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Nutrients for the Prevention of Colon Cancer

© David Olle

This article further describes the role of nutrition in the development of cancer; my first article on the subject was published on September 29, 2002. It is always better to prevent cancer than to try to treat the disease once it develops. Although drugs such as COX-2 inhibitors are showing promise in prevention of colorectal cancer, I will focus on the role of calcium, vitamin D, and folate in the prevention of this disease.

Calcium

Calcium performs a wide variety of functions in the body, but in terms of cancer, we will focus on its effect after binding to the calcium-sensing receptor protein on the surface of cells. This binding signals the activation of many chemical messengers within the cell. One result is an increase of calcium level within the cell, by releasing it from the endoplasmic reticulum. This released calcium binds with and stimulates protein kinase C, which promotes differentiation of cells (a healthy response). Protein kinase C signaling results in an inhibition of the cell cycle, thereby resulting in the arrest of abnormal cell growth. There is evidence to indicate that calcium may inhibit beta-catenin, which activates genes important in colon cancer. Several studies indicate the importance of calcium in regulating apoptosis, the programmed death of abnormal cells, such as cancer cells.

Vitamin D

After Vitamin D is absorbed into the blood from dietary sources or synthesis in the skin, it undergoes changes in the liver and kidney to a hormonal form called 1,25 dihydroxyvitamin D3. This hormonal form exerts its effect after binding to a vitamin D receptor located in the nucleus of the cell. The 1,25 vitamin D may be facilitated to enter the cell by a membrane bound receptor located on the surface of the cell. Vitamin D increases the expression of the tumor suppressor proteins p21 and p27. These tumor suppressors arrest the activity of the cell cycle, and thereby stop the abnormal proliferation of cells.

It is well known that vitamin D facilitates the absorption of calcium into cells. It is interesting that vitamin D stimulates the formation of calcium receptor protein and thereby enters the calcium metabolic scheme. Researchers believe that vitamin D has a more indirect role in the activities of other tumor suppressor or cancer causing genes. Vitamin D also induces apoptosis of abnormal cells by a variety of mechanisms.

Folic Acid

Folic acid is necessary to maintain adequate levels of purines and pyrimidines, the building blocks of DNA. Folic acid deficiency can lead to the syntheses of a defective DNA structure and chromosome breaks. Folic acid is also needed for the processes of methylation of certain sites on the DNA molecule. Inadequate methylation can lead to the activation of proto-oncogenes to cancer causing genes.