Nutritional Pearls: A Vegetarian Diet Is Not Necessarily Better for You

Your patient is a 36-year-old woman who is struggling to lose weight and is concerned about her risk of heart attack. Recently, she adopted a vegetarian diet that has so far failed to lead to significant weight loss. At a recent check-up, she asks if you think switching to a vegan diet may help her.

How would you advise your patient?

(Answer and discussion on next page

Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources including special diets for warfarin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance. 

Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, associate professor of medicine at Tulane University in New Orleans, and faculty chair of the all-new Certified Culinary Medicine Specialist program.

Answer: It’s the quality of the calories you consume that matters, not necessarily whether you are vegan, vegetarian, or neither.

I talk to my own patients about their diet, so I hear about (and debunk) dietary myths pretty frequently. One of the most persistent myths is that being a vegetarian means your diet is always more healthy than that of those who eat animal-based products. Unfortunately, as with so many things in the realm of nutrition, the truth is more complicated than "plants=good, animals=bad."

A study published in the Journal of the American College of Cardiology pretty convincingly shows that a vegetarian diet can indeed be bad for you. The study used data gathered through 3 long-term, large scale studies: The Nurses' Health Study, the Nurses' Health Study 2, and the Health Professionals Follow-up Study, which include nearly 210,000 men and women and gathered information for 22 years or more.

The Research

The authors analyzed the participants' diets from the food frequency questionnaires administered every 2 to 4 years. For the purposes of their study, they created 3 different dietary scoring systems:

• first, an overall plant-based diet index (PDI), which emphasizes more plants and less animal products;
• a healthful plant-based diet index (hPDI), which emphasizes healthier plant-based foods like whole grains (as opposed to refined grains), legumes, fruits and vegetables, and coffee or tea instead of sugar-sweetened beverages; then finally
• an unhealthy plant-based diet (uPDI) which includes unhealthy but plant-based foods like more refined grains, processed foods, and sugar-sweetened beverages.

For all 3 of the scoring systems the researchers assigned higher scores for closer adherence to the type of diet: for example, for the overall plant-based diet, those who ate the fewest plant-based items received a lower score than those who ate the most. For the unhealthy plant-based diet, however, those who consumed more of the less-healthy plant-based foods received a higher score than those who consumed more of the healthier plant-based foods.

For their results the authors focused on cardiovascular disease: specifically, myocardial infarction, regardless of whether the participant died of the heart attack or not. The dietary scores of those who experienced a heart attack were compared with those who did not.

The Results

After taking into account body mass index (and its changes over time), gender, smoking status, personal and family healthy history, and chronic conditions like high blood pressure or diabetes, the authors found that those who followed a more strictly plant-based diet, regardless of whether it was healthy or not, and consuming less than 3 or 4 servings of animal-based foods per day, were indeed less likely to experience a heart attack than those who consumed the highest level of animal-based foods per day (which was 5-6 servings per day). That said, the difference was only about 8%: a more plant-based diet, regardless of whether it was healthy or not, meant a person was only 8% less likely to experience a heart attack than those who ate more animal-based foods.

On the other hand, those who received the highest score for a healthy plant-based diet were 25% less likely to experience a heart attack than those with the lowest score for a healthy plant-based diet. Inversely, those with the highest score for an unhealthy plant-based diet were 32% more likely to have a heart attack than those with the lowest unhealthy diet score.

There's an important caveat here: these diets are plant-based, not plant-exclusive: again, the lowest level of animal intake was up to 3-4 servings of animal-based foods per day. That might mean red meat, or it might mean using cow milk in your coffee. A Mediterranean-style diet is just as plant-based: over the course of a week you might average 9-10 servings of animal protein (including meat, fish, and poultry) plus a total of 2-3 servings of other animal-based foods (dairy items like butter, milk, or cheese). That's well within the authors' cutoff of 3-4 servings of animal-based products per day.

What’s the “Take-Home”?

The take-home here should not be that everyone should go vegan, nor that a vegetarian diet is bad for you (or good for you). The real take-home is that it's the quality of the calories you consume that matters. And not just a little bit, but a lot: improving your Mediterranean Diet score by just 2 points—for example, by switching your daily lunch sandwich from white bread to whole wheat bread and from pastrami and cheese to peanut butter and jelly—can reduce your risk of death from all causes by 25%.

Reference:

Satija A, Bhupathiraju SN, Spiegelman D, et al. Healthful and unhealthful plant-based diets and the risk of coronary heart disease in US adults. JACC. 2017;70(4).