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About Nutrition
Nutrition Supplements
- DV = Daily Value
- IU = International Units
Off all the vitamins and minerals, the experts agree that there are only nine key ingredients that you need to zero in on. Why these nine? They're the ones our experts say are most likely to come up short in American diets — and to be present in multivitamins in amounts likely to be effective.
Chromium
Look for 50 to 200 mcg., a safe and adequate range set by the National Research Council.
Research indicates that the food we eat may not deliver even the minimum amount of chromium we need. This important mineral helps the body handle blood sugar; low levels of chromium may increase our risk of adult-onset diabetes.
You may not see a % DV for chromium; instead, there may be an asterisk (*) that indicates "Daily Value not established." That was the case until 1996, when the Food and Drug Administration set a DV for chromium of 120 mcg; it may take time for labels on some brands of supplements to catch up.
Extra chromium does seem to help building muscle on weight loss.
Vitamin A/Beta-carotene
Look for 5,000 international units (I.U.), which is 100% DV.
In most multivitamins, the vitamin A is a mix of preformed vitamin A and its precursor, beta-carotene. Even if a multivitamin is all preformed vitamin A or all beta-carotene, 5,000 I.U. is considered a very safe level of each.
Do not supplement above 10,000 I.U. Pregnant women: Don't go above 5,000 I.U. Too much preformed vitamin A can be toxic or cause birth defects. Can you get too much beta-carotene? Studies show that people with diets high in beta-carotene have lower risks of heart disease and cancer. In two studies of long-term smokers, the ones taking high-dose beta-carotene supplements (25 mg or more) developed more lung cancer. Until we know more, a reasonable limit for beta-carotene from supplements (not food) is 6 mg. (That's what you'd get if 10,000 I.U. of vitamin A were all from beta-carotene.)
Vitamin B6
Look for 2 mg (100% DV).
American women's diets are usually low in B6 (for some women, oral contraceptives may increase the need). Low intakes are linked to higher levels of heart-attack risk and poorer immune functioning in older people.
Do not overdo B6 (or any other vitamin or mineral, for that matter). Mega doses of 100 mg are associated with (reversible) nerve damage, and problems have been seen at intakes of 50 mg. Reports of high doses of vitamin B6 relieving carpal tunnel syndrome or premenstrual syndrome have not been confirmed by research.
Vitamin C
Try to take 200 to 500 mg of this antioxidant vitamin as a single supplement. Otherwise, your multivitamin should have at least 60 mg (100% DV).
Evidence: A study last year at the National Institutes of Health found that we need 200 mg of vitamin C to keep blood plasma at 85% saturation level. For 95% saturation, we need 400 to 500 mg (Proceedings of the National Academy of Science, April 1996). Researchers concluded that the current DV of 60 mg may be too low.
Vitamin C have lowers the rate of cancer and heart disease, may help lower risk of cataracts and help people with diabetes.
Look for: Vitamin C supplements in 100, 250 or 500 mg tablets. Or find chewable tablets (to protect tooth enamel, chew only one a day) or effervescent tablets or powder that dissolve in water. You may find 100 mg or more of vitamin C in some multivitamins.
Take it in the mornings and at afternoons, as after 12 hours, your body returns to presaturation levels, no matter what amount of vitamin C you've taken.
Can you get 200 to 500 mg from food? It's possible if you eat lots of vitamin-C-rich fruits and vegetables. An 8-oz. glass of orange juice from concentrate, for example, has 100 mg. A cup of fresh strawberries has 85 mg. One-half cup frozen broccoli cooked has 40 mg.
Although 1,000 mg of vitamin C yielded 100% saturation of blood plasma in the NIH study, some research (but not all) suggests taking that much vitamin C may increase risk of kidney stones. Diarrhea may occur at intakes of several thousand mg.
Vitamin D
Look for 400 I.U. (100% DV).
The body can manufacture vitamin D from the action of sunlight on the skin, but experts believe many people (especially the elderly and those who routinely use sunblock) may not be exposed to enough sun. (Comment: Other studies show that too much sun is dangerous and causes skin cancer)
Do not get more than 800 I.U. of vitamin D a day from supplements plus fortified foods on a regular basis. Be sure to count vitamin D from milk (100 I.U. per 8 oz. glass or per 1/3 cup nonfat milk powder) or fortified breakfast cereal (amounts vary).
Vitamin E
Consider taking 100 to 400 I.U. of this antioxidant vitamin.
Most multivitamins supply only about 30 I.U. (100% DV), much less than the levels some research indicates may fight illness, especially heart disease. If you don't take extra vitamin E, make sure your multivitamin has at least 30 I.U.
Evidence: Among the best indication that extra E may help is a British study of over 2,000 men and women with narrowed coronary arteries. Participants took either 400 or 800 I.U. of E, or a placebo. The result: After 18 months, E takers (of either dose) lowered chances of getting a nonfatal heart attack by 75% (Lancet, March 23, 1996). Other research suggests (but doesn't prove) extra E might reduce risks of cataracts and some cancers and help people with diabetes.
Folic acid (or folate)
Look for 400 micrograms, which is 100% DV. May be listed as 0.4 mg (same as 400 mcg).
Studies show that women taking supplements with 400 mcg folic acid prior to and in the first weeks of pregnancy give birth to fewer babies with serious brain and spine defects. Higher intakes of folic acid may help reduce risks of heart disease (by reducing blood levels of a substance called homocysteine) and colon cancer. But it's difficult to get 400 mcg in your diet, and most Americans' diets fall short.
Iron
Pre-menopausal women: Look for up to 18 milligrams, which is 100% of the Daily Value (DV). Adult men and menopausal women: Look for 0 to 9 mg. (0 to 50% DV). (Note: Daily Value is the new name for the old U.S. Recommended Daily Allowance — U.S. RDA — which some labels still use.)
Pre-menopausal women having periods lose iron each month and may need the help of a supplement to replace it. But women not having periods and adult men lose little iron normally. And since some research indicates excess iron raises risks of heart disease and colon cancer, many experts now advise men and menopausal women to look for supplements with no or low iron. (Check your breakfast cereal; some are heavily fortified with iron. Take that into account when you select a multivitamin.)
Be aware: Unless you're diagnosed with iron-deficiency anemia, there's no reason to take levels above 100% DV.
Magnesium
Look for 100 mg (25% DV).
This is the most you usually find in any single-dose multivitamin supplement (the size of the pill would get too big). In a divided-dose multivitamin, look for up to 400 mg (100% DV) in the day's total.
Americans eat much less than 100% DV of this interesting mineral that's tentatively linked to protection from diabetes, osteoporosis, arteriosclerosis, hypertension and migraine headaches.
Those with abnormal kidney function would not supplement magnesium without a doctor's supervision. Excess magnesium can lead to diarrhea.
Calcium
Depending on the calcium in your diet, consider single supplements containing about 500 to 1,000 mg of this crucial bone protector.
Evidence: It surprises many people that singe-dose multivitamin supplements are never "complete" with 100% DV for calcium (1,000 mg). In fact, that would be impossible — all that calcium would make a single tablet too big to swallow. Some single-dose multi-vitamin vitamins do have about 200 mg. But since surveys show many diets lag well behind recommended daily levels, a separate calcium supplement is worth considering.
Copper
Look for 2 mg (100% DV).
This is another mineral the everyday diet does not contain enough of. Copper plays a role in bone and heart health, blood-sugar regulation and iron use.
If your supplement has zinc, make sure it has copper, as well. Elevating zinc intake without taking in enough copper can suppress the absorption of copper .
Zinc
Look for 15 mg (100% DV).
Surveys show this may be the mineral most lacking in Americans' diets. Zinc is necessary for a strong immune system and proper healing of open wounds.
Do not take supplements with more than 15 mg a day on a regular basis. Too much zinc — in one study, 50 to 75 mg a day — can backfire and lower HDL cholesterol. (the good cholesterol)
Extras
What if other vitamins and minerals are present in a multivitamin? Consider them nice-to-have but not necessary. For vitamins C and E and calcium, keep on reading. For most of the others, it's preferable if levels stay in the 100%-DV-or-lower range. (Exception: People over the age of 60 may want to take extra vitamin B12 — from 200% to 500% DV — to make up for problems they may have in absorbing vitamin B12 from food.)
Look for: Vitamin E supplements in 100, 200 or 400 I.U. capsules. Also available in chewable or liquid form.
Natural vs. synthetic: Though natural vitamin E is more bioactive in the body than synthetic E, the difference in potency is taken into account in the International Unit. That means 100 I.U. of synthetic vitamin E is as potent as 100 I.U. of natural E. Most research, by the way, uses synthetic. To know which type your supplement has, read the list of ingredients. Natural E is d-alpha tocopherol; synthetic is d,l-alpha tocopherol or d,l-alpha tocopheryl acetate.
Best way to take: With a meal that contains at least a little fat, to help with absorption.
Can you get 100 to 400 I.U. vitamin E from food? Hardly! You'd need 2 cups of corn oil, one of the best sources to get 100 I.U.
Be aware: If you're on blood-thinning medication or at risk for uncontrolled bleeding, talk with your doctor before taking vitamin E at these levels.
Food Pyramid
