Vitamin D Usage

Wrongly termed a vitamin, vitamin D is actually what is known as a precursor hormone. The metabolic product of vitamin D, the hormone calcitriol, affects the key biological functions of over 2000...

Read more about Depression and Vitamin D.

Vitamin D plays a number of roles in the body, some of which are just now being discovered and confirmed. Its exact role in preventing or treating hypertension is not immediately clear. One...

Read more about Hypertension and Vitamin D.

Without question, if you are concerned about osteoporosis , you should take calcium and vitamin D. The combination appears to help prevent bone loss. ¹ This is true even if you are taking other treatments for osteoporosis; after all, you can't build bone without calcium, and you can't properly absorb and utilize calcium without adequate intake of vitamin D. Interestingly, vitamin D may also help prevent the falls that lead to osteoporotic fractures .

Other uses of vitamin D are less well documented.

Some evidence suggests that getting adequate vitamin D may help prevent cancer of the breast, colon, pancreas, prostate, and skin, but the research on this question has yielded mixed results. ² One study suggests that combined use of calcium plus vitamin D, but not either supplement separately, can help reduce risk of colon cancer. ³ However, an extremely large study involving over 36,000 post-menopausal women found that supplementing the diet with 1,000 mg of calcium plus 400 IU of vitamin D daily did not lower the risk of breast cancer over a period of 7 years. ⁴ Based on the results of this placebo-controlled study, there does not appear to be a connection between vitamin D and breast cancer risk.

Weak evidence hints that adequate vitamin D intake might reduce the risk of hypertension ⁵ and diabetes . ^{6 7} A very large randomized, placebo-controlled trial of over 36,000 postmenopausal women found daily supplementation with 1,000 mg of calcium plus 400 IU of vitamin D did not reduce or prevent hypertension during 7 years of follow-up. These results are possibly limited by non-study calcium use. ⁸ One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome. ⁹ A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality. ¹⁰ This article suggested, but did not attempt to establish, just how vitamin D might accomplish this.

Vitamin D is sometimes mentioned as a treatment for psoriasis . However, this recommendation is based on Danish studies using calcipotriol, a variation of vitamin D 3 that is used externally (applied to the skin). ¹¹ Calcipotriol does not affect your body's absorption of calcium, so it is a very different substance from the vitamin D you can purchase at a store.

It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for seasonal affective disorder ("winter blues"). A small double-blind, placebo-controlled trial conducted during winter on 44 people found that vitamin D supplements produced improvements in various measures of mood. ¹² However, a double-blind, placebo-controlled study of 2,217 women over 70 failed to find benefit. ¹³ It has been hypothesized that light therapy (used successfully for SAD) works by raising vitamin D levels, but there is some evidence that this is not the case. ¹⁴ Vitamin D supplements also do notappear to help enhance growth in healthy children. ¹⁵