Low Vitamin D Levels Linked to High Risk of Premenopausal Breast Cancer

A recent study has found a further link between low vitamin D levels and premenopausal breast cancer.

The study, by researchers from the University of California, San Diego School of Medicine, examined 1,200 healthy women and found that those whose serum vitamin D levels were low during the three-month period just before diagnosis had approximately three times the risk of breast cancer as women in the highest vitamin D group.

Several previous studies have shown that low serum levels of vitamin D are associated with a higher risk of premenopausal breast cancer. 

Principal investigator, Dr Cedric Garland, Professor in the Department of Family and Preventive Medicine at UC San Diego, says “While the mechanisms by which vitamin D could prevent breast cancer are not fully understood, this study suggests that the association with low vitamin D in the blood is strongest late in the development of the cancer.”

Analyses of vitamin D levels measured more than 90 days before diagnosis have not conclusively established a relationship between serum levels and risk of premenopausal breast cancer. However, this new study points to the possibility of a relevant window of time for cancer prevention in the last three months preceding tumor diagnosis –a time physiologically critical to the growth of the tumor.

According to Dr Garland, this is likely to be the point at which the tumor may be most actively recruiting blood vessels required for tumor growth.  “Based on these data, further investigation of the role of vitamin D in reducing the incidence of premenopausal breast cancer, particularly during the late phases of its development, is warranted,” he said.

The new study drew upon nine million blood serum specimens frozen by the Department of Defense Serum Repository for routine disease surveillance.  The researchers thawed and analysed pre-diagnostic samples of serum from 1,200 women whose blood was drawn in the same time frame – samples from 600 women who later developed breast cancer, and from 600 women who remained healthy. 

A 2011 meta-analysis by Dr Garland and colleagues estimated that a vitamin D serum level of 50 ng/ml is associated with 50 per cent lower risk of breast cancer.  While there are some variations in absorption, those who consume 4000 IU per day of vitamin D from food or a supplement normally would reach a serum level of 50 ng/ml.

Vitamin D can be found in foods such as oily fish, eggs, dairy products such as milk and cheese, fortified cereals and mushrooms. In addition, the body itself aslo makes vitamin D when exposed to the sun.  Small doses of sun exposure, outside of the heat of the day between 10am and 4pm, are recommended.

You may also want to talk to your doctor about vitamin D supplements.

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