Vitamin D, also known as cholecalciferol, plays an important role in bone health and muscle strength and is essential for the prevention of rickets (1). Cholesterol is a precursor of Vitamin D, which is endogenously produced in the body when ergosterol is exposed to UVB sunlight through the skin. It is also found in eggs, fatty fish and supplements (1).
A recent study by researchers in Japan found that higher levels of vitamin D may lower the risk of liver cancer. The study conducted by researchers at the Center for Public Health Sciences at the National Cancer Center in Tokyo suggests that people who suffer from low levels of Vitamin D may be at an increased risk for many different types of cancers; however the overall body of evidence is mixed (2,3).
This latest study was published in BMJ and explored biologically active forms of vitamin D in blood samples of over 30,000 middle-aged adults across Japan in the early 1990s. The follow-up for individuals was over a 16-year period. This analysis was based off a sample of 3301 participants who developed cancer during the study and 4044 randomly selected participants, of whom 450 developed cancer. The research team found higher levels of circulating vitamin D led to lower risk for cancers, overall, after controlling for age, sex, smoking status and family history of cancer. They also controlled for seasonal differences in circulating vitamin D. They did not find differences in the effect of vitamin D by sex; however, authors noted that participants in the lowest quartiles of vitamin D status had a 22% higher risk of cancer when compared to those in the highest quartiles. Additionally, they noted a 50% lower risk of liver cancers for those in the highest vitamin D group compared to the lowest, after adjusting for diet.
Vitamin D status was only measured at one point during follow-up, which serves as an important limitation. Additionally, inherent selection bias means that participants in the study may have been more health-conscious than the public at large. The number of rare cancer cases in the cohort was also small.
It is important to note that these latest findings apply primarily to Asian populations and higher levels of Vitamin D in these communities may lower risk for cancer; however, these findings cannot be translated across the board. It is important for those at risk of sun burns to avoid direct unprotected contact with the sun, which is a known risk factor for skin cancers. Additionally, lower levels of vitamin D may be an indication of poor health, overall (2,3).
Other health benefits of vitamin D have been seen in meta-analyses that have found a 31% reduction in falls among those supplemented with vitamin D. It also plays a role in improving the body’s response to infection among patients with cystic fibrosis (4). For populations in the US, vitamin D deficiency remains a problem in populations including African American communities, where according to the National Health and Nutrition Examination Survey (NHANES), 60% of people suffer from low levels (5,6). Through fortification of dairy products and supplementation, these numbers have reduced; however, greater attention including additional research is needed to reduce risk of deficiency, with added benefits to risk reduction for other health conditions, including cancers.
References:
- Khazai, N., Judd, S.E. & Tangpricha, V. (2008). Calcium and vitamin D: skeletal and extraskeletal health. Current Rheumatology Reports, 10(2), 110-117.
- Budhathoki, S., Hidaka, A., Yamaji, T., Swada, N., Tanaka-Mizuno, S., Kuchiba, A., Charvat, H., Goto, A., Kojima, S., Sudo, N., Shimazu, T., Sasazuki, S., Inoue, M., Tsugane, S., Inoue, M., Tsugane, S., & Iwasaki, M. (2018). Plasma 25-hydroxyvitamin D concentration and subsequent risk of total and site specific cancers in Japanese population: large case-cohort study within Japan Public Health Center-based Prospective Study cohort. The British Medical Journal, 2018, 360. https://www.bmj.com/content/360/bmj.k671
- Davis, N. The Guardian, Nutrition. (2018) Retrieved from: https://www.theguardian.com/science/2018/mar/07/vitamin-d-may-offer-protection-against-cancers-study-says
- Pincikova, T., Paquin-Proulx, D., Sandberg, J.K., Flodstrom-Tullberg, & M., Hjelte, L. (2017). Clinical impact of vitamin D treatment in cystic fibrosis: a pilot randomized controlled trial. European Journal of Clinical Nutrition, 71, 203-205.
- Jain, R.B. (2016). Recent Vitamin D data from NHANES: Variability, trends, deficiency and sufficiency rates and assay compatibility issues. Journal of Advanced Nutrition and Human Metabolism, 2. https://www.smartscitech.com/index.php/JANHM/article/view/1208
- Avenell, A., Mak, J.C., & O’Connell, D. (2014). Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database of Systematic Reviews, 14(4).
