In a global breast cancer study, scientists compared the rates of breast cancer for women in 107 countries, calculating the amount of sunlight (UVB) and blood levels of vitamin D. Women in countries with higher average vitamin D levels had lower rates of breast cancer. The farther from the equator, meaning less sunlight, the higher the rate of breast cancer. Doctors noted this is the first worldwide study to show that as vitamin D levels increase, breast cancer decreases.
In a breast cancer study, researchers measured vitamin D levels in 1,394 women with breast cancer, aged 50 to 74, and in 1,365 healthy women of matching ages, and followed up for four years. Women with high blood levels of vitamin D were 69 percent less likely to develop breast cancer than women with low levels. Even women whose vitamin D levels were slightly above average were 43 percent less likely to develop breast cancer than women with low levels. Among women with good vitamin D levels, those who had never taken synthetic hormone replacement therapy (HRT) were less likely to develop breast cancer compared to women who had taken or were taking HRT.
In another breast cancer study, investigators measured the amount of fatty acids in the blood of 363 women with breast cancer and compared them with women without breast cancer. Breast cancer risk rose as blood levels of trans-fatty acids increased, which doctors said reflected a diet of highly processed foods containing trans-fats.
In a breast tissue study, scientists examined the fatty breast tissue of 241 women with invasive breast cancer and 88 women with benign breast disease, not breast cancer, and found that as tissue levels of omega-3 fatty acid rose, breast cancer risk decreased. Risk was 61 percent lower for women with the highest levels of alpha-linoleic acid compared to those with the lowest levels. Risk was 67 percent lower for women with the highest ratio of omega-3 to omega-6, a result doctors said supports the theory that the balance between these fatty acids plays a role in breast cancer.
Reference: Carcinogenesis; 2008, Vol. 29, No. 1, 93-9.