Cancer and Vitamin D Supplementation

Several observational studies have suggested that low vitamin D levels may be associated with increased risk of cancer. These observations are supported by studies in humans as well as in animal models. However, prospective cohort studies have also examined the relationship between vitamin D intake and cancer.

In an early prospective study, Caucasian women with adequate dietary vitamin D were found to have a significantly reduced risk of breast cancer 20 years later. Similarly, the highest serum 25-hydroxyvitamin D concentrations were associated with a 35% lower risk of colorectal cancer-specific mortality.

There is also evidence that the lowest tertile of serum 25-hydroxyvitamin D levels is associated with increased risks of cardiovascular disease and cancer. In addition, this analysis suggests that people with metabolic syndrome (dyslipidemia, hypertension, and type 2 diabetes) are at a higher risk of developing these diseases.

Despite the potential benefits of vitamin D supplementation, the majority of observational studies have shown no association between high intakes of vitamin D and disease. Moreover, insufficient vitamin D status may have adverse consequences on glucose tolerance in type 2 diabetic patients. In this context, it is important to study vitamin D supplementation in well-designed clinical trials.

Although it is possible to obtain adequate amounts of vitamin D through diet, it may be difficult to achieve optimal levels. For example, if you have gastrointestinal disorders, have undergone gastric bypass surgery, or are a smoker, you may have a hard time absorbing enough vitamin D from your food. This is especially true if you have darker skin. It is also possible that inadequate sunlight exposure contributes to this problem.