The study involved over half a million participants of the European Prospective Investigation into Cancer Study (EPIC), and during the study 1,248 people were diagnosed with colorectal cancer. Those in the top fifth of blood levels of vitamin D had a 40% reduced risk.
This adds to a growing body of evidence that people living in the Northern hemisphere have an increased risk of a number of cancer, plus weakened immune systems possibly resulting in more winter-related infections. Indeed a meta-analysis of trials, published in the American Journal of Preventive Medicine also reported that higher blood levels of vitamin D were associated with a lower risk of colon cancer.
While there is a need for well designed studies giving people vitamin D supplements versus placebos, given that cancer is a long time coming and definite results may be a decade away, there is certainly a good logical basis for making sure you are in that top fifth of vitamin D status. The blood level that correlated with this lower risk was a level above 100 nmol/l.
To achieve this kind of level means a daily intake of vitamin D of at least 1000ius or 25mcg a day, assuming you have some basic sun exposure. That’s 25mcg a day. Most multis only give 5mcg a day. Mine (Optimum Nutrition Formula) is somewhat better, giving 15mcg a day but even this might not be enough in winter, depending on your diet and sun exposure.
A serving of mackerel gives you are 350iu (9mcg) so, on those days you eat a serving or oily fish you are in the right ballpark. But if you don’t eat oily fish you are likely to fal short. It does also emphasize the need for sun exposure during the winter. Other options are a winter holiday, to boost your vitamin D stores, ideally eating lots of fish, or occasional use of a sun bed, or additional vitamin D supplementation of about 10mcg a day, on top of a multivitamin providing 15mcg.
If you’d like to learn more about vitamin D, which is also good for your bones and your brain, helping to cheer you up in the winter, read my Special Report – Vitamin D – Why You Are Almost Certainly Not Getting Enough.