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Vitamin D

Vitamin D is an all-rounder as far as your brain and mental health are concerned. It helps neurotransmission and has anti-inflammatory and neuroprotective effects on the brain by reducing both inflammation and the oxidative stress.

Generally speaking, the lower your vitamin D, the worse your mood, which makes it especially important to supplement vitamin D from October to March if you live in the UK or at a similar latitude in the northern hemisphere, for during those months the angle of the sun is very low and you’re also less likely to get outdoors and expose your skin to sunlight. It’s best to assume that we are all vitamin D deficient in winter, unless we travel to the sun, and need to supplement at least 15mcg (600iu), although twice this may be necessary to correct deficiency.

Since vitamin D is stored in the body, there is no need to supplement daily. You can take a weekly dose. In the Norwegian study, they gave 20,000iu or 40,000iu weekly. Both worked and there wasn’t a big difference in the effect on mood. So, you can assume that 20,000iu weekly or 3,000iu daily would likely be sufficient.

Vitamin D deficiency increases the risk of Alzheimer’s.[1] 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.[2] Supplementing 800iu (20mcg) a day for 12 months has also been shown to improve cognitive function.[3]

Supplements may also help ward off dementia, according to a recent large-scale study involving over 12,000 dementia-free 70+-year-olds in the USA.115 More than a third (37 per cent) took supplements of vitamin D, and those who did had a 40 per cent lower incidence of dementia.[4]

However, the yardstick for what you need is really whatever gets your blood level into the optimal range. It is now well recognized that levels above 75nmol/l correlate with good health for many health measures, while levels above 100nmol/l might be even better is some respects. Our recommendation is to test yourself and consider anything below 50nmol/l to be deficient, and above 75 nmol/l to be sufficient, with an optimal level being closer to 100nmol/l. If you then supplement 3,000iu daily, or seven times this weekly, especially from October to March, retest yourself against these yardsticks.

Our vitamin D expert, Dr William Grant, says “All the evidence regarding cardiometabolic diseases, cancer, diabetes, infectious diseases and pregnancy outcomes shows that you need a blood level of vitamin D above 75 nmol/L to be healthy, and the same is proving true for the brain. This optimal level is impossible to achieve without supplementation in the winter. I recommend every adult and teenager supplements themselves with at least 1000 to 3000iu per day from October to March in line with a recent review by 35 vitamin D researchers. [5] The degree of obesity [6], darker skin colour [7] and living further North [8] increases need.

The following supplements provide at least 3,000iu of vitamin D.

Nutri-link & Nutrigold offers Food for the Brain a 10% discount. Visit and use this discount code FFB10 to claim your discount. ‘We at Nutri-link will match your discount with a 10% donation to the charity to support their essential research and education.
– Nutrigold: Vegan Vitamin D3get it here
– Nutrilink: Bio-D-Mulsion Forte get it here



1 -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.

2 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.

3 – 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.

4 Płudowski P et al Guidelines for Preventing and Treating Vitamin D Deficiency: A 2023 Update in Poland. Nutrients. 2023 Jan 30;15(3):695. doi: 10.3390/nu15030695. PMID: 36771403; PMCID: PMC9920487.

5 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.

6 Ekwaru JP et al The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers. PLoS One. 2014 Nov 5;9(11):e111265. doi: 10.1371/journal.pone.0111265. PMID: 25372709; PMCID: PMC4220998.

7 Ames BN, Grant WB, Willett WC. Does the High Prevalence of Vitamin D Deficiency in African Americans Contribute to Health Disparities? Nutrients. 2021 Feb 3;13(2):499. doi: 10.3390/nu13020499. PMID: 33546262; PMCID: PMC7913332.

8 Engelsen O. The relationship between ultraviolet radiation exposure and vitamin D status. Nutrients. 2010 May;2(5):482-95. doi: 10.3390/nu2050482. Epub 2010 May 4. PMID: 22254036; PMCID: PMC3257661.