A high protein diet is good for you.

No, a high protein diet is bad for you.

There are more opinions on this than you can shake a turkey leg at. And the answer is … it depends, both on you and the type of protein.

Nutritionist Kimberly Snyder has added a new word to the debate: protox (short for “protein oxidation”).

In her blog and in other publications, she has said “too much protein… makes our bodies age faster… [and] toxicity starts to amass in our bodies.”

high protein diets

Snyder maintains that cooking makes the problem worse. Most people cook their meat at high temperatures (think of the nice char on the outside of your steak). That method, Snyder says, creates “oxidative inflammatory molecules that… produce significant detriment to our health, above and beyond even just consuming too many grams of protein.”

Wait, it gets worse.

Shoppers buy meat that’s been sitting out in the case (and oxidizing), cook it (more oxidizing), then store the cut-up leftovers (even more oxidizing) and finally reheat them (for a final blast of oxidation).

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In defense of protein

Nutritional consultant Dr. Mike Roussell says that’s all hokum.

He’s a widely published expert with a degree in biochemistry from Hobart College and a doctorate in nutrition from Pennsylvania State University.

The whole protox thing “is a nutritional scare tactic,” Roussell told the Observer. “Everything can be oxidized in your body. You could make a similar argument for fat — but that doesn’t mean we need to stop eating both fat and protein.”

For Roussell the question of how much protein is enough is a little more complex and requires some definition of terms. For example, it’s too much if you’re comparing it to the amount of protein necessary to prevent illness.

“If our benchmark is the amount of protein necessary for optimal health, most people would benefit from eating protein throughout the day, and some of us, particularly women, would benefit from eating a little more,” he said “This idea of the negative effects of protein consumption within normal or even high-normal ranges leading to impaired health is totally baseless.”

Right now, there is nothing to show what happens to people when they eat protein. In fact, Roussell said protein is good for your health as you get older.

“Data in elderly people show that more balanced frequent protein intake is better for aging as it supports lean body mass preservation, reducing risk of falls and the spiral of negative health outcomes that spiral out of that,” he said. “Protein is probably your most important nutrient when it comes to fighting the negative effects of aging.”

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Type of protein matters

But before those older adults go looking for some baby back ribs, consider the following.

A study published in 2014 in Cell Metabolism found that eating a high-protein diet during middle age increased the risk of dying from any cause by 74 percent and the risk of dying from cancer by more than four times, compared to eating a low-protein diet.

The study included 6,381 adults ages 50 and older who were followed for 18 years.

This puts high-protein diets right up there with smoking, which according to the Centers for Disease Control and Prevention (CDC), increases the overall risk of death by three times, compared to not smoking.

While the largest difference in the 2014 study was between the high- and low-protein diet groups, people who ate moderate amounts of protein during middle age were still three times more likely to die of cancer later on than low-protein eaters.

Just what kind of protein is this anyway? Is it all red meat? After all, plants provide protein as well.

When the researchers looked more closely at the types of protein in the diet, they found that eating more protein from plants like soy and beans didn’t increase the risk of death.

“There’s a misconception that because we all eat, understanding nutrition is simple,” said study author Valter Longo, a professor of gerontology and biological sciences at the University of Southern California in a press release. “But the question is not whether a certain diet allows you to do well for three days, but can it help you survive to be 100?”

Protein is popular

In the meantime, more than half of Americans are trying to put more protein on their plates, according to a survey by research firm the NPD Group and reported this year in Prevention magazine.

That includes sprinkling protein powder into yogurt, oatmeal and smoothies and buying snack bars and even pasta with extra grams of the stuff.

Not necessary, said Dr. David Katz, director of the Yale-Griffin University Prevention Research Center. He told Prevention magazine the protein craze is a fad, like low-fat in the 1980s and low-carb in the early 2000s.

“All the focus on macronutrients has been a massive boondoggle—we cut fat and got fatter and sicker; we cut carbs and got fatter and sicker,” he said. “We need to stop focusing on macronutrients and instead focus on wholesome foods and healthy combinations and let the nutrients take care of themselves.”

Dietary guidelines for Americans recommend getting between 10 percent and 35 percent of your daily calories from protein. For women that means about 46 grams of protein per day would be enough to meet the Recommended Dietary Allowance (RDA) and prevent deficiencies. (Forty-six grams equals 1.6 ounces.)

That’s not very much. But that’s not the last word.

How protein works

Even Katz admits that certain types of people can benefit from greater protein intake.

That includes people doing a lot of resistance training or taxing endurance exercise whose bodies are tearing down muscle tissue that needs to be repaired and rebuilt.

“Protein is a source of essential amino acids that are the building blocks of the body's own proteins—and we can't make them; we get them from food or we don't get them at all,” Katz said. “If you're trying to build muscle cells and you don't have those amino acids, you don't build muscle.”

He compared the situation to building a house with too few bricks.

“Construction just doesn't happen,” he said.

“There's a reasonable amount of evidence to suggest that higher protein, depending on where the protein comes from, may help with low-calorie compliance by providing satiety,” Dr. Tom Rifai, regional medical director of metabolic health and weight management for the Henry Ford Health System in Detroit, told Prevention magazine.

Protein takes longer to digest and also stabilizes blood sugar, which has been shown to lower the desire to eat—helpful when trying to shed pounds.

“During weight loss, you want more protein—to prevent hunger, enhance satiety and minimize muscle loss, as long as there's some degree of physical activity,” Rifai said.

It’s not just meat

But don’t think more red meat is the answer.

Legumes are a particularly good source of protein. A 2014 study in the journal Obesity found that eating a daily serving of beans, chickpeas, lentils or peas increases fullness, potentially improving weight management and weight loss.

Katz said that anyone eating the typical American diet (think: bread, pasta, burgers and snack packs) can benefit from shifting toward more high-quality protein like egg whites, fish and lean meat.

“If you're getting a higher percentage of calories from protein, you’re getting less of the other stuff, like added sugar and carbohydrates,” Katz said.

The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OmniHeart), a randomized trial, found that people who replaced some carbohydrates with healthy protein (or healthy fat) saw lower blood pressure and lower levels of harmful LDL cholesterol than people on a higher-carbohydrate diet that was otherwise healthy.

“Older adults at risk of sarcopenia, the gradual loss of lean muscle mass, would benefit from more high-quality protein in their diet,” Katz said.

The extra protein helps to counteract the inevitable muscle loss that comes with aging.

A 2015 study from the University of Arkansas for Medical Sciences found adults aged 52 to 75 who doubled the Recommended Daily Allowance were better at building muscle—and keeping muscle—after just four days.

But, since these folks may already have high cholesterol or other cardiovascular risk factors, it’s a good idea to find that extra protein somewhere lower on the food chain.

Seeds, nuts and fish are what the doctor ordered.

Editor’s Note: This story was originally published on March 4, 2014 and was updated on September 9, 2016.