.

  • Written by Evangeline Mantzioris, Program Director of Nutrition and Food Sciences, University of South Australia
This is the first study to link a vegetarian diet to an increased risk of stroke. But the evidence isn't strong enough to cause alarm. From shutterstock.com

Research Checks interrogate newly published studies and how they’re reported in the media. The analysis is undertaken by one or more academics not involved with the study, and reviewed by another, to make sure it’s accurate.

A UK study finding vegetarianism is associated with a higher risk of stroke than a meat-eating diet has made headlines around the world.

The study, published in the British Medical Journal last week, found people who followed vegetarian or vegan diets had a 20% higher risk of having a stroke compared to those who ate meat.

But if you’re a vegetarian, there’s no need to panic. And if you’re a meat eater, these results don’t suggest you should eat more meat.

While we don’t fully understand why these results occurred, it’s important to note the study only showed an association between a vegetarian diet and increased stroke risk – not direct cause and effect.


Read more: Clearing up confusion between correlation and causation


What the study did and found

The researchers looked at 48,188 men and women living in Oxford, following what they ate, and whether they had heart disease or a stroke, over 18 years. The researchers grouped the participants according to their diets: meat eaters, fish eaters (pescatarians) and vegetarians (including vegans).

While vegan diets are quite different to vegetarian diets, the investigators combined these two groups as there were very small numbers of vegans in the study.

In their analysis, the researchers accounted for variables which are known risk factors for heart disease and stroke, including education level, smoking status, alcohol consumption, and physical activity.


Read more: Is vegetarianism healthier? We asked five experts


They found vegetarians had a 22% lower risk of heart disease than meat eaters. This is equivalent to ten fewer cases of heart disease per 1,000 vegetarians than in meat eaters over ten years.

Yet the vegetarians had a 20% higher rate of stroke, equivalent to three more strokes per 1,000 vegetarians compared to the meat eaters over ten years.

The decrease in heart disease risk seemed to be linked to lower body mass index (BMI), cholesterol levels, incidence of diabetes, and blood pressure. These benefits are all known to be associated with a healthy vegetarian diet, and are protective factors against heart disease.

This study showed fish eaters (who did not consume meat) had a 13% lower risk of heart disease, but no significant increase in the rate of stroke when compared to meat eaters.

As with any study, there are strengths and weaknesses

The main strength of this study is that it closely followed a very large group of people over a long period of time.

The major weakness is that being an observational study, the researchers were not able to determine a cause and effect relationship.

So this study is not showing us vegetarian diets lead to increased risk of stroke; it simply tells us vegetarians have an increased risk of stroke. This means the association may be linked to other factors, aside from diet, which may be related to the lifestyle of a vegetarian.

The study’s authors suggest a difference in vitamin B12 levels between the vegetarian and meat-eating groups may have contributed to the results. From shutterstock.com

And while vegetarian and vegan diets may be seen as generally healthier, vegetarians still may be eating processed and ultra-processed foods. These foods can contain high levels of added salt, trans fat and saturated fats. This study did not report on the whole dietary pattern – just the major food groups.

Another major weakness of this study is that vegans and vegetarians were grouped together. Vegetarian and vegan diets can vary considerably in nutrient levels.

So why would the vegetarian group have a higher stroke risk?

These kind of observational studies are unable to provide what scientists call “a mechanism” – that is, a biological explanation as to why this association may exist.

But researchers will sometimes offer a potential biological explanation. In this case, they suggest the differences in nutrient intakes between the different diets may go some way to explaining the increased risk of stroke in the vegetarian group.

They cite a number of Japanese studies which have shown links between a very low intake of animal products and an increased risk of stroke.


Read more: Eat your vegetables – studies show plant-based diets are good for immunity


One nutrient they mention is vitamin B12, as it’s found only in animal products (meat, fish, dairy products and eggs). Vegan sources are limited, though some mushroom varieties and fermented beans may contain vitamin B12.

Vitamin B12 deficiency can lead to anaemia and neurological issues, including numbness and tingling, and cognitive difficulties.

The authors suggest a lack of vitamin B12 may be linked to the increased risk of stroke among the vegetarian group. This deficiency could be present in vegetarians, and even more pronounced in vegans.

But this is largely speculative, and any associations between a low intake of animal products and an increased risk of stroke remain to be founded in a strong body of evidence. More research is needed before any recommendations are made.

What does this mean for vegetarians and vegans?

Vegetarians and vegans shouldn’t see this study as a reason to change their diets. This is the only study to date to have shown an increased risk of stroke with vegetarian or vegan diets.

Further, this study has shown overall greater benefits are gained by being vegetarian or vegan in its association with reduced risk of heart disease.

Meanwhile, other studies have shown meat eaters – particularly people who eat large amounts of red and processed meats – have higher risk of certain cancers.


Read more: Are there any health implications for raising your child as a vegetarian, vegan or pescatarian?


Whether you’re an omnivore, pescatarian, vegetarian or vegan, it’s important to consider the quality of your diet. Focus on eating whole foods, and including lots of vegetables, fruits, cereals and grains.

It’s equally important to minimise the intake of processed foods high in added sugars, salt, saturated and trans fats. Diets high in these sorts of foods have well-established links to increased risk of heart disease and stroke. –Evangeline Mantzioris


Blind peer review

The analysis presents a fair and balanced assessment of the study, accurately pointing out that no meaningful recommendations can be drawn from the results. This is particularly so since the majority of the data was collected via self-reported questionnaires, which reduces the reliability of the results.

While in many cases the media has reported an increased stroke risk in vegetarians, total stroke risk was not actually statistically different between the groups. The researchers looked at two types of stroke: ischaemic stroke (where a blood vessel supplying blood to the brain is obstructed) and haemorrhagic stroke (where a blood vessel leaks or breaks).

A statistically significant increased risk in the vegetarian group was only seen in haemorrhagic stroke – and even there it’s marginal. Statistically, and in total numbers of people affected, the reduced heart disease risk in the vegetarian group is more convincing. –Andrew Carey

Andrew Carey has previously received funding from the National Health and Medical Research Council of Australia, the Diabetes Australia Research Program, the Clive and Vera Ramaciotti Foundation and the CASS Foundation.

Evangeline Mantzioris does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Authors: Evangeline Mantzioris, Program Director of Nutrition and Food Sciences, University of South Australia

Read more http://theconversation.com/will-a-vegetarian-diet-increase-your-risk-of-stroke-123083

Outdoor Lighting Solutions – How to Make the Right Choice?

Whether it’s your patio, your deck, your porch, or your backyard – your outdoor space needs to be illuminated properly if you want your entire property to look good. This is also a way to boos...

Diana Smith - avatar Diana Smith

Climate change: why Sweden's central bank dumped Australian bonds

Sweden's central bank ways it will no longer invest in assets from governments with large climate footprints, even if the yields were high. ShutterstockWhat’s happening? Suddenly, at the level...

John Hawkins, Assistant professor, University of Canberra - avatar John Hawkins, Assistant professor, University of Canberra

The Conversation Yearbook 2019: celebrate with us and grab your discounted copy

The Conversation's Deputy Health Editor, Phoebe Roth, and Assistant Editor: Technology, Noor Gillani, agree this is the must-have read of 2019. Wes Mountain/The ConversationA little bit of authority ...

Molly Glassey, Digital Editor, The Conversation - avatar Molly Glassey, Digital Editor, The Conversation

Place your bets: will banning illegal offshore sites really help kick our gambling habit?

While total gambling spending in Australia decreased during 2016-17, sports betting increased by 15.3%, from A$921 million to A$1.062 billion. SHUTTERSTOCKThe Australian Communications and Media Auth...

Charles Livingstone, Associate Professor, School of Public Health and Preventive Medicine, Monash University - avatar Charles Livingstone, Associate Professor, School of Public Health and Preventive Medicine, Monash University

Stop the world, I want to get off! In Exit Strategies, one woman leaves and leaves again

The script for Exit Strategies was developed by performer Mish Grigor during an artist’s residency in the UK, against the backdrop of Brexit. Bryony JacksonTo perform an exit is not as simple as...

Sandra D'urso, Researcher, The Australian Centre, University of Melbourne - avatar Sandra D'urso, Researcher, The Australian Centre, University of Melbourne

Sri Lanka election: will the country see a return to strongman politics?

Gotabaya Rajapaksa, the frontrunner in Sri Lanka's presidential election, faces a lawsuit in the US for alleged extrajudicial killing and torture. M.A. Pushpa Kumara/EPASri Lanka’s presidential ...

Niro Kandasamy, Tutor, University of Melbourne - avatar Niro Kandasamy, Tutor, University of Melbourne

Is social media damaging to children and teens? We asked five experts

They need to have it to fit in, but social media is probably doing teens more harm than good. from www.shutterstock.comIf you have kids, chances are you’ve worried about their presence on socia...

Alexandra Hansen, Chief of Staff, The Conversation - avatar Alexandra Hansen, Chief of Staff, The Conversation

A surprising answer to a hot question: controlled burns often fail to slow a bushfire

Firefighters conduct property protection as a bushfire approaches homes at Woodford NSW, Friday, November 8, 2019. Calls for more controlled burning are common after a major bushfire. DAN HIMBRECHTS/A...

Trent Penman, Associate professor, University of Melbourne - avatar Trent Penman, Associate professor, University of Melbourne

71% of Businesses Believe the 2019 Holiday Season Will Boost Sales

As the holiday season approaches, businesses both online and on the high street are thinking about their profit margins. The winter of  2018 saw more cash spent on gifts than ever before, bu...

News Company - avatar News Company

Vital Signs. Might straight down the middle be the source of our economic success?

Australian roads are straight, as has been the trajectory of our economic policy for more than 30 years. ShutterstockWhat do a billionaire, a former vice president, and a US democratic socialist have ...

Richard Holden, Professor of Economics, UNSW - avatar Richard Holden, Professor of Economics, UNSW

Research funding announcements have become a political tool, creating crippling uncertainty for academics

There’s a lot of uncertainty in a research career. Most funding – and most jobs – are doled out by the project, or in chunks of a few years at a time. Recently, however, the situat...

Jodie Bradby, Professor of Physics, Australian National University - avatar Jodie Bradby, Professor of Physics, Australian National University

Friday essay: shaved, shaped and slit - eyebrows through the ages

In ancient China, India and the Middle East, the art of eyebrow threading was popular. It is now enjoying a resurgence. www.shutterstock.comEyebrows can turn a smile into a leer, a grumpy pout into a ...

Lydia Edwards, Fashion historian, Edith Cowan University - avatar Lydia Edwards, Fashion historian, Edith Cowan University

Is your teen off to schoolies? Here's what to say instead of freaking out

Schoolies is a rite of passage for many Australian teenagers as they finish their exams and leave school. But are you prepared? from www.shutterstock.comFor many parents whose teenage children are com...

Stephen Bright, Senior Lecturer of Addiction, Edith Cowan University - avatar Stephen Bright, Senior Lecturer of Addiction, Edith Cowan University

Public places through kids' eyes – what do they value?

One nine-year-old chose his local supermarket as a place he valued because he could "spend time with mum and help decide what goes in our trolley". ShutterstockChildren are too rarely asked their pers...

Fran Gale, Senior Lecturer, Social Work and Community Welfare, School of Social Science and Psychology, Western Sydney University - avatar Fran Gale, Senior Lecturer, Social Work and Community Welfare, School of Social Science and Psychology, Western Sydney University

New research shows Chinese migrants don't always side with China and are happy to promote Australia

Australian media coverage of China can feel alienating to Chinese migrants, but most still hold a positive view of their adopted country. Lukas Coch/AAPThe Australian government has indicated that &ld...

Wanning Sun, Professor of Media and Cultural Studies, University of Technology Sydney - avatar Wanning Sun, Professor of Media and Cultural Studies, University of Technology Sydney

Australia must engage with nuclear research or fall far behind

Nuclear power will likely remain part of the global energy mix. ioshimuro/Flickr, CC BY-NCMuch is made of the “next generation” of nuclear reactors in the debate over nuclear power in Aus...

Heiko Timmers, Associate Professor of Physics, School of Science, UNSW Canberra, UNSW - avatar Heiko Timmers, Associate Professor of Physics, School of Science, UNSW Canberra, UNSW

Grattan on Friday: When the firies call him out on climate change, Scott Morrison should listen

When five former fire chiefs held a news conference on Thursday to urge the federal government to take more action on climate change, it was a challenging moment for Scott Morrison. Those who fronted...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

Pro-Tips Every First-Time Homeowner Need To Know

Buying your first home can be overwhelming. Everyone knows the struggle it takes to own a home. And these troubles can further be escalated if you decide to construct your first home from scratch. W...

News Company - avatar News Company

Virtual tools, real fires: how holograms and other tech could help outsmart bushfires

In many countries including America, computer models are being used to predict how a fire will burn. Author providedAustralia continues to experience unprecedented destruction from bushfires. Now is t...

David Tuffley, Senior Lecturer in Applied Ethics & CyberSecurity, Griffith University - avatar David Tuffley, Senior Lecturer in Applied Ethics & CyberSecurity, Griffith University

Sick and Tired of Your Dead End Job? Try Teaching!

Tired of the same old grind at the office? Want an opportunity to impact lives both in your community and around the world? Do you love to travel and have new experiences? Teaching English is the perfect job for you! All you need is a willingness to ...

News Company - avatar News Company

The Impact of an Aging Population in Australia

There’s an issue on the horizon that Australia needs to prepare for. The portion of elderly citizens that make up the country’s overall population is increasing, and we might not have the infrastructure in place to support this. Australians h...

News Company - avatar News Company

LifeStyle

How to Make Your Girlfriend’s Birthday Extra Special

Your girlfriend’s birthday is your opportunity to show her how much you care. But how exactly do...

A Guide to Building Your Kid’s Confidence

As your child grows, confidence is key. Having low self-esteem as a child can have a detrimental e...

3 Hacks that Will Extend the Life of Your Hair Extensions

Everybody has the right to enjoy beautiful, long hair, including you! If you’ve always heard a...

Lessons in Empathy for Children

The ability to be able to understand and share the feelings of a fellow human being – empathy ...