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New Research Shows A Connection Between Low Vitamin D & Alzheimer's Disease Risk

Author:

Molly Knudsen, M.S., RDN

July 17, 2023

Registered Dietitian Nutritionist

By Molly Knudsen, M.S., RDN

Registered Dietitian Nutritionist

Molly Knudsen, M.S., RDN is a Registered Dietician Nutritionist with a bachelor’s degree in nutrition from Texas Christian University and a master’s in nutrition interventions, communication, and behavior change from Tufts University. She lives in Newport Beach, California, and enjoys connecting people to the food they eat and how it influences health and wellbeing.

Man taking a supplement with water looking out window

Image by Valentina Barreto / Stocksy

July 17, 2023

Alzheimer's disease is the leading cause of dementia, accounting for 60 to 80% of all dementia cases. And the number of people living with Alzheimer's disease is expected to triple (from 50 million) in less than 30 years. So there's an increasing interest and urgency to better understand the risk factors of the disease so that we can take a proactive approach to reduce our risk. And researchers have their eye on vitamin D levels as a potential indicator.

That's because there are numerous vitamin D receptors in the brain 1, and the vitamin is known to have neuroprotective properties and help prevent cognitive dysfunction. And a new study shows a connection between having a poor vitamin D status and the risk of developing Alzheimer's disease. Here's what you need to know.

Low blood levels of vitamin D are consistently linked to Alzheimer's disease

Researchers of a 2023 meta-analysis pooled data from six studies and almost 11,000 people to see if there was a correlation between low vitamin D levels and the likelihood of developing Alzheimer's disease (because past studies showed varying results).

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And sure enough, people with low blood levels of vitamin D [aka serum 25(OH)D]—defined as having serum levels less than 25 ng/mL—had a 59% higher risk of developing Alzheimer's disease than those who had vitamin D levels higher than that.

This study points to a convincing correlation, but it doesn't indicate whether vitamin D levels changed during a study's follow-up period, and researchers didn't look into the factors that impact vitamin D status (like diet, sun exposure, and supplementation).

While researchers did clearly define what low vitamin D means in the context of this study, the cutoff used doesn't necessarily align with what's generally considered deficient or sufficient.

Vitamin D deficiency 2: less than 20 ng/mL
Vitamin D insufficiency 2: 20-30 ng/mL
Vitamin D sufficiency 2: greater than 30 ng/dL

But sufficiency isn't necessarily good enough. You should really be aiming for serum 25(OH)D levels of 50 ng/mL or higher for optimal whole-body health.

So while this review further supports the notion that vitamin D deficiency can be detrimental to cognitive health, more research is needed to determine what vitamin D level is actually protective against cognitive conditions like Alzheimer's disease.

How to increase your vitamin D levels

A lofty 41% of people have insufficient vitamin D 3, and chances are, you may benefit from getting more of this beneficial vitamin daily.

Some foods do naturally contain vitamin D 4(like the flesh of fatty fish) or are fortified with it (like dairy or dairy alternatives). But your choices are quite limited.

Your body is also naturally able to synthesize vitamin D from the sun's rays, but too much sun exposure comes with its own health risks.

A high-quality vitamin D3 supplement (the body's preferred form of the vitamin) is likely the most effective option to increase insufficient levels. Research shows you need a minimum of 2,000 to 3,000 IU of vitamin D3 every day 5 to consistently achieve a 25(OH)D blood level greater than 30 ng/mL. To maintain optimal vitamin D levels, a higher dose of 5,000 IU daily may be needed. (If you're confused about where to start with a vitamin D supplement, here's a list of our top picks.)

The takeaway

Vitamin D plays an important role in cognition and brain health, and having a low vitamin D status may increase your chances of cognitive decline and developing Alzheimer's disease. You can get your vitamin D levels checked to see your current status and determine if you need to switch anything up in your routine (like starting a vitamin D supplement) to optimize your levels because vitamin D is not only important for neurological function, it's also essential for nearly every system in the body—like your heart, immune system, gut, and hormones.