Vitamins

Vitamins are needed for a variety of biologic processes, among them growth, digestion, mental alertness and resistance to infection. Vitamins can be either water-soluble or fat-soluble.

Water-soluble vitamins. Vitamin C, biotin and the seven B vitamins — thiamin (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), folic acid (B-9) and cobalamin (B-12) — dissolve in water (water-soluble) and aren't stored in your body in any significant amounts. Surplus water-soluble vitamins are simply excreted in your urine.

Fat-soluble vitamins. Any extra vitamin A, D, E or K not used by your body right after ingestion is stored in your body fat and liver. Excess fat-soluble vitamins can accumulate in your body and become toxic. You're especially sensitive to excess amounts of vitamins A and D. Because vitamins E and K affect blood clotting, talk with your doctor before taking a supplement that contains either of these vitamins if you're taking a blood thinner, such as warfarin (Coumadin).

Vitamin A = retinol, retinaldehyde, retinoic acid

Vitamin B1 = thiamin

Vitamin B2 = riboflavin

Vitamin B6 = pyridoxine, pyridoxal, pyridoxamine

Vitamin B12 = cobalamin

Vitamin C = ascorbic acid

Vitamin D = calciferol

Vitamin E = tocopherol, tocotrienol

Vitamin K = phylloquinone

A standard multivitamin supplement doesn't come close to making up for an unhealthy diet. It provides a dozen or so of the vitamins known to maintain health, a mere shadow of what's available from eating plenty of fruits, vegetables, and whole grains. Instead, a daily multivitamin provides a sort of nutritional safety net.

While most people get enough vitamins to avoid the classic deficiency diseases, relatively few get enough of five key vitamins that may be important in preventing several chronic diseases. These include:

• Folic acid (Vitamin B9)
• Vitamin B6
• Vitamin B12
• Vitamin D
• Vitamin E