New York: Eating 28 grams of walnuts everyday may change gut bacteria in a way that suppresses colon cancer, a new research has found. "Our results show for the first time that walnut consumption may reduce colon tumour development," said principal investigator Daniel Rosenberg of University of Connecticut Health Centre in the US. The researchers found that mice that ate seven-ten per cent of their total calories as walnuts developed fewer colon cancers. The effect was most pronounced in male mice, which had 2.3 times fewer tumours when fed walnuts as part of a western diet. That is equivalent to a human eating about an ounce of walnuts (28.3 grams) a day, the study said. "There is accumulating evidence that eating walnuts may offer a variety of benefits related to health issues like cancer. This study shows that walnuts may also act as a probiotic to make the colon healthy, which in turn offers protection against colon tumours," Rosenberg noted. The findings were reported in the journal Cancer Prevention Research. Walnuts are packed with compounds known to be important nutritionally. They have the most polyunsaturated fatty acids of all the commonly eaten tree nuts, as well as the highest ratio of omega-3 to omega-6 fatty acids, and high levels of a form of Vitamin E with anti-cancer properties. But walnuts are not merely the sum of their chemical parts, and it may be as a whole food that they pack the most significant anti-cancer punch against colon cancer, the third most common cancer in the world. To figure out why walnuts were beneficial, the team took fecal samples from the mice and analysed the communities of bacteria living in their digestive tracts. They found that walnut consumption tended to push the gut microbiome toward an ecology that was potentially protective against cancer. Because the studies were done only in mice, more testing needs to be done in humans before walnuts can be unequivocally recommended as a cancer-prevention agent.