High Volume of Vitamin D Intake Linked to Decreased Early-Onset Colon Cancer Risk

A high amount of vitamin D intake was associated with an approximately 51% decreased risk of early-onset colorectal cancer among a large cohort of women under the age of 50 years, according to recently published study results.

The data — which were printed in the journal Gastroenterology — also demonstrated that most of the protective factor against early-onset colorectal cancer came from the dietary intake of vitamin D, rather than the intake of supplements.

Previous study results have demonstrated that higher levels of vitamin D have been associated with a decreased risk of colorectal cancer incidence among the overall population, as well as an increased survival from the disease.

However, little has been known about the protective factors of vitamin D in the younger population.

“We decided to focus on vitamin D and early-onset colon cancer (because) there have been rising rates of vitamin D deficiency in the U.S. population over the last few decades,” said the study’s senior co-author Dr. Kimmie Ng in an interview with CURE®. “The rates of vitamin D deficiency and insufficiency are significantly higher than they were several decades ago, and the rise of vitamin D deficiency seems to parallel this other rise that we've been seeing in young-onset colorectal cancer.”

As a result, Ng, who is an associate professor of medicine at Harvard Medical School and the director of the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute in Boston, and colleagues sought to see if the rising rates of vitamin D deficiency may be contributing to the increase in colorectal cancer incidence among younger individuals.

Ng and colleagues analyzed the likelihood of an association between vitamin D intake and risks of early-onset colorectal cancer and precursors such as polyps among more than 90,000 women who were nurses between the ages of 25 and 42 years at the time of study enrollment in 1989. Those participants — who were enrolled on the Nurses’ Health Study II — were then asked to complete self-administered questionnaires on their demographics, lifestyle factors and medical and other health-related information every two years after enrollment.

The occurrence of early-onset colorectal cancer, considered the diagnosis of disease prior to the age of 50 years, was the main goal of the study from Ng and colleagues.

The study authors identified 111 occurrences of early-onset colorectal cancer during the follow-up of the results from 94,205 women from 1991 to 2015.

After reviewing the data, Ng and colleagues confirmed that the results showed that a higher amount of vitamin D intake was associated with a decreased risk of colorectal cancer incidence among people under the age of 50 years. Moreover, according to Ng, the consumption of 450 units of vitamin D or more per day was associated with the greatest benefit. However, she also explained that the researchers observed a protective benefit in those who consumed 300 units of vitamin D or more per day.

People, Ng noted, can obtain those levels of vitamin D from consuming approximately three glasses of milk each day.

She also advised that people can naturally increase their vitamin D levels with sun exposure. However, Ng cautioned people to avoid prolonged sun exposure because of the risk of skin cancer.

“So that is not necessarily the best way to raise your vitamin D status,” she said.

Generally, Ng explained, it is hard for people to obtain a substantial amount of vitamin D through their diet, which is why most people, particularly in the northeastern part of the U.S., rely on supplements to increase their levels of vitamin D.

However, as these study results demonstrated, a significant daily vitamin D level was not needed to experience a protective benefit against early-onset colorectal cancer.

“Three-hundred units per day was associated with about a 50% decrease in the risk,” Ng said. “The Institute of Medicine recommends that average risk adults have 600 units per day of vitamin D. So as long as you're meeting the regular dietary requirements, that should be associated with a benefit.”

The main thing that people should take from the study, according to Ng, is to consult their doctors on how they can improve their vitamin D levels.

Ng also explained that research into the incidence of early-onset colorectal cancer, such as this study, is extremely important. In fact, she said it is a complete mystery as to why the disease is increasing in young people. And the concern, as she highlighted, is that some studies estimate that colorectal cancer is predicted to become the number one cause of cancer-related deaths by 2030 among people between the ages of 20 and 49 years.

“The research into why this is happening is extremely important if we are to identify what the underlying causes are, as well as to identify what a high-risk profile is so we can target these people with the high-risk profile for earlier screening,” she concluded.

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