Lots of people swear by their daily vitamins and other supplements. Taking them, many believe, helps them achieve better health.
A new study suggests those beliefs may not always be supported by research.
According to this particular study, taking multivitamins did not reduce the overall risk of dying from cancer.
Jian-Bing Wang, PhD, of Peking Union Medical College in Beijing, China, was the lead author of this study.
For six years starting in 1985, Dr. Wang and fellow researchers began investigating the effects of taking multivitamins on cancer patients and cancer deaths. These researchers followed a total of 3,318 people aged 40 to 69 with precancerous squamous dysplasia of the esophagus.
The patients came from Linxian, China, a region with higher than usual rates of cancer of the esophagus and the stomach. It also was known for higher rates of vitamin and mineral deficiencies, the researchers wrote.
The patients were divided into two groups. Patients in one group were given vitamin supplements. Those in the other group were given placebos, or pills that looked like supplements but contained no active ingredients.
After those six years, the researchers found no statistically significant difference in the death rates of those two groups.
These researchers wrote that they stopped giving patients the supplements at the end of those six years. However, they did monitor patients for 20 years, ending in 2010, to see if those six years of taking supplements had any effects.
During that 20-year period, 2,239 of the 3,318 patients died. Almost half the deaths were from cancer.
Roughly a quarter of the deaths resulted from a lack of sufficient blood flow to patients' brains, which is called cerebrovascular disease. About 20 percent of deaths were from heart disease. And 12 percent of patients died from other causes.
The researchers also gave examples of what the supplements did or did not achieve.
Among male patients, those who took the multivitamins were about 27 percent less likely to die of heart disease than those who took the placebos.
But among female patients, those who took the multivitamin were about 25 percent more likely to die of cerebrovascular disease than those who took placebos.
As another example, the researchers wrote that older study participants who took the supplements were about 21 percent less likely to die of heart disease than older study participants who took placebos.
But younger patients who took supplements were about 42 percent more likely to die of cerebrovascular disease than younger patients who took the placebos.
Based on those varying results, the researchers concluded, "Overall, multivitamin supplements had no effect on total mortality or mortality from any of the specific causes of death examined, including cancer mortality, among all participants."
The researchers added that "...during six years of multivitamin supplementation and 20 years of post-intervention follow-up, we observed no effect of multivitamins on total or cause-specific mortality in a nutrient-deficient population. Together with data from previous trials, these results demonstrate little benefit of multivitamin supplementation on mortality in either well- or poorly nourished populations."
This study was published July 8 in the JAMA Internal Medicine.
The researchers reported no investments or other activities that would influence study design or outcomes.