Optimal levels of vitamin D may also help protect prostate health.19,54
Aware that low vitamin D levels are a major risk factor for prostate cancer,40,55,56 researchers examined the vitamin’s preventive effect in a cancer-prone mutant strain of mice.57 Mutant and control mice were given vitamin D for four months either before or after developing the first signs of cancer. Vitamin D substantially reduced the occurrence of early cancerous changes in tissue, yet appeared to have no effect on the androgen (male hormone) system. This is crucial, because many conventional prostate cancer drugs impair androgen function. Human prostate cancer cells in culture show similar reductions in cancerous changes and proliferation when treated with vitamin D3 and a synthetic retinoid (a vitamin A-like compound).58
A 1998 study demonstrated that vitamin D can reduce prostate cancer growth in human subjects. Seven men with recurrent prostate cancer following surgery or radiation (as measured by increasing levels of prostate-specific antigen, or PSA) were given a prescription form of vitamin D called calcitriol (Rocaltrol®) at increasing doses from 0.5 to 2.5 mcg (20-100 IU) per day. The rate of PSA increase (an indicator of disease progression) during treatment fell significantly compared to the rate before treatment in six of the subjects, suggesting a slowing of prostate cancer progression.59 In a related study, weekly dosing with calcitriol (at 20 IU per kilogram of body weight) increased median PSA doubling time in men who had been treated for prostate cancer.60,61 An increased PSA doubling time means that it takes longer for the PSA cancer marker to elevate (double), which is a favorable sign.
Treatment of existing prostate cancers with vitamin D also shows promise. In a 2006 Phase II clinical trial,62 researchers administered calcitriol three times weekly (at up to 12 mcg [480 IU] per dose) with the potent steroid dexamethasone. Thirty-seven men with androgen-independent prostate cancer were treated for at least one month. Eight patients had notable decreases in levels of PSA, a marker for tumor size. The researchers concluded that because there was minimal toxicity from this combination, it is a safe and feasible anti-tumor treatment.
Breast and Other Cancers
Abundant laboratory research demonstrates that vitamin D prevents human breast cancer cell proliferation and enhances the differentiation of cells into normal, healthy tissue.18,21-23,63,64 Powerful evidence also indicates that rates of breast cancer, like those of many other cancers, are lower in populations with greater exposure to sunlight or greater dietary intake of vitamin D.65-67
Similarly, enticing (though not yet clinically proven) evidence suggests a role for vitamin D supplementation in preventing or treating other cancers, including ovarian cancer, non-Hodgkin’s lymphoma, and cancers of the head and neck.20,47,68-70 Many cancer specialists advise checking vitamin D levels at least once a year, and supplementing with vitamin D if a deficiency is detected.6,40
Vitamin D Helps Alleviate Heart Failure
Heart failure—the heart’s inability to pump enough blood to meet the body’s requirements—is a leading cause of death in industrialized nations.71 Scientists believe that elevated levels of circulating pro-inflammatory cytokines may contribute to heart failure, and that vitamin D may offer heart-protective benefits by quelling these inflammatory mediators.72
Scanning electron micrograph of prostatic cancer cell.
In a recent double-blind clinical trial, 123 patients with congestive heart failure were randomly assigned to receive either vitamin D3 (50 mcg [2000 IU] per day) plus 500 mg of calcium or placebo plus 500 mg of calcium.72 Over the nine months of the study, patients who supplemented with vitamin D had greatly increased levels of the anti-inflammatory cytokine interleukin-10 and lower levels of the pro-inflammatory cytokine tumor necrosis factor-alpha. Scientists believe that by reducing the inflammatory environment in congestive heart failure patients, vitamin D3 holds promise as an anti-inflammatory therapeutic for people suffering from heart failure.
A 2005 study reported on the use of vitamin D and other nutrients in chronic heart failure.71 In a randomized trial, 28 chronic heart failure patients supplemented with 200 IU of vitamin D, 150 mg of coenzyme Q10, minerals, antioxidants, and B vitamins or placebo for nine months. The supplemented patients had an impressive 17% decrease in the heart’s left ventricular volume, which typically is increased in chronic heart failure and adds to the work required of the already-fatigued heart muscle. By contrast, left ventricular volume increased 10% in the placebo group. Supplemented patients also had a modest increase in quality-of-life scores. These findings indicate that vitamin D supplementation, in combination with coenzyme Q10, vitamins, and minerals, can offer important support for people with chronic heart failure.