(NaturalNews) Treatment with vitamin D supplements may slow the progress of prostate cancer, according to a study published in the journal BJU International.
In the United States, prostate cancer is the second leading cause of cancer death among men, after lung cancer. Approximately 240,000 new cases are diagnosed every year, leading to 30,000 deaths.
Researchers have suspected for nearly two decades that the so-called "sunshine vitamin" may play a role in the risk and progression of prostate cancer, but no studies have previously been conducted on its usefulness as a treatment.
"It's very interesting - there has been no significant trial of vitamin D," said lead researcher Jonathan Waxman of Imperial College London. "This is a treatment which is unlikely to have significant toxicity and is a welcome addition to the therapeutic options for patients with prostate cancer."
Waxman decided to do the study when he learned of a prostate cancer patient who recovered after his wife bought vitamin D pills for him. Waxman and colleagues recruited 26 men with prostate cancer and assigned them each to take a daily vitamin D supplement. In five of the men, reductions in levels of the prostate specific antigen (PSA) were reduced.
In men with prostate cancer, PSA levels are an indicator of disease severity. One participant experienced a decrease in PSA levels less than 25 percent, two experienced decreases of between 25 and 50 percent, and two experienced decreases of more than 50 percent. In one of the participants, PSA levels remained reduced for a full 36 months.
Vitamin D is synthesized by the body upon exposure to ultraviolet (UV) radiation from sunlight. It plays a critical role in calcium absorption and bone health, and deficiency in the vitamin can lead to rickets in children and osteoporosis in adults. Recent research has also suggested that vitamin D can help prevent autoimmune disorders and a variety of chronic diseases, including diabetes, heart disease and cancer. Some scientists have stated that if everyone increased the amount of time they spent in the sun, far more lives would be saved from cancers prevented than would be lost from increased skin cancer cases.
A light-skinned person can get enough vitamin D from getting 15 minutes of sun on the face and hands each day, while a darker skinned person might need up to 45 minutes. More sun exposure is needed at more extreme latitudes.
A connection between vitamin D and prostate cancer was first suggested in 1990, when researchers suggested that the vitamin might tie together a variety of observed risk factors for the disease. A wide body of research has demonstrated that prostate cancer risk is higher at northern latitudes (where people get less vitamin D), among older people (with reduced vitamin D synthesis) and black people (who absorb less UV rays). Researchers have also found that men diagnosed with prostate cancer in the summer or autumn, when vitamin D levels tend to be highest, have a better prognosis than men diagnosed in winter or spring.
In 1992, researchers also suggested that higher vitamin D consumption in Japan might account for lower rates of prostate cancer there, relative to the United States. Japanese men consume more fatty fish, which is high in both vitamin D and omega-3 fatty acids that increase the vitamin's stability in the body, and soy, which slows the rate at which bodily vitamin D breaks down.
Since then, studies have found that many prostate cancer cells contain vitamin D receptors, and that vitamin D can inhibit the growth of some of these cells.
Researchers also hypothesize that vitamin D might inhibit the action of the androgen receptor, which produces male sex hormones that have been linked to the disease.