Higher circulating vitamin D levels were significantly associated with a lower risk of colorectal cancer

Vitamin D can be produced by sunlight on the skin, which helps maintain calcium levels in the body, thus keeping bones, teeth and muscles healthy (http:// In recent years, there has been increasing evidence that vitamin D may be beneficial to other chronic diseases, including some cancers Recently, scientists from the American Cancer Association, Harvard University Chen Zengxi School of public health and other institutions found that higher levels of circulating vitamin D were significantly associated with a lower risk of colorectal cancer Previously, scientists hypothesized that vitamin D could reduce the risk of colorectal cancer through a variety of pathways related to cell growth and regulation However, previous prospective studies have been inconsistent on whether high levels of circulating 25 hydroxyvitamin D (25 hydroxyvitamin d) are associated with a reduced risk of colorectal cancer In addition, a few randomized clinical trials on vitamin D supplements and colorectal cancer (http:// completed to date have not yet demonstrated a link between the two To address the "inconsistencies" of previous studies, in the new study, scientists used standardized criteria analysis (http:// to analyze participants' vitamin D levels from 17 prospective cohort studies (participant level data, collected before being diagnosed with colorectal cancer) The analysis involved more than 5700 cases of colorectal cancer from the United States, Europe and Asia, and 7100 controls The results showed that during follow-up (5.5 years on average), participants with low levels of circulating vitamin D increased their risk of colorectal cancer by 31% compared with those with adequate levels of circulating vitamin D to ensure bone health The higher circulating vitamin D concentration than required for bone health was associated with a 22% lower risk of colorectal cancer Even after adjusting for known risk factors for colorectal cancer, these associations still exist Vitamin D can be obtained from the diet, supplements and "sun exposure," the researchers said However, experts recommend that vitamin d be obtained through diet as much as possible, as excessive UV radiation is a major risk factor for skin cancer.