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What role does Vitamin D, and specifically Vitamin D deficiency, play in cognitive disease? In this blog post, we’ll do a deep dive on what, if any connections, can be found in modern science between Vitamin D deficiency and memory loss.

According to a recent study published in the Fisher Center for Alzheimer’s Research Foundation, low levels of vitamin D may play a role in problems related to memory loss and the onset of Alzheimer’s disease and other various forms of dementia. These findings emphasize the importance of diagnosing low levels of Vitamin D in older adults. Researchers from the University of California Davis and Rutgers University have uncovered that memory loss declined two to three times faster in those with low blood levels of Vitamin D than those with adequate blood levels of Vitamin D. 

A recent study that observed over 1,600 seniors throughout six years concluded that those severely deficient in Vitamin D were more than twice as likely to develop Alzheimer’s and dementia than those with adequate levels. Mildly low participants in the study had an increased risk of 53%, while severely deficient participants had a 125% increased risk of developing a dementia-related illness. Based on his research, lead author David Llewellyn stated,

“We expected to find an association between low Vitamin D levels and the risk of dementia and Alzheimer’s disease, but the results were surprising - we found that the association was twice as strong as we anticipated.”

While researchers found a strong correlation between dementia and Vitamin D deficiency, they did not conclude that a Vitamin D deficiency causes dementia. There has been an alarmingly growing body of evidence linking low Vitamin D levels to cognitive decline in recent years. A study published by JAMA Neurology sought to demonstrate the significance of Vitamin D related to brain health. This study involved 382 participants with an average age of 75.5 years. Participants’ brain functions ranged from healthy to mild cognitive decline to severe mental deterioration.

Researchers also conducted cognitive tests that assessed episodic (short-term) memory, semantic (long-term) memory, visual perception, and executive function. These tests conclusively demonstrated that participants with lower Vitamin D levels showed a more significant decline in cognitive ability and episodic memory. Authors of the study commented,

“Vitamin D insufficiency was associated with significantly faster declines in both episodic memory and executive function performance, which may correspond to elevated risk for incident AD [Alzheimer’s disease] dementia.”
It is important to note that this study does not prove the two are related and, “it remains to be determined whether Vitamin D supplementation slows cognitive decline.”

What is Vitamin D?

Let’s explore what Vitamin D is and how it functions in our bloodstream. Vitamin D does not refer to a single essential nutrient but rather a group of secosteroids responsible for helping intestines absorb calcium, iron, magnesium, phosphate, and zinc. Aptly named the “sunshine vitamin,” Vitamin D is absorbed through...you guessed it, sunlight! ????

Vitamin D deficiency is common amongst older adults, partly because the skin's ability to synthesize vitamin D from the sun decreases with age. Certain ethnic groups are also particularly prone to vitamin D deficiency, including African-Americans and Hispanics, who cannot absorb sunlight through the skin. Among those groups and other darker-skinned individuals, low vitamin D should be considered a risk factor for dementia. However, doctors recommend getting Vitamin D through Vitamin D-rich, fortified foods or Supplements due to skincare concerns.

How to increase your Vitamin D intake

Ensuring adequate vitamin D levels through sun exposure, supplementation, or consuming certain foods is the first step towards preventing future cognitive decline.

Adults under the age of 69 should consume 600 IU/day, and adults over 70 should increase their consumption to 800 IU/day.

Most people produce Vitamin D by the skin as a response to sunlight. Achieving optimal Vitamin D levels through sun exposure can be challenging. However, increased exposure to sunlight may damage or age the skin, causing wrinkles and skin cancer in extreme cases. Also, depending on your geographical location, skin color, and sun exposure opportunities (especially in the winter months), achieving adequate vitamin D levels can be difficult. Daily supplementation may be the better and safer route.

Moderate and consistent Vitamin D3 doses are an effective way to maintain healthy levels of vitamin D, according to Dr. Joel Fuhrman, M.D.

“There is significant scientific agreement that a blood level of 25(OH)D (twenty-five-hydroxyvitamin D) should be at least 30 ng/ml for several aspects of health. Ingest a moderate daily dose of supplemental vitamin D3 (approximately 50 mcg or 2000 IU/day) to reach the 30-45 ng/ml window. If you do not supplement, it makes sense to have your 25(OH)D levels tested and be proactive about your health because a long-standing deficiency can be harmful.”

However, excessive doses can produce side effects, including digestive problems, headaches, irregular heartbeats, and extreme fatigue. You should not take more than the recommended daily amount. Here is a helpful chart for reference:

Vitamin D deficiency - 20ng/ml or less
Vitamin D insufficiency - 21-29ng/ml
Vitamin D sufficiency - 30ng/ml or greater

Vitamin D-rich foods include beef liver, cod liver oil, salmon, sardines, swordfish, tuna, Vitamin D-fortified milk, orange juice, cereal, oatmeal, or yogurt.

Can Vitamin D supplementation or increased sun exposure help prevent Alzheimer's and other forms of dementia?

While research studies indicate a link between Vitamin D deficiency and Alzheimer’s disease or other types of dementia, more research is needed to show cause and effect. Some studies have shown no association between low Vitamin D levels and dementia. It is premature to conclude that vitamin D deficiency is indeed a risk factor for cognitive decline and that sun exposure or the consumption of Vitamin D supplements can prevent or treat dementia. Nevertheless, it is vital to maintain adequate Vitamin D levels to prevent osteoporosis and hip fractures, especially in older adults over the age of 70. Vitamin D is essential to bone metabolism and calcium absorption.

As more extensive research and more detailed information become available, it is hopeful that in the future, we will arrive at a more definitive conclusion as to what role Vitamin D deficiency plays in memory loss and cognitive disease. Nevertheless, physicians strongly recommend the inclusion of Vitamin D blood levels when evaluating patients with cognitive impairment.

When to contact your doctor

If you suspect you may have a Vitamin D deficiency, contact your doctor and speak to them about your individual needs. Your doctor can order a blood test to measure your Vitamin D blood levels and determine whether supplementation is necessary, and if so, how much is required.

Vitamin D deficiency signs and symptoms include fatigue, bone pain, muscle weakness, muscle aches, muscle cramps, or mood changes that may lead to depression. Your doctor can help diagnose any deficiencies through routine Vitamin D level checks and work with you to develop a treatment plan.