By Patrick Holford
Did you know the length of your shadow can tell you if you’re able to generate vitamin D from sunlight?
If your shadow is longer than your body – you can’t produce vitamin D from sunlight. If you are in winter and live in a country of higher latitude (like the UK), this is happening now!
Vitamin D is an all-rounder as far as your brain and mental health is concerned.
It helps neurotransmission and exerts anti-inflammatory and neuroprotective activities within the brain by reducing both inflammation and oxidative stress (1).
—
Generally speaking, the lower your vitamin D, the worse your mood which makes vitamin D especially important to supplement from October to March if you live in the UK or a similar latitude, when the angle of the sun is too low and you’re also less likely to get outdoors exposing your skin to sunlight. It’s best to assume that we are all deficient in winter, unless you travel to the sun, and therefore need to supplement at least 25mcg (1000iu) although two or three times may be optimal and necessary to correct deficiency.
—
The lower your vitamin D level, the more depressed you are likely to feel. If your mood takes a dip in winter months this is a key sign that you might need more. That’s what researchers at the University of Tromso in Norway found on testing 441 volunteers who were given a test for depression and also a test for blood levels of vitamin D. The volunteers were then given Vitamin D supplements or placebo. Tested one year on, those given vitamin D, but not those given the placebos, had substantially lower depression ratings (2).
However, you don’t have to wait for a year to get a lift in your mood. An eight-week study in Australia found that some of those given vitamin D supplements had an improvement in mood in only five days (3). Another study, in Iran, gave a single vitamin D injection and reported improvement in depression when measured 3 months on (4).
Since vitamin D stores, there is no need to supplement daily. You can take a weekly dose. In the Norwegian study above they gave 20,000iu or 40,000iu weekly. Both worked and there wasn’t a big difference in the effects on mood. So, you can assume that 20,000iu weekly, or 3,000iu daily would likely be sufficient.
However, the yardstick for what you need is really whatever gets your blood level into the optimal range.
In the study above, those given 20,000iu a week averaged a blood level of 88 nmol/l, while those given 40,000iu averaged 111nmol/l. It is now well recognised that levels above 75nmol/l (30 ng/ml) correlate with good health for many health measures, while levels above 100nmol/l (40ng/ml) might be even better in some respects. My recommendation is to test yourself and consider anything below 50 to be deficient, and above 75 to be sufficient with an optimal level being closer to 100nmol/l (40ng/ml). If you then supplement 3,000iu daily, or seven times this weekly, especially from October to March, retest yourself against these yardsticks.
But it isn’t just vitamin D we need – it’s sunlight.
During the summer months, if you are spending half an hour outdoors, with short sleeves, shorts or even more skin exposure, in the sunlight, even a multivitamin that provides you 800iu (a quarter of what you need in the darker months) might be sufficient.
Sunlight promotes serotonin, the happy neurotransmitter.
Having good vitamin D levels is a vital part of your brain upgrade since it helps optimise your brain’s serotonin levels. That’s because a vital enzyme called TPH, which converts the amino acid tryptophan into serotonin, is enhanced in the brain by vitamin D, and selectively shut down in the gut. So, with sufficient vitamin D you get higher brain levels of serotonin, promoting good mood, and lower serotonin levels in the gut (5), protecting against gut inflammation.
The other way to boost your light exposure is with light therapy. Canadian researchers compared the effects of an anti-depressant (fluoxetine), placebo or 30 minutes daily of light therapy as soon as possible on waking for people with major depression. Light therapy was both superior to placebo and anti-depressants, which were also no better than placebo. I have a full spectrum light in my study, which I put on in the winter, when I’m writing in the early morning, before the sun comes up.
—
Interestingly, vitamin D deficiency is also associated with greater opioid addiction (7), suggesting the need to up vitamin D intake to reduce cravings. There’s also something else interesting about vitamin D, sun exposure and addiction. People can become addicted to sunbeds. In relation to opioids, the lower one’s vitamin D levels, the more addictive they become. Sun exposure, which promotes higher vitamin D levels, reduces opioid addiction.
—
The best food sources of vitamin D are oily fish and eggs. A serving of salmon or mackerel is likely to give you 400iu of vitamin D. Two eggs will provide about 130iu. In some countries, not the UK, milk is fortified with vitamin D but otherwise, it is not a great source. Some mushrooms are purposely fortified with vitamin D by exposing them to UV light.
In summary, the way up from down is to eat a low GL diet, with plenty of oily fish and eggs, avoid sugar, cut back on stimulants and alcohol, and make sure your daily supplements include omega-3, B vitamins, with extra B12 if your homocysteine level is high, vitamin D, zinc, magnesium, chromium, plus the amino acids 5-HTP with is the precursor of serotonin.
—
Vitamin D deficiency increases the risk of Alzheimer’s (9). In a study in France involving 912 elderly patients followed for 12 years, a total of 177 dementia cases occurred. Those with low vitamin D levels had a nearly three-fold increased risk of Alzheimer’s (10). Supplementing 800iu (20mcg) a day for 12 months has also been shown to improve cognitive function (11).
Supplements may also help ward off dementia, according to a recent, large-scale study involving over twelve thousand dementia-free 70+ year-olds in the US (12). More than a third (37%) took supplements of vitamin D. Those who did had a 40% lower incidence of dementia. Professor Zahinoor Ismail, of the University of Calgary and University of Exeter, who led the research, said: “We know that vitamin D has some effects in the brain that could have implications for reducing dementia, however so far, research has yielded conflicting results. Overall, we found evidence to suggest that earlier supplementation might be particularly beneficial, before the onset of cognitive decline.”
—
Having a higher vitamin D level or supplementing vitamin D at levels above 2,000iu a day also helps people recover from strokes (13) and other forms of brain injury.
I recommend 3,000iu a day or 21,000iu a week in winter but most importantly, monitoring your vitamin D level to keep it above 75nmol/l (30 ng/ml). A level of 100nmol/l may be optimal. That is why testing is so vital as winter approaches. Test again 3 months later so you know if you’re taking enough or too much and that will give you a good gauge as spring approaches when you can probably lower your intake to 600 to 1,000iu depending on sun exposure and diet to top up to over 1,000iu.
A breastfeeding mother must, at least, supplement omega-3 fish oils and ensure enough B vitamins for homocysteine to be below 7 mcmol/L, but many other nutrients are also necessary. Low vitamin D status in both the mother and newborn baby increases the likelihood of developing autistic spectrum disorder by 54% (14).
Without sufficient nutrients not only do brain cells not make the connections but the production and flow of neurotransmitters doesn’t happen optimally. Bruce Ames, Emeritus professor of Biochemistry and Molecular Biology at the University of California, thinks that “serotonin synthesis, release, and function in the brain are modulated by vitamin D and the 2 marine omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).” He says that ”insufficient levels of vitamin D, EPA, or DHA, in combination with genetic factors and at key periods during development, would lead to dysfunctional serotonin activation and function and may be one underlying mechanism that contributes to neuropsychiatric disorders and depression in children”. (15)
A study in Northern Ireland found that half of schoolchildren were deficient in vitamin D, with a level below 50nmol/l (I recommend above 75 nmol/l). Another finds that low vitamin D levels in childhood are related to behaviour problems in adolescence (16). Is it any wonder so many children are neurodivergent?
A placebo-controlled trial giving ADHD children magnesium together with vitamin D for eight weeks showed a major reduction in emotional, conduct and peer problems and improved socialisation compared with children treated with the placebo (17).
—
The bottom line is everyone, from children to older people, and especially anyone considering pregnancy, suffering with low mood or memory problems, must test their vitamin D, ideally, at the start of winter to guide them as to what to supplement, during winter perhaps at 3 months, and 6 months later, to learn what amount of vitamin D supplementation they need in summer and winter.
In summary, you want to get your blood level above 75nmol/l (30 ng/ml) which usually means supplementing 3,000iu from October to March for those in the Northern Hemisphere. The optimal level is, however, likely to be above 100nmol/l (40mg/ml). Your need for vitamin D is likely to be greater if you are overweight and have darker skin and live further North.
When spring returns, and throughout summer, 1,000iu a day may be enough depending on your sun exposure.
Thank you for reading!
Food for the Brain is a non-for-profit educational and research charity that offers a free Cognitive Function Test and assesses your Dementia Risk Index to be able to advise you on how to dementia-proof your diet and lifestyle.
By completing the Cognitive Function Test you are joining our grassroots research initiative to find out what really works for preventing cognitive decline. We share our ongoing research results with you to help you make brain-friendly choices.
Please support our research by becoming a Friend of Food for the Brain.
1 Jayedi A, Rashidy-Pour A, Shab-Bidar S. Vitamin D status and risk of dementia and Alzheimer’s disease: A meta-analysis of dose-response †. Nutr Neurosci. 2019 Nov;22(11):750-759. doi: 10.1080/1028415X.2018.1436639. Epub 2018 Feb 15. PMID: 29447107
2 Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K. Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial. J Intern Med. 2008 Dec;264(6):599-609. doi: 10.1111/j.1365-2796.2008.02008.x. Epub 2008 Sep 10. PMID: 18793245.
3 Khoraminya N, Tehrani-Doost M, Jazayeri S, Hosseini A, Djazayery A. Therapeutic effects of vitamin D as adjunctive therapy to fluoxetine in patients with major depressive disorder. Aust N Z J Psychiatry. 2013 Mar;47(3):271-5. doi: 10.1177/0004867412465022. Epub 2012 Oct 23. PMID: 23093054. Xxxx check the some in 5 days
4 Mozaffari-Khosravi H, Nabizade L, Yassini-Ardakani SM, Hadinedoushan H, Barzegar K. The effect of 2 different single injections of high dose of vitamin D on improving the depression in depressed patients with vitamin D deficiency: a randomized clinical trial. J Clin Psychopharmacol. 2013 Jun;33(3):378-85. doi: 10.1097/JCP.0b013e31828f619a. PMID: 23609390.
5 Patrick RP, Ames BN. Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism. FASEB J. 2014 Jun;28(6):2398-413. doi: 10.1096/fj.13-246546. Epub 2014 Feb 20. PMID: 24558199.
6 Lam RW, Levitt AJ, Levitan RD, Enns MW, Morehouse R, Michalak EE, Tam EM. The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. Am J Psychiatry. 2006 May;163(5):805-12. doi: 10.1176/ajp.2006.163.5.805. PMID: 16648320.Psychiary, No015
7 Kemény LV, Robinson KC, Hermann AL, Walker DM, Regan S, Yew YW, Lai YC, Theodosakis N, Rivera PD, Ding W, Yang L, Beyer T, Loh YE, Lo JA, van der Sande AAJ, Sarnie W, Kotler D, Hsiao JJ, Su MY, Kato S, Kotler J, Bilbo SD, Chopra V, Salomon MP, Shen S, Hoon DSB, Asgari MM, Wakeman SE, Nestler EJ, Fisher DE. Vitamin D deficiency exacerbates UV/endorphin and opioid addiction. Sci Adv. 2021 Jun 11;7(24):eabe4577. doi: 10.1126/sciadv.abe4577. PMID: 34117054; PMCID: PMC8195487.
8 Jayedi A, Rashidy-Pour A, Shab-Bidar S. Vitamin D status and risk of dementia and Alzheimer’s disease: A meta-analysis of dose-response †. Nutr Neurosci. 2019 Nov;22(11):750-759. doi: 10.1080/1028415X.2018.1436639. Epub 2018 Feb 15. PMID: 29447107
9 Chai B, Gao F, Wu R, Dong T, Gu C, Lin Q, Zhang Y. Vitamin D deficiency as a risk factor for dementia and Alzheimer’s disease: an updated meta-analysis. BMC Neurol. 2019 Nov 13;19(1):284. doi: 10.1186/s12883-019-1500-6. PMID: 31722673; PMCID: PMC6854782.
10 Jia J, Hu J, Huo X, Miao R, Zhang Y, Ma F. Effects of vitamin D supplementation on cognitive function and blood Aβ-related biomarkers in older adults with Alzheimer’s disease: a randomised, double-blind, placebo-controlled trial. J Neurol Neurosurg Psychiatry. 2019 Dec;90(12):1347-1352. doi: 10.1136/jnnp-2018-320199. Epub 2019 Jul 11. PMID: 31296588.
11 Feart C, Helmer C, Merle B, Herrmann FR, Annweiler C, Dartigues JF, Delcourt C, Samieri C. Associations of lower vitamin D concentrations with cognitive decline and long-term risk of dementia and Alzheimer’s disease in older adults. Alzheimers Dement. 2017 Nov;13(11):1207-1216. doi: 10.1016/j.jalz.2017.03.003. Epub 2017 May 16. PMID: 28522216.
12 Ghahremani M, Smith EE, Chen HY, Creese B, Goodarzi Z, Ismail Z. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimers Dement (Amst). 2023 Mar 1;15(1):e12404. doi: 10.1002/dad2.12404. PMID: 36874594; PMCID: PMC9976297.
13 Marek K, Cichoń N, Saluk-Bijak J, Bijak M, Miller E. The Role of Vitamin D in Stroke Prevention and the Effects of Its Supplementation for Post-Stroke Rehabilitation: A Narrative Review. Nutrients. 2022 Jul 4;14(13):2761. doi: 10.3390/nu14132761. PMID: 35807941; PMCID: PMC9268813.
14 Wang Z, Ding R, Wang J. The Association between Vitamin D Status and Autism Spectrum Disorder (ASD): A Systematic Review and Meta-Analysis. Nutrients. 2020 Dec 29;13(1):86. doi: 10.3390/nu13010086. PMID: 33383952; PMCID: PMC7824115.
15 Patrick RP, Ames BN. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J. 2015 Jun;29(6):2207-22. doi: 10.1096/fj.14-268342. Epub 2015 Feb 24. PMID: 25713056.
16 Sonia L Robinson, Constanza Marín, Henry Oliveros, Mercedes Mora-Plazas, Betsy Lozoff, Eduardo Villamor, Vitamin D Deficiency in Middle Childhood Is Related to Behavior Problems in Adolescence, The Journal of Nutrition, Volume 150, Issue 1,
2020, Pages 140-148, ISSN 0022-3166, https://doi.org/10.1093/jn/nxz185.
17 Hemamy M, Pahlavani N, 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 hyperactive children: a randomized controlled trial. BMC Pediatr. 2021 Apr 17;21(1):178. doi: 10.1186/s12887-021-02631-1. Erratum in: BMC Pediatr. 2021 May 12;21(1):230. PMID: 33865361; PMCID: PMC8052751.
