It was in April this year that Gulf Times reported more than 80% of the Qatari population suffer from low levels of Vitamin D, which is related to several chronic infirmities such as cardiovascular diseases, diabetes, several inflammatory diseases, and cancer. According to a large international study published last week in the Journal of the National Cancer Institute, US, Vitamin D may be protective against colorectal cancer. Incidentally, colorectal cancer is the third most commonly diagnosed cancer in Qatar and a leading cause of cancer-related deaths in both men and women in the country, it is learnt.
For both men and women, deficient levels of vitamin D were associated with a 30% increased risk of colorectal cancer, says Marji McCullough, a nutritional epidemiologist with the American Cancer Society and study co-author. People who had higher circulating blood levels of vitamin D, in a range deemed “sufficient,” had a 22% lower risk, she says. The study pooled findings from 17 previous studies that included 12,813 adults in the US, Europe and Asia. Those studies collectively looked at 5,706 people with colorectal cancer and 7,107 people of a similar age and race who didn’t have cancer. Women’s menopausal status was also taken into account.
To determine what role vitamin D might be playing, researchers looked at participants’ blood samples collected in the years before their cancer diagnosis. They also considered the established risk factors for colorectal cancer, including smoking, low physical activity and high body mass index. “Our findings suggest what’s optimal for bone health may not be optimal for colorectal risk reduction,” McCollough says, which could mean higher doses are needed to prevent cancer. Current recommendations for vitamin D supplementation are based solely on studies showing conclusively that it does preserve bone health.
An interesting observation in the study was that beyond a certain level, increasingly higher amounts of vitamin D in the blood had no effect: Levels of the vitamin that were higher than what is considered “adequate” were not associated with an even smaller risk. The take-home message is not to overindulge in vitamin D. The issue of whether vitamin D supplements should be used at all to prevent colorectal cancer is still up in the air. The study did not evaluate whether adding vitamin D through either food, sunlight, or supplements made a difference in cancer risk. It was limited to looking at the level of vitamin D in peoples’ blood.
People should talk with their healthcare provider about having a blood test to measure vitamin D levels. Vitamin D can be obtained from foods such as egg yolks, salmon, trout, swordfish, tuna and sardines. Numerous foods are fortified with vitamin D including cow’s milk, almond milk, soymilk, some cereals and some orange juices. Vitamin D is often called the “sunshine” vitamin, because exposure to sunlight can stimulate production of the vitamin. But, excessive exposure to sun is not recommended as a way to boost vitamin D, as it can raise the risk of melanoma and other skin cancers. So, moderation is the key.
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