Vegan and heart disease

Vegetarian heart health: Study identifies benefits and risks

The authors of a large, long term study conclude that pescatarianism and vegetarianism have an association with a reduced risk of ischemic heart disease, but they note that vegetarians have a slightly higher risk of stroke.

Share on PinterestA new, large scale study places the health effects of vegetarianism under the microscope once again.

Over recent years, increasing numbers of people have decided to reduce the amount of meat in their diet.

Vegetarians, vegans, and pescatarians (people who eat fish but not meat) are a growing demographic.

Following any one of these meat-free diets is nothing new, but due to the spike in popularity, researchers are keen to understand the possible health implications.

A recent study, which features in BMJ, looks specifically at plant based diets and their effect on the risk of stroke and ischemic heart disease (IHD).

IHD refers to any problems that occur due to a narrowing of the arteries to the heart. Without treatment, it can lead to a heart attack.

What do we already know?

Earlier studies have concluded that vegetarians have a lower risk of obesity and IHD, but as a review of relevant research explains, there is a need for more long term studies involving larger numbers of people.

As for stroke risk, only a few studies have looked into the relationship between a plant based diet and stroke risk. According to the authors of the current study, these “found no significant differences in risk of total stroke deaths between vegetarians and nonvegetarians.”

The latest study aimed to fill in some of these gaps. In all, the scientists took data from 48,188 people whom they followed for an average of 18.1 years.

The participants, who had an average age of 45 years at the start of the study, had no history of IHD or stroke.

The researchers assigned each participant to one of three groups:

  • Meat eaters: people who reported eating meat
  • Fish eaters: those who ate fish but no meat
  • Vegetarians and vegans: people who did not eat meat or fish

The team combined vegans with vegetarians for the main analysis due to the small number of vegans in the dataset.

Using food questionnaires, the researchers could also assess overall food intake and nutrient levels. Aside from dietary information, they collected information about factors such as body mass index (BMI), height, and blood pressure.

A double edged sword

During the 18.1 years of follow-up, there were 2,820 cases of IHD and 1,072 cases of stroke.

After adjusting for sociodemographic and lifestyle factors, the analysis revealed both positive and negative relationships between cardiovascular health and reduced meat intake.

The rate of IHD among pescatarians was 13% lower than that of meat eaters, while vegetarians had a rate that was 22% lower. To put these numbers into perspective, the authors explain:

“This difference was equivalent to 10 fewer cases of ischemic heart disease in vegetarians than in meat eaters per 1,000 population over 10 years.”

According to the authors, this positive association appears to be, at least partly, due to lower rates of hypertension and diabetes, as well as lower BMI and cholesterol levels. However, even after the scientists had adjusted the data to account for these factors, the effect was still “marginally significant.”

Conversely, vegetarians had 20% higher rates of stroke than meat eaters. This difference is equivalent to three more cases of stroke per 1,000 people over 10 years. This association was mostly due to hemorrhagic stroke rather than ischemic stroke.

No previous studies have shown this type of relationship between vegetarianism and stroke risk. The authors believe that this might be because earlier work reported stroke mortality rather than incidence. Strokes are only fatal in 10–20% of cases, so many cases would not count toward the reported total.

Why the scientists saw this increase in stroke risk is up for debate. The authors believe that it might be due to lower levels of other circulating nutrients in the blood of vegetarians. These might include essential amino acids and vitamins B-12 and D.

Strengths, limitations, and further work

The study has a number of strengths; first and foremost, the researchers used a large sample size and a long follow-up period. They also linked participants to their medical records to ensure the accurate collection of health outcomes.

In addition, the researchers checked the participants’ eating habits at two time points that were years apart, finding that adherence was good overall.

However, there were certain limitations. For instance, the participants self-reported their diet, which leaves room for error and misreporting. Diet can also fluctuate over days, weeks, and years.

Also, researchers did not have access to the use of drugs, including statins, among participants.

As the study is observational, it is not possible to conclude that the effect is causal. In other words, the changes in risk could be due to other factors that the scientists did not measure.

Lastly, because the participants were predominantly European and white, the findings may not be widely applicable.

An editorial by Prof. Mark A. Lawrence and Prof. Sarah A. McNaughton from Deakin University in Australia accompanies the paper.

In it, the authors call for caution, explaining how the conclusions are “based on results from just one study, and the increase is modest relative to meat eaters.”

They also explain that studies “have reported mostly protective associations between vegetarian diets and chronic disease risk factors.”

These results are sure to open debate and spark more research. That vegetarianism protects against IHD is not surprising given past findings. However, the fact that giving up meat might slightly increase stroke risk is unexpected. More work is sure to follow.

Vegetarian and pescetarian diets could lower the risk of coronary heart disease, according to research. But vegetarians and vegans are also more likely to have strokes than meat eaters.

The study involved 48,188 people from the U.K. who were recruited between 1993 and 2001 when they had no history of cardiovascular disease. This umbrella term includes conditions which affect the blood vessels, including heart attacks and strokes. They answered questions about their diets at the start of the study, and again in around 2010.

Researchers used this information to split the participants into three groups: meat-eaters; fish-eaters (pescetarians); and vegetarians, including vegans.

When compared with meat-eaters, pescetarians and vegetarians were found to have a 13 percent and 22 percent lower chance of developing coronary heart disease, respectively.

However, vegetarians and vegans were found to have a 20 percent higher risk of experiencing stroke than meat-eaters. This was largely associated with hemorrhagic stroke: a relatively uncommon form of the condition where weakened vessels rupture and cause bleeding in the brain.

This is the first study to look at whether strokes are linked to vegetarian diets, according to the authors.

Study co-author Tammy Tong, a nutritional epidemiologist at the University of Oxford, told Newsweek that as the research was observational the team couldn’t answer what underlies this link.

“There is some recent evidence that suggests while low levels of total or LDL cholesterol is protective against heart disease, very low levels might be linked to a slightly higher risk of haemorrhagic stroke, which is the subtype of stroke that was higher in the vegetarians in our study,” she said.

“Vegetarian and vegan diets may also be naturally low in some nutrients, such as vitamin B12, which is available for vegetarians in some fortified foods and from supplements, but is otherwise only naturally available from animal sourced foods. Some research has suggested there may be a link between B12 deficiency and higher stroke risk, but the evidence is not conclusive.”

Tong said more research is needed to determine the link of both cholesterol and individual nutrients like vitamin B12 with stroke risk. And as the study was based on the U.K. population and included mostly white European individuals, more research is needed to confirm whether the results are generalizable to people of other ethnicities or living in other regions of the world.

She highlighted that the team found a lower risk of coronary heart disease in both pescetarians and vegetarians and vegans, equivalent to six fewer cases of heart disease in the pescetarians and 10 fewer cases in the vegetarians, compared with meat-eaters, in every 1,000 people consuming these diets over 10 years. In contrast, there would be three more cases of stroke in the vegetarians than meat eaters over the same time period.

Speaking broadly on the current scientific consensus on the healthiest diet, Tong said: “There is good evidence that a number of healthy dietary patterns, including the Mediterranean diet, but also the Nordic diet or the DASH diet for example, is linked to lower risks of some chronic diseases.

Fruits, vegetables, whole grains, and legumes feature heavily in these diets, as well as low levels of red and processed meat, Tong said.

Scientists investigated whether diets including and excluding meat are linked to coronary heart disease. This stock image of a couple eating lunch. Getty

Vegetarian diets may lead to lower blood pressure, improved cholesterol levels, healthier weight and less incidence of Type 2 Diabetes, all of which can reduce the risk of heart disease and stroke.

A vegetarian diet consists of eating plant-based foods while avoiding meat.

A vegan diet is different from a vegetarian diet because it avoids all animal products and byproducts. This means removing all dairy and eggs from your diet. Some people may choose to exclude things like honey and gelatin as well.

Vegetarian and vegan diets can provide all the nutrients you need at any age, as well as some additional health benefits. Vegetarian diets often have lower levels of total fat, saturated fat and cholesterol than many meat-based diets, and higher intakes of fibre, magnesium, potassium, folate and antioxidants such as vitamins C and E.

A vegetarian eating plan can provide all the nutrients you need but requires careful planning.

We recommend that you:

  • Fill half your plate with vegetables and fruit.
  • Fill a quarter of your plate with whole grains.
  • Fill a quarter of your plate with plant proteins such as beans, lentils and tofu.
  • Include a small amount of unsaturated fat each day.
  • Satisfy your thirst with water.

A vegetarian or vegan diet requires planning to meet your nutrient needs. Here are the nutrients that require some special attention.

Protein

Plant-based foods can provide all the protein you need. Protein-rich plant foods include:

  • All soy products such as tofu, tempeh and beverages
  • Cooked beans, peas and lentils
  • Peanuts and peanut butter
  • Most nuts and seeds

It is no longer necessary to combine proteins for example, beans with grains, in the same meal in order to maximize protein absorption. Other protein options include eggs (also rich in zinc and iron) and milk (high in zinc). Whole grains such as quinoa also provide some protein and are great sources of minerals.

Iron

Vegetarians and vegans are at no more risk of iron deficiency than meat eaters. While the version of iron found in meat (heme-iron) is more readily absorbed than the non-heme iron found in plant sources, absorption can be enhanced by combining non-heme iron options with foods high in vitamin C such as citrus fruits, tomatoes, broccoli or berries. Good plant sources of iron include dark green leafy vegetables, dried beans or legumes, iron-enriched products (check labels), nutritional yeast and dried fruit. An example may be a romaine lettuce salad with mandarin oranges. See more heart-healthy vegetarian recipes.

Calcium and vitamin D

Calcium is important for strong bones and vitamin D is necessary for your body to be able to absorb calcium. Dairy products, almonds, sesame seeds, dark-green vegetables (such as broccoli, bok choy and kale), and black strap molasses contain calcium. Other products are fortified with calcium, including soy, almond and rice beverages and tofu (check the ingredients).

Vitamin D is often added to milk and some yogurt, soy, almond and rice beverages, and fortified margarine. While sunlight allows us to produce our own vitamin D through our skin, it is typically not sufficient during Canadian winters. As a result, these supplemented sources are important, especially for babies, children and older adults. We recommend for men and women over 50 years of age to take a daily supplement of Vitamin D of 400 IU.

Vitamin B 12

This vitamin is necessary for cell division and blood formation. It can be found in fortified cereals, soy and rice beverages, and some types of nutritional yeast. It’s important to read labels to ensure you are getting enough B 12. If you are vegetarian or vegan, consult your health professional about a B 12 supplement if you are not sure you’re getting enough from your diet.

Related information

You don’t have to be a vegetarian to reap the health benefits from eating more plant foods and less meat. Try these mouth-watering vegetarian recipes.

Get tips for eating at home.

Make smarter shopping choices with our grocery store basics.

Read the Dietitians of Canada’s healthy eating guidelines for vegans.

Why a Vegan or Vegetarian Diet May Lower Heart Disease but Raise Stroke Risk

Diets that call for avoiding either meat or all animal products get a lot of buzz for being healthy and contributing to weight loss. But there may be a catch to these diets, called vegetarian and vegan diets, respectively: a higher risk for a certain type of stroke.

In a study published in September 2019 in the BMJ, researchers observed that non-meat-eaters had a 22 percent lower risk for coronary artery disease, a type of heart disease, but a 20 percent higher risk for hemorrhagic stroke. At the same time, pescatarians, who eat fish but not meat, had the same risk of stroke but a 13 percent lower risk for heart disease compared with the meat eaters. (The authors did not formally compare these risks in fish eaters versus vegetarians.) To draw their results, the reasearchers followed 48,000 people in Great Britain for nearly 18 years.

“Our findings indicate that the vegetarians had higher stroke risk than meat eaters, mostly due to a subtype of stroke called hemorrhagic stroke that is related to bleeding in the brain,” says lead researcher Tammy Tong, PhD, a nutritional epidemiologist at the Nuffield Department of Population Health at the University of Oxford in England.

The study didn’t determine why, but past research offers a clue: Nutrient deficiencies common among non-meat-eaters may be tied to a higher risk for hemorrhagic stroke.

“A low cholesterol level is known to be protective against heart disease and ischemic stroke,” says Dr. Tong, “but some recent evidence suggests that low cholesterol may be linked to higher risk of hemorrhagic stroke, the subtype of stroke found to be higher in the vegetarians.” For example, a study published in May 2019 in Neurology found that women who had LDL cholesterol levels — considered the “bad” type of cholesterol — that were 70 milligrams per deciliter (mg/dL) or lower were twice as likely to have this type of stroke than women with levels that ranged from 100 to 130 mg/dL.

RELATED: What Are the Symptoms and Causes of Stroke?

A Closer Look at the Merits of Plant-Based Eating

A seemingly unshakable health halo has long encircled diets that focus on reducing or avoiding meat and other animal products. The validity of this approach exceeds that of celebrity-endorsed diet fads, too: Research has shown that plant-based eating styles, such as vegetarian and vegan diets, may reduce the risk for, and potentially help treat, obesity, heart disease, and type 2 diabetes. For example, studies cited in an article published in the Summer 2016 issue of The Permanente Journal suggested those health benefits and more.

Yet if followed improperly, vegan and vegetarian diets can also pose an elevated risk for deficiencies of nutrients such as vitamin B12. Tong says some previous studies have suggested that low B12 levels in vegetarians may contribute to higher stroke risk, but the evidence is not conclusive.

The important thing is to keep this potential health risk of plant-based eating in perspective.

According to the American Stroke Association, the most common type of hemorrhagic stroke occurs when a blood vessel in the brain bursts and leaks blood into surrounding tissue. The bleeding causes brain cells to die and the affected part of the brain stops working correctly. But almost 9 out of 10 are not hemorrhagic but ischemic, according to the Centers for Disease Control and Prevention (CDC). An ischemic stroke happens when blood flow through an artery is blocked, usually by a blood clot.

RELATED: 6 Common Misconceptions About Going Vegetarian, Explained

How Eating Fish May Help Lower the Risk for Stroke

Sarah Samaan, MD, a cardiologist with Baylor Scott and White Legacy Heart Center in Plano, Texas, suggests that vegetarians and vegans also may not be getting enough healthy omega-3 fatty acids in their diet. Fatty fish, such as salmon, herring, sardines, and trout, offer omega-3 fatty acids, and the American Heart Association recommends eating two servings of these types of fish each week to reduce stroke and heart disease risk.

“Although some nuts and oils provide omega-3s, the plant-based forms of this nutrient are not used very efficiently by the body, whereas we are able to process omega-3s from fish quite readily,” says Dr. Samaan, who is also the author of DASH (Dietary Approaches to Stop Hypertension) Diet for Dummies. “It is likely that the lack of certain animal-based nutrients, such as healthy fats, puts vegans and vegetarians at risk for hemorrhagic stroke.”

She underscores that fish tends to be lower in cholesterol than meat and less likely to cause inflammation of the blood vessels.

“The results appear to correspond to the lower risk of heart disease in pescatarians,” says Samaan, whose preferred diet for about the past 30 years has been a fish- and plant-based Mediterranean diet. “While there is more than one way to eat clean and healthy, the preponderance of nutritional research supports this diet when it comes to heart health, brain health, and cancer risk reduction.”

RELATED: A Complete Mediterranean Diet Food List and 14-Day Meal Plan

Among Plant-Based Dieters, the Higher Stroke Risk Was Small Compared With Their Lower Heart Disease Risk

The researchers also stress that, among the vegetarians and vegans, the higher risk from stroke in absolute numbers was small compared with the lower risk of heart disease. Over 10 years, there were 10 fewer cases of coronary heart disease in every 1,000 people, but 3 more cases of stroke per 1,000 in the vegetarians, according to the study.

“It is important to keep in mind the absolute risk differences of the two outcomes reported here, which suggest the higher risk from stroke is small compared with the lower risk from coronary heart disease,” Tong says.

The investigation results still suggest that a vegetarian or vegan diet may have many heart-healthy benefits, which is in line with advice from the American Heart Association.

“The lower risk of heart disease is likely related to the lower BMI (body mass index), cholesterol, blood pressure, and rate of diabetes in the vegetarians than meat eaters, which are all established risk factors for heart disease,” says Tong.

RELATED: 10 of the Best Plant-Based Sources of Protein

Why More Research Is Needed on the Link Between Stroke and Diet

There are other reasons to approach the current study’s findings with caution.

The authors point out that this is a single observational study, so whether any of these diets definitively contributes to or reduces the risk for stroke or heart disease is yet to be determined.

Also, the study included mostly white European individuals, and results may not be applicable to other populations. In addition, dietary information from participants was self-reported, which may have skewed the results. Overall, the scientists suggest that more research is necessary in other populations.

“For appraising the overall health of nonmeat diets,” Tong says, “other outcomes beyond what is covered in the current study should also be considered.”

Vegans and vegetarians at ‘lower risk of heart disease’, but have increased chance of stroke

Vegan and vegetarian diets are linked to a lower risk of heart disease but may increase the risk of stroke, experts say.

Advertisement

A study from the University of Oxford found that people who follow the diets have a 22 per cent lower risk of heart disease than meat eaters, while those who eat fish but no meat (pescatarian diet) have a 13 per cent reduced risk.

However, researchers found that vegetarians and vegans were a fifth more likely to suffer a stroke than meat eaters, which they suggest may be partly due to a lack of vitamins.

Read more about vegetarianism:

  • The artificial meat factory – the science of your synthetic supper
  • Which vegan milk is best for the environment?
  • The thought experiment: What would happen if everyone on the planet suddenly went vegan?

The study, published in the British Medical Journal (BMJ), included data for 48,188 people with no history of heart disease or stroke at the start of the study.

Over a follow-up of 18 years, 2,820 cases of ischaemic heart disease and 1,072 cases of stroke were recorded among the overall group.

After adjusting for factors that might influence the results, researchers found that fish eaters had a 13 per cent reduced risk of heart disease than meat eaters, while vegetarians and vegans had a 22 per cent lower risk.

This was equivalent to 10 fewer cases of ischaemic heart disease in vegetarians and vegans than in meat eaters per 1,000 people over 10 years.

Science Focus Podcast: Dr Giles Yeo talks to us about how our genes influence how hungry we feel and how much we eat, and what we should do about it.

The researchers said: “We observed lower rates of ischaemic heart disease in fish eaters and vegetarians than in meat eaters, which appears to be at least partly due to lower body mass index and lower rates of high blood pressure, high blood cholesterol, diabetes associated with these diets.”

But the study found 20 per cent higher rates of stroke in vegetarians and vegans than in meat eaters, equivalent to three more cases of stroke per 1,000 people over 10 years.

This was mostly due to a higher rate of haemorrhagic stroke – the type caused by bleeding in or around the brain.

The team said the increased risk of stroke could be down to lower levels of vitamins among the vegetarians and vegans in the study.

Read more about heart disease:

  • The discoveries bringing an end to heart attacks
  • Should you give the kiss of life to someone having a heart attack?
  • Xenotransplantation: could a pig’s heart save your life?

They said further investigation was needed, adding: “Vegetarians and vegans (in the study) have lower circulating levels of several nutrients (eg, vitamin B12, vitamin D, essential amino acids, and long chain n-3 polyunsaturated fatty acids), and differences in some of these nutritional factors could contribute to the observed associations.”

Researchers also suggested that low blood levels of total cholesterol among vegetarians and vegans may play a role.

They added: “Vegetarian and vegan diets have become increasingly popular in recent years, partly due to perceived health benefits, as well as concerns about the environment and animal welfare.

“In the United Kingdom, both the representative National Diet and Nutrition Survey 2008-12 and a 2016 Ipsos MORI survey estimated about 1.7 million vegetarians and vegans living in the country.”

Tracy Parker, senior dietitian at the British Heart Foundation, said: “This study provides further evidence that eating more plant-based foods can help lower our risk of heart disease.

“However, it also found that vegetarians, including vegans, are at a higher risk of stroke than meat eaters – potentially due to lack of certain nutrients.

“Whilst this is an interesting finding, this study is observational and doesn’t provide us with enough evidence, so more research in this area would be needed.

“Whether you’re a committed carnivore, a veggie, or a vegan, one way to reduce your risk of heart and circulatory diseases is to ensure you’re eating a balanced diet, packed with plenty of fruit and vegetables, wholegrains, beans, lentils, nuts and seeds. For those who do eat meat, cutting back to less than 90g of red or processed meat a day is advised.”

Advertisement

Follow Science Focus on Twitter, Facebook, Instagram and Flipboard

By Adam Vaughan

Are vegetarian diets better for the heart?

Westend61/Getty

Eating a vegetarian diet rather than consuming meat has been linked with a significantly lower risk of coronary heart disease.

While the environmental case for going vegetarian is unequivocal and powerful, the long-term health impacts of adopting a vegetarian or vegan diet are still poorly understood. To help fill the gap, Tammy Tong at the University of Oxford and her colleagues grouped 48,000 people in the UK by diet and followed them over 18 years.

The truth about diets: geneticist Giles Yeo at New Scientist Live

The results showed vegetarians had a 22 per cent lower risk of heart disease than their meat-eating counterparts. The finding, which is in line with some previous research, could be explained by vegetarians generally having lower cholesterol levels.

But the analysis has a sting in the tail: vegetarian diets were also associated with a 20 per cent high risk of stroke than that seen in meat-eaters. The reason could be vegetarians missing out on some nutrients only found in meat, such as the B12 vitamin. But that deficiency can be addressed with supplements, says Tong.

Read more: Living on the veg: Should we all go vegan?

While that might give people pause before joining the UK’s estimated 1.7 million vegetarians and vegans, Tong says it’s important to look at absolute numbers. Over a ten-year period in the cohort she studied, vegetarians had 10 fewer cases of heart disease per 1000 people than meat-eaters, but just three more cases of stroke per 1000. “You can say the lower risk of heart disease does outweigh the higher risk of stroke in this cohort,” she says.

Mark Lawrence and Sarah McNaughton of Deakin University, Australia, writing in a commentary in the BMJ, say the stroke risk should be kept in perspective, as it is a result from just one study and the increase is modest relative to meat-eaters.

Other possible explanations for the links were controlled for, including education, smoking, alcohol, exercise and fruit, vegetable and fibre intake. However, the results were not adjusted for income, and could also be explained by other unknown lifestyle factors among vegetarians, says Tong.

Read more: The truth about cheese: The terrible costs of our favourite food

She wouldn’t advocate people go vegetarian solely on the findings, but they should consider them. “Switching to a vegetarian diet is very much a personal choice,” she says.

Sarah Berry of King’s College London, who was not involved in the research, says: “Given the increase in vegetarianism for ethical and health reasons, and the likelihood that this is going to continue to gain momentum, this study addresses key issues regarding some of the purported health effects of a vegetarian diet over a meat diet.”

Thomas Sanders of King’s College London adds it is important to remember vegetarian diets are only health if they are well-balanced.

Journal reference: British Medical Journal, DOI: 10.1136/bmj.l4897

More on these topics:

  • diet
  • health

Vegetarians have a lower risk of coronary heart disease than meat-eaters but a greater risk of having a stroke, researchers have found.

Meat-eating has been decried as damaging for the environment, while there are also health concerns: the World Health Organization has classed processed meat as a cause of cancer, and red meat as a probable cause. But as alternative diets take off, researchers say further scrutiny is important.

“Vegetarian and vegan diets have increased hugely in popularity over the past years … but we actually know very little about the potential health benefits or hazards of these diets,” Dr Tammy Tong, first author of the study from the University of Oxford, told the Guardian.

Writing in the BMJ, Tong and colleagues report that they analysed data from more than 48,000 adults who signed up to a wider study between 1993 and 2001, and who had no history of heart attack, stroke or angina.

As well as being asked questions on lifestyle and medical history, on joining the study participants were also quizzed about their diet, allowing the team to classify individuals as meat-eaters, vegetarians, vegans or pescatarians. Some of these questions were asked again in 2010 and participants were re-classified if they had switched diet. As the study involved very few vegans, these individuals were grouped with vegetarians in the analysis.

The health of participants was followed through medical records until March 2016, during which time there were 2,820 cases of coronary heart disease and 1,072 cases of stroke.

The results reveal that once factors including age, sex, smoking status and socioeconomic status were taken into account, fish eaters had a 13% lower risk of coronary heart disease than meat-eaters, while vegetarians had a 22% lower risk.

Meanwhile, vegetarians had a 20% higher risk of having a stroke than meat-eaters. There was no clear effect for fish-eaters.

Overall, the findings mean that over a 10-year period, there would be 10 fewer cases of coronary heart disease in vegetarians than in meat eaters per 1,000 people, and three more cases of stroke.

While the latest study does not prove that meat-eating or vegetarianism is behind the differences in risk, Tong said the association between a vegetarian diet and coronary heart disease supports previous research.

“It was likely that the lower risk in both pescatarians and vegetarians are related to the fact that they have lower cholesterol, but also a lower BMI, lower blood pressure and also a lower rate of diabetes,” she said.

Tong suggested one reason vegetarians might have a higher risk of stroke could be due to lower levels of cholesterol, which could increase the risk of certain types of stroke. Alternatively, the association might be down to vegetarians having lower levels of certain nutrients, such as vitamin B12.

However, others said the data suggested that was unlikely. “It may well be that people who follow alternative diets are less likely to take blood pressure lowering medication for hypertension and as a consequence suffer a stroke,” suggested Prof Tom Sanders from King’s College London.

The study has limitations, including the fact that it is based on self-reporting, and that not all participants answered questions in 2010.The study also mainly involved white people living in the UK, so it is not clear whether the results would hold in other populations.

Dr Frankie Phillips, a dietitian from the British Dietetic Association, said vegetarians and vegans should not be alarmed by the results, stressing that the study does not show cause and effect.

Instead, Phillips said, everyone could benefit from eating more plants. “That doesn’t necessarily mean becoming completely vegan or vegetarian,” she said, adding that having a wide range of foods in the diet ensured it provided all the necessary nutrients.

The right plant-based diet for you

Plant-based diets can help reduce your risk of heart disease, but they’re not all created equal.

Updated: January 29, 2020Published: January, 2018


Image: © RomarioIen/Thinkstock

It’s clear that following a plant-based diet is associated with a lower risk of heart disease. But do all plant-based diets have the same effect? And do you really have to cut out all meat for your heart’s sake?

“For heart health protection, your diet needs to focus on the quality of plant foods, and it’s possible to benefit by reducing your consumption of animal foods without completely eliminating them from your diet,” says Dr. Ambika Satija of the Department of Nutrition at the Harvard T.H. Chan School of Public Health.

Make good choices

There are many types of plant-based diets, but they all emphasize certain foods associated with heart benefits, such as whole grains, fruits, vegetables, legumes, nuts, and healthy oils like olive oil. The diets that have been most studied for their impact on heart health include the Mediterranean diet, the DASH diet, and the MIND diet. These diets are rich in fiber, vitamins, and minerals that help lower blood pressure and LDL (bad) cholesterol, reduce the risk of diabetes, and help maintain a healthy weight, all of which can lower your risk of heart disease.

Yet, the types of plant foods and their sources are also important. For example, white rice and white bread are plant-based foods, so you would think they’re good to eat. But they are highly processed, and so are depleted of many heart-healthy nutrients and have a high glycemic index, which means they can make blood sugar levels spike and increase hunger, leading to overeating.

Drinking 100% fruit juice is not the same as eating the whole fruit, since juices can be high in sugar and squeeze out valuable fiber and vitamins. And many canned plant foods include extra additives, sodium, and sugar.

The look of a plant-based meal

A healthy plant-based meal should consist of proper portions of vegetables, fruits, whole grains, healthy protein, and healthy oils. What does this look like? The Harvard Health Eating Plate is a helpful visual guide created by nutrition experts at Harvard School of Public Health and editors at Harvard Health Publishing.

The meat of plant diets

The other question deals with a man’s appetite for animal products. When it comes to your heart, are all animal foods off the table? Maybe not — if you’re smart about your choices.

Dr. Satija led a study, published in the July 25, 2017, Journal of the American College of Cardiology, that examined the dietary data of about 209,000 adults (43,000 of whom were men) over two decades. The researchers compared the heart disease risk posed by these three categories of plant-based diets:

  • an overall plant-based diet that emphasized consumption of all healthy plant foods while reducing intake of all animal foods, like dairy (skim, low-fat, and whole milk; cream, ice cream, yogurt, and cheese), eggs, fish, meat (chicken, turkey, beef, and pork), and foods that contain animal products like pizza, soups, and mayonnaise

  • a healthful plant-based diet that emphasized consumption of only healthy plant foods, such as whole grains, fruits, vegetables, nuts, legumes, and healthy oils, while reducing intake of less healthy plant foods as well as animal foods

  • an unhealthful plant-based diet that emphasized consumption of less healthy plant foods, such as fruit juices, refined grains (pasta, white rice, and processed breads and cereals), potatoes (French fries and potato chips), and sugar-sweetened beverages, while reducing the intake of healthy plant foods as well as animal foods.

No surprise, they found that the people who followed the healthy plant-based diet (the second group) had the lowest risk for heart disease. They were also more active and leaner. On the other hand, those who followed the unhealthful plant-based diet (the third group) had a substantially higher risk for heart disease.

Thus, the study found that reducing animal foods doesn’t necessarily lead to a healthier diet and greater heart protection if the resulting diet is based on less healthy plant foods.

While this study didn’t look at which animal foods, especially meat, could have an impact on heart health, other research has shown that, as with plant foods, the type and amount matter most.

For instance, a study in the January 2017 American Journal of Clinical Nutrition found that eating 3 ounces of unprocessed red meat, three times per week, did not worsen blood pressure and total cholesterol levels.

However, a 2014 study from the American Heart Association showed that men ages 45 to 79 who ate 75 grams or more per day of processed red meat, like cold cuts, sausage, bacon, and hot dogs, had a 28% higher risk of heart failure compared with men who ate less than 25 grams.

Protect your arteries: Eat a high-energy breakfast

Need another reason to begin your day with a hearty, healthy breakfast? Doing so may lower your risk for atherosclerosis, the hardening and narrowing of the arteries caused by plaque buildup, says a study in the Oct. 10, 2017, Journal of the American College of Cardiology.

More than 4,000 adults who were free from cardiovascular disease or chronic kidney disease were classed into three groups: those who consumed less than 5% of their total energy intake in the morning (they either skipped breakfast or had only coffee or juice); those who consumed more than 20% (high-energy-breakfast consumers who ate complete meals with more whole grains and fruit); and those who consumed between 5% and 20% (low-energy-breakfast consumers who had meals like toast or pastries and coffee).

About 28% ate a high-energy breakfast, while almost 70% had a low-energy breakfast, and 3% skipped breakfast. Breakfast skippers were between 1.5 to 2.5 times more likely to have atherosclerosis compared with high-energy breakfast eaters, while low-energy breakfast eaters were about 1.15 times more likely.

Making the change

What is the right plant-based diet for you? You don’t need to go full vegetarian or vegan (avoiding all animal products, even eggs and dairy) to get the best heart health benefits. The focus should be on eating more of the right plants, avoiding the wrong kind, eliminating unhealthy foods, and moderating your intake of healthier animal products.

A heart-healthy diet doesn’t need to be daunting either. “For many men, this may be a matter of switching out their current foods,” says Dr. Satija. For instance, replace white rice with brown rice or other whole grains, and white bread with whole-grain bread. Choose oatmeal instead of processed cereal, and water instead of juice drinks.

If embracing a full plant-based diet feels intimidating, then begin small. “A moderate change in your diet, such as lowering your animal food intake by one to two servings per day and replacing it with legumes or nuts as your protein source, can have a lasting positive impact on your health,” says Dr. Satija.

Disclaimer:
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

(Olena Rudo/500px, Getty Images)

Following a vegan diet for five weeks may decrease risk factors for heart disease, new research shows.

The study included 50 African Americans who were asked to eat only prepared meals delivered to their homes. A cardiovascular risk calculator was used to assess their risk of heart attack or stroke over the next 10 years. For 36 participants who had pre- and post-diet risk scores, their risk fell by about 19% – from 10.83% to 8.74%.

“Heart disease is the leading killer of Americans, and African Americans have the highest risk of cardiovascular disease,” said the study’s senior investigator Dr. Kim Allan Williams Sr., chief of the Division of Cardiology at Rush Medical College in Chicago. “We did this study to see what we can do about it.”

The preliminary research was presented recently at the American Heart Association’s Scientific Sessions conference.

A vegan diet includes only plant-based foods. The meals the participants received included no meat, seafood or dairy. This means they had no dietary cholesterol. The meals also were low in sodium and calories.

Marcia Otto, an assistant professor of epidemiology, human genetics and environmental sciences at the University of Texas Health Science Center’s School of Public Health in Houston, said the findings suggest benefits of a low-salt, low-meat diet on LDL cholesterol and blood pressure, important risk factors for cardiovascular disease.

According to AHA statistics, about 60% of African American men and 57% of African American women ages 20 and older have some form of cardiovascular disease, such as heart disease, stroke, high blood pressure and other conditions.

A recent report from the Centers for Disease Control and Prevention found that for heart disease alone, death rates in 2015 were 21% higher in African Americans than in whites. Because the study found the five-week diet reduced cardiovascular risk by 19.4%, Williams said “with this diet, the excess risk is almost gone.”

But he and Otto agreed more research is needed.

The findings “need to be confirmed by additional investigations including a larger, more representative sample of African Americans to provide a stronger body of evidence supporting statements about long-term reduction in health disparities,” said Otto, who was not involved with the research.

Cardiovascular disease includes many types of heart and blood vessel diseases caused by atherosclerosis, a condition that occurs when a substance called plaque builds up in the walls of the arteries. This buildup makes it hard for blood to flow through the arteries, increasing the risk for a heart attack or stroke.

The study found the diet reduced LDL cholesterol levels by 14%. LDL is the “bad” cholesterol because it contributes to atherosclerosis.

The diet also reduced systolic blood pressure by 10 points. Systolic blood pressure, the top number in a blood pressure reading, represents the force of blood against the artery walls when your heart beats.

High cholesterol and high blood pressure both increase the risk of heart disease and stroke.

Although participants were on the vegan diet for only five weeks as part of the study, the 10-year reduction in risk assumes they remain on the diet for those 10 years.

“It would be particularly important to follow study participants to evaluate whether they would continue to follow a healthy diet after the end of the intervention,” Otto said, “and whether short-term benefits to cholesterol levels and blood pressure would be sustained over time.”

Find more news from Scientific Sessions.

If you have questions or comments about this story, please email [email protected]

Heart Disease

Cardiovascular disease is the leading cause of death in the United States and around the world. Eating habits and other lifestyle factors play a key role in determining the risk of heart disease.

Pioneering studies by Dean Ornish, MD, Caldwell Esselstyn Jr., MD, and others have shown that a low-fat, plant-based diet, combined with regular exercise and a healthy overall lifestyle, can prevent, delay, and even reverse heart disease and other cardiovascular events.

Dr. Ornish’s landmark study tested the effects of a plant-based diet on participants with moderate to severe heart disease. There were no surgeries or stents—just simple diet and lifestyle changes. Within weeks, 90 percent of chest pain diminished. After just one month, blood flow to the heart improved. After a year, even severely blocked arteries had reopened. At the Cleveland Clinic, Dr. Esselstyn tested the same approach on patients with severe heart disease and published similar results. Thirty years later, all of the compliant patients are still thriving.

Plant-based diets benefit heart health because they contain no dietary cholesterol, very little saturated fat, and abundant fiber. Meat, cheese, and eggs, on the other hand, are packed with cholesterol and saturated fat, which cause plaque buildup in the arteries, eventually leading to heart disease.

Vegetarians and pescetarians (people who eat fish but not meat) have a lower risk of developing coronary heart disease than meat-eaters, according to a study published late last week in The BMJ. But vegetarians — including vegans — are at a higher risk of having a stroke, the study also reports.

These findings are based on data collected during an 18-year period from more than 48,000 British adults, of whom about a third were vegetarians.

Vegetarians should not be alarmed, however. Although large and long running, the study is observational, which means it can’t prove that diet was the direct cause of the differences in disease risk. Other factors in the lives of the study’s participants — factors not addressed in the study — may also explain the results.

Also, the decreased risk of coronary heart disease observed in this study outweighs the increased risk of stroke, particularly given that heart disease is much more common than stroke.

Some experts have expressed skepticism about the stroke finding. Dr. Malcolm Finlay, a consulting cardiologist at Queen Mary University of London who was not involved in study, told the Science Media Centre that the study’s authors put “too much weight on a complex statistical method to try and correct for the fact that the vegetarians were very much healthier than meat eaters.”

“So, while this method can say the risk of stroke isn’t as low as one might expect it to be in vegetarians considering how much healthier they are in general compared to meat-eaters, their overall risk of a major life-changing cardiovascular event happening still appears much lower,” he added.

Unanswered questions

As background information in the study points out, vegetarian diets, including veganism, have become increasingly popular in recent years, not only because of their perceived health benefits but also for reasons having to do with global warming and growing concerns about animal welfare.

The potential benefits and risks of vegetarian diets are not fully understood, however. Previous research has suggested that vegetarians are at lower risk for heart disease, for example, but little is known about how vegetarian diets affect the risk of death from stroke.

The authors of the current study, a team led by epidemiologist Tammy Tong of the Nuffield Department to Population health at the University of Oxford, set out to address that research gap.

How the study was done

For the study, the researchers analyzed data collected from 48,188 adults living in the United Kingdom (average age: 45) who had been recruited between 1993 and 2001 into the ongoing EPIC-Oxford study, which is investigating the long-term effects of diet on health. None of the participants had a history of coronary heart disease or stroke when they entered the study.

At the start of the study, the participants filled out lengthy questionnaires, which included detailed questions about their diet. Based on their answers, 24,428 of them were categorized as meat eaters, 7,506 as pescetarians and 16,254 as vegetarians (a group that included vegans). All were sent a second questionnaire in 2010 to see if their eating habits had changed.

The study followed the participants for an average of 18 years. During that period, 2,820 of the participants developed coronary heart disease (caused by plaque buildup in the walls of the arteries that feed blood to the heart) and 1,072 had a stroke.

The stroke cases involved 519 ischemic strokes (ones in which a blood clot blocks the flow of blood and oxygen to the brain) and 300 hemorrhagic strokes (ones in which blood from an artery begins bleeding into the brain).

Key findings

Tong and her colleagues analyzed all this data to determine if there were any associations between type of diet and the risk of coronary heart disease and stroke. First, however, they adjusted the results to take into account other factors known to increase the risk of those two conditions, such as smoking, alcohol use, physical activity, use of dietary supplements and (in women) use of oral contraceptives and menopausal hormone therapy.

Here’s what they found:

  • The vegetarians in the study had a 22 percent lower risk of coronary heart disease than the meat eaters. Over a 10-year period, that drop in risk means there would be 10 fewer cases of coronary heart disease among vegetarians than among meat eaters for every 1,000 people.
  • The pescetarians had a 13 percent lower risk of coronary heart disease than the meat eaters. That equals 5.8 fewer cases of the disease for every 1,000 people over 10 years.
  • Vegetarians had a 20 percent increased risk of stroke compared to meat eaters. That’s the equivalent of three more cases of stroke per 1,000 people over 10 years. Most of the increase in stroke risk among the vegetarians was for hemorrhagic stroke
  • Pescetarians had no increased risk of stroke.

“Overall,” Tong and her colleagues conclude, “the present study has shown that UK adults who were fish eaters or vegetarians had lower risk of heart disease than meat eaters but that vegetarians had higher risk of stroke.”

Possible explanations

The reason for the lower risk among vegetarians for coronary heart disease is most likely due to the fact that they tend to have a lower body mass index (BMI) as well as lower blood pressure and cholesterol levels, the researchers point out. Vegetarians are also less likely to develop type 2 diabetes, a disease known to raise the risk of heart disease.

What might be behind the observed link between vegetarianism and a higher risk of stroke is more perplexing, particularly given that the vegetarians in this study had, on average, lower blood pressure than the meat eaters. High blood pressure is a major risk factor for stroke as well as for coronary heart disease.

The vegetarians in the study did tend to have lower levels of certain nutrients (such as vitamin B12), as well as lower levels of circulating cholesterol. Those differences might explain the higher risk of stroke, the researchers say. In other studies, low levels of LDL cholesterol (the so-called bad cholesterol) have been connected to a higher risk of hemorrhagic stroke.

That explanation is somewhat problematic, however. In other studies, low LDL levels raised the risk of stroke primarily when it occurred alongside high blood pressure. That wasn’t the case in this study.

Not the final word

Tong and her colleagues call for more research to see if the findings in this study can be replicated, particularly in more diverse populations.

In the meantime, as an editorial that accompanies the study stresses, no one should be altering their diet based on this (or any other) single study. Furthermore, the increased stroke risk identified in this study needs to be kept in perspective. “It is based on results from just one study and the increase is modest relative to meat eaters,” the editorial states.

FMI: You can read the study in full on The BMJ’s website. The BMJ was formerly known as the British Medical Journal.

About the author

Leave a Reply

Your email address will not be published. Required fields are marked *