Sun May Lower Risk of Endometrial Cancer?

A recent article published in Preventive Medicine titled "Is ultraviolet B irradiance inversely associated with incidence rates of endometrial cancer: an ecological study of 107 countries" suggests that the sun may lower the risk of endometrial cancer.

In this study, researches tried to relate the incidence of endometrial cancer in 107 countries to a long list of variables. After reviewing the data, they found a higher incidence of endometrial cancer in populations with low UVB irradiance, high intake of energy from animal sources, per capita health expenditure, and proportion of population overweight.

What does this mean? I'm not sure. This type of research is great at asking questions, but it rarely gives us any answers. Any conclusions from this point are quite speculative. The authors have suggested that the sun may reduce the risk of endometrial cancer, or perhaps those with low Vitamin D have a higher risk of endometrial cancer. Perhaps a future study will look at this, by reviewing the incidence of endometrial cancer in patients with Vitamin D deficiency? Or by looking at the risk of endometrial cancer in patients who have had long-term phototherapy? Or maybe UV exposure has nothing at all to do with endometrial cancer... but is related to another variable that was not analyzed? For example, perhaps those who live in an area with high incidence of UV, and from wealthy economies (spending more per-capita on health care) are more likely to use sunscreen? Does sunscreen put one at risk then for endometrial cancer? Or... maybe populations with low UV exposure are exposed to a carcinogen in winter that warmer climates avoid? Perhaps endometrial cancer risk increases by relaxing in-front of a fireplace? Or, perhaps, those in the Northern climates eat more meat, are more likely to be obese, and consume less fish, fruits and vegetables - and UV exposure has nothing at all to do with it.

The bottom line is that this is an interesting study, but drawing the conclusion that sun lowers the risk of endometrial cancer is misleading, and premature. It is interesting that the authors did not title the article "Eating meat may increase the risk of Endometrial Cancer...." or "Obesity may increase the risk of Endometrial Cancer."

FYI: Here are some excellent dietary sources of vitamin D:

Fish liver oil
Fatty fish (ie: salmon, catfish, mackerel, sardines, tuna, eel)
Mushrooms
Eggs
Many other foods are fortified with Vitamin D, including milk, cereal, and yogurt.