We all know by now that the best way to prevent lung cancer is to not smoke or use any tobacco products. But about ten to fifteen percent of nonsmokers still get lung cancer, a disease that accounts for more deaths than any other cancer type.
For nonsmokers, eating high amounts of tofu, edamame and other soy foods may lower their risk, finds a new study along with an analysis of the research.
The study was published in the American Journal of Epidemiology.
Study researchers first looked at the diet of approximately 71,000 women who were part of a health study in China. Almost all the women – 97 percent – didn’t smoke. The women answered questions about their typical diet at the start of the study and again two to three years later. They also gave information on their exposure to secondhand smoke and medical history.
After an average of nine years, the study found that women who consumed the most soy foods had almost 40 percent lower risk of lung cancer compared with those who ate the least amounts. This was after taking into account age, other dietary factors and smoking. (Of the 370 women diagnosed with lung cancer during those nine years, all but 30 had never previously smoked.)
Every five grams of dry-weight soy foods eaten per day – about one ounce or 28 grams of tofu – linked to a 7 percent lower risk. The reduced risk was even more pronounced for women with aggressive form of lung cancer, a form that resulted in the patient dying within 12 months of diagnosis.
AICR’s expert report found that diets high in fruits can reduce the risk of lung cancer, and the authors took fruits (and vegetable) consumption into account.
Then the authors conducted an analysis of the literature, which included 11 studies and almost a quarter of a million people. Some of the studies looked at both soy foods and soy foods and/or isoflavones, the group of compounds in soy that act as phytoestrogens.
The protective effect of soy foods was found primarily among nonsmokers: again, approximately 40 percent reduced risk for those who ate the most versus least soy foods and/or isoflavones. Every 1 gram of soy protein consumed a day – equal to a couple tablespoons of soy milk – linked to a 4 percent reduced risk.
Along with its isoflavones, soy foods provide calcium, fiber and phytochemicals that may play a role in protecting against lung cancer, the authors note.
This is one of the latest studies that points to soy foods protective effect for cancers. It comes at a time when there is now clear evidence that soy does not increase risk of recurrence or death for breast cancer survivors. For more about the soy-cancer link – along with nutrition information and tips on how to cook up soy foods – visit our new AICR’s Foods that Fight Cancer: Soy.