Of the 51,000 new supplements on the market, four might be of benefit for otherwise healthy people: omega-3 fatty acids to prevent heart disease, calcium and vitamin D in postmenopausal women to prevent bone thinning, and folic acid during pregnancy to prevent birth defects.

Omega-3 fatty acids

Like vitamins, omega-3 fatty acids aren’t made in the body, so they have to come from other sources. Some studies have shown that omega-3s protect against high blood pressure and heart disease; others haven’t. The best place to get them is in the diet, specifically in fatty fish such as salmon, in vegetable oils such as soybean, rapeseed (canola), and flaxseed, and in walnuts. To get enough omega-3 fatty acids, the American Heart Association recommends that people eat at least one serving of fatty fish at least twice a week. Most Americans consume about 1.6 grams of omega-3s every day, well above what is needed to maintain heart health.

Unfortunately, not everyone gets what they need. People who choose not to eat any of the rich sources of omega-3 fatty acids are often advised to take a supplement containing 500 milligrams a day. But not more than that: too many omega-3s (such as one finds in Eskimo diets) might actually increase the risk of bleeding and stroke.

Calcium

Calcium is the most abundant mineral in the body, required for vascular tone, muscle function, nerve transmission, and hormone secretion. Of interest, less than 1% of the total body calcium is necessary for performing these functions. The remaining 99% is stored in bones, where it supports bone structure and function. The problem with calcium occurs when people get older.

In children and teenagers, bone formation exceeds bone breakdown. In early and middle adulthood, these two processes occur at equal rates. Past the age of 50, however, especially in postmenopausal women, bone destruction exceeds bone formation. This problem isn’t trivial. When bones get thinner (a condition called osteoporosis), they break more easily.

About one in three postmenopausal women will fracture their spines, and one in five will fracture their hips. Indeed, every year more than 1.5 million fractures occur in the United States because of bone thinning. The best way to avoid this problem is to eat calcium-containing dairy products such as milk, yogurt, and cheese. Calcium can also be found in calcium-fortified fruit juices, beverages, tofu, and cereals.

To lessen the risk of bone thinning, postmenopausal women are advised to eat diets rich in calcium. Because most women get enough calcium in their diet, and because supplementary calcium has not been shown to reduce fractures in otherwise healthy postmenopausal women, the United States Preventive Services Task Force does not recommend supplemental calcium.

Vitamin D

Vitamin D and calcium are linked. People who take in adequate amounts of calcium might still have a problem with bone strength if they do not also get sufficient amounts of vitamin D. That is because vitamin D helps the body absorb calcium from the gut. The good news is that vitamin D is readily made in the skin when exposed to sunlight. To get an adequate amount of vitamin D, people need only expose their face, arms, hands, or back to sunlight (without sunblock) for ten to fifteen minutes a day at least twice a week. This will provide the 600 IU of vitamin D recommended by the Institute of Medicine.

Some people, however, either don’t get out into the sun much or live in climates where there isn’t much sunlight. For this reason, many foods are supplemented with vitamin D, such as milk, bread, pastries, oil spreads, breakfast cereals, and some brands of orange juice, yogurt, margarine, and soy beverages. Because most people get enough vitamin D in their foods or from exposure to sunlight, the United States Preventive Services Task Force does not recommend supplemental vitamin D. There are, however, two exceptions: babies who are exclusively breast-fed should receive 400 IU a day of supplemental vitamin D, because it isn’t contained in human milk and because they don’t get out into the sun much; and elderly adults over sixty-five years old should receive 800 IU daily because it’s been shown to reduce the high risk of bone fractures.

Folic acid

Finally, folic acid is a B-complex vitamin necessary for the production of red blood cells. Without folic acid, people develop anemia. But that’s not the biggest problem. Researchers have shown that folic acid deficiency can cause something far worse: severe birth defects. Pregnant women deficient in folic acid have delivered babies with malformations of the spine, skull, and brain.

To avoid folic acid deficiency, people need about 400 micrograms a day.Foods rich in folic acid include vegetables such as spinach, broccoli, lettuce, turnip greens, okra, and asparagus; fruits such as bananas, melons, and lemons; and beans, yeast, mushrooms, beef liver and kidney, orange juice, and tomato juice.

Although there are plenty of sources of this nutrient, many pregnant women weren’t getting enough folic acid in their diets. So on January 1, 1998, the FDA required manufacturers to add folic acid to breads, breakfast cereals, flours, cornmeals, pastas, white rice, bakery items, cookies, crackers, and some grains. Now it’s almost impossible to become folic-acid deficient. Nonetheless, women are advised to take 400 micrograms of folic acid every day, obtained either from foods or supplements or both. Because about half of pregnancies are unplanned and because birth defects occur very early in pregnancy, all women of childbearing age should make sure they’re getting enough folic acid.

In the end, if a medicine works (like folic acid to prevent birth defects), it’s valuable, and if it doesn’t work (like saw palmetto to shrink prostates), it’s not. “There’s a name for alternative medicines that work,” says Joe Schwarcz, professor of chemistry and the director of the Office for Science and Society at McGill University. “It’s called medicine.”

Excerpted from Do Your Believe in Magic? The Sense and Nonsense of Alternative Medicine by Dr. Paul Offit © 2013. Excerpted by permission of Harper Collins. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.


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