Vitamin OVERLOAD
Too rushed to eat as well as we should, many of us pop supplements to prop up our nutritional intake. But medical professionals warn we may be doing more harm than good.
HAVE YOU BEEN GIVING your daily vitamin supplements the side-eye lately? It seems as though a new study comes out every week, warning us that the very vitamins we’ve been told to load up on—here’s looking at you, vitamin D and calcium—might be endangering our health.
Dr. Tim Byers, associate director for cancer prevention and control at the University of Colorado Cancer Center in Aurora, Colo., ignited a heated debate earlier this year when he unveiled research indicating people who take high doses of some supplements are more likely to develop cancer than those who eschew a daily vitamin regimen. Even more surprising? Dr. Byers’ study isn’t an outlier. It’s part of a growing body of research suggesting some supplements do more harm than good. “Most people need very few supplements, if any at all,” says Dr. Dara Maker, family physician at Women’s College Hospital in Toronto.
VITAMIN D In recent years, several high-profile studies have linked low levels of the sunshine vitamin to a wide array of diseases, including multiple sclerosis and cancer. That prompted some health professionals, and many vitamin makers, to recommend supplements in doses of up to 10,000 international units (IU) a day. (International units measure the bioavailability, or absorption, of a vitamin. Other nutrients are measured solely by weight and expressed in micrograms or milligrams.)
But there is mounting pushback on the trend to increase your intake of the vitamin in supplement form. As it turns out, low vitamin D levels may be a symptom of disease rather than a cause. Dr. Maker says there is not enough strong evidence that megadoses offer any benefit. Rather, taking excessive amounts can have serious side-effects, such as hyperabsorption of calcium, which can lead to kidney stones, among other things.
the bottom line Canadian women should be getting at least 600 IU a day. At age 70, that rises to 800 IU a day. Many supplements offer 1,000 IU per tablet.
to avoid risk Don’t take more than 4,000 IU a day, unless advised by your doctor.
BETA- CAROTENE If you smoke, take note: Beta-carotene (which the body converts to vitamin A, a vitamin key to vision, among other functions) in the form of supplements has been found to increase the risk of lung cancer in smokers, without providing any benefits. There is also some evidence that taking high doses of the supplement could increase the risk of other forms of cancer, even in nonsmokers. the bottom line Eating foods high in betacarotene, such as carrots and sweet potatoes, will help ensure you get enough vitamin A. to avoid risk Avoid taking beta-carotene supplements if you smoke.
CALCIUM Crucial for the health of our teeth and bones, calcium is also a key factor in many metabolic functions such as hormone regulation and muscle function. Yet, numerous studies—including a 2011 report published in The BMJ— have found that women who take calcium supplements in excess of 500 milligrams per day may face a greater risk of heart attack and stroke. Dietary sources of calcium don’t pose the same risks. Dr. Ainsley Moore, general practitioner and associate professor of family medicine at Mcmaster University in Hamilton, says calcium is tightly regulated in the body, which has difficulty processing the high doses of supplements. Thankfully, it’s not difficult to get the recommended amount of calcium if you eat a balanced diet. the bottom line Make sure you’re getting 1,000 milligrams a day through food, which could be as simple as eating an English muffin, an orange, two cubes of Cheddar cheese, half a can of salmon (bones included) and 100 grams of yogurt. to avoid risk Don’t take calcium supplements, and if you do, take no more than 500 milligrams a day.
FOLIC ACID Some troubling research has linked high levels of folic acid, a nutrient known to prevent brain and spine defects in babies, to an increased risk of cancer. A 2014 study out of St. Michael’s Hospital in Toronto found that rats given high doses of folic acid were more likely to develop breast cancer. So far, humansubject trials are inconclusive. Dr. Maker says risks appear to emerge when people take doses that are well above recommended limits.
the bottom line Some grains and flours are fortified with folic acid. A slice of white bread contains 60 micrograms of folic acid, and a slice of whole wheat bread has 18. Folate, the naturally occurring form of the vitamin, is found in beans, broccoli and many other foods. Most women of childbearing age should get 400 micrograms of folic acid a day. to avoid risk Don’t exceed 1,000 micrograms a day. If you eat a balanced diet and take a supplement, you should still fall within the limits. But if you consume foods with high levels of folate and you take a supplement, you may be getting too much. For instance, 75 grams of chicken liver can have more than 500 micrograms of folate, and one-third of a cup of lentils has about 265 micrograms.
FISH OIL EPA and DHA, the omega-3 fatty acids found in fish, may lower the risk of cancer and heart disease while boosting brain performance. For those who don’t regularly dine on salmon or mackerel, supplements are a quick fix. But some experts argue that fish oil doesn’t have major health benefits and could cause prostate cancer. Dr. Howard Lewine, chief medical editor of the Harvard Health Blog, says supplements may not be a panacea, but eating a diet that contains fish and other seafood—which can help boost long-term health—is a sound strategy. the bottom line Eat EPA- and Dha-rich foods, such as salmon and trout, twice a week, and make walnuts, ground flaxseeds and eggs fortified with ALA omega-3s part of your regular diet. to avoid risk Talk to a health-care professional before starting to take—or ending your regimen of— fish-oil supplements.