Vitamin B-6 may provide cancer protection for smokers
Vitamin B-6 consumption could lower the risk of several types of cancer and be particularly important for individuals who smoke, US research suggests.
Vitamin B-6 converts the vitamin folate to a form that the body can use to produce thymine, a component of DNA, explain the researchers from Washington State University (WSU).
Without sufficient quantities of the vitamin the body does not make enough thymine and tries to â€œmake doâ€ by substituting uracil, which is not a component in DNA and stresses normal DNA repair mechanisms in the cell, explained lead researcher Dr Terry Shultz at the Experimental Biology meeting in San Diego.
â€œThis inefficiency in the normal repair mechanisms leads to breaks in DNA strands and instability of chromosomes â€“ a possible first step in the development of cancerous cells,â€ said Dr Shultz.
The researchers gave 12 people, split evenly between smokers and non-smokers, a diet depleted in vitamin B-6.
They discovered that after 28 days, all subjects had lower levels of the vitamin and higher numbers of DNA strand breaks.
Smokers who began the study with low vitamin B-6 levels had even lower levels of the vitamin at the one-month follow-up, although the two groups appeared to have similar numbers of DNA strand breaks.
For the next month the groups were given a diet that included 1.4mg of vitamin-B-6, which is around the recommended daily allowance (RDA).
The groups then went through a third month consuming 2.2mg per day of vitamin B-6.
In the fourth and final month of the study, subjects were allowed to eat whatever they wished but were given more than seven times the RDA of vitamin B-6.
As the amount of vitamin B-6 in the diet increased, body levels of the vitamin went up and DNA strand breaks decreased, beginning as early as the first month of vitamin B-6 supplementation.
After three months of consuming increasingly high levels of the vitamin, the status levels of the smokers became â€œacceptableâ€ but never caught up with their non-smoking peers, said the researchers.
â€œConsidering vitamin B-6â€™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,â€ said Dr Shultz.
He added, â€œThe good news from the WSU study is that adding vitamin B-6 to the diet rapidly improved both smokersâ€™ and non-smokersâ€™ vitamin B-6 status and, equally rapidly, decreased the number of DNA strand breaks in both groups.â€