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Chicken or egg? Scientists are still trying to figure out how vitamin D works

Vitamin D supplements – are they beneficial or not?

Natural Health News — A new analysis has concluded that while Vitamin D deficiency may increase risk for several major health disorders, supplementation may not reduce risk.

Although the media headlines might suggest this most recent study is the last word on the subject, in fact the meta-analysis raises more questions than it answers.

Vitamin D deficiencies and the use of supplementation have been the subject of debate for years. Several recent studies suggest that a number of factors, including increasingly indoor lifestyles, mean we are becoming vitamin D deficient. Vitamin D deficiency  is associated with a range of chonic health problems, but while there is no doubt that vitamin D plays a role in bone health, but its role in non-skeletal disorders remains unclear.

Researchers at the International Prevention Research Institute in Lyon, France  reviewed 290 prospective studies and 172 randomised trials, to help them understand more about vitamin D’s role in illness and the potential benefits of supplements. Their findings have just been published in the journal Lancet Diabetes & Endocrinology.

All of the studies included in the analysis used blood levels of vitamin D to determine whether participants were vitamin D sufficient or deficient before measuring health outcomes.

Benefits for heart disease and diabetes

The  trials used both cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) supplements . All trial participants had baseline concentration of vitamin D below 50 nmol/L (considered a minimum healthy level).

In the observational studies, vitamin D deficiency was associated with a higher risk of cardiovascular diseases, inflammation, glucose metabolism disorders, infectious diseases, mood disorders, declines in cognitive function, and even all-cause mortality.

Vitamin D sufficiency was associated with a lower risk of cardiovascular events (in 58% of the observational studies), diabetes (in 38%), colorectal cancer (in 33%), and all-cause mortality (in 29%).

Colorectal cancer, however, was the only cancer risk that appeared to be reduced by having enough vitamin D in your blood.

However, they found that none of the randomised clinical trials they reviewed confirmed this finding.

According to lead author Philippe Autier, MD, MPH and his colleagues, low blood concentrations of vitamin D were associated with a variety of acute and chronic health disorders through the inflammatory process involved with disease. This led the researchers to the conclusion that low vitamin D levels come naturally with age and are a consequence of ill health, not a cause.

But was the dose sufficient?

It should be noted that this meta-analysis included studies of different types of vitamin D in a wide variety of doses. This may account for the lack of consistency in the findings.  In addition, older trials may have used much smaller doses then we now know are necessary to help patients reach vitamin D sufficiency.

For instance, the single largest trial reviewed by the authors, the Women’s Health Initiative, only supplemented with 400iu per day – this may have skewed the overall results.

These days it is recommended that we need a daily maintenance dose of 600iu. To treat vitamin D deficiency, the daily dose is between 2,000-3,000iu per day. Newer trials use doses at this level.

In addition, very little attention is paid to what might aid the absorption of  supplemental vitamin D. For instance, a recent trial found that a healthy gut plays an important role in vitamin D sufficiency and that taking a probiotic supplement alongside vitamin D supplement could,  improves vitamin D status.

Even so, in a small number (34) of the clinical trials vitamin D deficient people did not improve after taking 50 mcg (2000iu) of vitamin D per day. However, in a subgroup of group of older patients, mostly women, supplementation with 20mcg (800iu) did slightly reduce all-cause mortality.

The researchers suggest that more trials of vitamin D supplementation are needed. These, they say being undertaken now and results of these may help clarify things.