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Vitamin D: Our most controversial vitamin?


Over the past two decades, we have learned a lot about vitamin D.

For a start, it shouldn’t really be called a vitamin, because it isn’t. A vitamin is defined as “A compound that is vital for normal growth and nutrition that is required in small quantities in our diet because it is not made by the body“. But vitamin D can be made by the body under the right circumstances. It should, more correctly, be called a prohormone, which is a substance that is converted into a hormone by our body.

Secondly, its benefits extend way beyond improving bone strength and regulating calcium metabolism and include protection against cardiovascular disease, cancer, infections, mood disorders, and dental conditions. A low vitamin D has also been associated with an increased risk of diabetes, high blood pressure, and multiple sclerosis.

But there is also a lot we don’t know, which has made it difficult for expert organizations to collectively agree upon a few significant issues. “What is the cut-off level for vitamin D deficiency?”, is one, with recommendations differing from 12 ng/ml of 25(OH)D up until 20 ng/ml. “What constitutes sufficiency?”,is another.

We also don’t know how effective supplementation actually is. Some studies have reported no benefit from vitamin D supplementation, but this may have been because baseline vitamin D levels of study participants were not taken into account, and many would have already been vitamin D sufficient. It does appear that those who benefit the most from supplementation are those with very low levels (less than 10 ng/ml). 

However, blood levels are not routinely tested because testing is more expensive than a supply of vitamin D tablets. In addition, most experts consider there is a huge safety margin for toxicity, although one cardiovascular study found 25(OH)D levels greater than 50 ng/ml were linked to an elevated risk of death.

What is clear is that vitamin D is a very important prohormone for our body and the best way to obtain it is the good old-fashioned way – ten minutes in the sun,  with your face and arms exposed, every day.

For more information about vitamin D see here.

Posted: October 2018

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