# Vitamin D and the Aging Brain: What the Research Shows **By Paula Gallagher** · 2026-11-06 ![Older man pausing thoughtfully at a café window table, hand to temple, tea and notebook nearby](https://cdn.shopify.com/s/files/1/0319/0960/9603/files/hero-84bcc6fb-900x600.png?v=1793800764&width=300&height=200&crop=center) We’ve known for years that low levels of vitamin D are correlated with higher risk of dementia. But correlation does not equal causation. In one small study, participants with mild cognitive impairment and sleep issues who took vitamin D performed 13% better on the Montreal Cognitive Assessment than did those who didn’t take it. But wait, there is a catch. They were taking 5,000 IU per day, which exceeds the safe upper limit of 4,000 IU/day for adults. Here’s what we know and what we don’t know about vitamin D, dementia, and how to optimize your vitamin D intake for healthy aging. ## Vitamin D and Cognitive Function in Aging The link between vitamin D and cognitive function in aging has drawn new attention from researchers studying dementia risk, and the findings are worth understanding before you reach for a higher dose. In one recent study, people with mild cognitive impairment and sleep disturbances who took vitamin D scored 13% better on the Montreal Cognitive Assessment (MoCA) than those who didn’t. Here is what that means, what it doesn’t, and how to approach vitamin D safely. ### The Sunshine Vitamin and Your Brain Low vitamin D levels have long been linked to a higher risk of dementia, and that's where most vitamin D dementia research starts. But correlation isn’t causation, and a link alone doesn’t show that low vitamin D causes cognitive decline. Research has associated low vitamin D with higher levels of tau, a protein studied in dementia research, including in younger adults. That suggests brain health and vitamin D status may be worth paying attention to well before older age. ### What the Vitamin D Dementia Research Shows A separate investigation published in Sleep Medicine included individuals at high risk for dementia who had mild cognitive impairment and poor sleep. Within that group, those who took high-dose vitamin D daily scored 13% better on the MoCA, a memory and thinking test often used to screen for dementia risk. The result held after the researchers controlled for other variables. Some important context: - None of the participants had been diagnosed with dementia. - Often thought of as a middle ground between normal aging and dementia, mild cognitive impairment could be an early window of opportunity to promote brain health. - It's a small study and the paper says there's an association between higher vitamin D intake and improved cognition. The paper doesn't say vitamin D causes the improvement. ### How Low Vitamin D Affects the Aging Mind ![Cinematic brain render comparing adequate and low vitamin D states with tau buildup labeled](https://cdn.shopify.com/s/files/1/0319/0960/9603/files/slot-body-1-82d2aa1a.png?v=1793800753) Vitamin D deficiency is much more common than we realize, but it won’t feel like catching a cold, so we may not even notice. It’s important to remember that vitamin D doesn’t just keep your bones healthy. Low levels have also been linked to the aforementioned buildup of tau, and with increasing rates of cognitive decline, studies are examining easily modifiable risk factors such as vitamin D intake. The only way to know your status is a blood test, and it’s the step we never skip. ### What Does Supplementation Mean? Supplementing means taking a vitamin or mineral to make up for an amount you aren’t getting from diet or sun exposure. It’s not a replacement for a balanced diet. It’s a top-up. With vitamin D, the goal isn’t just taking a pill. It’s reaching and maintaining a healthy level in your blood. That’s why dose and form matter, and why more is not always better. ### Choosing a Vitamin D3 Supplement ![Choosing a Vitamin D3 Supplement](https://cdn.shopify.com/s/files/1/0319/0960/9603/files/asset-1793797413919.png?v=1793800758) When people ask us about vitamin D3, the first thing we talk about is dose, not brand. In the study, participants received 5,000 IU per day. This exceeds the NIH’s recommended upper limit of 4,000 IU per day for adults, so don’t take that amount without first talking to your physician. Taking too much vitamin D can cause hypercalcemia, too much calcium in the blood, which can affect the heart, brain, bones, and kidneys. That’s not a reason to avoid vitamin D. It’s a reason to get tested first and dose accordingly. For many people, a lower daily dose is plenty. A product like [**Vitamin D 2000 IU**](https://myvillagegreen.com/products/bluebonnet-vitamin-d-2000-iu-180-vegetable-capsules "https://myvillagegreen.com/products/bluebonnet-vitamin-d-2000-iu-180-vegetable-capsules") fits comfortably under the upper limit. If you also want to support calcium metabolism, a combination such as [**Vitamin D3 Plus K2**](https://myvillagegreen.com/products/vitamin-d3-plus-k2 "https://myvillagegreen.com/products/vitamin-d3-plus-k2") may be worth discussing. A few things we talk through at the counter: - Get a blood test before choosing a dose, so you’re aiming for an actual number. - D3 and D2 both boost vitamin D levels, although D3 tends to be more efficient. - Don’t exceed 4,000 IU per day unless your physician directs you to. - For people with heart, bone or kidney disease, the higher doses should only be used under supervision by a doctor. - Revisit your dose when your levels change. ### Beyond Vitamin D - B12 and Other Cognitive Allies There are other nutrients associated with brain health. B12, for example, is a vitamin we often discuss with people worried about memory loss or low energy levels. It’s been shown that low B12 can contribute to fatigue and cognitive decline, and that deficiency in this vitamin is more prevalent in the elderly population, as well as certain vegan diets. Some of the options we get asked about most frequently are a [**B12 5000 Mcg,**](https://myvillagegreen.com/products/coenzymated-methylb-12-5000mcg-787500017119?variant=44255008915694 "https://myvillagegreen.com/products/coenzymated-methylb-12-5000mcg-787500017119?variant=44255008915694") [**B6 Folic Acid,**](https://myvillagegreen.com/products/bluebonnet-nutrition-vitamin-b6-b12-plus-folic-acid-60-tablets "https://myvillagegreen.com/products/bluebonnet-nutrition-vitamin-b6-b12-plus-folic-acid-60-tablets") a [**B-Complex 50**](https://myvillagegreen.com/products/b-complex-53 "https://myvillagegreen.com/products/b-complex-53"), and [**Magnesium Glycinate 400Mg**](https://myvillagegreen.com/pages/search-results-page?q=Magnesium%20Glycinate%20400Mg "https://myvillagegreen.com/pages/search-results-page?q=Magnesium%20Glycinate%20400Mg"), for folks who are really concerned about sleep quality, which relates to the sleep component in that study for dementia. A multivitamin can fill broad gaps, but it can’t address a specific deficiency the way a targeted dose can. That’s why testing is so worthwhile. If you’d like help reading your results, you can [**Book a lab review consultation**](https://www.myvillagegreen.com/pages/appointment-for-your-lab-review-consultation "https://www.myvillagegreen.com/pages/appointment-for-your-lab-review-consultation") with our team. ### Key Takeaways - While low levels of vitamin D have been associated with increased dementia risk, correlation does not equal causation. - In a small _Sleep Medicine_ study, high-risk participants who took vitamin D scored 13% better on the MoCA. - Participants took 5,000 IU daily, above the 4,000 IU upper limit for adults. - Too much vitamin D can cause hypercalcemia, so a blood test and your doctor’s input come first. ## Frequently Asked Questions ### Can vitamin D improve memory? Research is early. One small study found better MoCA scores in people with mild cognitive impairment and sleep problems who took vitamin D, but larger trials are needed. ### How much vitamin D is safe to take? The NIH sets the upper limit for most adults at 4,000 IU per day. Higher doses should only be taken under a doctor’s direction. ### Do I need a blood test before taking vitamin D? Yes. It will tell you if you have a deficiency and what dose to take, instead of guessing. ### Is D3 better than D2? They both raise your vitamin D levels but D3 is generally more effective. ### What does supplementation mean? It means adding a nutrient in measured doses to make up for a shortfall from diet or sun exposure. It complements a balanced diet and doesn’t replace it. _This article is for educational purposes only and isn’t medical advice. Talk to your healthcare provider before starting any supplement._ **Tags:** aging, cognitive, function, vitamin, vitamin d and cognitive function in aging, vitamin d dementia --- > Source: [Village Green Apothecary](https://myvillagegreen.com/blogs/post/vitamin-d-deficiency-symptoms-aging)