Saudi Arabian women with low vitamin D levels are at an increased risk of breast cancer, according to research published in the American Journal of Clinical Nutrition.
According to data from the Saudi Arabian National Cancer Registry, breast cancer was the most common cancer diagnosed in 2007, accounting for 26% of all newly diagnosed cancers in women. In Saudi Arabia, breast cancer is more commonly diagnosed in women under 40 than in the US. Past research has demonstrated a link between low vitamin D status and breast cancer risk. Fatimah Yousef, PhD and colleagues were interested in examining this association in Saudi Arabian women.
Saudi women are thought to have an increased risk of vitamin D deficiency because of their darker skin pigmentation and reduced UV exposure due to cultural clothing practices.
The researchers recruited 120 breast cancer cases and 120 age matched controls with no history of breast cancer. The women with breast cancer were between the ages of 18 and 75 with stage I-IV breast cancer. From June through August 2009, vitamin D status was assessed in all 240 women.
Mean vitamin D levels were significantly lower in women with breast cancer compared to controls (9 ng/ml and 15 ng/ml respectively). Sixty percent of cases and 38% of controls had vitamin D levels <10 ng/ml. Women with vitamin D levels <10 ng/ml had 6 times the odds of breast cancer compared with 4 times the odds of women with levels from 10-20 ng/ml.
These results confirm past research in other ethnic populations. The authors conclude:
“…the issue of vitamin D and breast cancer risk is a field of intense study, and many aspects of this association require further investigation. Here we provided evidence of a significant association between low concentrations of circulating 25(OH)D and a higher risk of breast cancer…of women residing in Saudi Arabia— a high-risk population. Importantly, although mean serum 25(OH)D concentrations were very low in the study sample overall, significant differences between cases and controls were observed.”