Nutrition and stroke prevention – The Food Medic

This article was written by one of The Food Medic team; registered dietitian – Maeve Hanan

As May is stroke prevention month, this article will outline the role nutrition can play in reducing the risk of a stroke.

What is a stroke?

A stroke is when blood supply is cut off from the brain. This can lead to serious medical issues including disability, brain damage or in some cases, death.

Most strokes occur as a result of a blood clot (i.e. an ischaemic stroke). A haemorrhagic stroke is when a bleed occurs in the brain due to a burst blood vessel.  A transient ischaemic attack (TIA) is when there’s a temporary interruption to the blood supply to the brain; this is sometimes called a ‘mini stroke’.

In the UK there are around 1.3 million people living with a stroke and roughly 100,000 strokes occur every year (1). 

A number of factors increase stroke risk including raised cholesterol or blood pressure, diabetes, an irregular heartbeat and lifestyle factors like smoking, high alcohol intake, low level of movement and the dietary factors discussed below.

See here for more information about strokes from the NHS.

What’s the best diet to prevent a stroke?

There is no single ‘best’ diet or food that will prevent a stroke from happening but consuming a balanced and healthy diet can reduce  stroke risk. For example, the NHS in the UK recommends following the Eatwell Guide. 

The Mediterranean diet is another eating pattern associated with a significantly reduced risk of stroke. For example, a study from 2018 found a 17% reduced risk of stroke in those following a Mediterranean diet (2). 

The Mediterranean diet includes:

• fruit and vegetables 
• wholegrains 
• beans and pulses
• oily fish
• olive oil
• nuts and seeds
• herbs and spices

The Dietary Approaches to Stop Hypertension (DASH) is a blood pressure-reducing diet that has also been linked with a 12% reduced risk of stroke, particularly in Asian populations (3). There are a lot of similarities between the DASH and Mediterranean diet, but the DASH diet doesn’t encourage as much healthy fats as the Mediterranean diet and emphasises reducing salt intake.  

The rest of this article will go through specific foods and food groups that can impact stroke risk. 

Fruit & vegetables

Fruit and vegetables provide important nutrients for healthy arteries and blood pressure such as antioxidants, nitrates, vitamin K, B-vitamins and potassium. 

A meta-analysis from 2014 found a 21% reduced risk of stroke in those consuming the most versus the least fruit and vegetables (4). The researchers also found that for every 200g (roughly 2.5 portions) increase in fruit and vegetables per day the risk was reduced by 32% and 11% respectively.

Unsaturated fats

Fats play an important role in keeping blood vessels healthy, which has a knock-on impact on stroke risk. 

Fats fall into two main groups:

• Saturated – found in red meat, butter, cheese, coconut oil and palm oil.
• Unsaturated – this can be further subdivided into monounsaturated fat (found mainly in plant-based foods like olive and rapeseed oil, nuts, seeds and avocado), polyunsaturated fat (like omega-3 found in oily fish and omega-6 found in plant oils like sunflower and soybean oil) and trans fat (found mainly in fried and processed foods).

For overall health, including healthy blood vessels, it is advised to consume more monounsaturated and polyunsaturated fats, and less saturated and trans fats (5). 

There have been some mixed findings when it comes to dietary fat and stroke risk. But an analysis of two studies in 2021 found a lower risk of stroke in those consuming more unsaturated and vegetable fats, and a higher risk in those consuming more non-dairy animal fats including red and processed red meat which is higher in saturated fat (6). 

It’s interesting that this study didn’t find dairy to be linked with an increased stroke risk. Although saturated fat is the main type of fat found in dairy, more evidence is emerging that the ‘dairy matrix’ (the complex combination of nutrients found in dairy or the ‘whole food effect’) may impact the health outcomes of consuming dairy. For example, consuming ordinary dairy products (i.e. not low-fat versions) doesn’t seem to be linked with an increased risk of heart disease or stroke, and may even reduce these risks — but ongoing research is needed (7, 8).  

Whereas previous research has also found red meat to be linked with an increased risk of stroke. A meta-analysis from 2016 found that red and processed red meat was associated with an increased risk of ischaemic stroke, but not hemorrhagic stroke (9). 

Nuts are a good source of unsaturated fats, as well as fibre, vitamin E and certain minerals. A higher intake of nuts has been linked with a lower stroke risk (10). A study published in 2021 that included almost 180,000 participants found that eating nuts more than five times per week, as compared to rarely or never eating nuts, was linked with a 19% reduced stroke risk (11).  

Similarly, increasing fish intake by 3 servings per week has been associated with a 6% reduction in stroke risk (12). The mechanisms behind this aren’t entirely clear as different types of fish contain a variety of nutrients. Oily fish are a particularly good source of omega-3 fats which has an anti-inflammatory effect and is needed for healthy blood pressure, and levels of fats in the blood called triglycerides (13, 14). However, consuming oily fish rather than omega-3 supplements has been seen to be better for blood vessels reducing stroke risk (15). 

wholegrains

Although wholegrains are beneficial for heart and overall  health, there have been some mixed findings about whether they are specifically protective when it comes to stroke risk. 

A meta-analysis from 2015 found that those consuming the most wholegrains had a 14% lower stroke risk as compared with those consuming the least wholegrains (16).

However, other studies haven’t found a clear association. For example, 2 prospective cohort studies analysed in 2017 (i.e. studies that follow a group of people over time to study specific factors and outcomes) found that overall wholegrain intake wasn’t linked to ischemic stroke risk (17). But the intake of wholegrain breakfast cereal was linked with a 12% lower risk, and total bran intake with a 11% lower risk of ischemic stroke. 

Salt 

Consuming a lot of salt can increase blood pressure, which in turn can increase the risk of a stroke. 

A meta-analysis from 2012 that included 12 studies found a high salt intake to be significantly linked to stroke risk (18). A more recent study that analysed trends in stroke occurrence, blood pressure and salt intake found a higher salt intake mapped onto an increased risk of ischaemic stroke in participants under 50, regardless of blood pressure (19). 

Checkout this article for more information about salt and health.

Alcohol

A high intake of alcohol is also linked with increased blood pressure. 

A large review of the evidence on this topic from 2014 found that a low intake of alcohol was linked with a 19% reduced risk of ischemic stroke, but no effect was found in terms of hemorrhagic stroke (20). However, a moderate intake of alcohol was not seen to impact this risk significantly, and heavy drinking was associated with a 20% increased stroke risk of total stroke.

In the UK, it’s recommended to drink no more than 14 units of alcohol each week, spread over 3 or more days. This works out as roughly 6 pints of 4% beer or 10 small 125ml glasses of wine (no more than 12% alcohol wine).  

See here for guidance from the NHS about low risk alcohol intake.

Tea & coffee

As well as providing fluid and caffeine, tea and coffee contain natural compounds called polyphenols that are associated with a number of health benefits such as reduced inflammation, healthy blood vessels, improved cholesterol and blood pressure levels and a reduced risk of certain diseases (21). Decaf tea and coffee also contains similar levels of polyphenols.

A large study from 2021 investigated the consumption of tea and coffee in terms of stroke risk (22). The researchers found that compared with those who drank no tea or coffee, having 2 – 3 cups of coffee and 2 – 3 cups of tea per day was linked with a 32% reduced stroke risk.

A very high intake of caffeine may be bad for blood pressure levels, so those with high blood pressure are recommended to have no more than 4 cups of coffee per day (23). 

Vitamin & mineral supplements

Although this article has mentioned specific vitamins and minerals that are important for healthy blood vessels, and hence reduced stroke risk, it is often best to get these nutrients from the diet rather than in supplement form. This is because of the ‘whole food’ benefits we get from food that we can’t get from supplements, and there can be higher risk of taking a dangerously high intake of micronutrients in supplement form. Although, this of course depends on each individual situation.

For example, although vitamin E may play a protective role due to its antioxidant effects, taking high doses of vitamin E supplements has been linked with a possible increased risk of hemorrhagic stroke (24). Another study found a 22% increased risk of hemorrhagic stroke and a 10% reduced risk of ischaemic stroke in those taking vitamin E supplements (25). 

Supplementing with a form of vitamin A called beta carotene has also been linked with increased haemorrhage stroke risk, but a slightly reduced overall stroke risk in men with a high alcohol intake (26). 

However, vitamin D is a supplement that many people living in the Northern Hemisphere benefit from taking, especially during late autumn to early spring. For example the typical recommended dose in the UK during this time of year is 10 micrograms per day (27). Vitamin D deficiency has also been found to be a risk factor for ischemic stroke (28). 

B-vitamin and folic acid supplementation may also play a role in stroke prevention, but this seems to depend on factors such as medical history and nutritional intake; more research is needed to look into this overall  (29, 30). 

Summary

Although many things impact stroke risk, some of which we can’t control like our genetics, there are a number of nutritional factors that can impact the risk of having a stroke. 

No foods need to be avoided or put on a pedestal when it comes to stroke risk, as it’s the overall nutritional balance over time that matters.

The best choices when it comes to reducing stroke risk are summarised by the Mediterranean and DASH diet which are high in fruit, vegetables, wholegrains 

legumes, olive oil, nuts, seeds and oily fish; while being low in salt without consuming excessive alcohol. This way of eating also benefits our overall health and reduces the risk of a number of other diseases. 

References:

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Nutrition and stroke prevention was last modified: April 23rd, 2022 by Maeve Hanan