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Are There Health Downsides To Vegetarian Diets?

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Jan. 18, 2018 -- It's becoming more popular to eat meat-free at least part of the time.

While more than 3% of Americans are full-time vegetarians, a recent poll by the Vegetarian Resource Group found that 37% 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 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, assistant professor of nutrition at the Harvard T.H. Chan School of Public Health.

However, 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 excludes meat, fish, and poultry always, according to the definition used by the Vegetarian Resource Group. A vegan plan also doesn't allow dairy products such as milk, eggs, cheese, as well as animal-based products like gelatin, and 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.

A Closer Look at Hair Loss

So can giving up meat lead to hair loss? A recent report found that 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 found in foods like dried beans and dark green, leafy vegetables, it’s harder to absorb iron from a pure vegetarian diet, Sun says. However, 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.

Zinc is found in grains, legumes, and nuts. B12 is in dairy products, eggs, and fortified soy milk and cereals.

Liz Weinandy, a registered dietitian at The Ohio State University Wexner Medical Center, Columbus, gives nutritional advice to people on a variety of eating plans

She tells vegetarians and vegans that protein deficiency can be a hazard, especially for vegans.

But in real life, "I have not had anyone complain about hair loss on a vegetarian diet," Weinandy says. “It has to be a protein deficiency going on for a while [to lead to hair loss]."

Vegetarians and vegans can get enough protein by eating a varied diet with enough calories. For vegans, good protein sources include soy, quinoa, whole wheat bread, broccoli, peanut butter, beans, kale, lentils, and almonds. Vegetarians can eat eggs a few times a week, or Greek yogurt and can be fine, Weinandy says.

People who eat no meat should know about the risk of low iron, vitamin B, and zinc levels, and be on the alert for symptoms that may point to a lack of those, Sun says. "The typical zinc deficiency symptoms include loss of appetite, hair loss, diarrhea, eye and skin lesions, weight loss, delayed healing of wounds, and taste abnormalities," he says. But these symptoms may also point to other health issues, he says.

Iron deficiency can cause fatigue, dizziness, lightheadedness, a fast heart rate, or palpitations, he says.

A range of symptoms may point to low levels of the various forms of B vitamins. Fatigue and loss of balance, for instance, could mean a B12 deficiency, Sun says. If you are concerned you may be deficient, he says, ask your doctor about getting blood tests to check your levels.

Mood Problems?

Can vegetarian and vegan diets sour your mood? Research on this is mixed, with some research finding going meatless improves mood and other studies finding the opposite. In one study of 400 new mothers, 80 reported postpartum depression. A vegetarian diet was one thing 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 they 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.

The quality of the plant-based foods matters, however, 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 2 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.

However, 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: 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, while not cutting out meat, still has benefits for heart health and for avoiding diabetes.

WebMD Health News Reviewed by Michael W. Smith, MD


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.

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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