D is for Dynamite!

In case you haven’t heard, we are officially crazy. Why, you might ask? On top of our already hectic schedules, we have started a daily internet radio show, Five to Thrive Live! That’s right, daily—Monday through Friday! The show airs at 5 pm PST (8 pm EST) at www.w4cs.com, The Cancer Support Network. While this has led us to the cliff edge of sane living, we are actually thrilled to have this opportunity because we are such big advocates of empowering people with trusted, relevant health information.

With that in mind, this Thrive Thought is an offshoot of a recent show we did with vitamin D expert, Gregory Plotnikoff, MD. A recent study published in the March 2012 issue of the Annals of Internal Medicine was funded by the National Institute on Aging to assess what dose of vitamin D would result in achieving normal vitamin D levels in the blood of post-menopausal women. This is an important question to answer to help guide population based Recommended Daily Allowances (RDA) of vitamin D. The RDA is the amount of a supplement that will meet the minimum needs (i.e. prevent deficiency) for 97.5 percent of the population.

In this study, researchers from Creighton University Medical Center wanted to determine the effect of increasing oral doses of vitamin D(3) on blood levels. The typical 25-(OH)D blood test for vitamin D status was used. The year long study featured 163 vitamin D deficient postmenopausal women. The women were randomly assigned to receive placebo (fake pill) or vitamin D(3) at a daily dose of 400, 800, 1600, 2400, 3200, 4000, or 4800 IU. Vitamin D levels were measured at 6 months and again at 12 months.

The researchers found that supplementation of 800 IU daily was the dose needed to correct the deficiency in the majority of the women and blood levels tended to plateau at a dose of 3200 IU daily. The study also found that obese women needed more vitamin D to correct their deficiency.

This study suggests that to prevent vitamin D deficiency, most post menopausal women will benefit by taking 800 IU of vitamin D3 daily. The study also provides us with a dosage range by suggesting that 3200 IU or more does not incrementally increase vitamin D levels. These dosage guidelines cannot necessarily be translated to everyone. As Dr. Plotnikoff explained on the Five to Thrive Live radio show, we can’t use a “one-sized fits all approach” to vitamin D dosage. This is one of the reasons, he emphasizes that doctors should request vitamin D (25-OH) blood tests for all of their patients.

Reference: Gallagher JC, Sai A, Templin T, Smith L. Dose response to vitamin D supplementation in postmenopausal women: a randomized trial. Ann Intern Med. 2012 Mar 20;156(6):425-37BMJ Open 2012;2: e000850. doi:10.1136/bmjopen-2012-000850

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