What 30 Years of Supplement Research Has Taught Us
Cancer risks, Covid-19 disappointments, and hidden health lessons
In 2001, a team of American cancer researchers launched one of the largest clinical trials ever conducted.
Known as the SELECT trial, the study was led by some of the country’s foremost cancer experts, including doctors at the National Cancer Institute, the Cleveland Clinic, and the Fred Hutchinson Cancer Research Center. They recruited more than 35,000 men who were at elevated risk for prostate cancer. Some of the men took a daily supplement containing 400 IU of alpha-tocopherol — an essential form of vitamin E that strong preliminary work had linked to anti-cancer benefits. Others took a placebo.
The trial was intended to last 12 years, but it had to be cut short. Rather than lowering the men’s risk for cancer, the vitamin E supplement seemed to have just the opposite effect. After years of follow-up monitoring, the study team determined that prostate cancer leaped by 17% among men taking vitamin E compared to those taking a placebo.
“The observed 17% increase in prostate cancer incidence demonstrates the potential for seemingly innocuous yet biologically active substances such as vitamins to cause harm,” the study’s authors wrote in a 2011 JAMA paper that summarized their findings.
The allure of health supplements is straightforward: by swallowing a concentrated dose of something that your body can use, you can improve your health or functioning. But over and over again, this formula has failed to spit out the expected result. In some cases, such as the SELECT trial, researchers have uncovered serious and unexpected dangers.
“You look at the research on vitamin E, beta-carotene, selenium, vitamin D — this highway is littered with roadkill,” says Mark Moyad, MD, a supplement researcher and the Jenkins/Pokempner Director of Preventive and Alternative Medicine at the University of Michigan.
“With few exceptions,” Moyad says, “nothing we’ve found suggests that the human body is designed to take in massive amounts of these compounds and derive a benefit from it.”