Higher vitamin D consumption, mainly from dietary sources, may help protect against young-onset bowel cancer or precancerous bowel polyps, according to a study published in the journal Gastroenterology.
It is the first research to show such an association and could potentially lead to recommendations for higher vitamin D intake to reduce bowel cancer risk in adults under the age of 50.
Although bowel cancer rates among people over age 50 have been declining, rates among younger adults have been on the rise, a worrying trend that has yet to be explained.
Perhaps uncoincidentally, the study authors noted that people had been consuming less foods containing vitamin D like fish, milk, mushrooms, and eggs over the past several decades.
Prior to this study, an association between total vitamin D intake and the risk of young onset bowel cancer had not been studied.

“It is critical to understand the risk factors that are associated with young-onset [bowel] cancer so that we can make informed recommendations about diet and lifestyle, as well as identify high risk individuals to target for earlier screening,” said senior co-author of the study, Kimmie Ng of the Dana-Farber Institute.

The researchers found that consuming 300 IU or more of vitamin D per day — roughly equivalent to either three 235 ml glasses of milk, 100 grams of salmon, or 150 grams of lean pork— was associated with around a 50 percent lower risk of developing young-onset bowel cancer. Other foods high in vitamin D include barramundi, sardines, fortified margarine spreads, tuna, lamb, eggs, lamb, mussels and crab, and shiitake mushrooms.

Although the association was stronger for dietary vitamin D than from vitamin D supplements, the authors said that could be due to chance or to unknown factors that are not yet understood.

Interestingly, the researchers didn’t find a significant association between total vitamin D intake and risk of bowel cancer diagnosed after age 50.
The scientists said more research with a larger sample will be necessary to determine if the protective effect of vitamin D is actually stronger in young-onset bowel cancer.