Researchers have long suspected a link between vitamin D intake and the risk of developing various types of cancer, based on what’s known about this vitamin’s role in supporting the immune system. While the disease processes that define cancer are complex, a common factor in all cancer is out-of-control cell growth — and the immune system plays a role in whether this growth takes place. Vitamin D is not widely found in food sources — the most common dietary sources of vitamin D include fortified milk, fortified breakfast cereals, other fortified products, and fatty fish (like trout, salmon, tuna, and mackerel). Vitamin D is also found in smaller amounts in beef liver, egg yolks, cheese, and mushrooms, according to the U.S. National Institutes of Health. Your skin can also produce vitamin D when bare skin is exposed to direct sunlight, but this is not a reliable source of vitamin D for most people. Vitamin D is widely available in supplements, both in multivitamins and by itself.
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For the latest study, researchers examined the relationship between total vitamin D intake and the risk of developing early-onset colorectal cancer (before age 50) or precancerous growths in a group of 94,205 women, as described in a Healio article on the study. These participants were 25 to 42 years old when they enrolled in the study, which lasted from 1991 to 2015 (not everyone was enrolled at the beginning of that period). Based on dietary surveys that included supplements, the researchers estimated each participant’s daily intake of vitamin D. During an average follow-up period of 13.3 years, 111 participants developed early-onset colorectal cancer.
Higher daily vitamin D consumption linked to lower early-onset colorectal cancer risk
The researchers found that compared with participants who consumed less than 300 IU (international units) of vitamin D, those who consumed at least 300 but less than 450 IU of vitamin D daily were 49% less likely to develop early-onset colorectal cancer. Those who consumed 450 IU of vitamin D or more daily were 51% less likely to develop early-onset colorectal cancer, suggesting that beyond an adequate intake of vitamin D, a larger dose doesn’t help prevent this type of cancer. But the researchers also found that food sources of vitamin D were linked to a greater cancer risk than supplemental forms of the vitamin. For every 400 IU increase in vitamin D intake from non-supplement dietary sources, the risk for early-onset colorectal cancer dropped by 66%.
A higher vitamin D intake from all sources was also linked to a 24% lower risk of developing conventional adenomas and a 15% lower risk of developing serrated polyps — two types of growths in the colon and rectum that sometimes develop into cancer.
The researchers noted that while more research is needed to gain a better understanding of factors that contribute to early-onset colorectal cancer — which has been increasing at an alarming rate in recent years — the latest study suggests that adequate vitamin D intake may play an important role in preventing this form of cancer. With more information on this risk, doctors may be able to screen people with the highest risk for early-onset colorectal cancer earlier than current screening recommendations for colorectal cancer suggest.
Want to see more vitamin D research? Read “Low Vitamin D Tied to Painful Diabetic Neuropathy,” “Vitamin D Improves Glucose Control After Knee Replacement,” and “Vitamin D Deficiency Tied to Higher COVID-19 Risk.”