Eat Your Leafy Greens: High Vitamin B Levels Linked to Lower Lung Cancer Risk

Kale and other leafy greens and meat are good sources of B vitamins.
Kale and other leafy greens and meat are good sources of B vitamins.

Higher blood levels of vitamin B6 and a common amino acid, methionine, are associated with a reduction of at least 50% in the risk of developing lung cancer, concludes a study of nearly 400,000 participants. The findings, published in the June 16 issue of the Journal of the American Medical Association, show that higher levels of B vitamins are associated with lower lung cancer risk, even in current or former smokers, as well as those who've never smoked.

Participants with the highest blood level of vitamin B6 were 56% less likely to develop lung cancer when compared to those with the lowest level. Similarly, those with the highest level of methionine had a 48% lower risk. The researchers further found an additional association for serum levels of folate, or folic acid, which was associated with a two-thirds lower risk of lung cancer when combined with B6 and methionine.

Lowest Cancer Risk Found With Highest Vitamin B, Methionine Levels

Previous research has suggested that deficiencies in B vitamins may increase the probability of DNA damage and subsequent gene mutations. But the researchers note that two randomized trials of folate supplementation and colorectal cancer failed to identify a protective effect. However, this study didn't find a causal link.

Paul Brennan, Ph.D., of the International Agency for Research on Cancer, based in Lyon, France, and colleagues used samples from the European Prospective Investigation into Cancer and Nutrition study, of which 899 samples had lung cancer. Brennan investigated B vitamins and methionine status in the samples, finding a lower risk for lung cancer among participants with higher levels of B6 and methionine, an essential amino acid.

Still, the main cause of lung cancer remains smoking tobacco, which is implicated in 90% of all cases of the disease. "Lung cancer remains the most common cause of cancer death in the world today and is likely to remain so for the near future," the authors pointed out. In 2006, almost 200,000 Americans were diagnosed with lung cancer, and almost 160,000 died of the disease -- more than breast, prostate and colon cancers combined.

B-Vitamin Deficiencies Rampant Despite "Enrichment"

The researchers emphasized the importance of first reducing the numbers of smokers, saying the study could perhaps help former smokers reduce their risk of lung cancer. If a causal link is found, the researchers say the next step is to identify optimum levels of the nutrients for reducing future cancer risk.

The study also found that B-vitamin deficiencies are rampant in many Western populations, despite folic acid fortification in flour and other foods in many countries, including the U.S. The Food and Drug Administration in 1996 implemented such a fortification program, which mandated folic acid addition to "enriched" cereal grain products, among other initiatives.

Folate can be easily boosted in any diet through the consumption of leafy green vegetables, legumes, liver and enriched flour products. Similarly, good sources of vitamin B6 include meats, whole grain products, vegetables, nuts and bananas, while high levels of methionine can be found in sesame seeds, Brazil nuts, fish, meats and some other plant seeds.