Optimal levels of THIS vitamin can protect you against dementia and Type II diabetes

Yesterday, I wrote about the ability of vitamin D—at the right doses—to prevent cancer and other chronic diseases, such as Alzheimer’s disease (AD), dementia, and Type II diabetes.

And now, two additional studies support my case. So, let’s jump right in…

Alzheimer’s risk skyrockets with low vitamin D blood levels

In the first study, researchers with the University of Exeter studied vitamin D levels in more than 1,600 older adults. At the start of the study, none of the participants had been diagnosed with AD or dementia. But some of them did have less-than-optimal vitamin D levels.

The researchers categorized vitamin D blood levels at—or greater than—50 nanomoles/Liter (nmol/L) as “sufficient.” They categorized levels between 25 and 50 nmol/L as “deficient.” And they categorized anything less than 25 nmol/L as “severely deficient.”

Over the next five years, 171 participants developed all-cause dementia, including 102 cases of AD. And it turns out, the participants who had “deficient” vitamin D blood levels at the study’s outset were 53 percent more likely to develop AD or dementia compared to those with “sufficient” levels.

And that’s not all…

The participants who had “severely deficient” vitamin D blood levels at the study’s outset were more than twice as likely to develop AD or dementia compared to those with sufficient levels.

Which means my advice for the last several years has been spot on. So, continue aiming to achieve vitamin D blood levels between 50 nmol/L and 75 nmol/L at bi-annual checks with your doctor.

Now, let’s move on to the second study…

Exploring the link between vitamin D and diabetes

The second new study was conducted by researchers at Laval University in Quebec, and it involved patients newly diagnosed with Type II diabetes or identified as “high risk” for developing Type II diabetes.

At the study’s outset, researchers measured markers of insulin function and glucose metabolism in all participants. They also checked the participants’ vitamin D blood levels. (They said about half of the participants had what they considered “low” levels of D.)

Next, researchers randomly split the participants into two groups. Half the participants took a placebo for six months. And the other half took 5,000 IU of vitamin D for six months. (The researchers defined this “high” dose of vitamin D as five to 10 times of the standard “recommended” dose. But—of course—I recommend an optimal 10,000 IU daily, based on the science.)

It turns out, the group that took vitamin D “significantly” improved their insulin function and glucose metabolism compared to the placebo group. And that’s a significant finding. Because controlling blood sugar is the only real way to prevent the onset and progression of Type II diabetes.

And remember, those results stemmed from supplementing with what I consider to be only half the optimal daily dose of vitamin D. Making these findings even more promising.

And one more point before I go…

Clearly, something is wrong with how the researchers categorized “normal” vitamin D blood levels. Because even those with supposedly “normal” vitamin D blood levels benefitted from vitamin D supplementation.

Of course, as always, the scientists said more research is needed. And they want you to continue following the current, paltry recommendations for low-dose vitamin D supplementation—even after their own study showed such levels are inadequate (as do many other studies)!

But we can’t afford to wait. Especially in places where the sun is too weak at this time of year to trigger your skin’s own natural production of vitamin D.

So, here are my recommendations on vitamin D. They’re worth repeating:

  • Continue supplementing daily with 10,000 IU of vitamin D, which you can find in easy-to-use liquid form with or without the potent marine carotenoid astaxanthin.
  • Continue spending 15 to 20 minutes in the sun daily without sunscreen.
  • Ask your doctor to check your blood levels of vitamin D twice a year. (Ideally, once at the end of summer and again at the end of winter.) Aim to achieve  optimal blood levels of 50 to 60 nanograms/milliliter (ng/mL). This level will help protect against dementia and Type II diabetes, as discussed today, as well as other chronic diseases.
  • Always discuss your family history and supplement use with your personal doctor.

And to continue staying on top of the science, continue tuning in to my Daily Dispatches and monthly Insiders’ Cures newsletter. Not yet a subscriber? All it takes is one click.


“Vitamin D and the risk of dementia and Alzheimer’s disease.” Neurology, August 2019; 83(10):920-8. doi.org/10.1212/WNL.0000000000000755

“Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomized, placebo-controlled trial.” European Journal of Endocrinology, 2019; 181(3): 287-299. doi.org/10.1530/EJE-19-0156