Ask the doctors: Study links vitamin B supplements to increased lung cancer risk

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Dear Doctor: I’m 67 years old and because I was told that it’s harder for folks my age to get enough vitamin B12, I started taking a B complex supplement. My husband, who is 72, did, too. But now it turns out that these are linked to lung cancer? What should we do?

Dear Reader: Over the years there have been occasional findings in a range of studies that certain B vitamins were associated with an increase in lung cancer risk. Known as one-carbon metabolism-related B vitamins for the way they behave in the body at a molecular level, they include B6 and B12, which are commonly found in B vitamin supplements. Because the data into the link between these particular B vitamins and lung cancer risk were inconsistent, and because the use of vitamin supplements is hitting an all-time high, researchers homed in on the topic. Their findings were published last year in the Journal of Clinical Oncology.

The scientists analyzed data collected from approximately 77,000 women and men who are taking part in a long-term study conducted by a cancer research center at the University of Washington. Known as the VITamins and Lifestyle (VITAL) Study, participants self-report health data through the use of questionnaires. DNA for analysis has been collected from about 70 percent of the study’s participants. They range in age from 50 to 76 and live in a 13-county area of western Washington State. The authors of the B vitamin study were primarily interested in those who had been taking B vitamin supplements for at least a decade.

According to the findings of the B vitamin study, male smokers who took B6 or B12 supplements at very high dosages had three to four times the risk of developing lung cancer than men who smoked but did not take the supplements. Non-smoking men who took the supplements doubled their lung cancer risk.

Surprisingly, these findings did not extend to the women in the study. The B vitamins that the study participants were taking came from individual supplement sources. They did not come from multivitamins. This is an important distinction because the link to cancer occurred in study participants who were taking B vitamins at high dosages. The supplements delivered more than 11 times the recommended daily amount of B6, and a whopping 23 times the RDA of B12. As the author of the study has pointed out and as you have probably noticed yourself, B vitamins are now in vogue. They’re so popular that, in addition to the scores of oral supplements, you see B12 shots regularly offered on demand in health food stores and some pharmacies.

B vitamins are vital to our well-being. However, the best way to get them is through a well-balanced and healthy diet. Eggs, dairy, fish and meat are good sources of B12. Many products, like breakfast cereals and soy or rice milk, are fortified with the vitamin. If you do need a supplement, read the label carefully and choose a product that doesn’t provide more than the recommended daily allowance.

Send your questions to askthedoctors@mednet.ucla.edu.


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