Vitamin D continues to hit the headlines, this time a study(1) finds an association between low vitamin D levels and increased risk of colorectal cancer.  Previously I wrote a detailed post regarding diet and lifestyle changes for colorectal cancer prevention which is certainly worth looking at in conjunction with this information.

The authors of the current study (1) wanted to examine the circulating blood vitamin D concentrations, dietary intakes of vitamin D and calcium, and the risk of colorectal cancer in European concentrations.  The researchers used data from more than 520,000 individuals, from these 1248 individuals with colorectal cancer (which developed after enrolment into the study), were compared/matched to 1248 control participants (without colorectal cancer). 

Low circulating vitamin D concentrations were linked to an increased risk of colorectal cancer and high circulating citamin D concentrations were linked to a reduced risk of colorectal cancer (1).  Analysis of data found that individuals with the highest circulating vitamin D concentrations had a 40% lower risk of colorectal cancer than those with the lowest levels.  Greater dietary intake of calcium was also associated with a lower colorectal cancer risk. 

This study only shows an association between low vitamin D levels and increased risk of colorectal cancer, no definitive conclusions can be drawn about whether low levels ‘cause’ cancer or not.  The authors of the study conclude that further randomised controlled trials are needed to assess whether increasing the circulating levels of vitamin D, through supplementation, can effectively decrease the risk of colorectal cancer (1).

In a press release (2) it was noted that some recent study publications have suggested maintenance of blood vitamin D levels at 50 nmol/l or higher are needed for colorectal cancer prevention (some doctors have recently been suggesting that blood levels of vitamin D of at least 40nmol/l are needed for optimal health).   The study, mentioned above, found that blood levels below the 50nmol/l mark were associated with an increase risk but that levels of vitamin D above the 75 nmol/l were not associated with any additional reduction in colon cancer risk. 

As mentioned in my previous posts on Vitamin D, frustratingly there is no consensus about the amount of daily vitamin D intake necessary to maintain blood levels at around 40-50nmol/l.  In the UK it is known that most people have low blood vitamin D levels. I would suggest most individuals in the UK would require a supplement of around 2000iu vitamin D daily.  Higher doses may be useful but I would not recommend such a regimen unless under the supervision of a medical doctor who can monitor blood levels regularly.

Of course, when it comes to colorectal cancer there are numerous other links between diet, lifestyle and risk – please read my previous post on the topic for more information. 

(1) Jenab et al.  2010.  Association between pre-diagnostic circulating vitamin D concentration and risk of colorectal cancer in European populations:a nested case-control study. BMJ.  340: b5500 DOI: 10.1136/bmj.b5500
(2)press release: BMJ-British Medical Journal (2010, January 22). High vitamin D levels linked to lower risk of colon cancer. ScienceDaily. Retrieved January 22, 2010, from http://www.sciencedaily.com/releases/2010/01/100122002340.htm
Written by Ani Kowal