LONDON (Reuters) – About a third of all common cancers in the United States , China and Britain could be prevented each year if people ate healthier food, drank less alcohol and exercised more, health experts said on Friday. Estimates from the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF) suggest that making simple lifestyle changes could prevent some 40 percent of breast cancers alone in Britain and the United States, as well as tens of thousands of colon, stomach and prostate cancers . "It is distressing that even in 2011, people are dying unnecessarily from cancers that could be prevented through maintaining a healthy weight, diet, physical activity and other lifestyle factors," Martin Wiseman , a WCRF medical and scientific adviser, said in statement. In China, 620,000 cases, or 27 percent are preventable, the WCRF said, as are about 35 percent, or 340,000, in the United States and 37 percent in Britain. Healthier lif...