You may have read the news headlines about a recent analysis that linked vitamin B intake to lung cancer. If you take vitamin B supplements, you may wonder what it means for you. Here’s what you need to know.

What Are B Vitamins?

There are eight essential B vitamins: B1 ( thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B12 and folic acid. The recent findings, published in the Journal of Clinical Oncology in August, focused on the link between lung cancer and B6 and B12.

Vitamin B6 helps keep nerves and blood vessels healthy, while vitamin B12 plays a critical role in metabolism, immune function and brain development in pregnancy and infancy. Both are found in animal foods, and you can also get B6 from fruits (except citrus), as well as potatoes and other starchy vegetables.

According to the National Institutes of Health, most people in the U.S. get sufficient amounts of B vitamins from food. Still, vitamin B supplements are popular; they’re often marketed as energy-boosting, despite the lack of scientific data to support this benefit.

Most multivitamins contain the U.S. Recommended Dietary Allowance for adults for B vitamins, which is 2.4 micrograms of B12 and 1.3 to 1.7 milligrams of B6 (depending on your age and gender). Vitamin B supplements, on the other hand, pack much higher doses. For example, Nature Made multivitamins have 2 mg of B6 and 6 mcg of B12, while a Nature Made B6 supplement has 100 mg of B6 (5,000 percent of the RDA), and a B12 supplement has 500 mcg (8,333 percent of the RDA).

[See: What Not to Say to Someone With Lung Cancer.]

The VITAL Study

The new analysis is based on data from the Vitamins and Lifestyle, or VITAL, cohort: about 77,000 adults ages 50 to 76 who were recruited between 2000 and 2002. Researchers at Fred Hutchinson Cancer Research Center at the University of Washington targeted supplement users to determine if there was any association between supplement use and disease. They collected information about vitamin and supplement usage by asking participants to recall what they took and at what doses (relying on participants’ recall and reporting of supplement usage is one limitation of the study). Researchers continue to analyze data from VITAL and follow-up with the cohort.

The August analysis found that men who were taking the highest category of vitamin B6 (more than 20 milligrams per day over 10 years) and B12 (more than 55 micrograms per day over 10 years) had a two-fold increase in risk of lung cancer compared with non-users, says Theodore Brasky, lead researcher on the vitamin B analysis and an epidemiologist at The Ohio State University Comprehensive Cancer Center — Arthur G. James Cancer Hospital and Richard J. Solove Research Institute. (Brasky reports no financial or other conflicts of interest.) Furthermore, Brasky and his colleagues discovered that men who smoked and took these high doses of vitamin B6 or B12 had a three to four times greater risk of developing lung cancer relative to men who smoked and did not take these supplements. They found no similar association in women or in people who were not smokers.

[See: 7 Things You Didn’t Know About Lung Cancer.]

What Does it Mean?

It’s important to point out that VITAL was an observational study and does not prove cause and effect. Additional studies are necessary to replicate and confirm these findings.

That said, the findings raise interesting questions about taking high doses of supplements and whether they have a protective or potentially harmful effect on the development of lung (and other) cancers.

Lung cancer is the biggest cancer killer in men and women; it kills more people than breast, prostate and colon cancer combined, says Dr. John Minna, a professor at UT Southwestern Medical Center. “We know that 50 percent of all lung cancers occur in people who quit smoking 10 to 20 years ago. These people are still at increased risk for lung cancer, and this risk probably persists for the rest of the smoker’s life.” So, the context of the VITAL analysis is important: Can we find ways to prevent lung cancer (for example, by taking supplements), or prove that something is an associated risk for developing cancer?

The major takeaway from VITAL is that people are taking vitamins under the assumption that they’re helping themselves, Minna says. “They think they are doing something healthy, yet men smokers who take high doses of vitamin B supplements greatly increase their chance of developing lung cancer.” This increase in risk is significant. Minna says if we could prevent the same percent of lung cancers that are associated with smokers taking high doses of B vitamins, it could have a major impact on the disease.

There’s no reason to believe that B vitamins cause cancer on their own, Brasky says, and since they’re water soluble, you excrete any excess through your urine. They don’t accumulate in your body. However, it seems that in the presence of smoking, they may promote the development of lung cancer for reasons we can’t yet explain.

[See: 7 Innovations in Cancer Therapy.]

The Bottom Line

Brasky says that if you’re a smoker who takes B vitamins and you’re concerned about lung cancer, your best bet is to quit smoking. “Smoking causes lung cancer and many other diseases,” he says.

Minna, meanwhile, adds that based on the results of VITAL, he would advise men who smoke not to take vitamin B supplements, particularly since most of us get sufficient quantities of B vitamins through food and daily multivitamins.

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Is There an Association Between Vitamin B and Lung Cancer? originally appeared on usnews.com