Nearly half of American adults take some form of daily vitamin. The market is saturated with a dizzying selection of brands and formats, all competing for the estimated $12 billion that consumers spend every year on multivitamins. But are these little pills really that beneficial, or could they actually hurt our health? In the case of vitamin B, more could actually more than double a person’s risk for lung cancer, according to a recent report.
The study analyzed 10 years’ worth of dietary data and health risks in over 77,000 adults. They found that men who consume high doses of vitamin B had a 30 to 40 percent increase in lung cancer. And the cancer risk was even more striking in men who smoke. Male smokers who take high doses of vitamin B6 had triple the risk of lung cancer. For those who smoked and took high doses of vitamin B12, the risk jumped to almost four times.
“High” doses vitamin B is defined as more than 20 microgram of vitamin B6, or 55 microgram of vitamin B12 a day. "If you look at B-vitamin supplement bottles ... they are anywhere between 50-fold the US recommended dietary allowance (to) upward of 2,100-fold," said Theodore Brasky, the study’s lead author. By this standard, most vitamin Bs on the market could be considered “megadoses.”
"Our data shows that taking high doses of B6 and B12 over a very long period of time could contribute to lung cancer incidence rates in male smokers. This is certainly a concern worthy of further evaluation,” said Dr. Brasky.
While this study implicates high doses of vitamin B to lung cancer, at least one study found the opposite to be true, and another found no effect at all. The authors speculate the discrepancy may have to do with how the studies were conducted. In particular, the current study analyzed dietary surveys, not blood samples. Another possibility is that lung cancer may be skewing the body’s own level of vitamin B. Brasky and colleagues are planning two follow-up studies, which they hope will make the link more conclusive.
Brasky is also quick to highlight that, in terms of lung cancer, the focus should be on quitting smoking rather than quitting vitamin B. "When we're talking about what to be concerned about most: If you're a male smoker and you want to take B vitamins, you can stop smoking," Brasky said. "Smoking is the most important thing here, and that's preventable."
Of note, vitamins B are important in cell metabolism. Some even have roles in DNA synthesis and repair. Fortunately, most people can get their required dose of vitamin B through a healthy diet, and vitamin B deficiency is usually rare for the average person.