What it is. An antioxidant nutrient, vitamin C is found in citrus fruits, strawberries, broccoli, kiwifruit, and other fruits and vegetables.

How it delays aging. Studies suggest that people who consume a high C diet have lower rates of cancer, heart disease, and high blood pressure. There's also evidence that vitamin C supplements may help stave off cataracts and may help thicken bones during the early postmenopausal years and in women who never used estrogen replacement therapy. Clinical studies suggest that it can fight high blood pressure.

What you'll find: Vitamin C supplements come in 250 , 500 , 1,000 milligram and even higher dosage tablets and capsules as well as powder that you can mix into water or juice.

Whatever form you buy, don't waste your money on natural vitamin C supplements. "There's no difference between synthetic and natural vitamin C it's exactly the same molecule," says Jeffrey Blumberg, Ph.D., chief of the antioxidants research laboratory at the US. D.A. Human Nutrition Research Center on Aging at Tufts University in Boston.

How much to take: The Daily Value is 60 milligrams, an amount researchers now concede is too low to prevent disease. Aim for 200 to 500 milligrams day, says Dr. Blumberg.

Be aware: Taking more than 1,000 milligrams of vitamin C a day can cause diarrhea in some people. If this happens to you, immediately stop taking vitamin C. If you want to take more than 1,000 milligrams, start with 250 milligrams and increase the dose every few days as your tolerance increases, says Dr. Blumberg.