As mentioned two days ago, studies into the association between diet and cancer show that food can have an impact in preventing cancer, or in reducing the aggressiveness of the disease. At the American Association for Cancer Research's Frontiers in Cancer Prevention Research meeting last moth, investigators reported some examples of these relationships.

Here is another reported finding. It involves the relationship between dietary antioxidants and oxidative damage in smokers: evidence of effect modification by lifestyle and genetic factors

Vitamin E in the diet of male smokers appears to protect against oxidative damage that can lead to cancer development, according to researchers from Columbia University's Mailman School of Public Health working with investigators from the NYU School of Medicine.

They found that male smokers who had high plasma levels of vitamin E had lower levels of oxidative-DNA damage in their white blood cells. Oxidative DNA damage is a mechanism by which tobacco smoking can increase risk of cancer. In addition, the protective effect of vitamin E was greatest among the men with a beneficial form of a common "detoxifying" gene, GSTM1. The investigators did not find a similar effect of vitamin E in women.

"There was a dose-response relationship, in that the more vitamin E we found in the blood of the men, the less there was of this cancer-related biomarker," said the study's senior investigator, Frederica P. Perera, Dr.P.H., Professor in the Division of Environmental Health Sciences at the Columbia University School of Public Health.

"This suggests that while working toward the goal of quitting smoking, which is the very best way to prevent development of smoking-related cancers, it could be helpful to eat a diet rich in vitamin E," she said, and added, "we don't yet know why this relationship was not found in women, but a good diet is beneficial to health in many ways."

The most active form of vitamin E (known as a-tocopherol) is believed to be a strong antioxidant, capable of preventing oxidative chemical reactions that damage DNA. The vitamin is found in certain vegetable oils, nuts, whole grains, fish, green leafy vegetables and other foods. Studies that have examined the ability of vitamin E to protect against cancer have shown mixed results, however.

The present study is unusual, the researchers say, because it measured two different markers in white blood cells drawn from 280 participants - people who smoked at least 10 cigarettes a day. These markers were the amount of vitamin E in blood derived from food (those who used vitamins were excluded from this study) and the quantity of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a measure of oxidative damage to DNA.

The researchers found a protective effect of plasma a-tocopherol on oxidative damage among smokers, but only among men. They next looked at the interaction between vitamin E and GSTM1, a gene variant known to produce enzymes that efficiently detoxify carcinogens in tobacco smoke, and found a greater effect of the vitamin among men with this gene.

"We all want to know if vitamins help protect us against disease, and measuring their effects in the blood using markers of cellular damage is the most direct way to do that," said Perera. "But we have a lot of work ahead before we can fully understand the role of antioxidants in the chemoprevention of tobacco-related cancer."

Of course many of us could point out to Perera just how thoroughly established the case is that vitamins do indeed protect us from disease but some researchers become so reductionist there is little point. We did not need this study to know that vitamin E confers these and many other benefits but the findings are certainly welcome.