And don’t get me started on metabolism. If you want to “supercharge your metabolism and energy levels,” Amazon can deliver you a tall bottle of B12 supplements by the end of the day. Your metabolic processes will be the envy of the neighborhood. (“Is Janice … on something?” “Yes—B12!”)
These are the sort of vague marketing claims that have propelled the cobalt-based compounds sold as B12 into American hearts and minds and blood in ever-growing quantities. They are extrapolations from the fact that B12 deficiency causes anemia, and correcting that deficiency will alleviate symptoms of fatigue and weakness. But as the National Institutes of Health notes, “Vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit.”
Nonetheless around 50 percent of people in the United States take some form of “dietary supplement” product, and among the most common are B vitamins. Worse than just a harmless waste of money, this usage could be actively dangerous. In an issue of the Journal of Clinical Oncology, published this week, researchers reported that taking vitamin B6 and B12 supplements in high doses (like those sold in many stores) appears to triple or almost quadruple some people’s risk of lung cancer.
This is a heavy claim about a very common substance, so it’s worth spending a minute on the methodology. Concerns about B-vitamin supplements and cancer have been percolating for years. They came up quietly in a large trial in Norway that concluded ten years ago. Starting in 1998, researchers assigned 6,837 people with heart disease to take either B vitamins or a placebo.
The researchers then watched as people died and contracted diseases in ensuing years—and the vitamin group raised concerns. In 2009, the researchers reported in the Journal of the American Medical Association that taking high doses of vitamin B12 along with folic acid (technically vitamin B9) was associated with greater risk of cancer and all-cause mortality.
Lung-cancer risk among men who took 20 milligrams of B6 daily for years was twice that of men who didn’t. Among people who smoke, the effect appeared to be synergistic, with B6 usage increasing risk threefold. The risk was even worse among smokers taking B12. Using more than 55 micrograms daily appeared to almost quadruple lung-cancer risk.
There was no apparent risk among women—which is not to say it doesn’t exist, only that it wasn’t apparent.
Why or how would B vitamins increase a person’s risk of cancer?
I asked Brasky what he thought was going on. It’s all hypothetical, and he has no clear idea bout the sex discrepancy. What he does know is that B vitamins all contribute enzymes and coenzymes to a metabolic pathway that breaks down folate in order to make the bases that comprise DNA. The pathway also regulates the expression of genes (by creating methyl groups that can essentially turn genes on and off). When we have too little of these B vitamins, this pathway can go wrong, leading to problems like incorporation of the wrong types of bases into DNA, which can cause breaks in the strands, and, in theory, lead to cancer.
Deficiency can also mean genes that should be inhibited are no longer inhibited, also potentially meaning cancer. Sufficiency of certain vitamins is important in cancer prevention, but avoiding excess appears to be similarly important.
Among smokers, who are already exposed to carcinogens, the effect of taking anything that impairs these cellular processes could be even more likely to lead to cancer.