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What is stroke?

Stroke is a medical condition in which blood flow to the brain is blocked, resulting in brain cell death1. Strokes can be classified into 3 main types: ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage.2

Stroke is one of the most common cardiovascular diseases (CVDs) worldwide3. In the US, an estimated 1 out of every 20 human deaths in the last year were caused by stroke4.

An intracerebral hemorrhage occurs when a brain aneurysm bursts or a weakened blood vessel leaks.

An ischemic stroke occurs when a vessel carrying blood to the brain is blocked by a blood clot.

A subarachnoid hemorrhage occurs when a blood vessel bleeds into the subarachnoid space, which is the area between the arachnoid membrane and the pia mater surrounding the brain. That area is full of cerebrospinal fluid and critical blood vessels carrying blood to the brain.

What are the common symptoms?

The onset of a stroke is almost always sudden. Though symptoms vary, a stroke generally involves one or more of the following2:

  • Arm and/or leg paresthesia (usually on only one side)
  • Arm and/or leg weakness (usually on only one side)
  • Facial weakness (usually on only one side)
  • Severe headache
  • Vertigo
  • Speech disturbance

A burning, tingling, tickling, pricking sensation, or numbness in a limb that can be caused by pressure on a nerve, reduced blood supply to a nerve, or damage to the central or peripheral nervous system.

 What are the causes?

Risk factors for stroke include:5

  • Alcohol or drug abuse
  • Diabetes
  • Hypercholesterolemia
  • Hyperglycemia/diabetes
  • Hypertension
  • Overweight/obesity
  • Preexistence of other CVDs
  • Sedentary lifestyle
  • Sleep apnea
  • Smoking
  • Unhealthy diet
  • Age, gender, genetic disposition, and previous stroke history

As with other CVDs, atherosclerosis is a common cause and very high risk factor for stroke, especially if it occurs in the walls of major intracranial arteries.6

Atherosclerosis refers to the accumulation of lipid material in arterial inner walls.

How does this topic relate to my microbiome?

Current evidence suggests links between strokes and the gut microbiota. For example, the gut microbiota produces the chemical compound trimethylamine (TMA), which is associated with the development of atherosclerosis and inflammation in animal models.7 The gut microbiota sources for TMA production are phosphatidylcholine choline, carnitine, and betaine, believed to be obtained mostly from eggs and red meat.8 Its derivate trimethylamine N-oxide (TMAO, produced in the liver from TMA) has been found to predict cardiovascular disease risk in humans9. The formation and rupture of arterial plaques may produce blood clots that can go through the bloodstream into the brain vessels and potentially block them, producing a stroke.

Some studies suggest that significant changes occur in the gut microbiota after a stroke,10 including an increase in gut barrier permeability, which may lead to increased inflammation.11 Studies of stool samples from stroke patients also showed altered microbiota metabolic activity post-stroke, as reflected through changes in the production of organic acids such as acetate and isovalerate.12

Trimethylamine (TMA) is a chemical compound produced by the microbiota in different parts of the body (especially in the gut) that is associated with the production of atherosclerosis plaques (see Cardiovascular disease).

Which diseases/topics are related to stroke?

Other conditions related to stroke are:

How can I take action?

In case of an acute episode of stroke, immediate medical care is essential. Appropriate identification of stroke symptoms is critical, as most treatment should begin in the first few hours of symptom onset for the best outcome.

Stroke prevention is possible. For preventive screenings, consult your healthcare provider. You can also avoid behavioral risk factors by:

  • Consuming a healthy diet (decreasing salt, sugar, meat, and fats; increasing plant-based foods; supplementing with probiotics and prebiotics)
  • Consuming alcohol in moderation
  • Increasing physical activity
  • Quitting smoking

Diabetes mellitus, hypertension, and obesity are also well documented risk factors, so proper management and treatment of chronic disease can help low the risk of strokes.13


1. Donnan, G. A., Fisher, M., Macleod, M., & Davis, S. M. (2008). Stroke. The Lancet, 371(9624), 1612–1623.

2. Yew, K.S., & Cheng, E. M. (2015). Diagnosis of acute stroke. American Family Physician, 91(8), 528–536.

3. Mendis, S., Puska, P., Norrving, B., World Health Organization, World Heart Federation et al. (2011). Global Atlas on Cardiovascular Disease Prevention and Control. Geneva: World Health Organization.

4. Yang, Q., et al. (2017). Vital Signs: Recent Trends in Stroke Death Rates — United States, 2000–2015. MMWR. Morbidity and Mortality Weekly Report, 66(35), 933–939.

5. Boehme, A. K., Esenwa, C., & Elkind, M. S. V. (2017). Stroke Risk Factors, Genetics, and Prevention. Circulation Research, 120(3), 472–495.

6. Banerjee, C., & Chimowitz, M. I. (2017). Stroke Caused by Atherosclerosis of the Major Intracranial Arteries. Circulation Research, 120(3), 502–513.

7. Wang, Z., et al. (2011). Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature, 472(7341), 57–63.

8. Tang, W. H. W., & Hazen, S. L. (2014). The contributory role of gut microbiota in cardiovascular disease. Journal of Clinical Investigation, 124(10), 4204–4211.

9. Randrianarisoa, E., et al. (2016). Relationship of Serum Trimethylamine N-Oxide (TMAO) Levels with early Atherosclerosis in Humans. Scientific Reports, 6(1), 26745.

10. Wen, S. W., & Wong, C. H. Y. (2017). An unexplored brain-gut microbiota axis in stroke. Gut Microbes, 8(6), 601–606.

11. König, J., et al. (2016). Human Intestinal Barrier Function in Health and Disease. Clinical and Translational Gastroenterology, 7(10), e196–e196.

12. Yamashiro, K., et al. (2017). Gut dysbiosis is associated with metabolism and systemic inflammation in patients with ischemic stroke. PLOS ONE, 12(2), e0171521.

13. Meschia, J. F., et al. (2014). Guidelines for the Primary Prevention of Stroke. Stroke, 45(12), 3754–3832.