Protein is one of the few nutrition topics where the marketing noise and the actual evidence point in roughly the same direction, which is unusual. Most people, particularly people over fifty, are eating less than would serve them.
The RDA is a floor, not a target
The often-cited figure of 0.8 grams per kilogram of body weight per day is a minimum designed to prevent deficiency in the general population. It was never intended as an optimum for maintaining muscle mass through aging, and it doesn't function well as one.
For adults actively trying to maintain or build muscle, the literature clusters around 1.2 to 1.6 grams per kilogram daily, with some support for the higher end during periods of weight loss or intensive training. Above roughly 1.6, the returns for muscle protein synthesis flatten in most people.
For a 175-pound person, that's roughly 95 to 125 grams per day. Most people I talk to are surprised by that number and are eating well under it.
Why older adults need more, not less
This is the part that gets it backwards in practice. Aging muscle becomes less responsive to protein, a phenomenon called anabolic resistance. The same dose of protein produces a smaller muscle protein synthesis response at seventy than at thirty.
The implication is uncomfortable but clear: the population that typically eats the least protein is the population that needs the most. Combine that with declining appetite and often reduced physical activity, and you have the setup for sarcopenia, the progressive muscle loss that drives falls, fractures, and loss of independence.
Muscle isn't vanity. Past sixty, it's the difference between recovering from a fall and not.
Distribution matters more than people think
Total daily intake is the primary variable, but spreading it across meals appears to work better than backloading it into dinner. Muscle protein synthesis responds to a per-meal threshold, roughly 25 to 40 grams for most adults, with the higher end more relevant for older adults given anabolic resistance.
In practice, that means the typical pattern of minimal protein at breakfast, moderate at lunch, and a large evening load leaves some of the potential response unused.
Doing this on a plant-based diet
I eat a whole-food plant-based diet, so this is a practical question I've had to solve rather than a theoretical one. It's entirely achievable, but it requires more intention than an omnivorous diet does.
Legumes, lentils, tofu, tempeh, seitan, and edamame carry the load. Soy protein in particular has a complete amino acid profile comparable to animal sources. Because most plant sources are somewhat lower in leucine, the amino acid most directly implicated in triggering muscle protein synthesis, aiming toward the higher end of the intake range is reasonable.
The thing to watch is that many people who move to plant-based eating simply subtract the meat without deliberately replacing the protein, and end up substantially under-eating it. That's a planning failure, not an inherent limitation of the diet.
A reasonable summary
Aim for 1.2 to 1.6 grams per kilogram of body weight daily. Spread it across at least three meals. Increase rather than decrease it as you age. And treat resistance training as the other half of the equation, because protein without a training stimulus doesn't build much of anything.