Adding vitamin D to the menu may be a low-cost way of preventing colorectal cancer in people under 50, a new study reveals. Researchers from the Dana-Farber Cancer Institute and Harvard have discovered a link between lowering cancer risk in younger adults and the amount of vitamin D they consume through food.

Although colorectal cancer rates are in decline, cases are actually going up among younger patients. While scientists can’t fully explain why this is happening, they note that the intake of vitamin D from foods such as fish, mushrooms, eggs, and milk has decreased over the past few decades.

During their review of over 94,000 women in the Nurses’ Health Study II, the researchers found that participants taking in more vitamin D from food had lower rates of young-onset colorectal cancer and fewer cases of colorectal polyps.

“Vitamin D has known activity against colorectal cancer in laboratory studies. Because vitamin D deficiency has been steadily increasing over the past few years, we wondered whether this could be contributing to the rising rates of colorectal cancer in young individuals,” says Kimmie Ng, director of the Young-Onset Colorectal Cancer Center at Dana-Farber, in a media release. “We found that total vitamin D intake of 300 IU per day or more – roughly equivalent to three 8-oz. glasses of milk – was associated with an approximately 50% lower risk of developing young-onset colorectal cancer.”

Vitamin D less effective after age 50?

All of the participants in the study were nurses between 25 and 42 years-old in 1989. Researchers followed their health, diet, and lifestyle habits from 1991 until 2015. During that time, doctors diagnosed 111 cases of young-onset colorectal cancer and detected 3,317 colorectal polyps.

Upon further review, the team discovered that women eating more vitamin D-rich foods significantly lowered their risk of both occurrences. Taking vitamin D supplements however, did not produce the same beneficial effect as consuming it in milk, eggs, and fish.

The study authors note the same link did not appear in people over the age of 50. It’s not clear why older adults receive less cancer benefits from their diets and the team says they’ll need to study a larger group of patients to see if vitamin D only protects against early-onset colorectal cancer.

“Our results further support that vitamin D may be important in younger adults for health and possibly colorectal cancer prevention,” Ng concludes. “It is critical to understand the risk factors that are associated with young-onset colorectal cancer so that we can make informed recommendations about diet and lifestyle, as well as identify high risk individuals to target for earlier screening.”

Common symptoms of the disease include bloody stool, persistent stomach pain, and unexplained weight loss. Health officials add colorectal cancer the second-leading cancer killer in the United States, but early detection helps to improve a patient’s chances of survival.