In an editorial in the March 2007 edition of the American Journal of Clinical Nutrition, a prominent group of researchers from leading institutions such as the University of Toronto, Brigham and Women’s Hospital, Tufts University and University Hospital in Zurich, Switzerland, lashed out at the conventional media for its inaccurate reporting of Vitamin D supplementation.3
The researchers wrote, “Almost every time the public media report that Vitamin D nutrition status is too low, or that higher Vitamin D intakes may improve measures of health, the advice that accompanies the report is outdated and thus misleading. Media reports to the public are typically accompanied by a paragraph that approximates the following: ‘Current recommendations from the Institute of Medicine call for 200 IU/day from birth through age 50 years, 400 IU for those aged 51–70 years, and 600 IU for those aged >70 years. Some experts say that optimal amounts are closer to 1,000 IU daily. Until more is known, it is wise not to overdo it.’ The only conclusion that the public can draw from this is to do nothing different from what they have done in the past.”
The researchers point out that supplemental intake of 400 IU per day barely raises blood concentrations of 25(OH)D, which is the circulating Vitamin D metabolite that serves as the most frequently measured indicator of Vitamin D status. To raise 25(OH)D from 50 to 80 nmol/L requires an additional intake of 1,700 IU Vitamin D per day.
The researchers went on to write that, “The balance of the evidence leads to the conclusion that the public health is best served by a recommendation of higher daily intakes of Vitamin D. Relatively simple and low-cost changes, such as increased food fortification or increasing the amount of Vitamin D in Vitamin supplement products, may very well bring about rapid and important reductions in the morbidity associated with low Vitamin D status.”
One of the challenges is the outdated acceptable upper limit for Vitamin D3 consumption, which was set at 2,000 IU. However, researchers point out that more recent studies have shown that 10,000 IU is the safe upper limit.4
Depression
Vitamin D3 deficiency is common in older adults and has been implicated in psychiatric and neurologic disorders. For example, in one study of 80 older adults (40 with mild Alzheimer’s disease and 40 nondemented persons), Vitamin D3 deficiency was associated with low mood and with impairment on two of four measures of cognitive performance.6
Back Pain
Musculoskeletal disorders have been linked to Vitamin D3 deficiency in a number of studies. One of the newest studies explored the role that low Vitamin D3 levels play in the development of chronic low back pain in women. Sixty female patients in Egypt complaining of low back pain lasting more than three months were studied. Researchers measured levels of Vitamin D3 in the women with low back pain and compared those levels to those of 20 matched healthy controls.
The study revealed that patients with low back pain had significantly lower Vitamin D3 levels than controls. Low Vitamin D3 levels (25 OHD < 40 ng/ml) were found in 49/60 patients (81 percent) and 12/20 (60 percent) of controls.7
Cognitive Enhancement
Scientists are developing a greater appreciation for Vitamin D3’s ability to improve cognition. In a recent study, Vitamin D3 deficient subjects scored worse on mental function tests compared to individuals who had higher levels of the Vitamin.9 The researchers wrote, “In conclusion, the positive, significant correlation between serum 25(OH)D concentration and MMSE [mental state examination scores] in these patients suggests a potential role for Vitamin D in cognitive function of older adults.”
Proper Dosage
In many of my patients, even after consuming 2,000 to 4,000 IU of Vitamin D3 per day, their test results indicate that their Vitamin D3 levels have not increased. These patients needed to consume 8,000 IU of Vitamin D3 per day to achieve proper blood levels of the Vitamin. Patients should, therefore, have their physicians test their serum 1,25-dihyroxy D3 levels to determine the proper level of supplementation required. Testing is very important due to the fact that, in a small number of patients, Vitamin D3 supplementation can raise calcium levels to an excessively high level. I have found this to be especially true in African American patients. Testing for 1,25-dihyroxy Vitamin D3, PTH and calcium blood levels should therefore become a part of every woman’s regular blood work.
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I'd take this writer with a shaker-full of salt. There is not necessarily a direct relationship between intake of "Vitamin D3" (cholecalciferol) and blood levels of the active/hormone form of the vitamin, 1,25-dihydroxycholecalciferol (which this writer is referring to as "1,25-dihydroxy D3").
If someone has begun ingesting thousands of units of cholecalciferol daily, and is still not getting normal blood levels of the 1,25-dihydroxy form (or even any increase at all, as the writer states), in the vast majority of cases this doesn't mean they need to up their intake of cholecalciferol. Much more likely, it means they have liver and/or kidney disease that is preventing them from converting as much of the inactive form to the active form as they need. And in that case, they need to be supplemented with the active form (which is available by prescription only, and is *very* harmful if taken excessively, because the body does not have any way of back-converting excess amounts).