A study published today in BMC Public Health notes that the inverse relationship between UVB exposure and crude colon cancer rates is stronger in older age groups. The study paves the way for future research to evaluate screening programs for vitamin D deficiency as a cancer prevention strategy. Author Raphael Cuomo discusses the study results on this blog.

Countries with more UVB sunlight have lower colon cancer rates

If you live in a country with more UVB sunlight, you may have an advantage in terms of cancer risk.

Ultraviolet B (UVB) sunlight is used by your skin to make vitamin D, which is anti-carcinogenic. For those of us farther from the equator, we get very little UVB, usually in the middle of the day (around 10 a.m. to 2 p.m., depending on where we live) and during the summer months. In comparison, people living in countries closer to the equator are bathed in UVB for most of the day all year round.

UVB sunlight, with reddish shades indicating stronger UVB. NASA data

How does vitamin D prevent cancer?

Vitamin D has a lot of effects on cells. In cancer research, vitamin D is DINAMIT! This acronym describes the sequence of events at the cellular level when vitamin D is low. DINOMIT spells Disjunction, initiation, natural selection, overgrowth, metastasis, involution, and Reconciliation (See accompanying illustration from Annals of Epidemiology). With good vitamin D levels, cells can communicate better with their neighboring cells due to the higher production of cadherin molecules. When vitamin D levels are low, the cells do not know that they are surrounded by other cells, so they divide uncontrollably and cause cancer.

You may not realize it until you are older

Garland CF et al. (2009). Vitamin D for Cancer Prevention: Global Perspective. Annals of Epidemiology 19 (7): 468-483.

Our research published in BMC Public Health suggests that the anti-cancer effects of vitamin D are barely noticeable in people under the age of 45. In this study, we analyzed the global differences in colorectal cancer, one of the most common types of cancer. We found that younger people in low-UVB countries had almost the same cancer rates as younger people in high-UVB countries. However, if you look at people over 45, those in countries had low UVB dramatic higher cancer rates than in countries with high levels of UVB radiation.

Does that mean you don’t need vitamin D until you get old? Not quite. The carcinogenic effects of a vitamin D deficiency take a long time to develop. (In fact, this is a major reason researchers in low-UVB countries didn’t find high cancer rates until they looked at older age groups.) Young or old, vitamin D could help you prevent cancer.

What should I do if I don’t live near the equator?

If you don’t live near the equator, you may need to take extra steps to make sure you have good vitamin D levels. This may include consuming foods rich in vitamin D (such as oily fish and dairy products) or taking a vitamin D supplement. You can also get a few extra rays of sun at lunchtime as long as you don’t get sunburned.

If you live near the equator, you probably don’t have to worry that much. However, if you work indoors and rarely go outside, consider alternative ways to get your vitamin D.

Regardless of where you live, you can ask your doctor to measure your vitamin D levels, or you can order a vitamin D test at home. Previous research suggests that 40 ng / ml is a good minimum target for cancer prevention.


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