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Are There Health Downsides To Vegetarian Diets?

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Nov. 4, 2019 -- It's becoming more popular to eat meat-free at least part of the time.

While about 4% of Americans are full-time vegetarians, with about half of those also vegan, a recent poll by the Vegetarian Resource Group found that 46% of respondents say they always or sometimes eat vegetarian meals when dining out. The top reason? Health.

Although vegetarian eating does have a stellar health reputation, recent news has focused on what could be bad about vegetarian diets and more stringent vegan plans, including reports of stroke risk, harms to brain health, hair loss, and depression.

So, are there downsides to these supposedly healthy eating patterns?

"For generally healthy people, I don't see any reason that eating a vegetarian diet is risky to health," says Qi Sun, MD, an assistant professor of nutrition at the Harvard T.H. Chan School of Public Health.

But Sun’s recent research and that of others strongly suggest that the quality of plant-based food matters when it comes to health benefits. As in: vegetables, yes; french fries, no.

A vegetarian diet always excludes meat, fish, and poultry, according to the definition used by the Vegetarian Resource Group. Vegans also don’t eat dairy products such as milk, eggs, and cheese, as well as animal-based products like gelatin. Followers do not use other animal products, including honey, wool, silk, and leather.

There are potential pitfalls to meatless eating, Sun says, but nutrition education and using supplements when needed can help people overcome them.

Downsides to Eating Vegetarian/Vegan?

Stroke risk: British researchers followed more than 48,000 men and women with no history of heart disease or stroke for about 18 years. Vegetarians had a 13% lower risk of heart disease than meat eaters. But they also had a 20% higher rate of stroke than meat eaters. That translated to three more strokes for every 1,000 people over 10 years.

This study should be taken with some caution, says Liz Weinandy, a registered dietitian at The Ohio State University Wexner Medical Center.

The study was an observational study, which doesn’t show cause and effect. And it was done in the U.K., and vegetarian eating there is probably different than in other areas, she says. It does suggest that perhaps a vegetarian diet does not lower stroke risk across the board; and the topic merits more study, she says.

Brain health: Another expert wrote that the trend toward vegetarian diets may lead to a "choline crisis." Choline is a nutrient that’s important for brain health and other functions. It’s found in meat and poultry, and the body can't make all that humans need.

"Vegetarian diets are definitely lower in choline," Weinandy says. "Eating a few eggs a week can really help boost intake for those who include eggs in what they eat." Vegans should consider  a supplement, especially women of childbearing age. The supplement should be USP certified, she says, as that means an independent company verified the ingredients and amounts on the label.

Hair loss: So, can giving up meat lead to hair loss? A recent report found that a severe lack of protein, among other diet shortcomings, can lead to it. That’s because meat contains iron, vitamin B, and zinc, which are all important for hair growth.

While iron is in foods like dried beans and dark green, leafy vegetables, it’s harder to absorb iron from a pure vegetarian diet, Sun says. But it is easy to take supplements, he says. Vegetarians and vegans must take special care to get enough iron. Supplements should be needed only if they don’t.

Mood Problems: Can vegetarian and vegan diets sour your mood? Research on this is mixed. Some studies have found that going meatless improves mood, and others have found  the opposite. In one study of 400 new mothers, 80 reported postpartum depression. A vegetarian diet was one factor that seemed to make it more likely to be depressed.

In another study, researchers compared vegetarians, vegans, and people who eat both plants and animals, and found the vegans had lower anxiety and stress levels than the meat eaters.

Other researchers looked at mental health problems in vegetarians and concluded they are more likely to have them, but on average, the mental problems were there before the people started eating a vegetarian diet. And the researchers emphasize they found no cause-and-effect link.

Benefits of a Meatless Lifestyle

Some health benefits of eating vegetarian or vegan are well-documented. Among the most solid perks:

Heart health: In one recent report, vegetarian and Mediterranean plans were linked with better heart health.

But the quality of the plant-based foods matters, says Sun, citing recent research from Harvard. Researchers tracked about 200,000 men and women enrolled in several different studies for more than 2 decades.

They assigned positive scores to plant-based foods and negative ones to animal foods. They scored healthy plant-based foods such as whole grains higher than unhealthy plant foods, such as french fries. People who ate healthier plant-based foods had a 25% lower chance of heart disease, while those who ate unhealthy plant foods had a 32% higher chance.

Avoiding diabetes: Several studies have found that vegetarians are up to two times less likely to have type 2 diabetes than non-vegetarians.

In studies comparing vegetarian and non-vegetarian diets, those on the vegetarian plans had better blood sugar levels and more weight loss.

Sun and his colleagues found that a diet that emphasized plant foods and was low in animal foods was linked with about a 20% lower chance of getting diabetes.

But when they looked more closely, they found that diets that emphasized healthy plant foods cut the chance of having diabetes by 34%, while diets with less healthy plant foods actually raised the risk of diabetes by 16%.

Healthy plant foods include whole grains, fruits, vegetables, nuts, legumes, vegetable oils, and tea and coffee. Less healthy ones include fruit juices, sweetened beverages, refined grains, pasta, potatoes, sweets, and desserts.

Caution: Don't Be a Junk Food Vegetarian

While people often view vegan or vegetarian diets as automatically healthy, that's not so, Sun says. He cautions people not to become junk food vegetarians.

"If you eat a vegan diet, but eat a lot of french fries, refined carbs like white bread, white rice," he says, that's not healthy. Besides avoiding those foods, he suggests "emphasizing fruits and vegetables. Not fruit juice but whole food. And nuts."

A meatless plan isn't palatable to everyone, Ohio State’s Weinandy says. She encourages people to borrow the benefits of vegan and vegetarian eating, such as eating plenty of fruits and vegetables and whole grains, to get some health benefits.

As research by Sun and others shows, eating more healthy plant foods in place of red meat has benefits for heart health and for avoiding diabetes. "Essentially, if you keep meat intake constant while increasing plant-based food intake, the energy intake will increase, which may itself lead to obesity and other issues," Sun says. "So when we say people should increase consumption of healthy foods, that always means people should decrease the intake of unhealthy foods so that their energy intake is constant."

Adds Sun: "The benefits of eating plant-based diets, including vegan and vegetarian diets, far exceed small risks in deficiency." 

WebMD Health News Reviewed by Brunilda Nazario, MD on November 04, 2019

Sources

Qi Sun, MD, assistant professor of nutrition, Harvard T.H. Chan School of Public Health, Boston.

Liz Weinandy, registered dietitian, The Ohio State University Wexner Medical Center, Columbus.

Vegetarian Resource Group.

British Medical Journal: “Risks of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study.”

British Medical Journal: Nutrition, Prevention & Health: “Could we be overlooking a potential choline crisis in the United Kingdom?”

Dermatology Practical & Conceptual: "Diet and hair loss: Effect of nutrient deficiency and supplement use."

Journal of the American College of Nutrition: "Vegetarian Diets in the Prevention and Treatment of Type 2 Diabetes."

PLOS Medicine: "Plant-Based Dietary Patterns and Incidence of Type 2 Diabetes in US Men and Women: Results from Three Prospective Cohort Studies."

Journal of the American College of Cardiology: "Healthful and Unhealthful Plant-Based Diets and the Risk of Coronary Heart Disease in U.S. Adults."

Current Cardiology Reports: "A Heart-Healthy Diet: Recent Insights and Practical Recommendations."

International Journal of Behavior Nutrition and Physical Activity: "Vegetarian diet and mental disorders: results from a representative community survey."

Nutrition Neuroscience: "Vegans report less stress and anxiety than omnivores."

Gastroenterology Hepatology from Bed to Bench: "Nutrition health issues in self-reported postpartum depression."

Nutrients: "Vegan diet, subnormal vitamin B-12 status and cardiovascular health."

Academy of Nutrition and Dietetics: "Position of the Academy of Nutrition and Dietetics: Vegetarian Diets."

 

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