Photo/IllutrationHalf-naked men enjoy sunbathing in Sapporo. (Asahi Shimbun file photo)

Higher blood levels of vitamin D, which is found in seafood, mushrooms and can be produced in the body through exposure to sunlight, decreases the risk of cancer, researchers have found.

A team of scientists from the National Cancer Center said the substance is likely associated with cancer prevention because it can prevent tumor cells from proliferating.

The findings were published in the British medical journal BMJ on March 8.

The research team examined 33,000 people aged 40 to 69 in Iwate, Okinawa and six other prefectures for 16 years on average from 1990, and measured vitamin D levels in the blood of 8,000 of them.

The subjects were then categorized into four groups according to their vitamin D levels.

The group with the lowest level was 20 percent more likely to develop cancer than the other three groups. The difference was especially large in connection with the risk of liver cancer, with the likelihood for the lowest blood level group being 50 percent higher than those with the highest vitamin D level.

Vitamin D is said to play an important role in bone growth, and a past experiment showed it could hinder cancer cells from proliferating and help kill dangerous cells that would turn into tumors.

But despite the new research, Taiki Yamaji, head of the center’s molecular epidemiology laboratory, said consuming too much seafood and mushrooms or excessive exposure to sunlight are not appropriate measures to decrease the risks of cancer.

“The cancer risk-decreasing effect (of vitamin D) will stop rising when its amount in the blood reaches a certain level,” he said. “People should enjoy moderate diets and sunbathing without making extreme efforts such as taking dietary supplements and going to tanning salons.”