Research at Washington State University suggests that eating more Vitamin B-6 will protect Americans from a variety of cancers. Increasing Vitamin B-6 consumption may be especially important for smokers.
Terry Shultz, a human nutrition scientist, recently reported his four-month dietary study to the recent Experimental Biology 2003 meeting in San Diego. Shultz said the Recommended Dietary Allowance of Vitamin B-6 may be too low to adequately protect people, especially smokers, from cancer.
In several large population studies, people with a higher intake of Vitamin B-6 were found to have a lower risk of colon, prostate, lung, gastric and pancreatic cancers.
Shultz says Vitamin B-6 converts the vitamin folate to a form that the body can use to produce thymine, a component of DNA. "If the body doesn't have enough Vitamin B-6, it doesn't make enough thymine and it tries to make do by substituting uracil. Uracil is not a normal component of DNA, and its presence stresses normal DNA repair mechanisms in the cell. This inefficiency in the normal repair mechanisms leads to breaks in DNA strands and instability of chromosomes - a possible first step in the development of cancerous cells." The American diet may not include adequate Vitamin B-6, and the WSU study suggests smokers would benefit from even higher levels of the vitamin than the rest of the population.
"The good news from the WSU study, Shultz says, "is that adding Vitamin B-6 to the diet rapidly improved both smokers' and non-smokers' Vitamin B-6 status and, equally rapidly, decreased the number of DNA strand breaks in both groups." Shultz says baseline data taken from six healthy, moderate smokers on the first day of his study, showed that four subjects had unacceptably low blood levels of Vitamin B-6. Moderate smokers was defined as less than a pack a day.
Only one of the otherwise comparable non-smokers had unacceptable Vitamin B-6 status.
In the first 28 days, six smokers and six non-smokers were given a carefully controlled depletion diet containing only marginal amounts of Vitamin B-6.
The diet was composed of commonly consumed foods and was adequate in all nutrients except Vitamin B-6.
At the end of this depletion period, the researchers found that all subjects had lower Vitamin B-6 levels and higher numbers of DNA strand breaks. Smokers who began the study with low Vitamin B-6 levels had fallen even lower; but the two groups appeared similar in the number of DNA strand breaks.
Shultz postulates this may be because the researchers measured the total lymphocyte profile rather than looking at subsets, which may have been affected differently.
During the study's second month, subjects ate a diet that included 1.4 mg of Vitamin B-6, which approximates the RDA.
Subjects continued to eat only what the researchers gave them during the third month, but Vitamin B-6 intake was raised to 2.2 mg per day.
During the fourth and final month, subjects were allowed to eat whatever they wanted, but their diet was supplemented with 10.3 mg of Vitamin B-6 per day, more than seven times the RDA.
As the amount of Vitamin B-6 in the diet increased, body levels of Vitamin B-6 went up and DNA strand breaks went down, beginning as early as the first month of Vitamin B-6 supplementation.
After three months of consuming increasingly high levels of dietary and supplemental Vitamin B-6, the smokers eventually reached acceptable status levels. But they never caught up with their non-smoking counterparts.
"Considering Vitamin B-6's role in DNA synthesis and repair, these results suggest that the current RDA for this critical vitamin is too low for even moderate smokers and even could be too low for the population as a whole," Schultz said.
Foods high in Vitamin B-6 include fortified cereals, beef, chicken, fish, legumes, soy products and bananas.