Definition for Water-Soluble versus Fat-Soluble Vitamins

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Vitamins are essential nutrients found in foods. The requirements are small but they perform specific and vital functions essential for maintaining health.

The two types of vitamins are classified by the materials in which they will dissolve. Fat-soluble vitamins -- vitamins A, D, E and K -- dissolve in fat before they are absorbed in the blood stream to carry out their functions. Excesses of these vitamins are stored in the liver. Because they are stored, they are not needed every day in the diet.

By contrast, water-soluble vitamins dissolve in water and are not stored; they are eliminated in urine. We need a continuous supply of them in our diets. The water-soluble vitamins are the B-complex group and vitamin C.

Water-soluble vitamins are easily destroyed or washed out during food storage or preparation. Proper storage and preparation of food can minimize vitamin loss. To reduce vitamin loss, refrigerate fresh produce, keep milk and grains away from strong light, and use the cooking water from vegetables to prepare soups.

Table 1: Water-soluble vitamins and their characteristics.
Common food sources	Major functions	Deficiency symptoms	Overconsumption symptoms	Stability in foods
Vitamin C (ascorbic acid)
Citrus fruits, broccoli, strawberries, melon, green pepper, tomatoes, dark green vegetables, potatoes.	Formation of collagen (a component of tissues), helps hold them together; wound healing; maintaining blood vessels, bones, teeth; absorption of iron, calcium, folacin; production of brain hormones, immune factors; antioxidant.	Bleeding gums; wounds don't heal; bruise easily; dry, rough skin; scurvy; sore joints and bones; increased infections.	Nontoxic under normal conditions; rebound scurvy when high doses discontinued; diarrhea, bloating, cramps; increased incidence of kidney stones.	Most unstable under heat, drying, storage; very soluble in water, leaches out of some vegetables during cooking; alkalinity (baking soda) destroys vitamin C.
Thiamin (vitamin B1 )
Pork, liver, whole grains, enriched grain products, peas, meat, legumes.	Helps release energy from foods; promotes normal appetite; important in function of nervous system.	Mental confusion; muscle weakness, wasting; edema; impaired growth; beriberi.	None known.	Losses depend on cooking method, length, alkalinity of cooking medium; destroyed by sulfite used to treat dried fruits such as apricots; dissolves in cooking water.
Riboflavin (vitamin B2)
Liver, milk, dark green vegetables, whole and enriched grain products, eggs.	Helps release energy from foods; promotes good vision, healthy skin.	Cracks at corners of mouth; dermatitis around nose and lips; eyes sensitive to light.	None known.	Sensitive to light; unstable in alkaline solutions.
Niacin (nicotinamide, nicotinic acid)
Liver, fish, poultry, meat, peanuts, whole and enriched grain products.	Energy production from foods; aids digestion, promotes normal appetite; promotes healthy skin, nerves.	Skin disorders; diarrhea; weakness; mental confusion; irritability.	Abnormal liver function; cramps; nausea; irritability.
Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine)
Pork, meats, whole grains and cereals, legumes, green, leafy vegetables.	Aids in protein metabolism, absorption; aids in red blood cell formation; helps body use fats.	Skin disorders, dermatitis, cracks at corners of mouth; irritability; anemia; kidney stones; nausea; smooth tongue.	None known.	Considerable losses during cooking.
Folacin (folic acid)
Liver, kidney, dark green leafy vegetables, meats, fish, whole grains, fortified grains and cereals, legumes, citrus fruits.	Aids in protein metabolism; promotes red blood cell formation; prevents birth defects of spine, brain; lowers homocystein levels and thus coronary heart disease risk.	Anemia; smooth tongue; diarrhea.	May mask vitamin B12deficiency (pernicious anemia).	Easily destroyed by storing, cooking and other processing.
Vitamin B12
Found only in animal foods: meats, liver, kidney, fish, eggs, milk and milk products, oysters, shellfish.	Aids in building of genetic material; aids in development of normal red blood cells; maintenance of nervous system.	Pernicious anemia, anemia; neurological disorders; degeneration of peripheral nerves that may cause numbness, tingling in fingers and toes.	None known.
Pantothenic acid
Liver, kidney, meats, egg yolk, whole grains, legumes; also made by intestinal bacteria.	Involved in energy production; aids in formation of hormones.	Uncommon due to availability in most foods; fatigue; nausea, abdominal cramps; difficulty sleeping.	None known.	About half of pantothenic acid is lost in the milling of grains and heavily refined foods.
Biotin
Liver, kidney, egg yolk, milk, most fresh vegetables, also made by intestinal bacteria.	Helps release energy from carbohydrates; aids in fat synthesis.	Uncommon under normal circumstances; fatigue; loss of appetite, nausea, vomiting; depression; muscle pains; anemia.	None known.