Vitamin D is a substance that functions like a vitamin (as a fat-soluble vitamin it is stored in fat tissue in the body), but it is also a hormone. Its many activities include regulating bone health, muscle health, immune system response, insulin and blood sugar levels, and calcium and phosphorus metabolism.
Vitamin D (in the form of D3) is manufactured by the body through exposure to sunlight and it can also be obtained from a limited number of foods, and through supplements. The body also needs co-factors in order to properly utilize vitamin D. These include magnesium, zinc, vitamin K, boron, and small amounts of vitamin A.
Vitamin D is called the sunshine vitamin because the body makes it when ultraviolet radiation from the sun hits the skin. Sunshine is the main and most efficient source of vitamin D, as few foods contain very high amounts, and most people don’t get enough of the vitamin D from their food (More “Sources of Vitamin D“). There are always vitamin D supplements but the RDA for vitamin D is notoriously low and so even if people do take supplements, they often do not get enough from this source.
About two decades ago, a scientist named Schwartz proposed that vitamin D deficiency may play a significant role in prostate cancer, along with being black, age, and living in a northern latitude. (Schwartz 1990) All of these factors had one thing in common: they were associated with a decline in the manufacture of vitamin D.
In 1992, Schwartz and a colleague noted that men in the United States were ten times more likely to develop prostate cancer than their counterparts in Japan, where men consumed great amounts of vitamin D and omega-3 fatty acids in fatty fish. (Hanchette 1992) Scientists now know that omega-3s help raise the active levels of vitamin D metabolites in the blood, so fatty fish are an especially good source of vitamin D. When these researchers analyzed deaths due to prostate cancer in relation to sunlight, they found that men who received more sunlight were significantly less likely to die from prostate cancer.
One year later, a team of scientists discovered that all three of the prostate cancer cell lines they were studying had a vitamin D receptor and that the active form of vitamin D “dramatically inhibited” the growth of two of the three cancer cell lines. (Skowronski 1993) Several years later, Miller and colleagues looked at seven prostate cancer cell lines and found receptors for vitamin D on all of them. (Miller 1995) They also showed that calcitriol inhibited the growth of four of the seven, and that the more vitamin D receptors there were, the greater the inhibition of the cancer cells.
At that point, it appeared that vitamin D was getting recognized as a substance that could help prevent and treat prostate cancer. After Miller’s study appeared, scientists at Stanford University confirmed the findings and stated that
“Based on these findings, we postulate that vitamin D may have protective actions on the development and/or progression of prostate cancer. We further hypothesize that vitamin D supplementation may have beneficial effects on retarding the development and/or progression of prostate cancer.” (Feldman 1995)
More Studies on Vitamin D and Prostate Cancer
A 2000 study found that young men who had vitamin D levels below 40 nmol/L (16 ng/mL) were three times more likely to develop prostate cancer than were men who had higher levels. (Ahonen 2000)
In 2003, Chen and Holick at Boston University School of Medicine conducted a review of the research and concluded that “adequate exposure to sunlight or oral supplementation might provide a simple way to increase synthesis of vitamin D in the prostate and, therefore, decrease the risk of prostate cancer.” (Chen 2003)
At the University of Toronto, researchers showed that 2,000 IU of vitamin D3 either reduced or prevented further increases in PSA in most of the men who had advancing prostate cancer. (Woo 2005) This was the first time it was shown that simple vitamin D was effective in fighting cancer in humans.
Although the issue remains controversial, some researchers believe a vitamin D deficiency increases the risk of developing prostate cancer. (Lou 2004) This idea is supported by research like that in a 2009 report in the British Journal of Urology International, in which the investigators reported that men with prostate cancer were more likely to have low levels of vitamin D compared to men who did not have the disease. (Trump 2009)
In a small study published in BJU International in November 2009, 26 men who had current prostate cancer were given a daily dose of vitamin D. The PSA levels in five men declined: two by more than 50 percent, two by 25 to 50 percent, and in one by less than 25 percent. In the remaining patients, their PSA levels stabilized after treatment with vitamin D for up to 36 months. (Newsome-Davis 2009)
In 2009, British researchers reported that vitamin D successfully reduced or stabilized PSA levels in 20 percent of men who had asymptomatic progressive prostate cancer, and they concluded that vitamin D therapy was effective, well tolerated, and would be a useful addition to a man’s therapeutic options. (Waxman 2009)
One of the most recent studies (January 2010) reported that vitamin D has anti-inflammatory activity in prostate cancer along with its ability to inhibit tumor angiogenesis (growth of new blood cells in a tumor), invasion, and metastasis. (Krishnan 2010) The Stanford University researchers hypothesized that calcitriol’s anti-inflammatory actions, along with its known anti-cancer effects, are important “in its potential use as a therapeutic agent for prostate cancer.”
Vitamin D may also impact the prostate in another way. At least one study has reported that a low level of vitamin D circulating in the blood is linked to a greater risk of having an enlarged prostate. (Galic 2008)
What is the best Vitamin D Level?
The Vitamin D Council recommends that both children and adults maintain a blood level of higher than 50 ng/ml (125 nmol/L). The only way to know your vitamin D level is to get a blood test. Then how much vitamin D do you need to take? The Vitamin D Council recommends that you take an amount necessary to bring your blood levels to 50 to 80 ng/ml. Generally, healthy adults should take 5,000 IU daily and then have their vitamin D levels checked after two to three months to see if how they are progressing.
Sources of Vitamin D
Sunlight
Most people have insufficient or deficient levels of vitamin D. One reason for this deficiency is that the main and most efficient way to get enough vitamin D is through exposure to sunlight. According to the Vitamin D Council, the skin produces about 10,000 International Units (IUs) of vitamin D in response to 20 to 30 minutes of summer sun exposure. That’s 50 times more than the US government’s (Institute of Medicine’s) recommendation of only 200 IU.
Unfortunately, modern lifestyles often are not conducive to regular sun exposure for a great number of people. Most people work and spend much of their time indoors, children do not play outside as much as they used to, and older adults are often homebound or have limited access to sunlight. Also, there is a widespread campaign to “cover up” when in the sun that may be another reason for the widespread deficiency.
Diet
Dietary sources of vitamin D are limited. The healthiest and richest food sources of vitamin D are salmon and sardines and, to a lesser extent, 2% cow’s milk, but eating normal amounts of these foods will generally not provide sufficient amounts of vitamin D. Also, food is not the best way to meet the body’s requirements for this vitamin, which is why sunlight exposure and supplements are so important.
Supplements
Two forms of vitamin D are used in dietary supplements: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Ergocalciferol is typically derived from plants, so it is preferred by some vegetarians. However, yeast is commonly used as a source of D2, so some individuals do not consider this a vegetarian supplement. The cholecalciferol form (vitamin D3) is more effective in supporting the body’s need for vitamin D and is the form most generally recommended. More on vitamin D supplementation
