The humble vitamin pill was spotlighted in March, and not in a good way. A Harvard Medical School report linked multivitamins with increased risk of colorectal cancer, and a large University of Washington study found that vitamin E could contribute to lung cancer.
Both of the findings were questioned by supplements experts, particularly the Washington, D.C.-based Council for Responsible Nutrition.
The Washington research, known as the VITAL study, tracked 77,721 men and women, age 50 to 76, who self-reported their 10-year average daily use of multivitamins, vitamins C and E, and folate supplements. Researchers found that none of the vitamins decreased the risk of lung cancer in study participants. They also reported there was a 28 percent increased risk of lung cancer in subjects who took 400 milligrams a day of vitamin E for 10 years. The U.S. recommended daily allowance for vitamin E is 15 milligrams.
Noting that "every study has limitations and needs to be put in the right context when communicating results," Andrew Shao, Ph.D., CRN's vice president for scientific and regulatory affairs, pointed out the flaws he saw in the VITAL study. Chief among them was a vitamin E benefit that researchers didn't elaborate on, he said. The study showed there was actually a reduction in lung-cancer risk observed with vitamin E doses between 42 milligrams and 215 milligrams a day, Shao said.
In addition, "the study clearly states that the risk in lung cancer associated with supplemental vitamin E was largely confined to current smokers," he said. "Clearly, the best way to reduce the risk of lung cancer is to stop smoking."
In a statement reported by HealthDay News, London-based Health Supplements Information Service spokeswoman Pamela Mason said the VITAL study findings that vitamins don't decrease cancer risk were not surprising.
"Vitamins are essential nutrients that act to maintain health and prevent deficiency," she said. "They were never intended to be used to prevent chronic diseases such as cancer. Indeed, it would be asking a lot of a vitamin pill to expect it to prevent cancer."
Harvard Medical School researchers also tackled the vitamins and cancer link in the March issue of the Harvard Men's Health Watch newsletter. Citing studies showing that B6, B12 and folic acid in multivitamins not only don't prevent disease, but that folic acid may actually cause cancer, the researchers argued against taking a daily multivitamin.
Harvard researchers cited one U.S. study showing that people who took folic acid had more colorectal adenomas and more prostate cancers than those who took a placebo. However, the researchers cautioned, the study involved only people who were at high risk for colorectal cancer, and who took 1,000 mcg of folic acid, two and a half times the recommended daily allowance.
The researchers also cited a 2007 report in which scientists traced colorectal cancers diagnosed in the U.S. and Canada between 1986 and 2002. In the mid-1990s, they found an extra four to six diagnoses of colorectal cancer per 100,000 people in each country. "The researchers don't know what caused the blip," the Harvard researchers wrote, but "the scientists speculated that folic acid may have contributed to the uptick in colorectal cancers —not because of multivitamins, but because of foods."
The Harvard researchers pointed out that government-mandated folic acid fortification in U.S. grain products has reduced the incidence of spinal cord birth defects by up to 50 percent since 1996, but cited an unproven theory that when those fortified foods are coupled with a multivitamin, blood levels of folic acid can increase to amounts that may be associated with increased risk of cancer.
The newsletter concluded: "There is no proof that a daily multivitamin is harmful. Still, it now seems possible that the high levels of folic acid achieved by well-intentioned people who take a multivitamin and eat healthful foods could increase the risk of colorectal and possible prostate and breast cancers. Perhaps, then, the answer is to give up the multivitamin, at least until scientists solve the puzzle of folic acid and cancer."
CRN's Shao said he was "a little bit disappointed" in the research the newsletter cited, noting that the folic acid research was "only one study. It may merit a follow-up, but it's only one study."
He said the newsletter's recommendation to jettison multivitamins is "clearly a premature action." Noting that multivitamins are vital to the vast majority of Americans, "who come up short when it comes to getting the recommended daily nutrition," Shao said "changes to the recommendations [that people take] multivitamins don't make sense at this point."
He also cited an October 2007 CRN study of 1,177 health-care professionals that found that 87 percent of doctors and 86 percent of nurses take multivitamins, and about three-quarters of them said "it is a good idea for patients to take a multivitamin."
Vicky Uhland is a Lafayette, Colo.-based freelance writer.
Natural Foods Merchandiser volume XXIX/number 4/p. 1,9