Why Older Adults Need More Protein

Dr. Peter Attia: All right. There's a lot we want to discuss today, and I'm a little hesitant to say this, but I reluctantly feel that we need to have one more discussion about a particular macronutrient that seems to get a lot of attention lately. I don't necessarily want to talk about this because I think it's especially interesting or because there's some new study that we need to shed light on. But it remains surrounded by some controversy. I will refrain from publicly speculating on why that controversy exists, although privately I'm very happy to speculate on all the reasons for it. With that said, let's talk about protein.

Dr. Rhonda Patrick: Let's do it. I think it's an important topic. You and I have probably talked to all the world's experts on protein. We were chatting a moment ago about the recommended daily allowance for protein, the so-called RDA. Really, it should be called the minimal daily allowance. "Recommended" almost sounds like "optimal." I think people confuse it with the optimal amount of protein, so it's tricky.

That's an important place to start. The RDA for protein is 0.8 grams per kilogram of body weight per day. I know that you've probably had countless experts on talking about this. I've had experts on talking about it, including Stu Phillips. There are many publications. People can start with a perspective by Stu Phillips, "Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance?" There are several of these papers.

If you have the time and willingness to read the scientific literature yourself, or listen to The Drive or my podcast with the actual experts talking about it, you will learn that many of the studies used to determine the RDA were flawed. They were called nitrogen-balance studies. I don't want to get into all the technical reasons they were flawed, but one is that different protein-containing foods have different nitrogen-to-protein ratios. The studies also collect urine incompletely. When you urinate in one of those cups, you don't collect all the urine.

Dr. Peter Attia: And we lose nitrogen through means other than urine.

Dr. Rhonda Patrick: Yes, exactly. We lose nitrogen through other means, so the signal-to-noise ratio is low. Countless experts now agree that the protein RDA has been underestimated for those reasons.

Newer studies use stable isotopes. The main method uses L-[1-13C]phenylalanine. These studies give a small group of people a known amount of protein with that isotope tracer. When phenylalanine is metabolized, the tracer is oxidized, and that oxidation is measured in the breath. That gives a much more accurate measurement of protein steady state and turnover.

The point is to determine the minimum amount of protein you need every day to avoid negative protein balance. This matters because we do not store amino acids as we store fatty acids in triglycerides or glucose in glycogen. The major source of our amino acid storage tank, so to speak, is skeletal muscle. You do not want to pull amino acids from skeletal muscle every day. We need amino acids because everything in our body requires proteins. Proteins do all the work in our body, and proteins are made of amino acids. We need a daily intake of amino acids to perform all those functions.

Dr. Peter Attia: I want to state that again because this very important and fundamental point gets glossed over. We take it for granted if we studied biochemistry. We can store fat in unlimited quantities. If you deprive someone of fat calories for a period of time, they have a long reservoir they can draw from, although not indefinitely.

We store carbohydrates, though not as much because we can store only so much glycogen in the muscle and liver. But when we break down fat, we keep making the substrate to make glucose, so we get into a rhythm. To your point, the only place an amino acid sits in residence in our body is in muscle. If we approach the point where we are not getting enough amino acids, we do not have a buffer or a rainy-day fund. We immediately start to catabolize, or break down, muscle.

I don't think we have to make the case that that's a bad idea, but for completeness, there is not a single clinically relevant scenario I can think of where it would be desirable to give up muscle mass. Maybe if you're Mr. Olympia, you can sacrifice muscle mass. But for you, me, and everyone listening to us, giving up muscle because we fall short on protein would be a strategic and unforced error.

Dr. Rhonda Patrick: Exactly, for short-term and long-term health. That's why it is important that the RDA is not enough. Going back to those isotope-tracer studies, multiple studies have shown that the minimum is closer to 1.2 grams per kilogram of body weight per day. That is what adults need to avoid negative protein balance.

Dr. Peter Attia: We'll link to these in the show notes so that people can read the papers instead of reading about them on social media.

Dr. Rhonda Patrick: Sounds good. Multiple papers have shown that approximately 1.2 grams per kilogram of body weight per day is needed to prevent adults from entering negative protein balance.

Dr. Peter Attia: That's quite a bit more than 0.8 grams. It's 50% more.

Dr. Rhonda Patrick: Most isotope-tracer studies indicate 30% to 50% more. That's important because nutritional surveys suggest that adults consume about 0.9 grams per kilogram of body weight per day, close to the current RDA but not to what it should be. Among older adults, men consume about 0.9 grams per kilogram, while women consume about 0.8. They are just meeting what we call the RDA, which we have established is not enough to maintain net protein balance. That suggests most adults are not in a good steady-state protein balance.

Dr. Peter Attia: Here's an interesting question, Rhonda. We know the rates at which muscle mass and skeletal mass decline by decade in an aging population. Is there any way to estimate what percentage of that decline is driven by insufficient amino acid consumption versus other factors? Other factors include anabolic resistance associated with aging, anabolic resistance associated with sedentary behavior, and insufficient resistance training. Many factors explain why a person typically loses muscle as they go from 50 to 60 to 70. It would be interesting to know how much is explained by the fact that they are barely meeting the minimum nitrogen requirement and, in many cases, falling below it.

Dr. Rhonda Patrick: I don't know of a direct way to answer that, but studies have shown that older adults are more susceptible to anabolic resistance, where muscle tissue is less sensitive to amino acids, largely because physical inactivity increases with age. When older adults consume 1.2 grams per kilogram of body weight per day, it nearly eliminates some of the age-related muscle loss.

That is evidence supporting what you said. If older adults increase protein intake by 50% to what the RDA should be, 1.2 grams per kilogram of body weight per day, they prevent much of the age-related muscle loss that occurs. Most experts agree that it's time to change the RDA to that minimum. We also know that older women who consume 1.2 grams per kilogram per day are 30% less likely to have frailty in old age, which is also very important. Increasing protein intake by 50% is clearly important for aging, muscle health, and getting us out of negative protein balance.

Dr. Peter Attia: So step one is moving the floor from 0.8 to 1.2.

Dr. Rhonda Patrick: Yes. The floor is the minimum amount of protein that we need each day. This is not optimal. We're going to discuss optimal intake. This is just the new RDA.