How much protein do you actually need?

Protein is having a moment. It's in the water, the popcorn, the coffee, and an entire aisle at Costco. The question is whether any of that is actually doing anything for you.

I tracked everything I ate for a few days before writing this, and my daily protein intake ranged from 60 grams to 150 grams depending almost entirely on whether my kids were having pasta for dinner. That's a wide spread. So let's talk about what the evidence actually supports.

Why protein is different from the other macronutrients

Carbohydrates and fats are, biochemically, pretty boring. They store energy, get broken down, and leave your body as water and carbon dioxide. Protein is more interesting. It's built from 20 amino acids assembled in every possible combination to make the stuff of your body: skin, muscle, hair, enzymes.

Nine of those amino acids are essential, meaning your body cannot synthesize them. If you don't eat them, you die. That's not true for any specific carbohydrate or fat. There is a disease of pure protein malnutrition called kwashiorkor, and it's what's behind the distended bellies you've seen in old images of famine. Those kids had calories. They didn't have protein.

The flip side: protein metabolism produces ammonia, which is toxic. Your kidneys handle it by excreting it as urea. Hold that thought.

How much protein do you actually need?

The government's recommended daily allowance is 0.8 g/kg per day. For a 180-pound person, that's about 65 grams. Most Americans already hit this. NHANES data shows the average woman gets about 75 grams a day and the average man gets a little over 100.

That RDA was designed around a minimum for institutional health, not optimization. The number you'll hear from fitness influencers is closer to one gram per pound of body weight, which for that same 180-pound person would be 180 grams a day. That is a lot. Hitting it takes real planning, and if you do it by simply adding food on top of what you already eat, you'll gain weight. The point is to shift the ratio, not pile on calories.

A more defensible target from the literature is around 1.6 to 2 g/kg for people actively trying to build or preserve muscle. Still a lot, but less absurd than a gram per pound.

What the evidence actually supports

The clearest case for higher protein intake is building and preserving muscle. That matters most in older adults, where maintaining muscle mass is the difference between falling and not falling. The Pro Muscle trial randomized 65 frail elderly people to 30 grams of milk protein daily versus placebo, with both groups doing resistance training. The protein group gained 1.3 kg of lean body mass and scored a point higher on the short physical performance battery. Modest, but real.

One critical caveat: protein alone does nothing. You have to lift something. If you eat the protein bar and stand around watching other people exercise, you are simply a person eating a protein bar. The amino acids will get broken down into sugar and used for calories, because your body is more than willing to do that.

What about timing? Mostly a myth. The data on athletes, who love to be studied, shows it doesn't matter whether you hit your protein target in one sitting or spread it across the day. The "30-minute anabolic window" is not supported.

For weight loss, a higher-protein diet may help a little, mostly through satiety and by making eating harder. A 2010 trial randomized men with diabetes to 35% vs. 15% protein diets at equal calories. The high-protein group lost about 3 kg more over four months. Not nothing. Not a GLP-1.

For brain health, the direct effect on dementia appears to be small or zero. There may be an indirect benefit: if more protein and resistance training keep you mobile and engaged with the world, that activity itself is good for cognition.

When more protein becomes a problem

I'm a nephrologist, so this is where I earn my keep. High protein intake increases kidney filtration rate, from about 100 mL/min up to 110 or 120. That's your kidneys working harder to clear the ammonia load as urea.

In people with existing kidney disease, the data are clear: lower protein intake preserves kidney function over time. Ten years ago we routinely told kidney patients to cut protein. We've backed off because muscle mass and mobility matter too, but I don't tell those patients to load up on protein either.

In people with healthy kidneys, we don't have long-term data on whether 2+ g/kg causes harm. We probably never will, because the people eating that much protein differ from everyone else in a hundred other ways.

There's also a theoretical cancer concern. Leucine, an amino acid that signals muscle growth, activates mTOR, a pathway implicated in cancer promotion. Growth is not universally a good thing. I'm not losing sleep over this, but it's worth knowing that the same signal telling your biceps to grow isn't selectively delivered.

Bottom line

Most people get enough protein to avoid deficiency without trying. If you're over 40 and lifting weights, if you're older and trying to preserve muscle, or if you're on a GLP-1 and trying not to lose lean mass, prioritizing protein in the 1.6 g/kg range is reasonable and supported by evidence. You'll probably need a protein shake to get there, because whole food alone makes it hard without blowing past your calorie budget.

If you have kidney disease, don't chase high-protein targets. If you're healthy and not doing serious resistance training, a gram per pound is overkill. And wherever possible, get protein from plant sources too, so you don't tank your fiber intake in the process.

I covered this in depth on Wellness, Actually. Listen below.

Wellness, Actually Podcast

"What's the deal with protein?" — Listen to the full episode, including the week's health news and listener Q&A.