Protein gets a lot of hype for good reason: The macronutrient can support muscle gains, help with weight management, and more. But, some say you can have too much of a good thing, and that going overboard on protein can come with potential side effects, like kidney issues and weight gain.

Here’s the thing: Definitive research confirming these links is lacking. And, there are other nuances to consider when it comes to striking the right protein balance, like whether someone has pre-existing health conditions and/or how active they are. Plus, it’s important to consider what qualifies as a “high-protein” diet.

So, we talked to experts to separate fact from fiction when it comes to high-protein diets.

Meet the experts: Mir Ali, M.D., medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA; Stephani Johnson, D.C.N., R.D.N., adjunct professor in the Department of Clinical and Preventive Nutrition Sciences at Rutgers University School of Health Professions

How much protein do you need per day?

The recommended daily allowance (RDA) of protein is 0.8 grams per kilogram per day for people age 18 and up. That ends up translating to about 55 grams of protein per day for a 150-pound person, for example.

But the RDA for protein hasn’t changed in decades, and there is some debate on whether it should be higher, especially in people who are active. Some experts say up to two grams of protein per kilogram of body weight per day is a better goal for certain groups. That would be as much as 136 grams of protein per day for that same 150-pound person.

Are high-protein diets dangerous?

Some common—but unproven or very dependent on context—claims about high-protein diets or protein supplementation include that too much protein could cause fat gain, kidney problems, or even raise the risk of certain cancers.

While these ideas are out there, a lot of the concerns around high-protein diets either haven’t been directly proven or stem from people who have underlying health conditions, points out Mir Ali, M.D., medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA.

“I haven’t found any evidence that high-protein diets are harmful for most people,” Dr. Ali says. “People with certain medical conditions—patients with kidney issues or problems metabolizing protein—have to be more careful.”

Researchers have suggested that high-protein diets may be hard on your kidneys, says Stephani Johnson, D.C.N., R.D.N., adjunct professor in the Department of Clinical and Preventive Nutrition Sciences at Rutgers University School of Health Professions. But this is “suggestive data” as one scientific analysis points out. Meaning, researchers haven’t proven that a high-protein diet leads to kidney issues, and in fact, this specific analysis found the opposite—higher protein diets (especially if they’re plant-based) were associated with a lower risk of chronic kidney disease.

Also, Johnson says that not all high-protein diets are created equal. “High-protein diets can vary significantly based on the sources of protein consumed,” she says. People who eat high-protein diets rich in saturated fat have a greater risk of developing cardiovascular disease than those who have a high-protein diet with less saturated fat, she says.

And a red meat-rich high-protein diet also carries risks: “Although not solely attributed to high protein intake, excessive consumption of red meat has been consistently associated with an increased risk of colorectal cancer,” Johnson says. But, she says, people who eat a lot of red meat aren’t necessarily on a high-protein diet—and you can be on a high-protein diet without eating red meat.

As for claims that too much protein will make you gain fat, Dr. Ali says it’s possible, but unlikely. “If you’re having so much protein that you’re getting in more calories than your body needs, you can gain weight,” he says. But given that protein is filling, Dr. Ali says it’s “hard to overdo it” with this macronutrient. “It’s harder to have more than your body needs with protein than with carbohydrates,” he says.

How to calculate a safe upper limit for yourself

Again, there’s still a lot that scientists are figuring out in relation to high-protein diets, but there is some guidance. The RDA cited above is the minimum amount most generally healthy people need to hit to avoid having health issues, Johnson notes. So, you can probably have more than that with no issue, provided you don’t have any underlying health conditions. But it’s always a good idea to talk to your healthcare provider before making any diet changes.

“For generally healthy individuals, protein intake of up to two grams per kilogram of body weight—approximately one gram per pound—is typically considered safe,” Johnson says. “At this level, the kidneys are generally able to manage the nitrogen load associated with protein metabolism without strain.”

What else should you keep in mind about high-protein diets?

While protein has a lot going for it, Johnson says it’s still important to focus on getting the other macronutrients.

“When protein intake is significantly increased, intake of carbohydrates and fats decreases,” she says. “Carbohydrate-rich foods provide a wide variety of essential nutrients not commonly found in high-protein foods. As a result, individuals following a very high-protein, low-carbohydrate, and low-fat diet may be at risk of inadequate nutrient intake, which can lead to negative health outcomes.”

Having too little fiber is also a concern with high-protein diets, Johnson says. That can raise the risk of digestive issues, along with deficiencies in vitamins and minerals like B vitamins, vitamins C and E, and potassium.

With that in mind, Dr. Ali says a high-protein diet is generally safe for most people. If you’re interested in ramping up your protein intake, Johnson recommends checking in with your healthcare provider or a registered dietitian to make sure there are no potential issues, especially if you have any underlying health conditions.

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