Vitamin D3, despite being labeled as a vitamin, is actually a hormone that is made from the skin by the sun (specifically something called UVB radiation). Essentially, the UVB radiation turns something called 7-dehydrocholesterol (a cousin of cholesterol) into the hormone vitamin D3 under your skin (1). This is pretty amazing and shows how much we need sunlight just to produce needed hormones in our bodies! And oh how much vitamin D3 is needed in our bodies! Not only is vitamin D important for calcium absorption, vitamin D deficiency is strongly associated with a lot of diseases, including mental illness such as anxiety and depression (1,2).
You'll notice here that I'm specifically referring to vitamin D3 rather than just vitamin D. That's because there are two different types of vitamin D: vitamin D2 and vitamin D3 (3). Vitamin D2 is usually in plant foods and fortified foods (think, breakfast cereals) and isn't as good at raising vitamin D levels in the blood (3). Vitamin D3 is the form that is made when you get out in the sun and is also found in some animal foods like egg yolks and fish (3). This form of vitamin D is much better at raising your blood levels though they are both pretty good at it (3).
Because a lot of us spend too much time inside and a lot of use copious amounts of sunscreen (with good reason, UV radiation can still damage your skin!), a lot of us are vitamin D deficient, especially for those of us who live far away from the equator. As a result, our providers might recommend that we take a vitamin D supplement, but the problem is, a lot of providers aren't really sure how much to give their patients. Sure, the recommendation right now is 400 IU per day, but that is really just based on how much is in a teaspoon of cod liver oil and was made to avoid high levels of calcium that can come from too much vitamin D (1, 4). We can also theoretically get enough vitamin D3 by getting around 15-20 minutes of direct sun exposure daily (2), though this certainly isn't always possible, especially on gloomy days in the Midwest and how much vitamin D3 you make depends on how much skin you have exposed and how dark or light your skin is (e.g. the darker your skin tone, the longer you have to be outside to get enough vitamin D). Daily dosing, though, ranging from 5000 IU/day to 50,000 IU/day (over 100 times the standard recommendation) was shown to be safe without causing high calcium levels (1). Another issue we run into when determining if someone is even vitamin D deficient is how we test for it. Right now, there really isn't an international consensus on what is considered too high or too low (2). In fact, given that prior to modern civilization, we spent way more time outdoors in the sun, some researchers suggest that we should aim for vitamin D levels more in the 140 nmol/L range based on populations who spend most of their time outdoors. In these folks who have higher levels than 140 nmol/L, they did have some issues with elevated calcium levels but lower than this seems to be safe (5,6). Maybe aiming for around 100 nmol/L would be ideal. That is unclear at this point though.
Okay, so we can see that vitamin D is vital for our overall health and most of us aren't getting enough of it since we stay inside all the time and lather ourselves in sunscreen (again, not a bad thing, just something that inhibits us from getting vitamin D3 made in our skin). What does this have to do with our mental health though? As it turns out, this hormone is really important for our brain to function optimally. Vitamin D receptors have been found on many areas of the brain including the prefrontal cortex, hippocampus (an area implicated in depression, specifically), cingulate gyrus, thalamus, hypothalamus (important for our circadian rhythm and appetite functions), and substantial nigra (important for dopamine production and is affected in Parkinson's disease) (2). There is also research that shows that vitamin D supplementation can help mental illness, and we're going to go through the research looking at vitamin D in three relatively common conditions: depression, anxiety, and ADHD.
Given that there are vitamin D receptors on the brain and on specific regions implicated in depression, it stands to reason that vitamin D levels have been examined as a contributing factor to depression. A number of studies have shown that the lower the vitamin D levels on average, the higher likelihood of depression symptoms (2, 7-10). So clearly, there is an association between low vitamin D levels and depression, but does improving the levels of vitamin D improve the symptoms of depression?
This seems to be the case in one study (2, 11). In an 8-week, double-blind randomized clinical trial (meaning that patients and investigators didn't know who got the treatment and who got the placebo), researchers showed that supplementing with 50,000 IU every 2 weeks improved subjective scores of depression severity and this was statistically significant (2, 11).
A similar story exists for anxiety. In one study, they took a group of people with anxiety disorders and a similar group of people without and compared their vitamin D levels. On average, the people with anxiety disorders have lower vitamin D levels than those without anxiety disorders (2, 12). When we look at supplementing vitamin D for folks who have anxiety, one study showed that vitamin D supplementation with 1600 mg daily (which is around 65,000 IU per day, and this is over 100 times the standard amount recommended per day) improved anxiety symptoms but interestingly, it did not improve depression symptoms significantly in this population (2, 13). This was also a small sample size so it may have been they simply needed more people in their study to see a significant difference. It may also be that vitamin D is just a part of the overall mental health picture and being deficient in this hormone is just a contributing factor.
Attention-deficit hyperactivity disorder is also relatively common in our society, and among adult women, it is becoming recognized more as it can often be missed when they were younger. Usually, stimulants and non-stimulants affecting a neurotransmitter called norepinephrine are used to help with the symptoms of difficulty with attention and motivation, forgetfulness, hyperactivity, and impulsivity. Interestingly, though, vitamin D has been studied as a treatment for folks with ADHD. If you remember from above, vitamin D receptors have also been found on the prefrontal cortex which is just one of the areas affected in ADHD. In one study, they looked at supplementing 50,000 IU/week of vitamin D in kids with ADHD and found that really only in those who were deficient did it make a difference in their symptoms (14, 15). In another study, they looked at both supplementing vitamin D and magnesium in children with ADHD and found significant improvement in all of the symptom domains of ADHD (14, 16). Though again, the average vitamin D levels before the treatment were pretty low among the kids in the study, and in the treatment group, the average vitamin D levels improved along with their symptoms (14, 16). This might suggest, then, that low vitamin D levels in kids with ADHD could lead to worse symptoms than those with normal vitamin D levels. This shows that overall there is more to the picture of ADHD than just a neurotransmitter imbalance; nutrition and sunlight also play an important role in improving symptomatology.
Now that we've looked at some of the more common mental health issues and how they're impacted by vitamin D, we can see how vital it is to get this hormone in our bodies. I really think that we've evolved to be in the sunshine: it makes us feel good on a sunny day, and we need it to make this hormone. Now I'm not saying to never wear sunscreen, but I'm also saying that we probably don't need to wear it all the time. In virtually all of my patients, because in the midwest, we often don't get enough sunlight, I test for their vitamin D levels as well as other important vitamins for mental health like vitamin B12 and folate. So, if you get anything from this blog post, just make sure to get a little sunshine each day and if you can't, consider supplementing vitamin D3!
References:
1. McCullough PJ LD, Amend J. Daily oral dosing of vitamin D3 using 5000 TO 50,000 international units a day in long-term hospitalized patients: Insights from a seven year experience. Journal of Steroid Biochemistry and Molecular Biology. 2019;189:228-239.
2. MG ASaK. Is Vitamin D Important in Anxiety or Depression? What Is the Truth? Current Nutrition Report. 2022;11:675-681.
3. Tripkovic L LH, Hart K, Smith CP, Bucca G, Penson S, Chope G, Hypponen E, Berry J, Vieth R, Lanham-New S. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. The American Journal of Clinical Nutrition. 2012;95:1357-1364.
4. Dowling GB PTE. Treatment of Lupus Vulgaris with Calciferol. The Lancet. 1946;247:919-922.
5. SI R-LJaR. Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels. Cureus. 2023;15:e38578.
6. BA WDaG. The vitamin D questions: how much do you need and how should you get it? Journal of American Academy of Dermatology. 2006;54:301-317.
7. Briggs R MK, O’Halloran A, Healy M, Kenny RA, Laird E. Vitamin D Deficiency Is Associated With an Increased Likelihood of Incident Depression in Community-Dwelling Older Adults. Journal of The American Medical Directors Association. 2019;20:517-523.
8. Sherchand O SN, Chaudhari RK, Khan SA, Baranwal JK, Pokhrel T, Das BKL, Lamsal M. Association between vitamin D deficiency and depression in Nepalese Population. Psychiatry Research. 2018;267:266-271.
9. Song BM KH, Rhee Y, Youm Y, Kim CO. Association between serum 25-hydroxyvitamin D concentrations and depressive symptoms in an older Korean population: A cross-sectional study. Journal of Affective Disorders. 2016;189:357-364.
10. Vidgren M VJ, Tolmunen T, Nurmi T, Tuomainen T-P, Voutilainen S, Ruusunen A. Serum Concentrations of 25-Hydroxyvitamin D and Depression in a General Middle-Aged to Elderly Population in Findland. Journal of Nutrition, Health, and Aging. 2018;22:159-164.
11. Kaviani M NB, Zand H, Yaghmaei P, Neyestani TR. Effects of vitamin D supplementation on depression and some involved neurotransmitters. Journal of Affective Disorders. 2020;269:28-35.
12. Bicikova M DM, Kalvachova B, Ripova D, Mohr P, Starka L. Vitamin D in anxiety and affective disorders. Physiological Research. 2015;64:S101-103.
13. Zhu C ZY, Wang T, Lin Y, Yu J, Xia Q, Zhu P, Zhu D. Vitamin D supplementation improves anxiety but not depression symptoms in patients with vitamin D deficiency. Brain and Behavior. 2020;10:e01760.
14. Pinto S C-d-ST, Sampaio-Maia B, Vasconcelos C, Moreira P, Ferreira-Gomes J. Eating Patterns and Dietary Interventions in ADHD: A Narrative Review. Nutrients. 2022;14:4332.
15. Dehbokri N NG, Ghaffari A, Mehdizadeh G, Sarbakhsh P, Ghaffary S. Effect of vitamin D treatment in children with attention-deficit hyperactivity disorder. World Journal of Pediatrics. 2018;15:78-84.
16. Hemamy M PN, Amanollahi A, Islam SMS, McVicar J, Askari G, Malekahmadi M. The effect of vitamin D and magnesium supplementation on the mental health status of attention-deficit hyperactiv children: a randomized controlled trial. BMC Pediatrics. 2021;21:178.
Dr. Eshleman Latimer, MD
126 Wellington Place
Cincinnati, OH 45219
Ph: 513-960-6526