Is a High-Protein Diet Bad for You?

We get to the meat and eggs of the matter.

Getting more protein can certainly jump-start weight loss efforts, build more muscle, and is essential to maintain muscle mass as we age. But can you get too much of a good thing?

With the popularity of the high-protein, low-carb diets like Paleo and Atkins, it’s smart to look at the research behind the long-term effect of getting so much of one macro nutrient — protein — at the expense of another macro, carbs. In general, high-protein diets are restrictive, cutting out whole food groups, which can lead to serious nutrient deficiencies. In these diets, some healthful foods are usually greatly limited or avoided: legumes, whole grains, dairy, starchy vegetables like potatoes and winter squash, and also fruits like bananas, which are higher in natural sugars.

So is it smart to eat a high-protein diet? Here are a few things to keep in mind.

Kidney health: According to researchers, the amount of protein alone in higher-protein diets is probably not a concern for healthy adults. However, because these low-carb diets have been suggested as an effective tool to help manage diabetes, kidney function should be carefully monitored. For people with impaired kidney function, high-protein diets aren’t recommended.

Gut health: The Paleo diet has been touted as a way to improve gut health, as it doesn’t allow processed foods and encourages lots of fiber-rich vegetables. Recently, however, researchers found that one important marker of gut health indicated that Paleo eating may not be good for the gut. Australian researchers examined the health of people on a Paleo diet and found that blood levels of the compound Trimethylamine N-oxide (TMAO). Increased levels of TMAO, which is produced in the gut, have been associated with a higher risk of heart disease.

One reason that gut health may be negatively affected by a Paleo or other low-carb, high-protein diet is the absence of whole grains, fruits and dairy foods. Whole grains are rich in non-digestible fibers known as prebiotics, which help nourish the good bacteria in the gut. Fruits are a natural source of carbohydrates and fiber, which contribute to the well being of beneficial intestinal bacteria. And yogurt — which is generally too high in carbohydrates to be included in higher protein diets — is rich in dairy-based probiotics which encourage gut health.

Heart health: High salt consumption is associated with greater risk of heart disease; but the paleo diet doesn’t allow salt. So if people who follow the Paleo high-protein diet also stay away from processed foods — the source of most of our salt consumption — this could be heart-healthy. Researchers examining the effects of putting people into ketosis on the low-carb, higher-protein, high-fat (and very restrictive) keto diet have found beneficial effects treating diabetes and cardiovascular risk factors.

However, many following Paleo and Atkins diets bulk up on bacon, steaks and other red meats high in saturated fat and salt. Eating more saturated fats is a contributor to increased blood cholesterol levels, which is linked to heart disease. And as previously mentioned, the higher levels of TMAO from increased meat consumption are also a cardiovascular disease risk.

Bottom line: If you want to cut carbs, nutritionists suggest eating more lean proteins and reducing added sugars. Fiber-rich plant proteins like lentils, along with lower-fat cuts of beef and poultry, healthy omega-3 fats-rich fish, and fermented dairy foods like yogurt and aged cheeses can all be a smart way to eat more protein.

Serena Ball, MS, RD is a registered dietitian nutritionist, food writer, and recipe developer. She blogs at and is the author of the best-selling The 30-Minute Mediterranean Diet Cookbook. Follow her @TspCurry on Twitter and Instagram.

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