---
title: 'This Supplement Could Cut Your Dementia Risk by 40%'
source: 'https://youtube.com/watch?v=tpFOA1AUFCk'
video_id: 'tpFOA1AUFCk'
date: 2026-07-31
duration_sec: 1035
---

# This Supplement Could Cut Your Dementia Risk by 40%

> Source: [This Supplement Could Cut Your Dementia Risk by 40%](https://youtube.com/watch?v=tpFOA1AUFCk)

## Summary

Dr. Rhonda Patrick breaks down a 10-year study of over 12,000 people showing that vitamin D supplementation is associated with a 40% lower risk of dementia. She explores the mechanisms, the APOE4 genetic risk, and practical dosing guidance.

### Key Points

- **Vitamin D associated with 40% lower dementia risk** [00:02] — Over a decade, vitamin D supplementation was linked to a 40% lower risk of dementia. After 5 years, 84% of supplement users were dementia-free vs 68% of non-users.
- **APOE4 genetic risk factor** [00:19] — APOE4 is a key genetic risk factor for neurodegenerative diseases. Up to 25% of the population carries at least one allele, which can double Alzheimer's risk; two alleles raise it up to 10-fold.
- **Vitamin D regulates thousands of genes** [00:50] — Vitamin D is converted into a steroid hormone that regulates over a thousand genes, including nearly 5% of the protein-encoding human genome.
- **70% of Americans deficient or insufficient** [01:06] — About 30% are deficient (<20 ng/mL 25-hydroxy vitamin D) and another 40% are insufficient (20–30 ng/mL).
- **Causes of widespread deficiency** [01:49] — Sun exposure is blocked by sunscreen, skin pigmentation (melanin), aging (70-year-olds make 4x less than 20-year-olds), northern latitudes (no UVB for months), and body fat (vitamin D stored in fat).
- **Mendelian randomization confirms link** [03:18] — Genetically low vitamin D levels increase dementia risk by up to 54%, strengthening causal evidence beyond observational studies.
- **Vitamin D protects white matter** [05:41] — Higher vitamin D levels are associated with lower volume of white matter hyperintensities, markers of brain damage on MRI.
- **Supplementation improves cognition in MCI and Alzheimer's** [06:53] — 800 IUs daily for a year led to significant improvements in memory, attention, and overall IQ in people with mild cognitive impairment or Alzheimer's, plus reduced amyloid beta 42.
- **Deep dive into 12,388-person study** [08:05] — 10-year follow-up: 2,000+ non-users developed dementia vs 679 users. Supplementing with any form of vitamin D associated with 40% lower dementia incidence.
- **Women derive greater benefit** [09:56] — Women supplementing had almost 50% lower dementia incidence vs 26% lower in men. Women have higher baseline dementia rates, so the absolute reduction is larger.
- **APOE4 carriers still benefit but less** [11:19] — APOE4 carriers saw a 33% dementia risk reduction with vitamin D, non-carriers 47%. Yet carriers still had a 16% higher risk than non-carrier non-users.
- **All forms of vitamin D work** [13:38] — Calcium vitamin D: 44% lower risk; D3: 37%; D2: 50%; combined forms: 50% lower dementia risk.
- **Recommendations: test and supplement** [14:06] — Aim for 25-hydroxy vitamin D levels between 30–60 ng/mL, avoid above 80. Most people need 2,000–4,000 IUs daily and yearly blood tests.
- **Mechanisms: vitamin D supports brain health** [15:33] — Vitamin D promotes amyloid beta clearance, reduces neuroinflammation, upregulates neurotrophic factors (NGF, BDNF), and decreases oxidative stress.

### Conclusion

The evidence is strong: vitamin D supplementation is a simple, low-cost intervention that can meaningfully reduce dementia risk. Regular blood testing and supplementation to maintain optimal levels (30–60 ng/mL) is a practical step for most people.

## Transcript

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 dementi 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 APOE E4. This is a key genetic risk factor for neurodeenerative diseases. Up to 25% of the population
has one of these alals and it can double the risk of Alzheimer's disease if you have one of them. If you have two of these alals, you can have up to a t-fold higher risk of Alzheimer's disease. Vitamin D is not just a vitamin. Vitamin
D gets converted into a steroid hormone that regulates over a thousand 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 encoding
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 nanogs per milliliter. The other 40% or so has levels that's known that have vitamin D levels above 20 nanogs per milliliter, but they're below
30 nanogs 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 to 4,000 IUs per day,
they can get to a sufficient level. There's a lot of reasons why vitamin D deficiency and insufficiency is so widespread. That is because we actually widespread. That is because we actually make vitamin D in our skin upon exposure
from UV radiation from the sun. So, anything that blocks out UVB radiation is also going to block out the ability to produce vitamin D3 in our skin. That includes sunscreen. It also includes skin pigmentation. So melanin,
this is this is the darker pigmentation that serves as a natural sunscreen that also blunts the body's ability to make vitamin D3 from UVB radiation. Age. As you get older, your body is less efficient and effective at producing
vitamin D3 from sun exposure. In fact, a 70-year-old makes four times less vitamin D from the sun than a 20-year-old where you live. So living in a northern latitude many months of the year
actually there's no UVB radiation even reaching the atmosphere. So people that are living in more northern latitude areas are not able to make vitamin D3 in their skin from the sun for many many months out of the year. So that also
really affects the ability to make vitamin D. And then also just body fat. So vitamin D is actually a fat soluble vitamin and it's stored in fat. And so the more body fat that you have, that means the less vitamin D3 is
bioavailable to be released into the bloodstream where that it undergoes further metabolic conversion to the steroid hormone, which is actually of them in the brain. Now, we're going to dive a little
bit deeper into the study that showed a 40% lower risk of dementia. But I want to mention first that this is not the first study to show this. I mean there first study to show this. I mean there are many many many what are called
observational studies that are looking at a correlation between low vitamin D studies have found this same association. And so one might say, well, people that are vitamin D deficient
might just be less healthy. They might be going out in the sun less. They're exercising less. And so vitamin D deficiency might just be biomarking some other health factor. So that is a I would say pretty relevant
argument. But we also have a whole host of other data to support the link dementia risk and Alzheimer's disease risk. So for example with these observational studies we can look at what's called mandelian randomization.
This is a way to use genetics to look at how something in the environment can affect an outcome. In this case, there's many different genes that regulate the ability of your body to pro to to produce vitamin D3 and convert it into
the steroid hormone. And some people do that less effectively because they have a certain variation in those genes that are not doing it quite as well. And so you can look at genetically low vitamin D levels. In other words, you just look
at someone's genes and if they have a certain variation of that vitamin D converting gene that makes it not as effective, you put them into the low with those genes actually do have low vitamin D. And then you compare them to
people that have the normal functioning genes that don't make them have low vitamin D levels. They don't have low 125 hydroxy vitamin D, which is the actual steroid hormone. And then you look at the risk for dementia and
Alzheimer's disease. And so what's been shown is that genetically low vitamin D shown is that genetically low vitamin D levels increase dementia risk by up to 54%. Again, this is really confirming that observational data which really
that observational data which really can't really show causation. And so it strengthens that data. But then you can go a step further and you can look at other studies that have shown vitamin D deficiency actually accelerates brain
aging. So there have been studies that have shown that have looked by fMRI at what's called white matter hyperintensities. So these kind of show up of as little white hypers spots if you're looking at a MRI image of the
brain and it's really a marker of damage to the white matter in the brain. And the white matter is where is it's it's so important for brain function for communication. It's how your brain is communicating. So when you have damage
to that white matter, it really does affect cognition. It affects communication and memory. For every 10 nanomal per liter increase in vitamin D, there was a small decrease in the volume of these white matter
hyperintensities, suggesting that having higher levels of vitamin D can protect against this type of brain damage. Even a step further, looking at vitamin D supplementation and how that can affect cognition. Now, there's
there's a lot of mixed data out there, particularly when it comes to vitamin D supplementation affecting cognition in normal healthy adults, but there have been a few trials that have actually looked at vitamin D supplementation in
people with either Alzheimer's disease or people with mild cognitive impairment. So both in both those scenarios and people with mild cognitive impairment if they took around 800 IUs of vitamin D daily for a year they had
significant improvements in multiple areas of cognition, memory, attention, overall IQ. And the same goes with the Alzheimer's disease study. So people that took again 800 IUs a day for over a year and these people were already
diagnosed with Alzheimer's disease. They also had improved scores on memory and trial I just mentioned. But additionally, there was also a reduction in blood biomarkers of amalloid beta pathology such as amaloid beta 42 which
is associated with Alzheimer's disease progression. So this data really strengthens the argument that low vitamin D can increase dementia risk and that supplementing with vitamin D can help lower that risk. which brings us
back to this recent study where vitamin D supplementation was associated with a 40% lower risk of dementia. So, let's dive into that a little bit closer. So, the study included 12,388 adults who were divided into two
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. Um 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 D was also associated with a greater 5-year dementiareree survival. So 84% of adults in the vitamin D group were free of dementia during this time period
while only 68% of the nonvitamin D users were de dementi-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, um 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. Um, 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 AIL. Having one alil can increase the
risk of dementia, Alzheimer's disease by twofold. Having two copies of that alil can increase the risk up to 10fold. So, it's really um important for people to understand that if they have one of these alals 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-arriers, vitamin D reduced the incidence of dementia by 47%, a surprising. And supplementing with vitamin D wasn't enough to outweigh the effects of carrying one or two copies of APOE4. These participants still had a
16% greater risk of dementia than non-arriers, even non-arriers who didn't use vitamin D. The same was true for another risk factor having mild cognitive impairment which elevated dementia incidents by nearly
400% compared to people that had normal cognitive function even in the presence of vit vitamin D supplementation. So in other words you if you have an ApoE4 alil or if you had mild cognitive impairment at the baseline then you just
you had a tremendously higher risk of getting dementia Alzheimer's disease. However, the vitamin D supplementation did still help. It didn't it just didn't help as much as someone that was healthy and had normal cognitive function and
was a non-arrier 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 people that had mild cognitive impairment had a 400% higher risk of
having dementia compared to people that had normal cognitive function at the 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. Um, 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 this the findings of this study but the other 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 125 hydroxy vitamin D. And you want to have your 25 hydroxy vitamin D levels between you know 30 to 60 nanogs per milliliter is a great I would say level to have your vitamin D levels. You don't
really want to go above 80 nanogs 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 where your blood levels are at and keep keep their
vitamin D levels within that, you know, 40 to 60 range. So, it's good to kind of do a annual vitamin D blood test just to make sure you're not taking too much or enough to raise your levels into that sweet spot. And lastly, I just want to
mention how vitamin D can support brain health. So vitamin D can enhance the protein that's linked to Alzheimer's disease by promoting its elux from the brain. Now I mentioned in that study it was a randomized control trial in people
a day. People that already had Alzheimer's disease. It lowered their amaloid beta plaque burden. Um vitamin D also is an immune modulator. So vitamin D receptors on micro ga and
aststerittytes in the brain help reduce excess neuroinflammation. So it it basically helps lower the pro-inflammatory cytoine response in the brain. We know that neuroinflammation plays a major major role in the cause uh
of dementia and Alzheimer's disease. Vitamin D also upregulates a variety of neurotrophic factors including nerve growth factor and um also brain drive neurotrphic factors. So this is helping support neurotransmitters, supporting
learning and memory. And then lastly, vitamin D also decreases oxidative stress. It's been shown in the the mild cognitive impairment trial that I control trial. Those individuals that took vitamin D also had decreased levels
compared to people that were given the placebo. Um, and so, you know, oxidative stress is an indirect way that can lead to a variety of, you know, inflammatory
processes and stuff in the brain as well. So, there's several different support brain health. And again, it's pretty simple to get a vitamin D test and to take a relatively inexpens
inexpensive vitamin D supplement as well. I'm Dr. Rhonda Patrick and I'll well. I'm Dr. Rhonda Patrick and I'll talk to you soon.