What Happens When You Consume Too Much Protein? Understanding Risks

"Protein will make you sick!" – or so many headlines claim these days. Most articles focus on how a high protein intake could harm your kidneys and overall health. But is there any truth to it? Is too much protein actually harmful?
We've dug deep into the topic, read numerous studies, and put together a quick summary for you. So let’s get to it: what happens with too much protein?

Knowledge to go: What happens with too much protein?

• A consistently high protein intake can potentially lead to health issues over time.
• Where exactly the line is between “normal” and “too much” isn’t entirely clear. But according to expert organizations, consuming up to 2 g of protein per kg of body weight is considered safe.
• We still need more long-term studies to understand the full effects of high protein intake.

Overview – What happens with too much protein?

Let’s start with some reassurance: if you’ve ever devoured a whole pack of protein bars because you just couldn’t stop, that’s not inherently dangerous. Sure, you might experience a bit of a stomachache, but there are no long-term effects like a "protein overdose." But what happens when someone consumes large amounts of protein every day for a long time?

Kidney overload: Myth or fact?

What happens to our kidneys with too much protein? This question has been around for years, and many studies have explored it. Still, there's no definitive scientific consensus—surprising, right?

What we do know: a high protein load means more work for the kidneys, and that can be a strain. In individuals with pre-existing kidney issues, this strain can definitely be too much and lead to overload.

But what about people with healthy kidneys? Most recent studies agree that up to 2 g/kg of protein is safe for healthy kidneys. It challenges them, yes—but it doesn’t damage them directly. Anything beyond that is still a scientific gray area.

Update: High protein intake may lead to increased calcium excretion, which theoretically could raise the risk of calcium-based kidney stones. In practice, though, this rarely seems to be the case.

Pro tip: To support your kidneys, make sure you drink plenty of water!

Metabolism: Type 2 diabetes & more

What happens to our metabolism with too much protein? A high protein intake might increase the risk of type 2 diabetes. But—brace yourself—even the scientists say the exact mechanism is unclear. Other metabolic disorders also fall under the category of “might, but doesn’t have to.”

Cancer from too much protein?

Is there a link between high protein intake and cancer? Recent studies on various cancer types give us some relief—most findings show no clear increase in cancer risk.
An exception: milk protein and prostate cancer. High intake of milk protein (estimated around 30 g/day) may raise the risk of prostate cancer.

But: many of these studies are not optimal, so the results aren’t 100% reliable.

Digestive issues from too much protein

Stomach issues after too much protein? Yes, that can happen!
High protein intake can lead to digestive problems like bloating, constipation, or diarrhea. Why? Maybe you don’t tolerate the specific protein source, or you’ve drastically increased your intake and overwhelmed your digestive system.

Protein and your cardiovascular system

Is too much protein bad for your heart? Once again—no definitive answer. Current evidence suggests no link between high protein intake and high blood pressure.
Next question: what about our arteries? (Think arteriosclerosis.) Some recent studies suggest a possible link, but most are animal studies or small human studies, so results aren’t conclusive.

Your liver doesn’t mind—if you’re healthy

High protein from animal sources can lead to fatty liver in some people, particularly older, overweight individuals who eat a lot of meat. So for most of us, it’s not a major concern.

Impact of protein on your bones

What happens to your bones when you consume too much protein? As mentioned earlier, it can lead to increased calcium excretion. Bad news for bones? We don’t know yet. It’s still unclear whether this has any real impact on bone health or conditions like osteoporosis.

One thing is clear: an appropriate protein intake can have positive effects on bone health.

So—are proteins dangerous?

Thinking “Okay, I’m never eating protein again” after reading this? Understandable!
But no need to panic—protein is essential and completely safe in recommended amounts.
All the scary consequences mentioned above apply to excessive intake beyond official recommendations. That’s why we keep asking: what happens when you consume too much protein?
The safe intake for the general population is 0.8 grams per kg of body weight (up to 2 g/kg for some groups). You can read more in our article "How much protein per kg?"

Also, you’ve probably noticed we’ve used words like "might," "possibly," or "potentially" in nearly every section. Why? Because solid scientific evidence is limited. Many studies are short-term or conducted on people with pre-existing conditions. That means results aren’t always applicable to everyone.
Think of it this way: “You could fall off a roof tomorrow.” It’s possible, but not likely. The risk increases if you spend a lot of time on rooftops doing tricks with your eyes closed. Get the analogy? A sensible approach to both rooftops and protein is the way to go.

The role of protein powders & co.

When we talk about protein, we often think of eggs, meat, or legumes. And studies mostly focus on these sources. But more and more people are consuming protein shakes and protein bars daily.
What about these high-protein products? Can protein powders cause side effects? Side effects are definitely possible—bloating or diarrhea are common. But how exactly these products affect long-term health still needs more research.

Smart protein habits

What can you do to avoid panic-Googling "what happens with too much protein" after your 20th shake?

1. Like everything in life: moderation is key. Stick to recommended amounts.

2. Choose quality protein sources that contain healthy fats, vitamins, minerals, and fiber. Even with high-protein products, check the ingredients and opt for high-quality options.

3. Listen to your body. Look out for signs like bloating or other digestive issues.

Conclusion: What happens with too much protein?

So, what’s the verdict? Truth is—we still don’t fully know. Long-term data is limited. But we do know that up to 2 g/kg is considered safe by experts.
The takeaway: too much and too little protein can both be harmful. Stick to the recommended range and be mindful with protein products like shakes.

FAQ – Frequently Asked Questions

Can you eat too much protein?
Yes—especially if you’re consuming a lot of high-protein products like shakes. Always follow recommended intake guidelines.

Is protein powder harmful?
No—high-quality protein powder normally is not harmful and can help you meet your daily needs. But remember: moderation!

What happens with too much protein?
Excessive protein intake can be harmful and lead to health issues in some cases.

Literature & Sources

1. DGE (Deutsche Gesellschaft für Ernährung e.V.) (2023). Leitlinie Protein. Evidenzbasierte Leitlinie zum Einfluss von Protein auf gesundheitsbezogene Endpunkte. https://www.dge.de/
   wissenschaft/dge-leitlinien/
   leitlinie-protein

2. Raschka, C. & Ruf, S. (2017). Sport und Ernährung. Wissenschaftlich basierte Empfehlungen, Tipps und Ernährungspläne für die Praxis. 3. Auflage. Georg Thieme Verlag KG, Stuttgart.

3. Zhang, X., Kapoor, D., Jeong, S., et al. (2024). Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk. In: Nature Metabolism, 6(2).

About the Author

Melanie Seyfarth is a nutrition scientist (B.Sc.), certified supplement consultant, and an expert in vegetarian and vegan nutrition. Since 2018, she’s been diving deep into the science behind food and health. On this blog, she shares insights on nutrition, fitness, and lifestyle—plus delicious recipes. Her articles are based on current research, practical experience, and the goal of making complex knowledge easy and fun to understand.

Got questions? Send me an email—I'm happy to hear from you! :)