Minggu, 20 Januari 2008
Vitamins
Vitamins and minerals are essential to our good health. They build immunity against colds and flus, protect the heart, keep our bones strong, and prevent neural tube birth defects. Vitamin C, or ascorbic acid, is an antioxidant that keeps the immune system strong and responsive, and many people faithfully consume large daily quantities to ward off colds. In fact, recent studies indicate that a daily dose of up to 250 mg of vitamin C is sufficient to strengthen the immune system and lower the risk of developing heart disease, cancer or cataracts.1,2,3 However, smokers require almost double that amount to receive the same benefits.2,4 Doses of up to 2,000 mg per day of vitamin C appear to be safe and have been shown to reduce allergy and cold symptoms and result in fewer workdays lost due to illness.2,5,6 One orange contains 70 mg of vitamin C, a cup of cranberry juice provides 108 mg, and a single half-cup serving of broccoli contains 60 mg. Other good sources of vitamin C include lemons, grapefruits, strawberries, peaches, raspberries, red and yellow peppers, tomatoes, cauliflower, Brussels sprouts and baked potatoes.
Vitamin E is another antioxidant that strengthens the immune system and may cut the risk of heart disease. Growing evidence suggests that the optimal daily intake of vitamin E is around 100 mg, or 100 IU.7,8 But avoid taking high daily doses of vitamin E, since they can depress the immune system,9 and excess quantities are stored in the liver. Good sources of vitamin E include vegetable oils, nuts, green leafy vegetables, apricots, peaches, seafood, wheat germ and whole grains.
Calcium and vitamin D work together to maintain the body and bone mass. Women under 25 require 1,200 mg of calcium daily to maximize their bone mass and reduce the risk of osteoporosis later in life. Adults require about 1,000 mg of calcium per day, but women over 50 not taking estrogen, pregnant women, and women who are breast-feeding need at least 1,500 mg to maintain their bone mass. Other good sources of calcium include spinach, broccoli, canned salmon with the bones, tofu made with calcium sulphate, almonds, brazil nuts and sunflower seeds.
A glass of milk contains approximately 100 IU of vitamin D. Folic acid has also been implicated in the prevention of cancer and heart disease in both men and women.17,18 Fruits and vegetables, particularly romaine lettuce, spinach, and broccoli are good sources of folic acid.
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