells in the stomach. Loss of these cells reduces vitamin B12 absorption. • Pernicious anemia can affect people of all ages, races, and ethnic origins. Without treatment, nerve degeneration from vitamin B12 deficiency becomes irreversible and ultimately proves fatal. In fact, pernicious means “leading to death.”
Vitamin C and Collagen Synthesis • Vitamin C plays an important role in the formation of collagen, a fibrous protein that helps reinforce the connective tissues that hold together the structures of the body. • Collagen is made up of individual, linear proteins that wrap around one another like a cord of rope, forming a triple helix that imparts strength and flexibility. It is the most abundant protein in our bodies and the main fibrous component of skin, bone, tendons, cartilage, and teeth. It also is the major protein in connective tissue, which binds cells and tissues together, and in scar tissue.
Can Folate Prevent Cancer? • When women took multivitamins containing folate for at least 15 years, they had a 75 percent reduction in colon cancer risk, according to the Harvard Nurses’ Health Study. • Folate intakes of more than 600 milligrams per day reduced breast cancer risk by 50 percent.