Plant-Based Pitfalls: When Can the Vegan Diet Go Wrong?

People who follow a vegan diet are at risk for vitamin deficiencies, because some nutrients come mainly from animal sources.

While institutions from the American Medical Association to Harvard Medicine agree that a plant-forward diet can improve cardiovascular, physical and overall health, there are certainly ways to be unhealthy while following a vegan diet. Dreamstime/TNS

By Hanna Webster From Pittsburgh Post-Gazette

PITTSBURGH—The vegan diet, over the past 20 years, has received plenty of flack about its extreme and at-times in-your-face style, made famous by the animal activism group People for the Ethical Treatment of Animals, or PETA.

Not getting enough nutrients is not always a main point of contention.

While institutions from the American Medical Association to Harvard Medicine agree that a plant-forward diet can improve cardiovascular, physical and overall health, there are certainly ways to be unhealthy while following a vegan diet. It can be easy to skip whole foods and opt instead for highly processed ones. Oreos, chips, Sour Patch Kids, and Pringles are all vegan, but they’re not necessarily healthy. Here are common pitfalls of the vegan diet.

Too Many Processed Foods

While a 2023 Gallup poll showed the number of vegans in the U.S. hasn’t changed much since the early 2000s, the demand for vegan products has. A trend analysis by the market research group Technavio shows the vegan food market is expected to grow by billions of dollars within the next few years.

Now, you’re likely to find a Beyond or Impossible burger as an option at a burger chain, and you can stock up on nondairy Ben & Jerry’s, Field Roast vegan sausage, JUST Egg vegan egg replacement and Daiya cheese at typical grocery stores.

But replacing animal products with vegan alternatives may not be the best path toward “healthful” eating, say nutritionists.

With a vegan diet, “[a] very common pitfall is eating a lot of processed foods,” said Michelle Thompson, doctor of osteopathic medicine specializing in lifestyle medicine at UPMC. “For breakfast they may have a bagel, for lunch a peanut butter and jelly sandwich and for dinner, a frozen veggie burger. I encourage people to eat foods that come from a plant, not made in a plant,” she said.

Many of these vegan alternatives contain food additives that place them in the “ultra-processed” category—which can lead to metabolic issues and hormone imbalances—including oils, modified food starches, and added sugars.

“Just because it’s vegan, doesn’t mean it’s healthy,” said Will Cole, a functional medicine doctor and author in Westmoreland County.

Not Getting Enough Vitamins or Nutrients

People who follow a vegan diet are at risk for vitamin deficiencies, because some nutrients come mainly from animal sources.

“Regardless of your diet, not everyone gets the vitamins and nutrients they need in a day,” said Alianna Anselmi, dietitian lead at Allegheny Health Network.

Deficiencies in vitamin B12 and iron are most common when following a vegan diet. B12 helps create red blood cells and helps nerves work properly; symptoms of a deficiency may include tingling in the fingertips or hands. And iron is crucial for blood development and oxygen transfer in the body, and it impacts energy if levels dip too low.

Those following a plant-based diet can get vitamin B12 from fortified foods, such as nutritional yeast, plant-based milks, whole-grain cereals and plant-based meat alternatives, said Caroline Passerrello, a dietician and nutritionist at Pitt School of Health and Rehabilitation Sciences, via email. Vegetarians can also get B12 from dairy and eggs.

“For omega-3 fatty acids, flaxseeds, chia seeds, and walnuts are options,” she said. “With iron, consuming foods like lentils, tofu and spinach along with a source of vitamin C (like red peppers or citrus fruits) will help the body absorb the iron from plants more efficiently.”

Some dietitians also encourage vitamin supplementation if following a vegan diet.

“I don’t believe that a vegan diet is the most nutrient-dense way to eat for most people, but we live in such a time where, through supplementation and access to food, we can really come up with the best vegan diet for them, if that’s what their preference is,” said Cole. “You can build a nutrient-dense, bioavailable vegan diet.”

Too Many Refined Carbs

Most bread products are vegan—and delicious—which can lead to an overreliance on carbs and a subsequent energy crash.

Some vegans are “depending too much on carbs for fuel, because it’s A, easier, and B, the human body enjoys it, because it’s highly palatable and kind of hits those dopamine centers in the brain,” said Cole. “But it’s not necessarily going to set you up for energy and optimal health and vitality longer term.”

It’s not about cutting out all junk food, carbs, and sugar, he said, but about being more intentional about where your food comes from and thinking about it in a balanced way.

It’s part of what Thompson teaches in lifestyle medicine, which focuses on food as medicine.

She will sometimes encourage her patients to compare their bodies to a car and think about what it needs to run efficiently and effectively.

“If you put sugar in the gas tank and oil where the windshield wiper fluid goes, of course that car is going to run poorly,” she said. “We don’t want people living out of packages. We want them spending money at the grocery store instead of at the pharmacy.”

Gut Health is Overlooked

Functional medicine physicians like Thompson and Cole spend a lot of time with their patients trying to optimize gut health.

An unhappy gut has been linked to anxiety and depression, irritable bowl syndrome, inflammation, and hormone imbalances. And just as with any diet, being vegan might not be paying off health-wise if your gut is dysregulated.

Cole likes to say “you have to meet your gut where it’s at.”

“We are what we absorb,” he said. “And if your gut isn’t in the best place ... you have to look at, if you’re using your meals as medicine, is your body making good use of it?”

Many foods that are naturally vegan are also high in FODMAPs, or fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Bacteria in the gut love to ferment high-FODMAP foods and, thus, these foods are poorly absorbed by the body. This can create an imbalanced gut microbiome and cause constipation, cramping, diarrhea, gas, and bloating.

Gluten, beans, garlic, onions, cashews, bananas, apples, broccoli, and processed soy proteins are just some examples of foods high in FODMAPs—and foods that could be daily essentials for vegans.

This can put people who are vegan for ethical reasons in a tricky situation. Cole will sometimes encourage his patients to switch to a meat-heavier diet temporarily if they’re trying to heal their gut, but vegans with gut problems have to work around that.

A Symptom of a Larger Trend

“Plant-based isn’t the problem,” said Cole, but a symptom of a larger trend that has amped up the processing of foods for convenience and a lower price.

“We are facing, as a society, epidemic levels of gut health and microbiome issues, and, in turn, inflammatory health problems,” he said. “Our grandparents, our great-grandparents and all the generations before them, they were not exposed to the things we’re exposed to.”

Herbicides, pesticides, forever chemicals, microplastics, and ultra-processed ingredients have been receiving more attention as possible culprits for chronic diseases such as obesity, diabetes, and hormone problems.

“It’s not necessarily the plant-based diet’s fault as much as the massive assault on the human and soil microbiome, and that’s disabling the human body from properly digesting and absorbing food,” Cole added. “I don’t see it as a plant-based problem. I see it as a human health problem.”

Be Open to Change

Neither Cole, Thompson nor Anselmi prescribe a specific diet for all their patients.

Everyone is different, Thompson stressed, and thus has different needs—like an eyeglass prescription.

Anselmi said she hopes vegans aren’t discouraged from reaching out to a dietitian if they want guidance. “There are so many great plant-based dietitians and ways to make the diet nutritious and interesting,” she said.

“No one is going to tell you you have to do it a certain way,” said Thompson. “Just because you ate one way for your whole life doesn’t mean you have to forever.”

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