New Study Finds Correlation Between Low Vitamin D Levels and Breast Cancer
Like many vitamins, vitamin D is versatile. It has long been associated with bone development, but severe deficiency can result in diseases, such as rickets. Recent studies found some correlation between vitamin D levels and cardiovascular health, the development of multiple sclerosis, tuberculosis infection and now pre-menopausal breast cancer. Researchers at the San Diego School of Medicine of the University of California have found that low levels of serum (blood) vitamin D are associated with a crucial period of tumor formation for breast cancer.
Breast cancer is the most common form of cancer for women in the United States and it is one of the cancers where early diagnosis is crucial. For many purposes, doctors consider breast cancer in two somewhat different development tracks – pre and post menopause. As a woman’s body chemistry changes through menopause, so too do the types and behavior of breast cancer formation.
Pre-menopausal breast cancer may have different hormonal triggers as well as other subtle conditions not found in post-menopausal cancer, so researchers tend to conduct their experiments somewhat differently for each. In the case of the San Diego study, the blood serum levels of vitamin D from 1200 healthy pre-menopausal women were the basis for the analysis. The serum came from the more than 9 million blood serum specimens frozen by the U.S. Department of Defense Serum Repository. Among the 1200 women, 600 later developed breast cancer (and 600 remained healthy).
Analysis of the vitamin levels pointed to a definite pattern: women whose vitamin D levels were low during a three month period just prior to diagnosis had three times the risk of breast cancer as women with the highest levels of vitamin D. Three times the risk is a persuasive correlation, but the researchers stress that their study does not conclusively establish either the link or the biochemical explanation.
Doctors speculate that the three-month period prior to diagnosis of breast cancer is the time when the tumor or tumors are in an aggressive formation stage and require the development of a blood vessel system (vasculature) to support the rapid growth. Vitamin D seems to have a retardant effect on this blood vessel formation. Conversely, the lack of vitamin D allows for more rapid tumor growth.
In 2011, the same researchers, headed by Cedric Garland at UC San Diego, found in another study that a blood serum level of 50 nanograms per milliliter (ng/ml) is associated with a 50 percent lower risk of breast cancer. To achieve this level, women need to take 4000 International Units (IU) of vitamin D per day. To date, studies indicate that this is a safe level of vitamin D, whether acquired from food or man-made supplements. However, it is also recommended that women discuss taking this amount of vitamin D with their doctor before proceeding. In most cases, it’s advisable to test for a blood serum level of 25-hydroxyvitamin D (the natural form created by the body through the skin or in the kidneys).
As far as the researchers could tell from the data, using different forms of vitamin D (there are two main forms – vitamin D2 and D3) does not make a difference in the effect. They also caution that taking megadoses of vitamin D should be avoided except where a doctor prescribes them for short-term use.
This study, published in the journal Cancer Causes and Control, does not establish the fundamental explanation for why vitamin D has a positive effect on limiting the development of breast cancer. In this, it is very much like most other vitamins, where the correlations between health and the vitamin are common, but detailed biochemical explanations are lacking. This accounts for at least some of the apparently contradictory studies that abound in the vitamin research field.
In this case, the UC San Diego researchers are continuing their work on the timing of vitamin D levels, which should be highest at about three months before tumors are possibly diagnosed. They are looking for ways to make the analysis of vitamin D levels a reliable indicator of risk for breast cancer. They are also considering the possible chemical pathways that lead vitamin D to play such a (possibly) important role in halting or abetting the growth of breast cancer.