In this article, I will be exploring the roles of vitamin D in colon cancer. Research evidence reveals how vitamin D influences the composition of the gastrointestinal microbiome; the collection of microbes living in the human gut (1). The alteration of the microbe populations present in the large intestine contributes to the development of colon cancer and the deficiency of vitamin D is identified as a contributing factor (2). In colon cancer, there is a gradual destructive alteration of the epithelium of the large intestine. This type of cancer is a major health problem and a leading cause of cancer-related death worldwide. The large intestine is the last part of the digestive system. It functions by absorbing water from the remaining indigestible food materials, after which the waste materials are excreted from the body. The large intestine comprises the cecum, colon, rectum, and anal canal. Interestingly, the intestine has the highest expression of vitamin D receptor and vitamin D3 (calcitriol) is the most active vitamin D metabolites with many important regulating actions in the large intestine (2).
How about vitamin D
Vitamin D is fat-soluble and exists naturally in some foods, added in fortified foods, and is available as a food supplement. Also, it is synthesized endogenously through ultraviolet rays from sunlight on the skin. The form of vitamin D obtained from food sources, supplements and sun exposure is biologically inactive. Therefore, vitamin D must be transformed into the body for it to be active. The first transformation takes place in the liver and converts vitamin D to 25-hydroxyvitamin D also called calcidiol. The second transformation takes place in the kidney and converts vitamin D to 1,25-dihydroxyvitamin D also called calcitriol or vitamin D3.
Research highlights on Vitamin D in colon cancer (3,4,5)
- Colon cancer is the uncontrolled growth of cells that are most often linked to vitamin D deficiency.
- Vitamin D3 (Calcitriol) inhibits the spread, movement, intrusiveness and the growth of new blood vessels of colon carcinoma cells.
- Vitamin D3 promotes the separation of colon cancer cells and prepares them for destruction.
- Vitamin D3 reduces the pro-tumour effects of colon cancer.
- Vitamin D3 regulates the biology of intestinal immune cells and thereby enhancing the array of microbes in the gut.
- Vitamin D ensures the correct level of antimicrobial peptides in the secretion and maintains epithelial integrity.
Other beneficial roles of Vitamin D in colon cancer
Vitamin D3 has a wide immune regulating effect by acting on a range of immune cells. It acts as an anti-inflammatory agent by maintaining regulatory homeostatic role of the immune system against adverse situations. It acts as a repressor thereby preventing over-activation which could lead to undesirable consequences in the colon.
Vitamin D3 plays a vital role in the detoxification process in the intestine by controlling the expression of antioxidant, the enzymes involved in the catabolism of compounds including bile acids and other compounds that promote the development of colon cancer.
Dietary Vitamin D and recommended levels
The human body obtained Vitamin D through sun exposure and also from natural and fortified foods, and dietary supplements. Sun exposure, dietary vitamin D with calcium intake, and serum vitamin D concentration reduce the risk of colon cancer (4). A recent study suggests that optimal circulation of vitamin D of between 75 and 100 nmol/L concentrations is necessary for colon cancer risk reduction (5).
Sadly, the prevalence of vitamin D deficiency is on the increase worldwide with about half of the world’s population having a low level of vitamin D (levels below 75 nmol/L). Fortunately, 80% of the vitamin D needed by the human body can be synthesized in the presence of ultraviolet rays from sunlight. The remaining 20% can be obtained from the diet and food supplements. Foods rich in vitamin D include fatty fish such as tuna, mackerel, and salmon, beef liver and cheese. People who have inadequate exposure to sunlight such as house bound elderly and the sick need to have an adequate supply of vitamin D from the diet or food supplements.
The requirements for vitamin D are higher for adolescents, pregnant and lactating women. A recommended serum level of 75 nmol/L is the minimum vitamin D necessary to maintain good health. A supplementation of 2000IU to 5000IU/day is considered adequate to achieve and maintain the recommended serum vitamin D levels (6). A low vitamin D diet and vitamin D receptor deficiency has been shown to cause an imbalance between the types of the organism in the gut of experimental mice. This kind of imbalance in human’s natural microflora can lead to a range of ill conditions (5).
Conclusion
Evidence of the beneficial effect of vitamin D in colon cancer prevention is strong. Also, epidemiological data associate vitamin D deficiency with a higher risk of colon cancer. The indirect antitumor effect of vitamin D is credible and needs to be utilized in practice. The mechanism of vitamin D3’s protective effects against colon cancer is by acting on carcinoma cells, immune cells and also the gut microbiota.
