Scientists at the Aichi Cancer Center in Nagoya, Japan, believe sushi and fresh fish are the reason lung cancer rates in Japan are markedly lower than those in the United States and Britain, even though the Japanese smoke as much as Westerners.
"Japanese people love their fresh fish, particularly sushi," Professor Toshiro Takezaki said in a statement. "We think that is why, even though the Japanese smoke as much as people in the UK, their rate of lung cancer is only two-thirds as high."
In a study published in the British Journal of Cancer, Takezaki and his colleagues studied the eating habits of 4,000 healthy people and 1,000 lung cancer sufferers to determine how much of an impact diet had on the disease.
They found that people who ate large amounts of fresh fish or sushi were less likely to develop lung cancer, the leading cause of cancer death in the world.
Fresh fish seemed particularly to prevent the adenocarcinoma type of lung cancer. People who ate the most sushi and fresh fish had half the risk of developing the rare tumor than people who ate the least fresh fish.
Salted or dried fish did not seem to protect against the disease. Other scientific studies have indicated they could increase the risk of lung cancer.
Scientists are not sure how fresh fish helps to lower lung cancer risk in smokers but suspect it is due to polyunsaturated fatty acids present in fish oil.
Results of other studies looking into the relation between eating fresh fish and reduced lung cancer risk have been inconclusive.
"It has been suspected but this study shows a strong correlation with this particular type of lung cancer," Brad Tims of the Cancer Research Campaign (CRC), a leading British charity, told Reuters.
Lung cancer is the deadliest of all cancers. The five-year survival rate for lung cancer is about 10 percent and an estimated 80 percent of lung cancer patients die within a year of being diagnosed.
Smoking is a leading cause of the disease. Researchers estimate that one billion people will die of lung cancer in the 21st century if current smoking trends continue.
"The most important thing anyone can do to cut their risk of lung cancer is to give up smoking, but for those people who are unable to quit, eating lots of fresh fish could be a useful way to moderate their risk," said Professor Gordon McVie, the director general of the CRC.