Data from 500 men and women revealed that increased vitamin B6 levels, but not folate, were associated with lower levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker for oxidative stress, but the association was only valid for men.

“The present finding adds to evidence to support a protective role of vitamin B6 against oxidative DNA damage,”​ wrote researchers from the National Center for Global Health and Medicine in Tokyo and Kyushu University.

“Intervention studies are required to confirm whether increase of vitamin B6 can decrease oxidative DNA damage.”​

Homocysteine and oxidative stress​

Writing in the journal Nutrition​​ the Japanese scientists note that B vitamins such as folate and B6 can affect the metabolism of homocysteine, an amino acid that, at elevated levels, has been linked to adverse effects, including oxidative stress and damage to DNA, which can, in turn, influence carcinogenesis.

To examine if increased levels of B vitamin levels are associated with DNA damage, the researchers analyzed data from 293 men and 207 women aged between 21 and 66.

Results showed that pyridoxal – one of three forms of vitamin B6 – was associated with 8-OHdG levels for men, but not women. In addition, the association in men was limited to non-smokers and men who did not drink a lot of alcohol.

“We are not aware of any study that showed sex difference in the association between vitamin B6 and oxidative stress marker,” ​wrote the researchers. “Interestingly, a protective association of vitamin B6 intake with colorectal cancer was observed only in men but not in women in a Japanese cohort, a finding that appears to be consistent with that of our study. ​

“Further study is needed to determine whether or not smoking status or alcohol use status can modulate the relationships between vitamin B6 and oxidative DNA damage or carcinogenesis.”​

Commenting on the potential mechanism, the researchers noted that there is biological plausibility for vitamin B6 to protect against oxidative DMA damage. Data from animal studies have shown that insufficient or deficient B6 levels may decrease levels of the antioxidant glutathione, which subsequently increases 8-OHdG, while other studies have suggested a role for homocysteine to increase damage, but no association with homocysteine and 8-OHdG was observed in this study, they said.

Source: Nutrition​​

Published online ahead of print, doi: 10.1016/j.nut.2013.03.014

“Serum vitamin B6, folate, and homocysteine concentrations and oxidative DNA damage in Japanese men and women”​

Authors: K. Kuwahara, A. Nanri, N.M. Pham, K. Kurotani, A. Kume, M. Sato, K. Kawai, H. Kasai, T. Mizoue