Vitamin D & Depression: Can the Sunshine Vitamin Drive Away the Grey Clouds?
You may have heard of the connection between Vitamin D and mood, especially if you read my recent post on the subject.
In today’s article, dietetic intern Yiran Wang will be taking us on a deep discussion into the role of Vitamin D and mental health. Yiran wrote this article in it’s entirety, and it’s definitely a good one!
Any questions you may have had about Vitamin D and depression will be answered.
Vitamin D is called the sunshine vitamin as it is mainly formed through our skin under sunlight [1]. It can also be obtained through fortified food (milk, margarine, etc.) or from natural sources (fatty fish).
Many people are aware of vitamin D’s benefits for bone health.
Furthermore, this popular nutrient is important in many key body functions, including our immune system, hormones and signals within our nervous system[1, 2]. There is a hot but controversial discussion about vitamin D and mental health when it comes to its role in the prevention and treatment of depression.
Although sunshine produces vitamin D, sunshine does not go hand in hand with countries with long winters, such as Canada. This means that Canadians generally have a higher risk of vitamin D deficiency. Other contributors also include our country’s Northern geography (lack of direct sunlight) and common use of sunscreen (block vitamin D conversion in skin).
In winter, about 40% of Canadians had less vitamin D than their bodies required to maintain bone health when compared a 25% of inaadequancy of vitamin D in summer [3]. In the meantime, around 5.4% of Canadians reported symptoms of depressive mood disorder, with 4.7% reporting major depression [4].
How Does Vitamin D Play a Role in Depression?
The basis for using vitamin D to prevent or treat depression comes from the following evidence and theories:
1. Vitamin D receptors are spread throughout the human brain, and vitamin D has been shown to play an important part in brain signalling and may have neuroprotective effects [2, 5, 6]. Therefore having enough vitamin D may help to promote mental health.
2. Observational studies (studies where an investigator observes individuals without interfering) showed that people with higher vitamin D levels had a lower rate of having depression[7-9].
Does This Mean We Should Use Vitamin D Supplementation to Prevent or Treat Depression?
Let’s not get ahead of ourselves. Firstly, we should note that the results of the “observational studies” do not confirm that higher vitamin D levels cause a lower risk for depression. This could be caused by something else that is also linked to higher vitamin D levels. People who suffer from depression indeed tend to have lower serum vitamin D levels, but we can not conclude low vitamin D levels are the cause of depression.
Let’s think about the opposite situation: people who are depressed may encounter difficulties having an optimal intake of vitamin D from food, or enjoying outdoor activities. Thinking about it this way, it makes sense that their vitamin D level would be lower compared to people without depression. This is called “reverse causality.”
Aside from the evidence from observational studies, we also need to look for carefully designed experiments and summaries, which include randomized controlled trials, systematic reviews, and meta-analyses.
1. Randomized controlled trials (RCTs) are a type of experiment that provides interventions while lowering the risk of bias. There are mixed results about vitamin D’s roles on preventing or treating depression. A large RCT was done with 18353 adult participants (≥ 50 years old) with a daily supplement of 2000IU vitamin D for years showed no impact on vitamin D in preventing depression or the reoccurrence of depression [10]. However, it is important to note that participants’ vitamin D levels were generally adequate before they began to supplements. This could mean that additional supplementation may not be helpful for those who already have good enough vitamin D levels when it comes to preventing depression. One RCT found no benefits of preventing or relieving depression in older females, while half of them were vitamin D adequate[11]. However, another small RCT found improvement among patients with moderate or severe depression, especially in females and overweight patients[12].
2. Systematic reviews and metal analyses use RCTs to exam the results and determine what is most likely to be true. They are the scientific review and evaluation of other individual studies.
Two earlier meta-analyses drew a similar conclusion that vitamin D supplementation may not be able to prevent depression. However, vitamin D seems to be helpful for people with depression to reduce the symptoms. One analysis showed that vitamin D supplements at (≥800IU/day) were likely to be effective in reducing depressive symptoms in people who showed improved vitamin D levels after supplementation [13]. Another analysis concluded that supplementation may be effective for people with depression but not for those without clinical symptoms [14]. Both results suggest the potential of using vitamin D supplementation for adults with depression as a treatment tool.
A 2020 study examined existing evidence and came up with a similar conclusion [15]: vitamin D supplementation is not suitable for universal supplementation in the prevention of depression; however it may be considered for people with depression who also have vitamin D deficiency.
Take-Away Messages
1. If you concerned about vitamin D deficiency (some risk factors include: darker skin, lack of sunlight exposure, daily use of sunscreen, lack of intake of vitamin D fortified food (dairy products) or fatty fish), please consult your doctor regarding the need for a blood test.
2. Consult your dietitian about the strategies in improving vitamin D intake.
3. If you are getting enough vitamin D, taking more vitamin D is not likely to improve your mood.
4. If you are vitamin-D deficient and having mood problems, consult your dietitian and doctor regarding the need for supplementation.
Contributed by: Yiran Wang MSc., MPH (c)
Thank you to Yiran for contributing amazing and insightful review on such an important topic. Hope you enjoyed today’s article!
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References:
1. Bikle, D.D., Vitamin D metabolism, mechanism of action, and clinical applications. Chemistry & biology, 2014. 21(3): p. 319-329.
2. Cass, W.A., M.P. Smith, and L.E. Peters, Calcitriol protects against the dopamine- and serotonin-depleting effects of neurotoxic doses of methamphetamine. Ann N Y Acad Sci, 2006. 1074: p. 261-71.
3. Statistics Canada. Vitamin D blood levels of Canadians. 2015 11/27 [cited 2021 02/09]; Available from: https://www150.statcan.gc.ca/n1/pub/82-624-x/2013001/article/11727-eng.htm.
4. Government of Canada. What is Depression? 2016 2016/12/30 [cited 2021 02/08]; Available from: https://www.canada.ca/en/public-health/services/chronic-diseases/mental-illness/what-depression.html.
5. Eyles, D.W., et al., Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain. J Chem Neuroanat, 2005. 29(1): p. 21-30.
6. Annweiler, C., Vitamin D in dementia prevention. Ann N Y Acad Sci, 2016. 1367(1): p. 57-63.
7. Ganji, V., et al., Serum vitamin D concentrations are related to depression in young adult US population: the Third National Health and Nutrition Examination Survey. Int Arch Med, 2010. 3: p. 29.
8. Hoang, M.T., et al., Association between low serum 25-hydroxyvitamin D and depression in a large sample of healthy adults: the Cooper Center longitudinal study. Mayo Clinic proceedings, 2011. 86(11): p. 1050-1055.
9. Kjærgaard, M., R. Joakimsen, and R. Jorde, Low serum 25-hydroxyvitamin D levels are associated with depression in an adult Norwegian population. Psychiatry Res, 2011. 190(2-3): p. 221-5.
10. Okereke, O.I., et al., 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, 2020. 324(5): p. 471-480.
11. Sanders, K.M., et al., Annual high-dose vitamin D3 and mental well-being: randomised controlled trial. Br J Psychiatry, 2011. 198(5): p. 357-64.
12. Alghamdi, S., et al., Vitamin D Supplementation Ameliorates Severity of Major Depressive Disorder. J Mol Neurosci, 2020. 70(2): p. 230-235.
13. Spedding, S., Vitamin D and depression: a systematic review and meta-analysis comparing studies with and without biological flaws. Nutrients, 2014. 6(4): p. 1501-1518.
14. Shaffer, J.A., et al., Vitamin D supplementation for depressive symptoms: a systematic review and meta-analysis of randomized controlled trials. Psychosom Med, 2014. 76(3): p. 190-6.
15. Menon, V., et al., Vitamin D and Depression: A Critical Appraisal of the Evidence and Future Directions. Indian journal of psychological medicine, 2020. 42(1): p. 11-21.