Vitamin D is being studied for its ability to reduce the risk of many different types of cancer, ranging from colon, breast, and prostate cancers to ovarian, esophageal, renal, and bladder cancers. Researchers believe that vitamin D may improve treatment outcomes in those already diagnosed with cancer. Research has suggested that 50,000-70,000 Americans die prematurely from cancer each year due to insufficient intake of vitamin D.1
Vitamin D also has applications in promoting bone strength, as well as in mitigating autoimmune conditions such as multiple sclerosis, type I diabetes, and rheumatoid arthritis. Other potential benefits include promoting dental and skin health, and helping to prevent stroke, metabolic syndrome, and musculoskeletal pain.
Studies suggest that the active form of vitamin D may help to promote cell differentiation and support apoptosis (programmed cell death), as well as help to prevent metastases (spread of cancer). Vitamin D’s role in supporting calcium absorption may also contribute to its ability to fight cancer.
Vitamin D’s effects in reducing cancer risk have been studied most extensively in colorectal cancer, the second leading cause of cancer death in the US. Individuals with vitamin D intake of 1000 IU or more daily or with serum vitamin D (25-hydroxyvitamin D) levels of 33 nanograms per milliliter (ng/mL) experienced a 50% lower risk of colorectal cancer. A daily dose of 1000 IU of vitamin D is half the safe upper limit established by the National Academy of Sciences.
An epidemiological review conducted in 2005 at Harvard Medical School corroborated vitamin D’s protective effects against colorectal cancer and noted that typical dietary intake of 200-400 IU per day is probably too low to confer appreciable benefits. The Harvard study noted that a person’s vitamin D status at the time of cancer diagnosis and treatment may influence survival.
Recent evidence indicates that the active form of vitamin D promotes differentiation and inhibits proliferation, invasiveness, and metastasis of human prostate cancer cells.
In a recent study, investigators examined the relationship between sun exposure and prostate cancer. Comparing 450 men with advanced prostate cancer with 450 unaffected men, they found that those with a high level of sun exposure had a 50% lower prostate cancer risk than men with low sun exposure. The researchers believe sunlight helped protect the men against prostate cancer by promoting vitamin D synthesis. Because of the association between sun exposure and certain skin cancers, however, the scientists noted, “increasing vitamin D intake from diet and supplements may be the safest solution to achieve adequate levels of vitamin D.
The prostate is below the bladder and should be clear, but due to the presence of a tumor it appears cloudy. The urethra shows narrowing caused by the pressure from the tumor.
Another study in 2005 demonstrated a therapeutic role for vitamin D in prostate cancer. Sixteen men who had previously been treated for prostate cancer supplemented with 2000 IU daily of vitamin D. The investigators then monitored prostate-specific antigen (PSA) levels for over two years. PSA is a marker of prostate cancer recurrence or progression. In nine patients, PSA levels decreased or remained unchanged after vitamin D supplementation began. In patients with rising PSA levels, supplementation with vitamin D3 significantly lengthened the PSA doubling time, by an average of 75%. (The rate at which PSA increases or doubles is correlated with disease prognosis, with longer PSA doubling times associated with better outcomes.) These findings indicate that vitamin D may help to slow or prevent disease recurrence or progression in patients who have been treated for prostate cancer.10
Vitamin D has also been reported to benefit patients whose prostate cancer has metastasized to the bones. This patient population commonly develops vitamin D deficiency. Supplementing these individuals with vitamin D was found to reduce pain, boost muscle strength, and improve overall quality of life.11