Islamabad - Men who don’t smoke and eat a lot of soy may have a lower risk of lung cancer, according to a new study.

Soy contains isoflavones, which act similarly to the hormone estrogen, and may have anti-cancer qualities in hormone-related cancers of the breast and prostate, the researchers note in the American Journal of Clinical Nutrition. Cells in the lung have properties that suggest they may also respond to isoflavones.

Dr Taichi Shimazu, of the National Cancer Center in Tokyo, and colleagues studied more than 36,000 Japanese men and more than 40,000 Japanese women, 45 to 74 years old and free of cancer at the start of the study.

The researchers followed the women for about 11 years, after surveying their food intake, smoking status, medical history, and other lifestyle factors between 1995 and 1999.

Overall rates of lung cancer were small: 481 men — or about one in 75 — and 178 women, or about one in 225 — were diagnosed during the 11 years of the study. Among the slightly more than 13,000 men who never smoked, there were 22 lung cancer cases among men who ate the least soy, and just 13 lung cancer cases among those who ate the most. Shimazu said men’s soy intake from food varied widely, from about 34 to about 162 grams per day.

After taking a number of factors into account, the risk about halved in the highest versus the lowest intake group.

There were even fewer lung cancer cases among women, so researchers could draw no conclusions about their risks.

The authors note that men it may not be the act of eating soy that lowered lung cancer risk in the men in their study. Men who eat soy may be more likely to take part in other activities that may lower the risk, or may be more likely to eat other healthy foods. But they did take many of those factors into account.

However, the current study did not gather data on isoflavone supplement use, nor did it look at exposure second-hand smoking. That means these findings should be confirmed among Japanese and other populations, the authors conclude. In other words, the study does not provide enough evidence to suggest a change in eating behavior, Shimazu told Reuters Health by email.

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Tests on more than 300 samples of canned tuna from the top three brands in the United States revealed that more than half contained mercury levels above what’s considered safe by the Environmental Protection Agency. Researchers from the University of Nevada, Las Vegas (UNLV), found that 55 percent of the samples had mercury levels higher than the EPA standard of 0.5 parts per million (ppm) and 5 percent had levels higher than the 1.0ppm safety level set by the U.S. Food and Drug Administration for commercially sold fish. The health effects of mercury poisoning include central nervous system damage, hearing loss and vision problems.

“Canned tuna accounts for up to a quarter of the nation’s seafood consumption and creates some significant regulatory challenges,” study author Shawn Gerstenberger, an environmental and occupational health professor, said in a UNLV news release. “With pregnant women and children the most susceptible to mercury poisoning — yet also among the top consumers of canned tuna — federal agencies need to urge distributors to expressly state mercury levels in their products.”

The researchers found significant differences in mercury concentration by type (white and light) and brand. One brand had consistently elevated mercury levels, and white tuna from all three brands had the highest concentrations of mercury. White tuna comes from albacore, a different species of fish than “light” tuna.

“Mercury concentration in fish has a lot to do with the environment they’re in, but since the locations of where the fish are harvested are not made available to consumers, it is very difficult to positively identify and reduce the source of the exposure,” Gerstenberger said.

The researchers said federal regulators should require canned tuna producers to provide detailed information to consumers about the mercury content of each product and to disclose tuna harvest locations. In addition, the EPA and FDA need to have similar tuna consumption guidelines to lessen consumer confusion.

Many states have adopted EPA guidelines on tuna consumption, which suggest an average child consume only one can of tuna roughly every two weeks to ensure an acceptable level of mercury exposure.