Vitamins B6 and B12 have been promoted by the supplement industry for many years, touting benefits such as increased energy and higher metabolism. A new study suggests that these high-dose vitamin supplements are associated with increased risk for lung cancer in men, particularly in smokers (Journal of Clinical Oncology, Aug. 22, 2017).
Researchers from Ohio State University and National Taiwan University used data from the VITAL (Vitamins and Lifestyle) cohort study that followed the daily vitamin supplement usage, including dosages, of 77,000 participants. During the 10-year study, 808 of the participants developed lung cancer. Men who took the B6 or B12 supplements (not multivitamin pills) had double the risk for lung cancer compared to non-users, and men who smoked and took B6 or B12 had almost four times the risk for lung cancer. In women, the use of these vitamins was not associated with increased lung cancer risk. The authors concluded that "vitamin B supplements are not chemopreventive for lung cancer and may be harmful."
How Vitamins in Pills Differ from Vitamins in Foods
All of the vitamins necessary for human life and health come from foods, with the exception of vitamin D which comes primarily from sunlight. Most vitamins, particularly all of the B vitamins, are parts of enzymes that start chemical reactions. The food that you eat is loaded with hundreds, perhaps thousands, of enzymes that keep on breaking down the chemicals formed by reactions in your body until you end up with carbon dioxide and water and other chemicals that pass out in your urine.
Vitamin pills contain only the vitamins that we know about and are missing many of the enzymes regularly found in food, so taking vitamin pills can drive certain chemical reactions in your body and not others, which may cause you to accumulate end products that can harm you. The accumulated end products can damage your arteries to increase risk for heart attacks and damage your DNA in cells to increase risk for certain cancers. For a detailed explanation and diagram of the process see my recent report on Do You Need Vitamin Pills? This report also includes a lengthy list of studies that have shown lack of benefits or even harmful outcomes from taking vitamin pills.
North Americans almost never suffer from vitamin deficiencies except for lack of vitamin D, yet more than 50 percent of the population spends more than 30 billion dollars each year for vitamin pills and other nutritional supplements that they do not need. Forty-five percent of those who take vitamin pills believe that they will improve their health, but we have no good evidence that they do (JAMA Internal Medicine, Feb. 4, 2013). Many people say that they take vitamin pills because they may not be eating the right foods, but a lousy diet with vitamin pills is still a lousy diet.