What Vitamin D Has To Offer For Cancer Patients?

Vitamin D, a fat soluble vitamin, is recognized for its favorable effects on human bones and teeth. A proper maintenance of bone structure requires regulation of calcium and phosphorus levels in the blood. Vitamin D aids the absorption of these minerals from the intestine.

It is also studied for its potential benefits in general medical problems like type 1 diabetes, hypertension and heart diseases. In the recent years, vitamin D has also been extensively studied for its beneficial effects on various types of cancers.

Vitamin D is proposed to play a preventive role in many cancers

Several studies have attempted to establish the relationship between vitamin D and cancerous conditions of breast, colon, prostate, skin and pancreas. Most of the studies produced promising results, especially for breast, prostate and colorectal cancers. To understand how vitamin D helps in these diseases, we have to briefly consider how it works in the body.

It is a well-established fact that human body can synthesize vitamin D via the action of sunlight on skin. Ultraviolet B rays of the sun act upon a substance called 7-dehydrocholesterol in the skin and convert it into Vitamin D₃ (cholecalciferol). A major share of the vitamin is synthesized by the body and a minor share is obtained from dietary sources such as fish, eggs, dairy products and juices fortified with vitamin D. Animal sources provide vitamin D₃ and plant sources provide vitamin D₂ (ergocalciferol).  But both of these natural forms of vitamin D are in their inactive state. A series of metabolic processes that take place in the liver and kidney convert inactive vitamin D to the active form called calcitriol. This metabolite has more of a hormonal activity. It is this active metabolite that carries out a wide range of functions, one of which is proposed to be the cancer-preventive effect.

The action of calcitriol is mediated through receptors that specifically bind with this metabolite of vitamin D. These are intracellular receptors called Vitamin D Receptors, or VDR, and they are present in many organs. Intestine, kidneys and bones are the main target organs of calcitriol. The important function of calcitriol is the regulation of blood calcium and phosphorus levels. These two minerals are absorbed from the intestine and utilized in bone formation and maintenance by a series of reactions mediated by the vitamin D-VDR complex.

Studies explain the mechanism by which vitamin D exerts its anti-cancer effect

Several studies have identified that in addition to the intestine, kidney and bones, many organs of the human body like brain, heart, skin, breast and prostate glands express vitamin D receptor. The degree to which a tumor cell in these organs expresses the receptor determines the cell’s response to calcitriol. The receptors are expressed to a higher degree in the early stages of cancer and they are poorly expressed during advanced stages and metastasis.

See Also: Vitamin D - How Much Do We Need And How Do We Get It?

Calcitriol is suggested to inhibit tumor growth and prevent metastasis by three specific actions on the tumor micro-environment:

• It maintains differentiation – When immature cells grow into mature cells, they take the specific structure and functions particular to the organ they are constituted of. This is called differentiation. They grow to resemble the normal cells of the organ and are called well-differentiated. When a tumor cell divides it may form well-differentiated cells (cells resembling the normal cells of the organ) or poorly-differentiated cells (cells that stay immature). Calcitriol helps to maintain differentiation in a tumor tissue.
• It promotes apoptosis –The genetically determined ‘programmed cell death’ that happens through a cascade of events to all normal but old and damaged cells is called apoptosis. This process is essential to remove unwanted cells. Cancer cells avoid this process thus resulting in unlimited cell growth and division. Calcitriol promotes apoptosis and limits tumor growth.
• It inhibits angiogenesis – A growing tumor requires a lot of blood supply. In order to meet this requirement, new networks of blood vessels are continuously formed as the tumor grows. This facilitates the spread of tumor to the nearby tissues and distant organs (metastasis). The process of formation of new blood vessels is called angiogenesis. By inhibiting this process, calcitriol prevents tumor growth and metastasis.

Vitamin D Has The Potential To Increase Survival Rates In Breast Cancer Patients

With strong evidences to prove the potential anti-cancer and cancer-preventive effects of vitamin D, researchers have explored the vitamin in recent years to bring about the best out of it in cancer management.

A recent study reports that low vitamin D levels in breast cancer patients were associated with low survival rates of those patients. The researchers of the University of California reported that breast cancer patients with high levels of vitamin D in their serum have twice the survival rate when compared to those patients who have low levels of the vitamin. Though further studies are still needed to fully confirm these findings, they support the view that vitamin D in safe recommended dosages has to be added as a part of therapy in breast cancer treatment. Researchers urge that measuring the levels of vitamin D in a breast cancer patient at the time of diagnosis would help to control early cancer by supplementing vitamin D in that patient.

Vitamin D has potential anti-cancer and cancer-preventive effect on many other cancers

Several studies with regards to the beneficial effects of vitamin D on various cancers have been performed. Animal studies conducted on mice reported that administration of vitamin D₃ can inhibit tumor growth in early stages of prostate cancer while at later stages it is not that effective.

See Also: Vitamin D And Bone Health

Though most of the studies support the use of this vitamin as a supplementary therapy in cancer prevention and treatment, the clinical results are often inconsistent. At present, the recommended daily dose of vitamin D for adults is 600 IU which comes to 15 micrograms per day. For elderly people over 70 years, the dose recommended is 800 IU (20 micrograms). Though vitamin D is an essential micro-nutrient, very high doses may result in an unwanted increase in serum calcium levels which is also detrimental. Researchers understand the complexity of this issue and suggest performing trials to analyze the beneficial effects of other forms of vitamin D (Vitamin D analogs) which may very well have anti-cancer and cancer-preventive effects without producing the undesirable effects.