While Americans are still in varying states of awareness about the keto, paleo and Whole 30 diets, along comes another new eating regimen, labeled "pegan".

This hybrid of "paleo" and "vegan" was introduced in a 2014 blog post by physician and author Mark Hyman.

After Hyman included the pegan diet in his February 2018 diet book, Food: What the Heck Should I Eat in February 2018, searches related to the pegan diet spiked, landing it on a number of trend lists for 2019.

While the pegan diet is more moderate - and potentially easier to follow - than either of its dietary parents, it does restrict many nutritious foods for reasons that aren't quite supported by science. Here are the pros and cons.

The pros: Lots of plants and healthy fats

The pegan diet is at its core a plant-based diet, which research shows is good for personal and planetary health. If you want to go pegan, plan to shop for a variety of deeply colored fruits and vegetables - they'll make up about 75 percent of your diet.

That's definitely one of the diet's selling points, says registered dietitian Wesley Delbridge, a spokesman for the Academy of Nutrition and Dietetics.

"Most Americans aren't getting enough fruits and vegetables," he says, adding that upping produce also increases fiber intake, helping us get the 25 to 35 grams we need daily.

"That has many health benefits, including heart health and reduction of cancer, especially colon cancer."

Chicago-based registered dietitian Christine Fitzgerald likes the diet's plant-based focus. "I do think that we're not eating enough plants, fruits and vegetable and getting the fiber in," she says.

"I think for people who like the plant-based way of eating, but feel overwhelmed and can't completely commit to a plant-based diet, this gives them some options."

However, she's concerned that the pegan diet limits fruits to low-glycemic berries, because, it claims, other types of fruit spike blood sugar.

"What if you don't like berries? We can do other things to reduce the impact on blood sugar, like pairing fruit with protein," she says.

The diet also emphasizes fatty fish and flaxseed - sources of omega-3, another dietary element Delbridge says Americans don't get enough of, as well as nuts, avocados, olives and associated oils, which provide healthy unsaturated fats.

The diet also allows some saturated fat from grass-fed or sustainably raised meat, butter and ghee, along with organic coconut oil and coconut butter.

The mixed bag: Protein, processed food and affordability

The pegan diet considers animal proteins a "condiment" and suggests choosing fish and seafood with lower mercury levels; both recommendations are completely in tune with a healthy "flexitarian" diet.

But it also warns to eat beans only "once in a while" and limit them to ½ cup per day, something Delbridge takes issue with.

"Beans are nature's superfood," Delbridge says. "They have protein, they have fiber, they have starch. Beans have been a staple in diets across the world, and beans have shown so many health benefits, including a reduction in cancer risk."

He also points out that beans are inexpensive, and that limiting them highlights one of the pegan diet's downsides: "If you are low income, I'm not sure that you can afford to buy the foods that he's suggesting."

Indeed, the pegan diet prescribes "organic", "sustainably grown", "pasture-raised", "grass-fed" food. Although this may have environmental and health benefits, and that is still a matter of debate, it can be costly.

The diet limits foods with added sugars to occasional treats and has a long list of "avoids", including pesticides, antibiotics, hormones, genetically modified ingredients, chemicals, additives, preservatives, artificial colors, MSG and artificial sweeteners.

Hyman has famously said that the pegan diet can be broken down into one simple rule: "If God made it, eat it; if man made it, leave it."

"To me that's very simplistic, with how complicated our bodies are and what they need nutritionally every day," Delbridge says.

I agree. For one thing, organic farming uses approved pesticides.

Furthermore, attempting to completely adhere to that "avoid" list could contribute to orthorexia - an unhealthy obsession with eating healthy - by feeding into the idea that we can disease-proof ourselves if we eat "perfectly."

It may also lead to social isolation if a person fears exposure to forbidden foods.

The cons: Going against the grains and dairy

The diet prohibits wheat and other gluten-containing grains, other than occasional intake of the ancient wheat einkorn, falsely claiming that most wheat is genetically modified "Frankenwheat".

Although modern wheat does have nutritional downsides, there are countless varieties of heirloom wheat in addition to the ancient wheats einkorn, emmer and spelt.

The pegan diet also limits gluten-free grains like quinoa, brown rice, oats and amaranth. The claim? They raise blood sugar and can trigger autoimmunity.

There isn't good science to support the autoimmunity claim for the general population, and any carbohydrate-containing food, including vegetables, can raise blood sugar.

Hyman appears to have softened his stance somewhat on dairy since his 2014 blog post, in which he advised avoiding all dairy because for most people it contributes to a number of chronic diseases, a claim that research does not support.

He now allows occasional yogurt, kefir, butter, ghee or cheese, preferably from goat or sheep milk, and always organic and grass-fed.

The bottom line

The pegan diet restricts many nutrient-rich foods, partly because some people can't tolerate them. While it's true that some people are intolerant to lactose or gluten, or have trouble digesting the fiber in beans, that's not the case for most people.

Fitzgerald says that if someone follows the pegan diet because they struggle with inflammation or digestive health, it may get in the way of actually discovering the root cause of their health problems.

While Delbridge views the pegan diet is a fad diet, he says it does have one thing going for it - besides the abundant produce, omega-3s and low sugar.

"The first pro of going on any sort of diet is you are now starting to think about your food. You are prepping in advance. You are controlling your portion size. You're not just running out and grabbing fast food or just shoving anything in your mouth because you're hungry," he says.

"To me, we should always be doing that."

Fitzgerald has a slightly different take. "I prefer to not have everyone follow a specific diet, because that puts them in a black-or-white position: They're either following the diet or they're not," she says.

"Promoting heart-healthy fats and increasing plant-based eating are such good pros, but understand that you can increase those foods without going down the diet path, so you don't get trapped in the diet mentality."

Dennett is a registered dietitian nutritionist and owner of Nutrition by Carrie.

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This article was originally published by The Washington Post.