Link Between High Vitamin D Levels And Lower Risk Of Colorectal Cancer

22.01.2010

A large European study published on bmj.com today reports that high blood levels of vitamin D are associated with a lower risk of colon cancer. The risk dropped by as much as 40 percent in people with the highest levels compared with those in the lowest. 

Colorectal cancer is the combination of colon and rectal cancer cases. The link between vitamin D and colorectal cancer had already been highlighted in a number of earlier studies. But with limited information from European populations, the evidence has been uncertain. 

In order to find out more, researchers from across Europe began to study the association between circulating vitamin D concentration as well as dietary intakes of vitamin D and calcium with colorectal cancer risk in Western European populations. 

Results are based on the European Prospective Investigation into Cancer Study (EPIC). It is a study that included over 520,000 subjects from ten Western European countries. 

All participants completed detailed dietary and lifestyle questionnaires, between 1992 and 1998. Blood samples were collected. The subjects were then monitored for several years. During follow-up, 1,248 cases of colorectal cancer were diagnosed and these were matched to 1,248 healthy controls. 

Findings indicated that participants with the highest levels of blood vitamin D concentration had a nearly 40 percent decrease in colorectal cancer risk when compared to those with the lowest levels. 

On the other hand, for colorectal cancer prevention, some recent publications have recommended maintenance of blood vitamin D levels at 50 nmol/l or higher. Consequently, the authors also compared low and high levels of blood vitamin D concentration to a mid-level of 50-75 nmol/l. This evaluation indicated that while levels below the mid-level were associated with increased risk, those above 75 nmol/l were not associated with any additional reduction in colon cancer risk compared to the mid-level. 

The results support a function for vitamin D in the study of the cause of colorectal cancer. But the authors warn that very little is known about the association of vitamin D with other cancers. Moreover, the long term health effects of very high circulating vitamin D concentrations are still not fully investigated. Those vitamin D concentrations would be potentially obtained by taking supplements and/or widespread fortification of some food products. 

The authors explain that with respect to colorectal cancer protection, it is still unclear whether inducing higher blood vitamin D concentration by supplementation is better than average levels. Those standard levels can be achieved with a balanced diet combined with regular and moderate exposure to outdoor sunlight. 

There are conflicting findings from earlier randomized trials. The authors conclude that new trials should be carried out to determine whether increases in circulating vitamin D concentration can in fact reduce colorectal cancer risk without inducing serious adverse events. 
At this time, the best recommendations to reduce the risk of colorectal cancer are to: 

• stop smoking 
• increase physical activity
• reduce obesity and abdominal fatness
• limit intakes of alcohol and red and processed meats

Source:  Stephanie Brunner (B.A.)