Wellness Wednesday: Is A High-Protein Diet Dangerous?

We recently received an insightful email from one of our readers, Matt B. from Colorado. He wrote:

"I've heard mixed messages about protein. Some say to limit how much protein you eat, while others say you should pretty much only eat protein. I'm trying to figure out if a high-protein diet is actually safe. Can you help clear this up?"

Matt's question highlights a common confusion many people face, especially with the conflicting advice from healthcare professionals and fitness influencers alike. It’s a concern that has been debated for years, and it's easy to see why so many people are left wondering what’s true. Is protein something we should prioritize, or can too much of it be harmful?

To answer Matt’s question, we’re diving into a two-part mini-series. In this first blog, we’ll explore where the fear around protein comes from and why some believe it could lead to negative health effects.

Why Is Protein Feared?

Despite its known benefits, protein often carries an unwarranted stigma. While athletes and fitness enthusiasts swear by high-protein diets, others are concerned that too much protein may harm their kidneys and liver, or even shorten their lifespan. In reality, the average American diet is still more reliant on carbohydrates and fats than on protein, suggesting that protein fears are still prevalent.

Concerns about high-protein diets date back over 30 years. One of the major claims is that too much protein can overburden the liver and kidneys, potentially leading to diseases such as cancer. But where did this fear originate, and does it have any scientific backing?

The Origin of Protein Fear: The China Study and Aflatoxin

The fear of protein largely stems from The China Study, a controversial book by Dr. T. Colin Campbell. Based on observational research conducted in China, the book claims that high consumption of animal protein is linked to cancer and other chronic diseases. While The China Study sparked interest in plant-based diets, it’s important to note that it was an observational study, not a randomized controlled trial, meaning it could only show correlations—not causation. Moreover, the book’s findings have been questioned by other researchers.

One of the main arguments in The China Study is the potential link between animal protein intake and hepatocellular carcinoma, a type of liver cancer. This concern is partly due to aflatoxin, a toxin produced by mold that can contaminate foods, particularly those high in protein.

Aflatoxin and Liver Cancer: What the Research Really Says

Aflatoxin is indeed a carcinogen, but it’s important to understand the context in which it poses a threat. Aflatoxins are produced by certain molds that grow on crops such as peanuts, corn, and grains, and chronic exposure to high levels of aflatoxins can increase the risk of liver cancer. However, the levels of aflatoxin contamination in foods in the U.S. and other developed nations are tightly regulated by the FDA and other agencies.

The World Health Organization (WHO) has classified aflatoxins as Group 1 carcinogens, meaning there is enough evidence to confirm their link to cancer. However, in practical terms, the exposure necessary to cause harm is extremely high and unrealistic for most people. For instance, Dr. Chris Masterjohn, a nutrition scientist, explained that you would need to consume an astronomical amount of contaminated food to reach a dangerous level. He cited an example involving peanut butter, where one would need to eat approximately 270,000 peanut butter sandwiches over four days to reach a toxic dose.

In short, while aflatoxin can be dangerous, it’s extremely rare to consume enough through a typical diet to cause harm, and it certainly doesn’t make protein itself harmful.

Is Protein Dangerous for Liver Health?

The notion that high-protein diets damage the liver has been largely debunked by modern research. A healthy liver is more than capable of metabolizing protein, and there is no evidence to suggest that a diet high in protein causes liver disease in healthy individuals.

A systematic review published in Nutrients in 2019 evaluated the effects of protein intake on liver health and concluded that there is no significant risk of liver damage from high-protein diets for those without pre-existing liver conditions. In fact, protein may be protective in some cases. A study in The American Journal of Clinical Nutrition found that individuals with non-alcoholic fatty liver disease (NAFLD) who consumed a higher-protein diet experienced improved liver function and reduced liver fat.

However, individuals with certain liver diseases, such as hepatic encephalopathy, may need to moderate their protein intake. In this condition, the liver’s ability to process protein is impaired, and excessive protein can lead to the accumulation of toxins in the bloodstream, causing cognitive issues. But for those without liver disease, protein is not harmful.

Is Protein Harmful to Kidneys?

Concerns about kidney damage from high-protein diets are another common myth, but they are largely unfounded for healthy individuals. The fear originates from the fact that protein metabolism increases the workload of the kidneys, leading some to believe that over time, this could cause damage. However, the kidneys are designed to handle this function efficiently.

The main marker of kidney health is the glomerular filtration rate (GFR), which measures how well your kidneys are filtering waste from your blood. A decline in GFR is an indicator of kidney disease. In people with existing kidney disease, high protein intake may indeed worsen their condition, as excess protein can place additional stress on already compromised kidneys.

However, for individuals with normal kidney function, the evidence does not support the idea that high-protein diets cause kidney damage. A 2020 review in the Journal of Nutrition found no significant negative effects of high protein intake on kidney function in healthy individuals. Furthermore, a randomized controlled trial published in the American Journal of Clinical Nutrition showed that even diets containing up to 3.4 grams of protein per kilogram of body weight per day—well beyond typical consumption levels—had no harmful effects on kidney function in healthy adults.

That being said, individuals with pre-existing kidney disease or conditions like diabetes (which can affect kidney health) should monitor their protein intake with the guidance of a healthcare professional.

The Bottom Line: Separating Protein Myth from Fact

For the vast majority of people, there is no need to fear protein. The claims that high-protein diets lead to liver damage, kidney disease, or early death are not supported by solid scientific evidence, especially in healthy individuals. The fear surrounding aflatoxin and protein is based on rare and extreme cases that have little relevance to typical dietary practices.

However, it's important to note that individuals with existing health conditions, such as liver disease or kidney disease, may need to moderate their protein intake. For everyone else, a balanced, protein-rich diet can be part of a healthy lifestyle without the risk of harm.

In the next part of this series, we’ll dive into how much protein you should be eating based on your goals, and what the research says about optimal protein intake for health, performance, and longevity. Stay tuned!

Have more questions? Feel free to reach out to us—we're always happy to help you on your health journey.