Over the last 30 years, evidence has accumulated that shows higher vitamin D status intake or higher 25-hydroxyvitamin D levels may prevent cancer. Since 1980, 16 different cancers have been shown to be associated with low vitamin D!
Studies in cultured cells done with calcitriol (active vitamin D) show that it may affect cancer in numerous ways. Some of the most important capabilities of calcitriol seem to include the following:
Suppressing the proliferation of cells; cancer arises from abnormal cell proliferation
Promoting the death of abnormal cells that may become cancerous
Preventing blood vessels from forming in a developing tumor, which keeps nutrients from the tumor and prevents it from getting bigger
Stopping cancer cells from spreading to other parts of the body, thereby preventing metastases, the spread of cancer to healthy organs
Doctors are not yet at the point where they can recommend a specific level of 25-hydroxyvitamin D in the blood that can prevent or help to treat any specific cancer.
How vitamin D promotes normal cell growth
When vitamin D is converted to calcitriol, it can decrease cell division and increase normal maturation of cells. Both of these events should slow the development of cancer. Calcitriol may do this in a number of ways:
Stimulates the production of proteins, such as p21 and p27, which stop cells from multiplying.
Stimulates the production of E-cadherin, a protein that binds cells together. When E-cadherin is lost, cancer can leave the tumor and spread.
Inhibits the function of beta catenin, a protein that regulates genes that cause cells to multiply. Increased activity of beta catenin is involved in a number of cancers, including skin cancer, colorectal cancer, and ovarian cancer.
Blocks the production and action of prostaglandins, fatty substances that promote the construction of blood vessels and stimulate cell growth.
How vitamin D encourages the death of abnormal cells
Calcitriol not only protects against the development and growth of cancer cells, but also destroys cells that may turn into cancer. It causes apoptosis (death) of cells that have acquired changes that could make them cancerous or malignant.
Calcitriol may cause cell death in two ways. First, it may stimulate apoptosis by prompting the release of calcium from special storage spots inside cells. In cancer cells, calcitriol can also block the production of proteins that prevent cell death while enhancing the production of proteins that cause cell death.
As a result, calcitriol may also sensitize cancer cells to cancer treatments like radiation therapy and chemotherapy, which further enhances the death of cancer cells.
How vitamin D protects cells from things that cause cancer
Scientists have been using new and sophisticated tools to examine all the ways that calcitriol might influence normal or cancerous cells. These studies have shown that calcitriol affects more than just controlling how cells multiply or die. Some of these new roles include:
Induces the production of proteins that repair damage to the genes caused by factors like UV light from sunlight. DNA damage to genes is what causes mutations, and these mutations can affect the function of a gene thereby starting the process of cancer.
Regulates the ability of cells to control molecules that can damage DNA or proteins. These molecules are called reactive oxygen species (ROS).
Suppresses the production of chemicals that cause inflammation. Inflammation is a process that can make cancer develop more quickly or aggressively.
Vitamin D’s effect for those who already have cancer
The current thinking is that vitamin D, as calcitriol, may help your body ward off cancer before it forms or that it slows and kills cancer cells at the earliest stages (soon after they’ve formed) so that it never develops into a disease that needs treatment by a doctor.
The reason for this is that cancer is a creative disease. It figures out ways to get around all of the protections your body has to fight it. For example, whereas your immune system normally recognizes abnormal cells and kills them, tumors have developed ways to shut down this protection.
The same thing also seems to be happening with vitamin D. There is evidence that as a cancer moves through the stages to become more advanced, the cancer makes it harder for vitamin D to work. In some cancers the level or function of the vitamin D receptor is reduced; in others, enzymes that break down calcitriol are increased; and in others, the production of calcitriol is shut down in the cancer tissue.
However, doctors have seen all the good things that calcitriol appears to do to cancer cells in cell cultures, so they have also been trying to use calcitriol or drugs based on its structure as a way to treat established cancer. Calcitriol has been used alone and in combination with anti-cancer drugs.
One major problem is that calcitriol is so potent at controlling calcium metabolism that the levels needed to treat established cancer cause hypercalcemia (excessively high blood levels of calcium). Hypercalcemia, in any patient, can cause nausea, vomiting dehydration, weight loss, muscle weakness, confusion, and even coma and death. Consequently, calcitriol has been largely abandoned as a potential cancer treatment.
If it proves effective, the form of vitamin D that might become used in the treatment of cancer is not the vitamin D that you eat or that you make in your skin, but it will be a synthetic drug which has some similarity to calcitriol, the active form of vitamin D.