Higher vitamin D intake linked to 50% lower risk of young-onset colorectal cancer

Consuming higher amounts of vitamin D — primarily through dietary sources — may significantly reduce the risk of developing young-onset colorectal cancer or precancerous colon polyps, according to a new study.

The research, published in Gastroenterology, is the first to show an association between total vitamin D intake and reduced risk of colorectal cancer diagnosed before age 50.

Scientists from Dana-Farber Cancer Institute, the Harvard T.H. Chan School of Public Health, and other institutions suggest the findings could inform future prevention strategies, potentially using vitamin D as a low-cost complement to cancer screening in younger adults.

A growing concern in younger adults

Although overall colorectal cancer rates have declined, cases among adults under 50 have been rising steadily in recent decades, a trend that remains poorly understood.

Researchers noted that vitamin D intake from foods such as fish, mushrooms, eggs, and milk has decreased over time, while vitamin D deficiency has become more common.

“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,” said Kimmie Ng of Dana-Farber Cancer Institute.

“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 percent lower risk of developing young-onset colorectal cancer,” Ng said.

How the study was conducted

Researchers analyzed data from 94,205 women in the Nurses’ Health Study II, a long-running prospective cohort study tracking nurses aged 25 to 42 at enrollment beginning in 1989.

Participants completed questionnaires every two years covering diet, lifestyle, and medical history, allowing researchers to calculate total vitamin D intake from both food and supplements.

The study tracked cases of colorectal cancer diagnosed before age 50, as well as colorectal polyps identified through colonoscopy or sigmoidoscopy, which can be early precursors to cancer.

Key findings

Between 1991 and 2015, researchers documented:

  • 111 cases of young-onset colorectal cancer
  • 3,317 cases of colorectal polyps

Higher total vitamin D intake was associated with a significantly lower risk of both young-onset colorectal cancer and colorectal polyps.

The protective association appeared stronger for vitamin D obtained from dietary sources — particularly dairy products — compared with supplements, though researchers noted this may require further investigation.

Dietary vitamin D and prevention potential

Participants with higher vitamin D intake showed up to a 50 percent reduction in risk of developing early-onset colorectal cancer compared with those with lower intake levels.

However, the researchers did not observe a similar association for colorectal cancer diagnosed after age 50, suggesting that age-related biological differences may play a role.

Further research is needed to clarify whether vitamin D has a uniquely stronger protective effect in younger populations.

What the findings mean

The results add to growing evidence that vitamin D may play an important role in colorectal cancer prevention, particularly among younger adults.

“Our results further support that vitamin D may be important in younger adults for health and possibly colorectal cancer prevention,” Ng said.

Researchers emphasize that identifying modifiable risk factors is critical as young-onset colorectal cancer continues to rise, helping guide dietary recommendations and earlier screening strategies for high-risk individuals.

Next steps

While the findings are promising, the researchers note that additional studies in larger and more diverse populations are needed to confirm the results and better understand the biological mechanisms involved.

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