Higher blood levels of vitamin D may not reduce the risk of developing rarer cancers, reports a new US study.
In the study, data based on blood samples originally drawn for ten individual trials were combined to investigate whether people with high levels of vitamin D were less likely to develop rarer cancers such as non-Hodgkin lymphoma or cancer of the endometrium, esophagus, stomach, kidney, ovary, or pancreas (1). Over 12,000 men and women from the United States, Finland, and China participating in one of the studies were followed for the development of cancer for up to 33 years, depending on the study. Investigators then compared cancer rates in participants whose levels of 25-hydroxyvitamin D (25(OH)D) in stored blood were high (above 75 nanomoles per liter) or low (less than 25 nmol/L) with rates in participants whose levels of vitamin D were within the normal range (50 to 75 nmol/L). The results showed no lower cancer risk in persons with high vitamin D blood concentrations compared to normal concentrations for any of the cancers, and no higher cancer risk for participants with low levels.
Experts commented that these results are not surprising as cancer is a multifactorial disease and vitamin D is not a magic bullet for preventing cancer development. While vitamin D is essential for healthy bones, calcium absorption, and immune function, the evidence that higher levels of vitamin D are associated with a lower risk of cancer is inconsistent.
As in other studies, individuals with higher vitamin D levels were more likely to be male, lean, and physically active. Those with higher levels also reported greater intake of multivitamins, calcium supplements, and foods rich in vitamin D. Many people around the world have low concentrations of 25(OH)D.