How Vitamin D Status Relates to Dementia Risk

Dr. Rhonda Patrick here. A new study found that vitamin D supplementation was associated with a 40% lower risk of dementia over a decade. After just 5 years, 84% of the vitamin D supplement users were dementia-free compared to 68% of the non-users. This was a study of over 12,000 people, and vitamin D reduced dementia risk by around 33% in adults with mild cognitive impairment and also had ApoE4. This is a key genetic risk factor for neurodegenerative diseases. Up to 25% of the population has one of these alleles, and it can double the risk of Alzheimer's disease if you have one of them. If you have 2 of these alleles, you can have up to a tenfold higher risk of Alzheimer's disease. Vitamin D is not just a vitamin.

Vitamin D gets converted into a steroid hormone that regulates over 1,000 genes in our body. It enters the nucleus of our cells and it regulates, it activates and turns on, or it suppresses and turns off up to nearly 5% of the protein-coding human genome. This is very relevant because up to 70% of Americans fall into a range known as deficient or insufficient. So almost 30% of Americans actually are vitamin D deficient. They have levels of 25-hydroxy vitamin D below 20 nanograms per milliliter. The other 40% or so has levels that's known as insufficient. So these are people that have vitamin D levels above 20 nanograms per milliliter, but they're below 30 nanograms per milliliter.

And there's really a simple solution to avoiding this deficiency and insufficiency, and that is a vitamin D supplement. Usually people that are vitamin D deficient, if they take around 2,000 to 4,000 IUs per day, they can get to a sufficient level. So the study included 12,388 adults who were divided into 2 groups. Those who reported using vitamin D supplements in any form— it could be calcium vitamin D, it could be the active form of vitamin D, it could be vitamin D2. So any form of vitamin D, it didn't matter what form. And then the other group it was divided into is those that did not take any form of vitamin D supplement. There was a 10-year follow-up, and during that period, supplementing with vitamin D was associated with a 40% lower incidence of dementia.

Over 2,000 participants who reported never using vitamin D supplements developed dementia compared to just 679 of those participants who actually did report using vitamin D supplements. Supplementing with vitamin D was also associated with a greater 5-year dementia-free survival. So 84% of adults in the vitamin D group were free of dementia during this time period while only 68% of the non-vitamin D users were dementia-free during that same period. And this was also true regardless of whether or not the participants had baseline mild cognitive decline or normal cognitive function. So vitamin D seemed to provide a benefit in both of those scenarios.

And while dementia prevalence was higher in adults with mild cognitive impairment, it was around 15% lower in this group for adults who supplemented with vitamin D compared to those who didn't. So in other words, even if you already had some sort of mild cognitive impairment, you still had a lower risk of actually transitioning to dementia if you were supplementing with vitamin D. Although vitamin D supplementation reduced dementia risk among all groups, there were several interesting findings regarding the benefits of vitamin D for certain populations. So for example, Women derived the greatest benefit from vitamin D. They actually experienced less dementia compared to men who supplemented.

And while vitamin D-using men had a 26% lower dementia incidence than non-users, vitamin D-using women had almost a 50% lower incidence compared to non-using women. So really, there's a much bigger difference in terms of women having a lower incidence. And I'm wondering if that's because Generally speaking, women get dementia and Alzheimer's disease about twice as higher of a frequency than men do. So there just might be more of a signal here to lower. That's one possibility. Adults that had normal baseline cognitive function had a 56% lower dementia incidence if they supplemented with vitamin D. But adults that did have mild cognitive impairment only had a 33% lower incidence of dementia if they supplemented.

So in other words, If you were already, if you started out dementia-free and healthy, vitamin D had a more robust effect on lowering your dementia incidence, which makes sense. If you're already in a state of mild cognitive impairment, it's much harder to kind of reverse damage that's already been done. And this brings us to ApoE4. So I mentioned earlier, ApoE4 is the biggest genetic risk factor for Alzheimer's disease. 25% of the population carries at least one allele. Having one allele can increase the risk of dementia and Alzheimer's disease by twofold. Having 2 copies of that allele can increase the risk up to tenfold.

So it's really important for people to understand that if they have one of these alleles, that, that they really need to try to do everything they can within their lifestyle to lower their dementia risk. And so people that had APOE4 that supplemented with vitamin D did reduce their incidence of dementia by around 33%. And among non-carriers, vitamin D reduced the incidence of dementia by 47%, a little bit higher, which is not surprising. And supplementing with vitamin D wasn't enough to outweigh the effects of carrying 1 or 2 copies of APOE4.

These participants still had a 16% greater risk of dementia than non-carriers, even non-carriers who didn't use vitamin D. The same was true for another risk factor, having mild cognitive impairment, which elevated dementia incidence by nearly 400% compared to people that had normal cognitive function, even in the presence of vitamin D supplementation. So in other words, if you have an APOE4 allele, or if you had mild cognitive impairment at the baseline, then you just, you had a tremendously higher risk of getting dementia and Alzheimer's disease. However, the vitamin D supplementation did still help. It just didn't help as much as someone that was healthy and had normal cognitive function and was a non-carrier at the start of this study. Okay, so let's dig a little bit deeper.

Participants with mild cognitive impairment who didn't supplement with vitamin D had more than a 600% increase in dementia risk compared to the adults with normal, normal cognitive function, even those who didn't use vitamin D. So in other words, I just mentioned that people that had mild cognitive impairment had a 400% higher risk of having dementia compared to people that had normal cognitive function at the beginning of the trial, but that was only if they supplemented with vitamin D. People that didn't supplement with vitamin D had a 600% higher risk of developing dementia if they started with mild cognitive impairment. It also didn't matter what form vitamin D was used. All of them were associated with a lower dementia risk.

Specifically, using calcium vitamin D was associated with a 44% lower risk of dementia, and using vitamin D3 was associated with a 37% lower risk of dementia. And then using vitamin D2, which is the plant version, was actually associated with a 50% lower risk of dementia. Using combined forms of vitamin D was associated with a 50% lower risk. So I think here in concluding thoughts, Overall, not only the findings of this study, but the other studies that I talked about really do give strong support to this idea that everyone should probably be supplementing with at least some vitamin D to make sure they're avoiding deficiency. And I mentioned, as I mentioned earlier, deficiency is a widespread, you know, problem in the United States. Up to 70% of people are either deficient or insufficient.

So getting a simple blood test is one of the best things you can do. Measure your 25-hydroxy vitamin D levels. This is the precursor to the active steroid hormone, 1,25-dihydroxyvitamin D. And you want to have your 25-hydroxy vitamin D levels between, you know, 30 to 60 nanograms per milliliter is a great, I would say, level to have your vitamin D levels. You don't really want to go above 80 nanograms per milliliter. Then you start getting into a pretty high range. Most people can take a supplement in the range of 2,000 to 4,000 IUs a day, depending on where your blood levels are at, and keep their vitamin D levels within that, you know, 40 to 60 range. So it's good to kind of do an annual vitamin D blood test just to make sure you're not taking too much or to make sure that you're actually taking enough to raise your levels into that sweet spot.