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A new international study by scientists from various institutions (including Oxford University in England) came to the conclusion that high concentrations of circulating vitamin D in the blood are associated with a reduced risk of colorectal cancer. The concentration of the vitamin for the prevention of colorectal cancer could therefore be higher than previously assumed in other studies.
What is colorectal cancer?
Colorectal carcinomas are carcinomas of the large intestine (colon) and rectum. They account for around 95% of malignant bowel tumours. In Germany, colorectal cancer is the th most common cancer in men after prostate and lung cancer, and the second most common in women after breast cancer. Colorectal cancers rarely show symptoms at the beginning. They develop from benign intestinal polyps. Every year, around 30,000 people in Germany die from colorectal cancer.
Study: Vitamin D reduces the risk of bowel cancer
Vitamin D plays a special role in bone metabolism, in supporting the immune system and in regulating calcium-phosphate metabolism. Scientists have long assumed that the vitamin also reduces the risk of colorectal cancer by positively influencing various processes in the body. However, studies carried out to date have shown negative or no results as to whether higher concentrations of circulating 25-hydroxyvitamin D are associated with a lower risk of colorectal cancer. 25-hydroxyvitamin D is the precursor of biologically active vitamin D and is used to determine the vitamin D status in the blood. The sometimes small number of test subjects in the studies or the short duration of intake as well as different measurement methods could have contributed to the fact that no positive effect could be shown.
In order to explain these discrepancies in more detail, the scientists analysed 17 studies conducted in the USA, Europe and Asia. They analysed the concentration of 25-hydroxyvitamin D for 5,706 colorectal cancer cases and 7,107 controls. The proportion of men and women was almost equal. About one third of the participants had their status redetermined. The vitamin D measurements were calibrated in order to be able to compare the existing 25-hydroxyvitamin D values in the blood.
Results of the vitamin D study
An insufficient concentration of vitamin D in the blood (below 30 nmol/L) led to a 31% higher risk of developing colorectal cancer during follow-up (average 5.5 years) than subjects with a blood concentration of 50-62.6 nmol/L. It is known that a concentration of 50-62.6 nmol/L maintains bone health. Concentrations of 87.5-100 nmol/L led to a 27% reduced risk of bowel cancer. Values above 100 nmol/L did not yield any additional positive results. At concentrations above the bone health limit, the positive effect was significantly more pronounced in women than in men. This could be due to the fact that oestrogen has a positive effect on vitamin D activity.
Conclusion
High vitamin D status leads to a reduced risk of colorectal cancer. Women were more affected by this than men. According to the study, the optimal vitamin D concentration in the blood is 75-100nmol/L to reduce the risk of colorectal cancer. Nevertheless, further studies are needed here too.
P.S.: As excessive ultraviolet radiation is a major risk factor for skin cancer, we recommend taking the vitamin via supplements. Our Nutri-Plus Sun Vitamin is ideal for this purpose.
