Low vitamin D and memory problems while having an underactive thyroid

Photo: Julian Howard/Unsplash. Design: BOOST Thyroid.

Photo: Julian Howard/Unsplash. Design: BOOST Thyroid.

Vitamin D is necessary for brain activity—it regulates metabolism of calcium, reduces inflammation (1–3), and it’s quite active in brain areas important for focus and memory (4, 5).

Research has shown that vitamin D deficiency in people with an underactive thyroid may lead to memory and focusing problems, which increases the risk of depression and lower day-to-day life quality in people diagnosed with Hashimoto’s (6, 7).

Vitamin D deficiency is considered lower than 50 nmol/L (20 ng/mL) (8).

The most common issues with vitamin D deficiency (9):

  • Feeling tired all the time

  • Feeling down or depressed

  • Muscle or bone pain

  • Losing hair

  • Getting sick often (repeated infections)

The most common symptoms of vitamin D deficiency in people with Hashimoto’s are:

  • Feeling tired

  • Problems focusing

  • Problems with short-term memory

  • Feeling down or depressed

Low blood levels of vitamin D are often found in people diagnosed with Hashimoto’s (10,11), and can cause problems with focusing and memory, resembling early stages of Alzheimer’s (12).

Vitamin D is important in fighting off inflammation, one of the main reasons for problems with memory and focus. Research has shown that Hashimoto’s patients have an increased level of inflammatory molecules circulating in their bodies and causing inflammation in different parts of the body (13, 14). Vitamin D is known to block these molecules from causing inflammation, but only when vitamin D levels are high enough (15).

Vitamin D deficiency often coexists with higher TSH and TPO levels, as well as higher TG antibodies. Whether low vitamin D causes an increase in TSH remains to be researched, but it shows a connection between vitamin D and TSH (16–20). It’s unknown if low vitamin D levels is a cause or a consequence, because a lot of people diagnosed with Hashimoto’s have other conditions too, and these conditions might affect production or how vitamin D is used in the (by the) body (20).

Making sure your vitamin D levels are in a good range is important the whole year round.

During the summer a part of your vitamin D will come from sunlight-activation in your skin (21), and during the winter you might need to opt to take vitamin D supplements and vitamin D fortified foods to keep your vitamin D levels in a good zone.

What is the recommended daily intake of vitamin D?

The recommended daily intake (RDA) of vitamin D for people between ages 9 and 70 is set at 15 μg/d (600 iu/d) in the USA and 5 μg/d (200 iu/d) in most of Europe (the upper limit is 100 μg/d (4000 iu/d)), and 20 μg/d (800 iu/d) in Germany, Austria, and Switzerland.

Blood levels of vitamin D3 should be above 30 μg/L, while at least 37.5–50.0 μg/d (1500–2000 iu/d) of vitamin D may be the optimal level (22–24).

Vitamin D rich foods

A few foods contain vitamin D: egg yolk, salmon, tuna, mackerel, fish liver oils, as well as beef liver (25, 27). Mushrooms with enhanced levels of vitamin D2 from being exposed to ultraviolet light under controlled conditions are also available. Cooking won’t will not destroy much of the vitamin D content found in food (28).

Ready-to-eat breakfast cereals often contain added vitamin D, as do some brands of orange juice, yogurt, margarine, and other food products.

If milk products are not fortified with vitamin D, they are low in vitamin D — the only exception is butter because it’s high in fat (26).

What are the best vitamin D supplements?

What will determine how good is vitamin D is how well it is absorbed in by the gut.

25-hydroxyvitamin D (25-OHD)-the best form of vitamin D. There are vitamin D drops (in both oil and alcohol) and vitamin D pills, which might be as oil capsules or pills using either cellulose or lactose as a carrier.

According to research oil-based capsules and drops yield the best results and best increase in vitamin D levels (28).

Genetic factors play a role in how well a person is able to absorb and use vitamin D in/from their bloodstream (29, 30).

How long does it take to improve focus and memory problems caused by vitamin D deficiency?

If your vitamin D levels are low, it might take some time to improve them. You can retest yourself after 5–6 weeks of taking vitamin D — at that time you should see improvement in your vitamin D levels ().

Your memory should improve within 6–8 weeks.

How do you know if your vitamin D levels are okay?

The most accurate way to measure how much vitamin D is in your body is the vitamin D blood test.

Super high levels of vitamin D might not help, and might even be counterproductive in a long term.

You can track vitamin D in BOOST Thyroid app.


  1. Amer M, et al. Relation between serum 25-hydroxyvitamin D and C-reactive protein in asymptomatic adults, 2012

  2. Perez-Lopez FR, et al. Vitamin D and aging: beyond calcium and bone metabolism, 2011

  3. Sommer A, et al. Vitamin D regulates cytokine patterns secreted by dendritic cells to promote differentiation of IL-22-producing T cells, 2015

  4. Annweiler C, et al. Vitamin D and cognition in older adults: updated international recommendations, 2015

  5. Eyles DW, et al. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain, 2005

  6. LeMoult J, Gotlib IH. Depression: a cognitive perspective, 2018

  7. Scanlan JM, et al. Cognitive impairment, chronic disease burden, and functional disability: a population study of older Italians, 2007

  8. Ovesen L, et al. Geographical differences in vitamin D status, with particular reference to European countries, 2003

  9. Kennel KA, et al. Vitamin D Deficiency in Adults: When to Test and How to Treat, 2010

  10. Bakr HG, et al. Relevance of 25 (OH) vitamin D deficiency on Hashimoto’s thyroiditis, 2017

  11. Nalbant A, et al. Association of vitamin D insufficiency/deficiency with thyroid artery Doppler ultrasonography in patients with Hashimoto thyroiditis, 2017

  12. Beydoun MA, et al. Vitamin D status and intakes and their association with cognitive trajectory in a longitudinal study of urban adults, 2018

  13. Mikos H, et al. The clinical role of serum concentrations of selected cytokines: IL-1beta, TNF-alpha and IL-6 in diagnosis of autoimmune thyroid disease (AITD) in children, 2017

  14. Sun L, et al. Elevated interleukin-1beta in peripheral blood mononuclear cells contributes to the pathogenesis of autoimmune thyroid diseases, especially of Hashimoto thyroiditis, 2016

  15. Culley DJ, et al. Systemic inflammation impairs attention and cognitive flexibility but not associative learning in aged rats: possible implications for delirium, 2014

  16. Makariou S, et al. Novel roles of vitamin D in disease: What is new in 2011? 2011

  17. Plum LA, et al. Vitamin D, disease and therapeutic opportunities, 2010

  18. Holick MF. Vitamin D deficiency, 2007

  19. Holick MF, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an endocrine society clinical practice guideline, 2011

  20. Kivity S, et al. Vitamin D and autoimmune thyroid diseases, 2011

  21. IOM (Institute of Medicine) Dietary Reference Intakes for Calcium and Vitamin D, 2011

  22. Deutsche Gesellschaft für Ernährung, Österreichische Gesellschaft für Ernährung, Schweizerische Gesellschaft für Ernährungsforschung, Schweizerische Vereinigung für Ernährung. Referenzwerte für die Nährstoffzufuhr, 2008

  23. EFSA Panel on Dietetic Products NaAN. Scientific opinion on the tolerable upper intake level of vitamin D, 2012

  24. Holick MF, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline, 2011

  25. U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 24, 2011

  26. Schmid A, et al. Natural Vitamin D Content in Animal Products, 2013

  27. Mattila PH, et al. Effect of different vitamin D supplementations in poultry feed on vitamin D content of eggs and chicken meat, 2011

  28. Grossman RE, et al. Evaluation of vehicle substances on vitamin D bioavailability: A systematic review, 2010

  29. Brannon PM. Key questions in vitamin D research, 2012

  30. Larcombe L, et al. Vitamin D in a northern Canadian first nation population: dietary intake, serum concentrations and functional gene polymorphisms, 2012

  31. Roy S, et al. Correction of Low Vitamin D Improves Fatigue: Effect of Correction of Low Vitamin D in Fatigue Study (EViDiF Study), 2014