Eat more protein, and your body will let you know when it's too much. Regularly going above 2 grams per kilogram of body weight-especially with supplements-can put extra pressure on your kidneys, cause dehydration, and lead to stomach problems and fatigue. The high-protein trend is everywhere, but more isn't always better.
Protein is essential. It helps repair muscles and tissues, keeps hormones in check, and supports basic body functions. But most healthy adults only need about 0.8 grams per kilogram of body weight. That's around 46 grams a day for most women and 56 grams for most men, according to the 2025 Dietary Guidelines for Americans. Your needs depend on your size, sex, and activity level, but most people already get enough without thinking about it.
For healthy adults, the EFSA sets a baseline protein requirement at 0.83 g/kg body weight per day-nearly identical to the U.S. RDA of 0.8 g/kg. This is a minimum, not a universal upper limit, and most nutrition shake labels reflect serving sizes that align with these benchmarks.
When protein goes too far
Piling on protein-especially from powders and shakes-can backfire. Your kidneys have to filter out extra nitrogen from protein, which leaves the body as urea. This can cause dehydration and, over time, may put extra strain on your kidneys. Too much protein for too long can bring on headaches, tiredness, stomach trouble, diarrhea, and even bad breath from ketosis. Some people with certain medical needs may need more, but for most, the risks outweigh the benefits.
People with chronic kidney disease (CKD) are usually told to eat less protein-typically 0.6-0.8 g/kg/day for those not on dialysis, and up to 1.3 g/kg/day for those on dialysis, according to nephrology guidelines. For healthy adults, though, moderate increases in protein haven't been shown to harm kidney function, based on recent clinical reviews and reports from university medical centers.
Claims Check: While some brands market high-protein shakes as essential for muscle gain or weight loss, clinical evidence shows that exceeding 2.0 g/kg/day is rarely necessary for healthy adults. Regulatory authorities such as the FDA require that any health claims on protein supplements be substantiated by robust scientific evidence and not mislead consumers about disease prevention or treatment.
There's also an environmental angle. The nitrogen-rich urea from excess protein doesn't just leave your body-it ends up in wastewater, adding to environmental concerns. What you eat can have effects beyond your own health.
How to get the right amount
Start by figuring out how much protein you actually need. Mix up your sources: include both plant and animal proteins, and pick lean animal options when possible. Be careful with supplements, which can quickly push your intake too high. For most adults, a varied diet covers all your protein needs-no shakes or bars required.
Protein is just one part of eating well. If you're thinking about heart health, your choices about meat and protein sources matter, as discussed in this earlier article.
For most healthy adults, chasing higher and higher protein numbers doesn't pay off. The evidence is clear: meeting your daily target supports muscle, energy, and long-term health without extra risk. The goal is a balanced plate-enough protein, but not too much.
For more on official protein recommendations and safety, see the EFSA scientific opinion on dietary protein and the NIH protein fact sheet.
