Can You Eat Too Much Protein?
For healthy adults, it's hard to eat a harmful amount of protein from normal food. Intakes up to about 2 g per kg of body weight a day appear safe over the long term, and short studies in people who lift weights have found no obvious harm even above that. The real caution is for anyone with kidney disease, and the more everyday risk is that a very high-protein diet crowds out fibre, fruit, vegetables and wholegrains.
How much is "a lot"?
For context, the minimum recommendation is 0.8 g/kg. People who strength-train often aim for 1.6–2.2 g/kg. So for a 75 kg person:
- Minimum: about 60 g
- Typical muscle-building target: 120–165 g
- Around 2 g/kg: 150 g
- Very high (3 g/kg): 225 g, which is hard to reach without lots of shakes
Check where you sit with the protein calculator. There's more on setting a daily target in how much protein do I need a day?
The kidney question
High protein intake makes the kidneys filter more. For people with healthy kidneys, research generally hasn't found that high-protein diets cause kidney damage. For people with chronic kidney disease or reduced kidney function, though, doctors often recommend limiting protein, sometimes quite a bit. Many people with early kidney disease don't know they have it; it's more common with diabetes, high blood pressure and older age. If any of those apply, ask your doctor before going high-protein.
Other things worth knowing
- Calories still count. Protein has 4 calories per gram, the same as carbohydrate. Extra protein on top of your usual diet can still lead to weight gain.
- Fibre can drop. If protein replaces beans, wholegrains, fruit and vegetables, you can end up short on fibre, which affects digestion and gut health. Constipation is a common complaint on very high-protein diets.
- Source matters. A diet heavy in processed meat is a different thing from one built on fish, eggs, dairy, beans and tofu. The World Health Organization's cancer agency classifies processed meat as carcinogenic and red meat as probably carcinogenic, so it's wise not to get most of your protein from bacon and sausages.
- Hydration. Processing protein produces waste that your kidneys flush out, so drink enough water, especially when training in the heat.
- Supplements. Protein powders are convenient but less tightly regulated than medicines. Choose products that are independently tested for contaminants, especially if you're a competing athlete.
Is there a point where extra protein stops helping?
Yes. For building muscle, benefits tend to level off around 1.6 g/kg a day, with some people gaining a little more up to about 2.2 g/kg. Beyond that, extra protein is mostly used for energy. It isn't dangerous for healthy people, but it's often expensive and doesn't add much. When dieting, slightly higher intakes (up to around 2.4 g/kg) can help protect muscle and control hunger.
Signs your balance might be off
- Your meals are mostly protein, with little fruit, veg or wholegrains
- You're relying on several shakes or bars a day
- Your digestion has changed, often constipation
- You're spending a lot of money chasing a number above what research supports
A balanced approach
Aim for your target range, not beyond it; get most of your protein from whole foods; and fill the rest of your plate with vegetables, fruit, wholegrains and healthy fats. If you're tracking, the macro calculator helps keep protein, carbs and fat in proportion. And if you're over 65, your needs are a bit different: see protein for older adults.
Frequently asked questions
How much protein is too much?
For healthy adults, intakes up to about 2 g per kg of body weight a day appear safe long term. People with kidney disease may need much less and should follow medical advice.
Can too much protein damage your kidneys?
In people with healthy kidneys, studies generally haven't found that high-protein diets cause kidney damage. People with existing kidney disease are often advised to limit protein.
What are the side effects of eating too much protein?
Common issues are low fibre intake and constipation, extra calories, and a diet that lacks variety. Heavy reliance on processed meat carries its own health risks.
Is 200 grams of protein a day too much?
For a large, very active person it may be within a high but safe range; for most people it's more than needed. It's worth checking with a doctor if you have any kidney concerns.