Two independent studies suggest that taking a daily dose of vitamin supplements may not be as health-promoting as previously believed and may even be harmful. Their findings are only the latest in a series of clinical study reports that have questioned the benefits of the popular nutrition-enhancers.
Taking High Doses of Vitamins and Supplements
May Be Useless If Not Outright Harmful
In one study, researchers from the University of Minnesota followed over 38,000 women in an still ongoing survey called the “Iowa Women’s Health Study.” The participants were in their early 60s when the project was started in 1986. The focus of this study was on the women’s use of vitamin supplements for about 18 years on average.
As it turns out, the women who took daily doses of supplements had a higher mortality rate by two and a half percent compared to those who didn’t take any.
“Our study, as well as other similar studies, have provided very little evidence that commonly used dietary supplements would help to prevent diseases,” said Dr. Jaako Mursu, an epidemiologist at the University of Minnesota School of Public Health and lead author of the study report, which was published in the Archives of Internal Medicine (10/11/2011). “We would advise people to reconsider whether they need to use supplements, and put more emphasis on a healthy diet instead,” he added.
Dr. Mursu admitted that the study was not designed to determine if there was a specific cause for the increased mortality risk of the supplement users. The study did however distinguish between the different kinds of supplements the participants took. For example, the women who took iron supplements had a four percent higher probability of dying. Others who used multivitamins, folic acid, vitamin B6, magnesium and zinc also showed higher rates. Only calcium seemed to have a positive effect, decreasing the risk for most women who took it.
A second study, sponsored by the National Cancer Institute (NCI), found that men who took daily a high dose of vitamin E ran a 17 percent greater risk of developing prostate cancer. These results, which were published in the Journal of the American Medical Association (JAMA), came as a surprise, considering that vitamin E was believed to be actually helpful in the prevention of prostate cancer.
The vitamin E study, named the “SELECT” trial, began in 2001. It was designed as a double-blind, placebo-controlled research project, the highest standard in scientific testing. The initial goal was to find out how vitamin E and selenium (a mineral mostly found in soil) can reduce the risk of prostate cancer.
“I was surprised by the results of this trial,” said Dr. Eric Klein, an urologist at the Cleveland Clinic and the national coordinator of the study. “There really is not any compelling evidence that taking these dietary supplements above and beyond a normal dietary intake is helpful in any way, and this is evidence that it could be harmful.”
The increase in health risks could be derived from the high concentration of nutritional compounds that many supplements contain. Most of these micronutrients are present in much smaller amounts in regular foods, so they can become toxic when they are consumed over long periods of time and accumulate in the body, according to Dr. Mursu.
While vitamins and minerals are necessary for healthy nutrition, excess intake can create serious problems. It is also important that consumers understand the differences between the supplements they are taking.
For example, overdosing on water-soluble vitamins like vitamin C and B-complex is possible but unlikely. Excessive amounts pass through the system and get eliminated in the urine.
Fat-soluble vitamins like vitamins A, D, E and K, on the other hand, are stored in fat cells and can eventually build up to toxic levels. Minerals like calcium, chloride, chromium, copper, fluoride, iodine, iron, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, sodium and zinc are absorbed in the body as well and can become harmful to the liver and kidneys. Some supplements can interfere with medications a person is taking and also negatively affect the metabolism of other nutrients.
For these reasons and others, many nutrition experts warn that supplements should not be considered as a substitute for a well-balanced diet, notwithstanding their enormous popularity. Over half of American adults take at least one supplement a day. It is estimated that vitamin and supplement sales in the U.S. amount to $20 billion plus per year.
It’s tempting to rely on supplements. In our fast-food culture, it may even sound reasonable to take extra vitamins to make up for nutritional deficiencies. Ironically, the people who use the most supplements are the ones who already eat the healthiest. So, they may want to reconsider. But for the millions of Americans who adhere to a less than perfect diet, it makes good sense to keep adding a basic multivitamin a day.