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Guarding Against the Dangers of Vitamin D Deficiency

May 2007

By Tiesha D. Johnson, BSN, RN

Prostate Cancer

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.

Vitamin D: What You Need to Know
  • Low dietary intake and limited sun exposure have led to an epidemic of vitamin D deficiency. Health experts now advise adults to regularly check their blood levels of vitamin D and to address deficiencies with supplemental vitamin D.
  • Vitamin D plays many essential roles throughout the body—enhancing calcium absorption, contributing to healthy bone mass, supporting immune function, quelling inflammation, and helping to fight cancer.
  • Clinical studies support vitamin D’s role in preventing and treating colon and prostate cancers, and emerging studies suggest vitamin D may help avert cancers of the breast, ovaries, head, and neck, among others.
  • Vitamin D quells inflammation that may exacerbate chronic heart failure, and in combination with other nutrients, benefits people with chronic heart failure. Vitamin D also shows promise in preventing both type I and type II diabetes, and offers important support for immune health. Vitamin D may help prevent wound infections and flu, support the body’s defense against tuberculosis, and boost immune function in patients with kidney failure.
  • Vitamin D likewise may help to alleviate seasonal affective disorder (SAD), a type of depression experienced during the winter months due to decreased sunlight.

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.

Ensuring Optimal Vitamin D Levels

Health experts urge all adults to have regular (at least annual) checks of vitamin D levels in their blood.7 There is a good chance that you will be deficient for at least part of the year if you live in North America, according to those experts.6,55 Once a deficiency is identified, supplementation can safely restore levels to the normal range. Checking vitamin D status again after a few months of supplementation is also advised.

While the federal government’s recommended dietary allowance (RDA) of vitamin D is 400 IU (10 mcg) daily,83 many health experts now advise daily doses of at least 800 IU (20 mcg) of vitamin D.84 Life Extension recommends that healthy adults supplement each day with at least 1000 IU of vitamin D. Elderly adults may benefit from higher doses such as 2000 IU daily, and even up to 5000 IU daily. Research published over the last decade suggests that vitamin D toxicity is unlikely at daily intake levels of less than 10,000 IU (250 mcg).14,85-88

Comprehensive research reviews conducted by a leading authority on vitamin D, Dr. Michael Holick, suggest that a healthy serum level of vitamin D (25-hydroxyvitamin D) is 75-125 nmol/L. Serum levels within this range have been associated with improved bone health and muscle strength, as well as protection against numerous cancers.6,7,89

As with many supplements, an appropriate dosage is critical for efficacy and safety. Long-term supplementation with very high doses of vitamin D can cause dangerous elevations in blood calcium levels.90,91 Too much calcium in the blood can rapidly cause poor muscle and nerve function,92 and long-term elevations increase the risk of kidney stones.93 Anyone taking extremely high doses of vitamin D should be monitored for signs and symptoms of vitamin D toxicity, which include nausea, vomiting, poor appetite, constipation, weakness, heart arrhythmias, kidney stones, and elevated blood levels of cholesterol, calcium, or liver enzymes.83,84 Vitamin D is contraindicated in individuals with hypercalcemia (high blood calcium levels).83,84 People with kidney disease and those who use digoxin or other cardiac glycoside drugs should consult a physician before using supplemental vitamin D.83,84

Life Extension recommends that all adults check their blood vitamin D levels at least once a year. If levels are low, discuss supplementation with your health care provider, and then follow up with repeat testing after a few months.