Samantha Gemmel August 08, 2019

Lack of vitamin D is one of the most common deficiencies worldwide, with 1 in 5 UK residents suffering from low levels.(1, 2) Recent research has suggested that low vitamin D levels can contribute to the risk of a stroke, so we've put together this guide to help you understand everything from causes to prevention. 

What is a stroke?

A stroke occurs when the blood supply to part of the brain is cut off, usually due to a blockage. This stops nutrients and oxygen from reaching the brain cells, causing them to become damaged or even die. In most cases, the blockage is caused by a blood clot or a build-up of cholesterol in the blood vessels, also known as atherosclerosis.3

What causes a stroke?

There are many factors that are known to contribute to a stroke. Smoking, drinking too much alcohol and an unhealthy diet can damage blood vessels and increase the risk of clots forming. Health concerns such as high blood pressure, high cholesterol and type 2 diabetes can also increase the risk of stroke.4 However, recent research suggests that specific nutrient deficiencies may also play a role in causing stroke. Some studies have explored the potential benefit of nutrients such as vitamin C and B-group vitamins for reducing stroke risk,5,6 but there is also growing interest in the role of vitamin D in cardiovascular health.

The role of vitamin D in the body

Vitamin D is not truly a 'vitamin' like other nutrients. It is closer to the definition of a hormone, exerting effects throughout the body.7 Originally, vitamin D was known for its benefits for bone health, but current research is discovering a much more complex role. Vitamin D increases the absorption of several nutrients, including calcium, phosphate and, to some extent, magnesium. Although these nutrients are essential for bone health, they are also required for muscle contractions through the body, including those in blood vessel walls.8 In addition to this, Vitamin D plays many roles throughout the immune system, as well as preventing excessive inflammation and nourishing nerve cells.9,10,11

Vitamin D and heart health

Given that vitamin D has a number of effects throughout the body, it's no surprise that it is also essential for maintaining a healthy heart and blood vessels. Vitamin D has been found to have an anti-clotting effect, which could minimise the chance of blood clots forming in the blood vessels, therefore reducing the risk of a stroke caused by blood clots.12 Inflammation is another common cause of damage to the heart and blood vessels, but research has found that having healthy levels of vitamin D can inhibit inflammation before it becomes a problem.10 On top of this, vitamin D also supports nitric oxide production. Nitric oxide is essential for cardiovascular health, as it relaxes blood vessels and reduces blood pressure.13 This can protect the heart and blood vessels from the damage that high blood pressure can inflict.14

Can vitamin D deficiency lead to a stroke?

There is a range of evidence to suggest that vitamin D deficiency is a risk factor for stroke.15 One way that vitamin D deficiency can cause a stroke is related to its role in the production of nitric oxide. Without vitamin D stimulating nitric oxide production to relax blood vessels, blood pressure can increase.13 This can damage the blood vessels, causing a build-up of cholesterol and increasing the risk of stroke.14 In addition, vitamin D deficiency can contribute to stroke through inflammation. Research has found that the immune system cannot stop an inflammatory cascade when there are low levels of vitamin D.10 As such, evidence suggests that chronic inflammation can contribute to the risk of stroke caused by blood clots or cholesterol build-up.16 What's more, research has found that vitamin D deficiency is also strongly linked to risk factors associated with stroke such as type 2 diabetes, high cholesterol and high blood pressure.17 It's clear that vitamin D plays an important role in protecting your heart and blood vessels. When it comes to severity and recovery, one study found that low vitamin D levels may cause more severe strokes and poor recovery post-stroke.18,19

Correcting a vitamin D deficiency

The major source of vitamin D for humans is its synthesis in the skin on exposure to UV rays from the sun. In the UK, however, sunlight is not strong enough for adequate vitamin D production for 6 months of the year.2 During these months, Public Health England advise that everyone boosts their vitamin D intake through dietary and supplemental sources. Although vitamin D is not naturally found in many foods, there are moderate amounts in oily fish such as sardines and mackerel, as well as some fortified foods.2 If you aren't able to consume enough vitamin D through diet, a high-quality vitamin D supplement might be an option to consider. For more information on how to prevent stroke by maintaining vitamin D levels, see our guide on how to absorb vitamin D naturally.

For more information on how to keep your heart healthy, see our heart health hub.

1 The new guidelines on vitamin D - what you need to know NHS, 2018
2 New advice on vitamin D. British Nutrition Foundation, 2018
3Ischaemic stroke, Stroke Association, 2018
4Are you at risk of stroke?, Stroke Assocation, 2018
5. Chen, G.C., Lu, D.B., Pang, Z. and Liu, Q.F. (2013). Vitamin C intake, circulating vitamin C and risk of stroke: a meta‐analysis of prospective studies. Journal of the American Heart Assocation 2(6)
6. Saposnik, G. (2011). The role of vitamin B in stroke prevention: a journey from observational studies to clinical trials and critique of the VITAmins TO Prevent Stroke (VITATOPS). Stroke 42(3)
7. Norman, A.W. (2008). From vitamin D to hormone D: fundamentals of the vitamin D endocrine system essential for good health. The American Journal of Clinical Nutrition 88(2)
8. Holick, M.F. (2004). Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. The American Journal of Clinical Nutrition 80(6)
9. Aranow, C. (2011). Vitamin D and the immune system. Journal of Investigative Medicine 59(6)
10. Zhang, Y. et al. (2012). Vitamin D inhibits monocyte/macrophage proinflammatory cytokine production by targeting MAPK phosphatase-1. The Journal of Immunology 59(6)
11. Puchacz, E. et al. (1996). Vitamin D increases expression of the tyrosine hydroxylase gene in adrenal medullary cells. Molecular Brain Research 36(1)
12. Khademvatani, K. et al. (2014). The relationship between vitamin D status and idiopathic lower-extremity deep vein thrombosis. International Journal of General Medicine 36
13. Andrukhova, O. et al. (2014). Vitamin D is a regulator of endothelial nitric oxide synthase and arterial stiffness in mice. Molecular Endocrinology 28(1)
14. High blood pressure dangers: Hypertension's effects on your body. Mayo Clinic, 2016
15. Majumder, M.M.I. et al. (2018). Low Serum Vitamin D is Independently Associated with Acute Ischemic Stroke. Medicine Today 30(1)
16. Lindsberg, P.J. and Grau, A.J. (2003). Inflammation and infections as risk factors for ischemic stroke. Stroke 34(10)

17. Anderson, J.L. et al. (2010). Relation of vitamin D deficiency to cardiovascular risk factors, disease status, and incident events in a general healthcare population. The American Journal of Cardiology 106(7)
18. Sun,Q. et al. (2012). 25-Hydroxyvitamin D levels and the risk of stroke: a prospective study and meta-analysis. Stroke 43(6)
19. Turetsky, A. et al. (2015). Low serum vitamin D is independently associated with larger lesion volumes after ischemic stroke. Journal of Stroke and Cerebrovascular Diseases 24(7)

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.



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