ROLE OF VITAMIN D

IN

PREVENTION OF CANCER

PRESENTED BY:MR. ASHWIN THOMAS, MSN

HIND COLLEGE OF NURSING,

LUCKNOW, U.P.

INTRODUCTION: Among the diseases of modern times,

the term cancer has encircled the health sectors nowadays. Because of the limited treatment modalities available in medicine today, the emphasis is shifting on finding a way or ways to prevent cancers.

In that relation, recent research results and studies are pointing towards vitamin D as the possible aid in preventing malignancy.

OVERVIEW OF VITAMIN D:

Vitamin D is a group of fat-soluble prohormones the two major forms of which are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). The term vitamin D also refers to metabolites and other analogues of these substances. Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B radiation.

FUNCTIONS OF VITAMIN D:

Maintenance of organ systems.

Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestines, and by promoting re-absorption of calcium in the kidneys. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts.

In the absence of vitamin K Vitamin D can promote soft tissue calcification.

It inhibits parathyroid hormone secretion from the parathyroid gland.

Vitamin D affects the immune system by promoting phagocytosis, and immunomodulatory functions.

VITAMIN D IN CANCER PREVENTION AND RECOVERY:

The vitamin D hormone, calcitriol, has been found to induce death of cancer cells. Although the anti-cancer activity of vitamin D is not fully understood, it is thought that these effects are mediated through vitamin D receptors expressed in cancer cells, and may be related to its immunomodulatory abilities. The anti-cancer activity of vitamin D observed in the laboratory has prompted some to propose that vitamin D supplementation might be beneficial in the treatment or prevention of some types of cancer.

Vitamin D regulates the expression of genes associated with cancers and autoimmune disease by controlling the activation of the vitamin D receptor (VDR), a type 1 nuclear receptor and DNA transcription factor. Research has indicated that vitamin D deficiency is linked to colon cancer and more recently, to breast cancer.The Canadian Cancer Society recommends that adults should consider supplementing with 1,000 IU of vitamin D per day during the fall and winter. They base this recommendation on the growing evidence for a link between vitamin D and a reduced risk for colorectal, breast and prostate cancers.

Cancer prevention specialists have concluded that taking 1,000 international units (IU) of vitamin D3 per day may lower an individual’s risk of developing certain cancers, including breast, colon, prostate, and ovarian, by up to 50 percent.

In 2007, scientists released a study which demonstrated a beneficial correlation between vitamin D intake and prevention of cancer. Drawing from a meta analysis of 63 published reports, the authors showed that intake of an additional 1,000 international units (IU) (or 25 micrograms) of vitamin D daily reduced an individual's colon cancer risk by 50%, and breast and ovarian cancer risks by 30%. Research has also shown a beneficial effect of high levels of calcitriol on patients with advanced prostate cancer.

A randomized intervention study involving 1,200 women, published in June 2007, reports that vitamin D supplementation (1,100 international units (IU)/day) resulted in a 60% reduction in cancer incidence, during a four-year clinical trial, rising to a 77% reduction for cancers diagnosed after the first year (and therefore excluding those cancers more likely to have originated prior to the vitamin D intervention).In 2006, a study at Northwest University found that taking the U.S. RDA of vitamin D (400 IU per day) cut the risk of pancreatic cancer by 43% in a sample of more than 120,000 people from two long-term health surveys.

A 2008 study using data on over 4 million cancer patients from 13 different countries showed a marked difference in cancer risk between countries classified as sunny and countries classified as less–sunny for a number of different cancers. Research has also suggested that cancer patients who have surgery or treatment in the summer therefore make more endogenous vitamin D and have a better chance of surviving their cancer than those who undergo treatment in the winter when they are exposed to less sunlight.

The breast cancer study, published online in the current issue of the Journal of Steroid Biochemistry and Molecular Biology, pooled dose-response data and found that individuals with the highest blood levels of 25-hydroxyvitamin D, or 25(OH)D, had the lowest risk of breast cancer.

New research published this month shows that vitamin D supplementation produces an astonishing 77 percent reduction in all cancers in women, making it the single most effective medicine for preventing cancer that has ever been discovered by modern medical science.

Recently, research led by Kimmie Ng, M.D., M.P.H., of the Dana-Farber Cancer Institute has revealed that vitamin D can improve the survival rates of people with colorectal cancer. The findings of this study are very significant because, in a way, they break new ground. While previous research had largely centered on how vitamin D levels reduce colorectal cancer incidence, this study has established a connection between vitamin D levels and the survival chances of people who have already gotten the disease.

FUTURE DIMENSIONS OF DISCOVERY:

Although the cohort findings are likely to increase enthusiasm for the cancer prevention potential of vitamin D, inherent limitations of observational epidemiologic studies combined with a history of prior disappointments with other potential chemo preventive agents suggest caution in their interpretation.

Two decades ago there was intense interest and hope that supplementation with beta-carotene might reduce the risk of several cancers. Epidemiologic studies have consistently reported that men and women with the highest dietary intakes of beta-carotene as well as with elevated blood levels experienced lower risks of respiratory, gastrointestinal, and other cancers. The zeal was crushed, however, when randomized trials in the United States and Finland showed increased rather than decreased risks of lung cancer among adults receiving beta-carotene supplements.

Vitamin E was similarly touted as an inhibitor of cancer, as well as of cardiovascular disease, but again the "gold standard" of randomized trials failed to confirm the preventive correlations noted in cohort and case–control studies.

In each of these examples, the agents may have demonstrated benefit with modification of the dose, formulation, or timing of the intervention or with longer follow-up, but the sobering lesson is that trends observed in non experimental settings, including cohort studies, are not always confirmed experimentally when tested in randomized clinical trials.

Science, after all, is a continual process of hypothesis formulation, testing, and refinement.

Ecologic (e.g., geographic correlations) and analytic (e.g., cohort and case–control) studies provide the evidence-based clues to cancer etiology, but randomized trials are generally needed to confirm these leads and develop effective disease prevention strategies.

CONCLUSIONS:The role of vitamin D in cancer

prevention is strongly suggested by epidemiologic observations and potential mechanisms have been identified by experimental studies. The promising results from both observational and laboratory studies should usher in a new era of intervention studies of vitamin D and cancer risk. Because many public health scientists are already clamoring for higher levels of vitamin D supplementation for bone and other health, randomized trials of vitamin D and cancer risk should be undertaken speedily.

If the promise of vitamin D holds, a brief walk in the sun may turn out to be a step toward cancer

prevention.

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