This blog tracks updates to the Blood Sugar 101 Web site.

Friday, October 3, 2008

Raising Low Vitamin D Levels Does Not Improve Glucose Tolerance

Page Changed: Supplements That Work

Added information about and link to study published in the journal Nutrition where glucose tolerance was studied before and after people deficient in Vitamin D were given a large infusion of the vitamin sufficent to raise their levels to normal. No change in glucose tolerance or insulin sensitivity was demonstrated.

This raises the question of whether Vitamin D deficiency is a byproduct of the diabetic state rather than a cause of abnormal glucose metabolism or insulin resistance.

1 comment:

Anna said...

I hope this doesn't discourage people from following up on their Vitamin D status, though.

Even if Vit D supplementing doesn't improve glucose tolerance, low Vitamin D stores in the body are associated with a number of poor health conditions, including CVD, osteoporosis, dental cavities, and some common cancers, not to mention poor immune resistance and increase flu susceptibility. It is clearly a very important and critical substance in the body; deficiency and sub-optimal levels are very common in modern industrial populations. The Vitamin D Council says skin production of the Vit D precursor drops after the age of 40, too.

And the recommended supplement doses are often too low to raise Vit D stores to adequate, let alone optimal levels. The RDA, for example, is only enough to prevent rickets in a child, not enough for adults. Some sources say that overweight and obese people need much higher doses to maintain adequate Vit D levels. There is also evidence to suggest that different people (with metabolic abnormalities?) have different "burn rates" of Vitamin D, so need higher amounts. There's no way to tell what someone's dose needs to be except to have Vit D levels tested twice a year (mid-summer and late winter) - and the test should be the 25 (OH) test and the supplements should be same kind the body makes - Vit D3-cholcalciferol, *not* D2 - ergocalciferol, the artificial D.

I was tested in Dec '07 after supplementing at a 2000iU+ per day D3 dose for almost 8 months, and my 25 (0H) D test was still in the low end of the lab's reference range - not deficient certainly, but no where near the optimal level. Out of curiosity, I stopped supplementing last spring and tried to get a bit more sun instead (I live in sunny So Cal, so that isn't hard to do), plus we vacationed two weeks in very sunny Italy last summer where I had much more sun exposure than I usually get at home, but when retested at the end of summer, my levels had gone down a bit.

So clearly, I need to supplement not only at a higher level, but year 'round, despite my sunny local climate and attempts to get more sun exposure (without burning, of course). Plus I do eat make sure to consume pastured meat, eggs, and dairy, which has somewhat more natural Vit D3 content than grain-fed confined livestock products (though food is generally not the best source of Vit D, as humans evolved to get it primarily from sun exposure.

Interestingly, my endocrinologist was fine with my low test levels (because they were still inside the ref range), but my new primary care physician, who takes a more holistic and preventive view, suggested more Vit D supplementing to bump my Vit D status up higher.

There's great Vit D info on the non-profit Vitamin D Council website - , run by a group of Vit D research scientists. Dr. Davis's Heart Scan log also has a number of posts about the importance of adequate Vit D levels for good health.