Vitamin D And Depression: What You Need To Know 2024

The feel of sunlight warming your skin can make your soul sing. But the energy causing that warmth is also fueling a chemical reaction vital to your survival. The ultraviolet radiation transforms cholesterol in your skin cells into the precursor for vitamin D, which travels through the bloodstream to the liver and kidneys, where it is converted into the active form of vitamin D. Vitamin D is called the sunshine vitamin because 50-90% of the vitamin D we need comes from sunlight exposure. Vitamin D can also be obtained by eating vitamin D-rich foods or consuming vitamin D-fortified foods. 

Vitamin D is critical for physical health and mental well-being. The role of vitamin D in calcium absorption and maintenance of healthy bones is well-established, but recent research has illuminated how this fat-soluble vitamin works in the brain to help treat depression.

Many studies have investigated the effects of vitamin D on depression, but the results have been inconsistent. Researchers explain that drawing conclusions is difficult because the quality of the studies varies tremendously. Meta-analyses that account for differences in study design can help clarify previous studies.

Meta-Analyses

A meta-analysis of high-quality randomized controlled trials revealed a large effect from vitamin D supplements in reducing depression symptoms^[1] in people who had a vitamin D deficiency. Results showed that when deficiencies were resolved with vitamin D supplementation, the improvements in depressive symptoms were comparable to those achieved in antidepressant trials. 

This underscores the value of meta-analyses by which methodologically flawed studies can be excluded in the analysis; without that more thorough vetting, the results were inconclusive and showed that depression actually increased with vitamin D supplements. Flawed studies tell lies. 

Another meta-analysis found that treatment with at least 4,000 IU per day for at least 8 weeks reduced negative emotions^[2] both in participants with depression and in those with a vitamin D deficiency. Similarly, a meta-analysis of 41 RCTs found that vitamin D supplements reduced depressive symptoms^[3] in people with major depressive disorder and women with postpartum depression.

Clinical Studies

In a depression treatment study, participants were randomized to receive either 1,500 IU daily of vitamin D₃  plus 20 milligrams of fluoxetine or 20 milligrams of fluoxetine alone. The results answered the question of whether or not vitamin D₃ helps with depression^[4] by showing that the combination treatment was significantly more effective than fluoxetine alone after 4 weeks.

A study investigating the effect of 50,000 IU per week of vitamin D in women with type 2 diabetes, elevated depressive symptoms, and vitamin D deficiency, found significant improvements in depression^[5] with supplementation. With six months of treatment, 63% had achieved remission from depression. 

A randomized clinical trial studying vitamin D supplements for moderate to severe depression in older adults showed improvements in depression^[6] with supplementation. Before the intervention, all participants were deficient in vitamin D, indicating that supplementation is beneficial for older adults with depression.

A study investigated the effects of long-term Vitamin D supplementation on depression and mood in adults over age 50 who did not have depressive symptoms at baseline. The results showed no difference in the incidence or recurrence of depression,^[7] clinically relevant depressive symptoms, or changes in mood scores between those who received vitamin D supplements versus placebo over 5 years. These results suggest that vitamin D supplements do not prevent depression in those with otherwise baseline good mental health.

How Does Vitamin D Affect Depression?

Vitamin D receptors are widespread in the brain. The binding of vitamin D to a vitamin D receptor can trigger a cascade of physiological events in the brain, including the production of neurotransmitters,^[8] growth and development of neurons,^[9] and defense against inflammation^[10] and infection. A review examining the evidence from previous studies highlights several mechanisms by which vitamin D deficiency could impact depression:^[11]

• Restoration of calcium and neurotransmitter balances.
• Involvement in cellular communication.
• Modulation of inflammatory cytokines,^[12] as increased systemic inflammation is associated with depression.
• Increase the concentration of vitamin D receptors in brain regions for mood regulation, like the prefrontal and cingulate cortices, thalamus, amygdala, and hippocampus.
• Regulation of the hypothalamic-pituitary-adrenal axis that drives the synthesis of neurotransmitters (epinephrine, norepinephrine, and dopamine) and defends against dopamine and serotonin depletion leading to depression.

Can Vitamin D Deficiency Cause Depression?

Research consistently identifies an association between vitamin D deficiency and depression. A large cohort study of adults aged 18 to 65 in the Netherlands found a dose-dependent inverse relationship between vitamin D levels and depression:^[13] the more severe the depressive symptoms, the lower the vitamin D levels. Results demonstrated that each standard deviation increase in vitamin D blood levels was associated with a 10% decrease in the risk of depression and that having deficient vitamin D levels was associated with a 1.74 higher risk of depressive symptoms at follow-up.

A study of female undergraduates demonstrated that lower baseline vitamin D levels predicted depressive symptoms^[13] four weeks later, even after controlling for race/ethnicity, time spent outdoors, diet, and BMI. Blood levels of vitamin D were inversely associated with depression such that as circulating vitamin levels decreased, depression severity increased.

Is There Evidence For A Type Of Vitamin D Deficiency Depression?

These studies all indicate a relationship between vitamin D deficiency and depression, but does that mean deficiency leads to depression? Not necessarily. Finding evidence of an association between vitamin D levels and depression does not mean one causes the other. You cannot say that deficiency actually causes depression. More research is needed to understand the if there is an actual process in the play of one causing the other or if they just go together.

Alternatively, experiencing clinical depression can increase the risk of developing a vitamin D deficiency or exacerbate a deficiency, but only indirectly. When people are depressed, they often avoid outdoor activities, which decreases the sun exposure needed to produce vitamin D. Additionally, depression often causes changes in appetite that can lead to low dietary intake of vitamin D. In this respect — indirectly, not directly — the relationship between vitamin D and depression can be thought of as bidirectional.

Signs Of Vitamin D Deficiency And Depression

According to the NIH,^[15] a blood serum level greater than 30 nanograms/milliliter is necessary to maintain healthy levels of vitamin D. Deficiencies can cause rickets^[16] in children and osteoporosis^[17] in adults. Vitamin D deficiency has also been associated with the inflammatory nature of cancer, cardiovascular disease, diabetes, autoimmune disorders like multiple sclerosis, and depression. 

Risk factors for vitamin D deficiency include obesity, being elderly, reduced sun exposure due to prolonged hospitalization or institutionalization, liver or kidney disease, having darker skin, and absorption problems after bariatric surgery.^[18] Higher levels of melanin in the skin cells of those with darker skin can block the synthesis of vitamin D. 

Signs Of Vitamin D Deficiency

Symptoms associated with vitamin D deficiencies include:

• Bone pain.
• Joint pain.
• Muscle pain.
• Depressed mood.
• Fatigue.
• Muscle twitching.
• Weakness.

Depression Symptoms

Depression is a serious mental health condition that makes work, interacting with others, and self-care nearly impossible. Roughly 5% of adults will experience depression, which is the leading cause of disability worldwide. The WHO presents this list of depression symptoms:^[19]

• Feeling sad, irritable, or empty.
• Loss of pleasure, interest, etc., in previously enjoyable activities.
• Poor concentration.
• Excessive guilt or low self-worth.
• Hopelessness.
• Thoughts of death or suicide.
• Sleep disruptions.
• Changes in appetite or weight.
• Low energy/fatigue.

If you or someone you love experiences any of these symptoms for more than two weeks, see a healthcare professional who can determine whether a diagnosis of depression is warranted. It is important to know that the leading cause of suicide is untreated or inadequately treated depression.  

Risks

Vitamin D supplements are generally well-tolerated with no side effects. However, toxicity can occur at serum levels above 100 nanograms/milliliter and results in hypercalcemia, i.e.,  excess calcium. Hypercalcemia is serious and can lead to confusion, vomiting, excessive thirst and urination, muscle weakness, and even death. As with any supplement, consult a healthcare professional before taking vitamin D supplements. The NIH recommends supplementation only for those with low vitamin D levels.

Vitamin D For Depression Dose

The dose of vitamin D needed to resolve a vitamin D deficiency depends on the severity of the deficiency. The NIH^[15] recommends beginning with 6,000 IU daily or 50,000 IU weekly for 8 weeks for people who have a vitamin D deficiency. If blood tests show that serum levels are higher than 30 nanograms/milliliter, continue with a daily dose of 1,000-2,000 IU to maintain optimum levels.

How Much Vitamin D Should I Take For Depression?

If you are experiencing symptoms of depression and have a vitamin D deficiency, a higher dosage may be necessary; first, however, you must consult your professional health provider. A meta-analysis of 41 randomized controlled trials found a substantial benefit^[3] for doses over 4,000 IU per day. Doses between 2,000-4,000 IU per day improved depression symptoms but to a lesser degree. Remember that studies of vitamin D supplementation^[7] for depression have shown that supplementation is beneficial^[2] only for those who had deficiencies,^[3] so consulting with a healthcare provider to determine your vitamin D status is essential.

Supplements usually contain one of two types of vitamin D, either vitamin D₂ or vitamin D₃, which leads to confusion as to which vitamin D is best for depression. Answer: vitamin D₃ is preferable^[20] because it is more effective at raising serum vitamin D levels.

Other Depression Treatments 

There are effective treatments for depression,^[19] including cognitive behavioral therapy or mindfulness-based cognitive therapy. Many forms of therapy are available online, including group therapy. Medications like selective serotonin reuptake inhibitors and tricyclic antidepressants are often used to treat moderate or severe depression. Research suggests that supplementing with vitamin D can help reduce remaining symptoms in those who also have a vitamin D deficiency. 

The Bottom Line

Vitamin D is critical for the healthy functioning of the body and brain. Lifestyle factors like time spent outdoors with sun exposure and dietary intake of vitamin D can rectify lower vitamin D levels, but supplementation may be necessary for those with deficiencies. Many studies have shown that low vitamin D levels are consistently associated with clinical depression and that supplementation can be used to reduce depressive symptoms in people with low vitamin D.

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