Protein is having a moment. Supermarket shelves are full of high-protein yoghurts, bars, shakes, cereals and snacks. Fitness advice often starts with “eat more protein” before it asks what the rest of the diet looks like.
A recent NZ Herald feature is a useful reminder that more is not always better.
Protein is essential. It helps repair tissue, maintain muscle strength, make new cells, support immunity, and keep us full for longer. Health New Zealand lists good sources across meat, seafood, eggs, dairy, legumes, nuts, seeds, tofu, tempeh and wholegrains.
The problem is not protein itself. The problem is treating protein like the only nutrient that matters.
How much is enough?
The Australia and New Zealand nutrient reference values put the adult RDI at about 0.84 g/kg for men and 0.75 g/kg for women, with higher targets for people over 70.
That is a baseline requirement, not a muscle-building target. If you are older, frail, actively strength training, healing from injury, or training hard, more protein can make sense. The useful question is whether extra protein is improving the diet or pushing out the foods that make the diet healthier.
The same nutrient reference guidance notes that moderate protein intakes around 1.0-1.5 g/kg are probably optimal for bone health, and suggests a prudent upper limit of 25% of energy from protein for the general population because long-term evidence above that level is limited.
Five ways too much protein can backfire
1. It can become a calorie surplus
Protein helps with fullness, but it still contains energy. A protein bar, shake or “high-protein” dessert added on top of normal meals can quietly become extra calories.
Health New Zealand is blunt about this: too much protein can make you put on weight. If the extra protein replaces pastries, sugary drinks or ultra-processed snacks, great. If it just gets added to an already adequate diet, it is not free.
2. It can put pressure on vulnerable kidneys
For healthy people, high protein intake is not automatically a kidney disaster. The evidence is more nuanced than that, especially in active people.
But if you already have kidney disease, diabetes, high blood pressure, a history of kidney stones, or abnormal kidney blood tests, protein targets become more personal. Health New Zealand notes that people with kidney disease may need less protein. The National Kidney Foundation explains why: more protein waste means the kidneys have more work to remove it.
This is the main group that should not copy fitness-influencer protein targets without clinical advice.
3. It may increase calcium loss and stone risk
Health New Zealand also warns that too much protein can increase calcium in urine, which is not good for bones.
This does not mean protein is bad for bones. Very low protein is also a problem, especially as we age. The more useful point is balance: enough protein, enough calcium, plenty of fruit and vegetables, and not an extreme protein-heavy diet.
Kidney stones are another reason to be careful. The National Kidney Foundation links too much meat, poultry, fish, sodium and added sugar with calcium stones, and too much animal protein with uric acid stones.
4. It can crowd out fibre
The easiest high-protein diet is often a low-fibre diet: meat, eggs, cheese, powders and bars, with fewer beans, oats, fruit, vegetables and wholegrains.
That trade is bad for long-term health. The World Health Organization recommends at least 400 g of fruit and vegetables per day for everyone older than 10, plus at least 25 g of naturally occurring dietary fibre for adults.
If protein intake rises while fibre intake falls, the diet is moving in the wrong direction. Legumes, tofu, tempeh, nuts, seeds, oats and quinoa solve this nicely because they bring protein and fibre together.
5. It can drag saturated fat and sodium with it
Protein does not arrive alone. It comes packaged inside foods.
Fish, lentils, beans, low-fat yoghurt, tofu and lean meats are very different from bacon, sausages, fatty steaks, cheese-heavy meals and salty protein snacks. WHO notes that switching toward more plant-based protein can reduce diet-related disease risk in many adult diets, especially when the shift is away from red meat.
If “more protein” means more processed meat, more cheese, more saturated fat and more sodium, the health halo disappears quickly.
The better rule
Do not chase maximum protein. Chase adequate protein inside a good diet.
A good daily pattern looks like this:
- Include a protein-rich food with each meal.
- Strength train, because resistance training is what tells the body to keep or build muscle.
- Prefer whole foods over powders and bars.
- Keep legumes, vegetables, fruit and wholegrains high.
- Choose fish, seafood, tofu, tempeh, beans, lentils, yoghurt, eggs, nuts, seeds and lean meat more often than processed meat.
- If you have kidney disease, diabetes, gout, kidney stones, or high blood pressure, ask a doctor or dietitian before pushing protein high.
The longevity version is simple: eat enough protein to preserve muscle, but not so much that protein becomes the diet.