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Vitamin D Benefits for Brain Health & Sleep

Written by Joe Cohen, BS | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Joe Cohen, BS | Last updated:

Though vitamin D is famously known as the “sunshine vitamin,” it might be just as important for the body and mind during nighttime. Research suggests sunlight gives us a boost of vitamin D during the day to support our energy levels, balanced mood, and mental health. During the night, healthy vitamin D levels help the brain get restful sleep. Read on to learn more about vitamin D’s relationship with the brain.  

Vitamin D, Brain Health & Sleep Snapshot

  • Healthy vitamin D levels contribute to quality sleep
  • Vitamin D supports brain health and development
  • Low vitamin D levels have been linked with cognitive problems and depression
  • Supplementation may be beneficial in people who are deficient

The body naturally makes vitamin D when exposed to sunlight. Getting regular, moderate sun exposure is a safe way to maintain normal vitamin D levels during the summer months.

Vitamin D is also found in certain foods, such as fatty fish like salmon and sardines. Additionally, many vitamin D supplements are available on the market.

Taken at the recommended doses, vitamin D supplements are considered safe. However, taking too much can be harmful. Vitamin D supplements may also interact with prescription medications. Remember to talk to your doctor before supplementing!

Normal vitamin D levels support emotional balance and quality sleep. People who are deficient or at risk of deficiency may benefit from supplementation.

Vitamin D May Improve Sleep Quality

Vitamin D levels may play a role in sleep disorders [1].

In one study, higher concentrations of this vitamin were associated with better maintenance of sleep [2].

In the National Health and Nutrition Examination Survey (NHANES) study, lower vitamin levels were associated with shorter sleep duration [1].

Some studies suggest improved sleep quality with vitamin D supplementation. It has been hypothesized that deficiency is central to a recent “epidemic” of disturbed sleep patterns, though large-scale studies are needed to confirm these findings [3].

One study reported a high prevalence of vitamin D deficiency in people with obstructive sleep apnea. This is a widespread disorder characterized by episodes of breathing cessation due to upper airway tract obstruction during sleep. Deficiency is more pronounced in severe sleep apnea and associated with abnormal glucose production [4, 5, 6].

More studies are needed to prove the relationship between sleep quality and vitamin D supplementation.

Though vitamin D seems to contribute to healthy sleep patterns, more research is needed to determine the benefits of supplementation.

Vitamin D Supports Brain Health & Development

Some scientists view vitamin D as a hormone active in the brain or neurosteroid [7, 8].

The vitamin D receptor (VDR) and the enzyme responsible for the synthesis of the active form of this vitamin are present in the brain [9, 10, 11].

Studies indicate that this vitamin is important for brain development, while deficiency has been associated with a wide range of psychiatric and neurological diseases [7, 12, 13, 14].

Limited research suggests that vitamin D may protect brain cells by activating detoxification pathways (production of the antioxidant glutathione, inhibition of nitric oxide). Furthermore, some scientists believe that it also helps produce proteins that increase the survival of brain cells in the aging brain and in neurological diseases (neurotrophins). More research is needed [15, 16, 17].

According to epidemiological studies, low concentrations of vitamin D are associated with:

  • impairments in cognitive function such as memory and orientation problems [18, 19, 20].
  • diagnosis of dementia and Alzheimer’s disease [21].
  • higher rates of psychotic experiences and schizophrenia [22, 23, 24].
  • depressive symptoms [25, 26, 27].

However, clinical studies have yet to determine the safety and efficacy of supplementation in people with cognitive, neurological, and mental health problems.

Vitamin D supports healthy brain development and cognition. Low levels have been linked with memory problems and low mood. The benefits of supplementation in these cases are still an active area of research.

Vitamin D May Improve Mood & Cognition

Effects on Cognitive Function

Studies suggest that low levels of blood vitamin D are associated with low mood, impaired cognitive functions, and dementia [20, 19, 28, 18].

However, other studies suggest that supplementation doesn’t influence cognitive or emotional functioning. In one study, supplementation of 5,000 IU/daily of this vitamin for 6 weeks did not have beneficial effects on memory, depression, anxiety or anger [29, 30].

Though low vitamin D levels have been linked with mood and cognitive problems, the existing evidence does not support supplementation.

Effects on Mood & Depression

In two studies, vitamin D deficiency was associated with an 8 – 14% increase in the prevalence of depression and a 50% increase in suicide rates. Large-scale studies are needed to confirm these findings [31, 32].

According to limited research data, supplementation may reduce depressive symptoms and improve physical functioning in patients with depression [33, 34].

However, other studies revealed that supplementation neither worsened nor improved depressive symptoms. In a study of elderly postmenopausal women, vitamin D and hormone therapy had no effect on depression, individually or in combination [35].

Though some studies have linked vitamin D deficiency with depression, limited clinical studies suggest that supplementation likely does not improve depressive symptoms. More research is needed.

Vitamin D & Neurological Diseases

May Reduce the Risk of Parkinson’s Disease

Some scientists hypothesize that vitamin D deficiency may contribute to the development of Parkinson’s disease. They determined deficiency early in the disease, and vitamin levels tend to decline further as the disease progresses [36, 37, 38].

Additionally, scientists posit that chronically inadequate intake of this vitamin leads to a loss of dopaminergic neurons in the substantia nigra, the region of the brain affected most by Parkinson’s disease [38, 39, 40].

However, these studies had small samples and the above-mentioned theories remain speculative. Large-scale studies should replicate their findings.

Other research teams suggest that maintaining normal vitamin D levels might reduce the risk of Parkinson’s disease, though their findings are also far from conclusive. In one study, higher vitamin D blood levels were associated with reduced risk of developing Parkinson’s disease. People with blood levels of at least 50 nmol/l had a 65% lower risk than those with values under 25 nmol/l [39].

In another study, patients with Parkinson’s disease were more likely to have an insufficiency of this vitamin compared to age-matched patients with Alzheimer’s disease. Further studies should include more people and compare their blood levels to healthy controls over a period of time [36, 37].

Limited research suggests that normal vitamin D levels may be protective against Parkinson’s disease, though solid evidence is still lacking.

Plays a Role in Alzheimer’s Disease

Similar to the theory mentioned above, some scientists suspect that vitamin D deficiency is prevalent in Alzheimer’s disease and dementia patients. In a couple of studies, Alzheimer’s disease patients had lower blood levels of this vitamin compared to age-matched healthy individuals [41, 42].

In one study, blood levels of this vitamin under 50 nmol/L were associated with a higher risk of Alzheimer’s disease and dementia [43].

Though these findings are promising, additional studies are needed to determine the link between vitamin D deficiency and Alzheimer’s disease. Ideally, future studies should also take genetic factors (including APOE4 genotypes) into consideration.

Animal and cell-based studies suggest that vitamin D may prevent Alzheimer’s by stimulating immune cells to break down built-up amyloid-β in the brain, which plays a causative role in the disease. Human studies have not confirmed these findings [44, 45].

Though data linking vitamin D deficiency and Alzheimer’s disease risk are promising, more research is needed before drawing a conclusion.


Normal vitamin D levels support emotional balance and quality sleep. Vitamin D is also needed for proper brain development and cognitive function. Limited studies have linked vitamin D deficiency with cognitive problems, sleep disorders, depression, and neurological diseases like Alzheimer’s and Parkinson’s. However, the existing evidence doesn’t support supplementation in people with these conditions. More research is needed. On the other hand, people who are deficient or at risk of deficiency may benefit from supplementation to prevent other health problems. Be sure to talk to your physician before supplementing.

Watch SelfDecode founder & CEO Joe Cohen and Dr. Mercola discuss the importance of vitamin D in episode 1 of The Joe Cohen Show podcast:

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About the Author

Joe Cohen, BS

Joe Cohen, BS

Joe Cohen flipped the script on conventional and alternative medicine… and it worked. Growing up, he suffered from inflammation, brain fog, fatigue, digestive problems, insomnia, anxiety, and other issues that were poorly understood in traditional healthcare. Frustrated by the lack of good information and tools, Joe decided to embark on a learning journey to decode his DNA and track his biomarkers in search of better health. Through this personalized approach, he discovered his genetic weaknesses and was able to optimize his health 10X better than he ever thought was possible. Based on his own health success, he went on to found SelfDecode, the world’s first direct-to-consumer DNA analyzer & precision health tool that utilizes AI-driven polygenic risk scoring to produce accurate insights and health recommendations. Today, SelfDecode has helped over 100,000 people understand how to get healthier using their DNA and labs.
Joe is a thriving entrepreneur, with a mission is to empower people to take advantage of the precision health revolution and uncover insights from their DNA and biomarkers so that we can all feel great all of the time. 


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