Vitamin D & Depression: What the Research Shows

Vitamin D is best known for keeping bones strong, but it’s involved in many processes in the body, including in the brain. Over the past decade, there’s been a lot of interest in whether vitamin D is linked to mood. Here’s what the research shows.

What is vitamin D?

Vitamin D works more like a hormone than most vitamins. It helps the body absorb calcium and phosphate for healthy bones and muscles. Vitamin D receptors are also found in the brain, which is one reason researchers have looked at its possible role in mood.

There are two main forms:

• Vitamin D2 is found mainly in mushrooms, especially those exposed to UV light.

• Vitamin D3 is made in the skin when it’s exposed to UVB light from the sun. It’s also found in small amounts in oily fish, eggs and liver.

Who is more likely to have low vitamin D?

• People who spend most of their time indoors, including many shift workers
• People with naturally darker skin
• People who cover most of their skin for cultural or religious reasons
• Older adults and people in residential care
• People living with obesity or some medical conditions that affect absorption

How is vitamin D measured?

Your doctor can check your vitamin D level with a simple blood test (25-hydroxyvitamin D). In Australia, a level below 50 nmol/L is generally considered deficient (Healthy Bones Australia).

Is vitamin D linked to depression?

Depression is common and complex, with biological, psychological and social contributors. It isn’t caused by a single nutrient.

Here’s what the research says:

• Observational studies have found that people with lower vitamin D levels are more likely to experience depression (Anglin et al., 2013). This doesn’t prove that low vitamin D causes depression. Spending less time outdoors, being less active or being unwell can lower vitamin D levels and also affect mood.
• The VITAL-DEP trial gave more than 18,000 adults aged 50 and over either vitamin D3 or a placebo for about five years. Vitamin D didn’t reduce the risk of developing depression (Okereke et al., 2020).
• A 2022 meta-analysis of 41 randomised trials found that vitamin D supplements were associated with a reduction in depressive symptoms, with larger effects in people already diagnosed with depression. However, the certainty of the evidence was rated very low (Mikola et al., 2022).

In short: if you have low vitamin D, correcting it is good for your health. Vitamin D isn’t a treatment for depression on its own, and for most people with normal levels, extra supplements are unlikely to prevent it.

How much vitamin D is safe?

More isn’t better. The Australian upper limit for adults is 80 micrograms (3,200 IU) a day from all sources (NHMRC Nutrient Reference Values). Higher doses should only be taken if your doctor prescribes them after a blood test. Too much vitamin D can raise calcium levels in the blood.

Getting vitamin D safely

Most people need only 8-10 minutes of sun on their skin, and sun protection still matters.

• Check the UV index on the SunSmart app or the Bureau of Meteorology website.
• When the UV is 3 or above, use sun protection. For most people, short periods of incidental sun on the arms in the mid-morning or mid-afternoon are enough (Queensland Government).
• People with darker skin may need more time in the sun, and people with very fair skin or a history of skin cancer should talk to their doctor first.
• Shift workers and people who work indoors may find a short outdoor break during daylight hours helpful. My post on morning sunlight has more ideas.
• Food sources such as oily fish (salmon, sardines), eggs and UV-exposed mushrooms add a little vitamin D.

When to see your GP

Talk to your GP if you’re concerned about your vitamin D level, or before starting a supplement, especially if you take other medicines or have kidney problems.

If you’ve been feeling low for more than two weeks, losing interest in things you usually enjoy, or finding it hard to cope, please reach out to your GP. Support is available, and depression is treatable.

References

1. Anglin RES, et al. (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry, 202(2), 100–107. https://doi.org/10.1192/bjp.bp.111.106666
2. Okereke OI, et al. (2020). Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: a randomized clinical trial. JAMA, 324(5), 471–480. https://doi.org/10.1001/jama.2020.10224
3. Mikola T, et al. (2022). The effect of vitamin D supplementation on depressive symptoms in adults: a systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition, 63, 11784–11801. https://doi.org/10.1080/10408398.2022.2096560
4. NHMRC / Eat For Health. Nutrient Reference Values: Vitamin D (Upper Level of Intake 80 µg/day). https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/vitamin-d
5. Healthy Bones Australia. Vitamin D and bone health. https://healthybonesaustralia.org.au/your-bone-health/vitamin-d-bone-health/
6. Queensland Government. Sun exposure and vitamin D. https://www.qld.gov.au/health/condition/skin-health/skin-cancers/sun-exposure-and-vitamin-d