A Primer on Protein, Exercise and the Latest Research with Dr. Stuart Phillips

Welcome to the Canadian Nutrition Society podcast Nutrition Conversations, a podcast dedicated to exploring the latest research in nutrition and health in Canada. In each episode we invite expert guests to share their insight and knowledge on the wide range of topics from dietary patterns to sports nutrition, food insecurity and food sustainability. Whether you're looking to improve your own health and wellness or simply stay up to date on the latest development in the field of nutrition, we hope you'll join us on this journey to better understand the role food plays in our lives. Please note that the views expressed by speakers in CNS podcasts are those of the speaker and not necessarily of CNS. Being in the host chair in this episode is the scientific director of the Canadian Nutrition Society, Dr. Sharon Panahee, who will be joining us and talking to Dr. Stewart Phillips in this inaugural conversation on protein, exercise and the latest research. Maintaining muscle mass is one of the key elements of longevity. As we age, our protein requirements increase, but that is only part of the picture. Exercise is a key ingredient too. So Stewart Phillips, whose no stranger to CNS, is a tier one Canada research chair in skeletal muscle health, professor of kidney theology at McMaster University and director of the McMaster University Physical Activity Center of Excellence, also known as PACE. If you've been reading about skeletal muscle protein turnover, there's a good chance you've come across some of Dr. Phillips over 230 original research papers. He has the reputation of being an excellent mentor to so many students and trainees. And with that, I welcome Dr. Phillips to the first episode of Nutrition Conversation. Thanks very much for having me, Sharon. It's a pleasure to be here. Well, we're super excited to have you as our first guest of this new CNS initiative and to have you share your expertise about the increased importance of dietary protein and exercise, particularly as we age. And I think this is a nice topic to start off with considering that March is also National Nutrition Month. And so protein is so important and it's become so big these days and we always seem to be concerned about getting enough. And beyond its nutritional role as a source of energy and amino acids for protein synthesis, I usually think about its role in appetite regulation, weight management, goals aligned with athletic performance and mostly in relation to muscle strength and muscle building, particularly with respect to weight maintenance or rather maintenance of lean muscle mass. And I know that your research is focused on the impact of nutrition and exercise on skeletal muscle protein turnover. And that you also have a keen interest in the area of aging and sarcopenia. And so I thought you could maybe start off by telling us a bit about how you became interested in your area of scientific research. Yeah, that's a great question. I think I've told the story a few times but I did my undergraduate here at McMaster University and I was a rugby player for the entire time. I did my undergraduate. In the last year I was going into my final year, I was convinced I was going into indomedicine and two weeks before I came back, I broke my leg. So I couldn't play rugby and then I went into the thesis and I was pretty enamored with the experience that I had. And in my last semester of my last year I took a course with Dr. Stephanie Ackinson who I'm sure lots of you will know. She was my master's advisor and really Stephanie's course kind of opened my eyes to the world of nutrition and the rest as we like to say is history. I got to give a shout out to Mark Tarnal-Balski as well. During my masters and show me how we could combine my knowledge of biochemistry with exercise and protein turnover and really kindled my interest in skeletal muscle as well. Oh, that's super. And so maybe we can focus a little bit on protein since you mentioned that's a little bit of your background. We know how much daily protein one requires depends on life stage, health status, body weight or goals and also our level of physical activity. And so maybe we can focus sort of on the average adult in Western populations and in Canada and the US. And have your thoughts on whether the current recommended dietary allowance of 0.8 grams of protein per kilogram of body weight per day is really the optimal amount to support an adult as they're aging. And what we sort of mean by optimal and optimal for what really? Yeah, great question. I mean, I think probably nobody would be surprised to hear my views that the recommended dietary allowances, a minimal intake is opposed to an optimal intake. And I think that that's based on my critique over the years of the nitrogen balance methodology and the shortcomings that it has. So I prefer to talk about, and I don't disagree for the record that the RDA is probably sufficient. The question is about optimal and so maximizing protein requiring processes. And when you're younger, obviously that would be growth, or if you're an athlete trying to support lean mass. But as you get older and the big question is when does start copenia or when does muscle loss start? And every year older I get that target keeps moving. So this year it's around 58 or something like that. No, in seriousness, probably for some people muscle loss begins in their fourth decade of life. And then we're talking about protein to try and mitigate that muscle loss. And as you said, there are some other tangential benefits around appetite regulation and satiety that could be other reasons to consume protein as well. But it's a much more difficult proposition to define optimal as opposed to defining minimal. And I think the RDA does a fairly good job with the minimal level and not as good with the optimal level. Right. And so we talk a lot about protein quantity and you just talked a little bit about what the minimal intake is. And so we note that there's also considerable interest on the patterns of protein intake throughout the day. So the usual protein intake distribution of the North American adults is typically skewed with a lower intake at breakfast. And for a lot of us, including myself as well, much of the time higher intake that dinner. So I was wondering if you could talk a little bit about the timing of when we should be taking in our protein and that distribution of protein intake. Yeah. You know, you're spot on with this sort of skewed distribution, a small amount of breakfast relatively modest amount of lunch and a large amount of dinner. You know, ourselves and a few other labs around the world, Professor Luke Fenloon and former PhD student in my Dan Moore at U of T have really looked at what we call per meal feedings that tend to maximize anabolism and the anabolism that we're talking about here will be skeletal muscles. So skeletal muscle protein synthesis. And for older individuals that tends to be quite a bit of a higher intake as opposed to younger individuals. Mainly we think because of their muscles insensitivity to the key amino acid to trigger muscle proteins synthesis, which is loose scene. And when you take all of this into an account, it would really suggest that a better or more optimal way to consume protein would be to consume it in a balanced pattern across the day. So maybe borrowing some of that protein that you're eating at the dinner time meal and putting it at the breakfast meal. You know, it's interesting now after 26 years here at McMaster, every study that we've ever done, which is fed isolated protein sources. We always bring people in after an overnight fast. So it really represents the breakfast meal. And you know, when you look at all of those studies, it really does sort of pattern the day if you like when you consume a relatively higher amount of protein at breakfast. So if there's any shift that you would speak to athletes or older people and making, it would be try and make breakfast a more protein containing meal than most people usually do. Right. And what are we looking at in terms of numbers throughout the day for that distribution? You're saying more for breakfast and then maybe kind of trying to keep that equally distributed, I guess, throughout the day. Yeah. So I think that this comes back a little bit to my recommendations are that I think most older people should be consuming at least 1.2 grams of protein per kilo per day. So that's 50% above the RDA and mainly athletes could probably go up as high as 1.6 or twice the RDA. And then if you divide that over, you know, say three or four eating occasions at the breakfast time meal, you're really talking about something minimal. about 0.3 grams of protein per kilogram per meal if you're a younger person, maybe going up as high as 0.5 if you're an older person. So it's not an insignificant amount of protein I'll admit to that and it could be something that for older people it's a pretty conscious decision to try and eat protein in those sorts of ranges for sure. Right, absolutely. And obviously we know that not all protein is created equal. So I was also wondering if you could speak a little bit to the quality of the protein as well. Yeah, this is an area that over the time I've been here at McMaster and the more work we've done in this space and reading other friends, colleagues, collaborators work that I've changed my position on. The science, if you'd asked me probably 25 years ago, I'd have given you back the answer standard, you know, animal-based proteins are higher quality, they're more digestible. And then, you know, 10 years ago, I said, yeah, I'm pretty sure that's still true for the most part. And the majority of, you know, work that we had done, we were always comparing usually milk-based proteins in athletes, for example, with, you know, the protein isolator concentrate. And that was soy. But, you know, these days, there's lots of isolated sources of vegetable protein, plant-based protein, pea, rice, hemp, lots of different things. And the more that we test those, I find that they're actually pretty comparable to the animal source proteins in terms of their anabolic or stimulatory properties. It may be an issue for older individuals, because of this, what we call anabolic resistance or the insensitivity of their muscle. But I really do think that things are getting much, much closer, particularly with isolated protein sources. And I would say even with food as well, you know, we've done some work in collaboration with a group in Brazil and others, we've got some projects going on with that Dutch group right now that really show that even plant-based foods, when you consume them, are much closer than I ever would have predicted based on the standard, you know, pdcast score and all of these sorts of things. Not that I don't love talking about pdcast or diast or something like that, but, you know, the reality when we scale up to human physiology, the proteins are actually much closer than I once would have thought. I know that upsets people, they, "Oh, you change your mind." And I'm like, "Well, you know, that's how science works, right? You know, you had a thesis and then you kept testing it and then it didn't really work out. And you're like, "Okay, well, maybe it's not such a big deal." And it's become much, I think, much, much easier to find plant-based proteins for people who make that choice for whatever reason, you know, products and we could argue they're probably processed to some degree, but they certainly weren't available, you know, even as long as five years ago. So it's a much easier eating pattern now than it used to be for sure. Right. So I guess we would want to have protein from many different sources, including both animal and plant and blended sources. So I guess that would be the recommendation. I'm going to shift gears a little bit. We've been focusing a little bit on the nutrition side of things. We know protein ingestion is important, but I know you also work in the area of exercise and resistance training. And so I was wondering if you could talk a little bit about how that sort of factors into all of this. Yeah, you know, I live and work in a department of kinesiology. So we rarely do feeding alone studies. We do a few of them, but they're always usually in combination with exercise. And I'll be honest that, you know, my own sort of view on this is evolved is, you know, I've gotten a little bit older where it was always about younger or more sort of athletic populations in the early phases of my career. And now it's a lot more about older individuals. And, you know, what we can do to help them maintain their peak performance. And I get it. It's not, you know, a metal around your neck on the podium, but it's certainly activities of daily living and obviously living a, you know, a healthy lifestyle and everything. So, you know, the dearer grub parts of that are clearly, you know, it's two things, right? It's nutrition and it's exercise. And I know people get tired of me saying it, but I use Jacla Lane's quote here where, you know, exercises, Kang nutrition is queen, put them together and you've got a kingdom. And a lot of people go, I'm what about sleep? Sleep should be in there. And I'm like, yeah, sleep, sleep too. Well, you know, sleep is the, you know, I don't know the the the jack or the nave or something like that. The prince would every who well. But, you know, when you when you put those two things together, things tend to line up pretty well. So, we always talk about exercise as a priming stimulus for muscle in particular, but other mechanically sensitive tissues bone is one to be receptive to the effects of nutrition and protein is no exception to that. Absolutely. No, that's great to hear. And so, I actually want to focus on one of your your papers that you had recently published, you and your team conducted a systematic review and meta analysis examining whether daily protein ingestion contributes to gaining lean body mass muscle strength and physical performance and healthy participants. And I gather that the protein came from both animal plant resources sort of from from all. And so, I was wondering if you could tell us a little bit about that study and what you found, what some of those outcomes you were testing were and whether one would need more protein to get the benefits of exercise. Yeah, well, you know, as a as a card carrying McMaster faculty member, I have to say the word evidence based medicine at some point. So, it was a systematic review. It was a pretty exhaustive one. Took a long time to do that actually. And it was a little bit of a coded project as well because we couldn't be in the lab. So, I'll be honest about that. But we basically went back and redid a search that we had done previously, but we modeled the data a little differently across protein doses. So, we categorized protein as, you know, the RDA or below and there are some intakes in that range. And then the RDA up to about 1.2 and then from 1.2 up to 1.6 or above. Again, this is an area where my opinion, and you know, you can't ignore the data that you generate yourself, right? It's an area that I've changed a lot of my mind on. And I think the biggest change is that the effect of protein is there. It does result in a small incremental gain and muscle mass and a little bit of a change in strength, but it's a very small effect. And so, you know, the meta-malysis had about 2,300 different individuals and from a variety of ages. And I think the biggest thing you can say is you probably do need to creep up into those higher intakes, 1.2 and up to 1.6 or above. To see that effect, but it's a real thin slice on the top of what exercise alone does. So, you know, the simple takeaway is going to the gym and lifting some weights is what really drives the gain and muscle mass and protein adds a little bit. And unfortunately, the other big message, the takeaway is that age is the big detractor of that. And so, this, even if we're physically active, as you get a little bit older, that anabolic response or the adaptability of the tissue becomes a little bit less. So, it's still a great, you know, exercise form and definitely recommend engaging in it. But the protein is not as big a fact as well. I think as we once said, or as I once said, and a lot of people have sort of come out and said, well, you got to get protein. And I'm like, you do, but it's not as big a deal as we once thought, for sure. And speaking of aging, you mentioned that many of us will have many experience. We're all doing it. We're all aging. So, it's a great one to talk about. Nobody's immune, right? So, absolutely. No, for sure. So, and as we gain age, we're going to experience that decrease in muscle mass and function, which will exacerbate the likelihood of mobility and paramedics disease development. Are there other sort of issues that come up? And you mentioned that resistance training seems to provide a cause of effective low cost means by which to prevent sarcopenia progression and improve multiple aspects of overall health. But I also wonder if older individuals sort of can with higher protein offset, you know, sarcopenia and also at what point would higher protein not be beneficial anymore? Yeah, a great question. I mean, the meta-analysis suggested that there weren't even enough studies that we could detect the effect of protein on, you know, whether it could mitigate losses in lean mass. So, I think that's a function of two things. First, none of the studies out there have been big enough, not enough people, or long enough to detect those types of changes. When you think about the sort of traditional age-related sarcopenia is occurring at about one percent. per year. Let's say, you know, between 50 and 51, for example, I've done some back of the envelope calculations. You probably need, depending on the method you used, something like, you know, about 800 people to see, you know, a significant change. If you could get them to eat protein at a higher intake for an entire year. So it's pretty difficult to detect. There are some observational analyses which suggest that high-urbrotene is associated with, you know, better skeletal muscle mass and preservation of function. And a few other things that, you know, make you think, okay, there's something out there. It's maybe a little grayer than we thought. But it's, you know, it's probably predicated against, you know, be physically active. That's the choice that you want to make. You know, where does protein start to, you know, the benefits start to diminish. I'd imagine it's probably beyond 1.2. I do think between 0.8 and 1.2. You can actually see some pretty significant differences. But once you get beyond 1.2 and, you know, obviously, the closer you get to saturating, if you like, the protein-requiring process is the much, much more difficult it would be to show a benefit. And it's assuredly it's a dose response. It's, you can't, you know, I keep saying to people, is unlike carbohydrate or fats, there's no other store protein. So you got to eat and use it. And so there's really, there's a finite capacity to which the protein containing tissues like your muscle can actually use amino acids. And, you know, it's probably pretty close to about 1.6 grams of protein per kilo per day. Okay, because that would, I guess, seem a little bit higher. So I guess in terms of other health impacts that I kind of wanted to touch on. And that's related to the often cited and how belief that higher protein intakes lead to kidney failure and reduce bone health. And, and you would, you know, think that and older age, that would be a problem. So I wonder if there's any evidence to support that or if you can maybe talk a little bit about that. Yeah. Well, so I think there's probably two that I, you know, as soon as I finish talking about protein, everybody says, oh, well, protein causes your, your bones to, you know, dissolve as usual word, but they sort of say, you know, protein leads to blood acidity, blood acidity, results in calcium resorption from the bone. Calcium resorb from bone is excreted in urine. So you increase your, your fracture risk. And, you know, interestingly enough, it's the exact opposite. If you have calcium and vitamin D levels dialed in to where they should be. So, you know, about a thousand milligrams of calcium and, okay, pick your target for vitamin D. But let's say 600 I use, then protein is actually a bone supportive nutrient. It's, I think it's a news flash for a lot of people to say, you know, your bone is about 40% by composition protein, right? It's not just the stick of chalk. There's, there's collagen there as well. So it's, it's, it's not true. The, you know, higher protein causes increased fractures, et cetera. The other one, yeah, around renal failure or kidney failure. And that's, that's about a 50 to 60 year old thesis that's, you know, you can call it the Brenner hypothesis, which is essentially goes something like, you know, protein is a solute generating macronutrient in the form of urea. And your kidneys have to excrete that solute. And so the more work your kidneys have to do eventually they get sort of fatigued. And you begin to lose the functional units of your, your kidney or the, or the nephrons they, they die out, they, they drop out. You know, ourselves, several of the groups have looked for evidence of this in systematic reviews of randomized controlled trials. And we've been unable to, to find any evidence of that observationally. It's the same story. There's really no consistent pattern. And then usually what gets put back to me at that point is, well, you know, absence of evidence is an evidence of absence. And I'm like, that's, that's perfectly true. But here we are 50 to 60 years after Brenner proposed the original hypothesis. And we're still searching for the, you know, whatever you want to call it, smoking gun, so to speak, that, that the protein cause kidney failure. And I think then we get into this sort of, I call it reverse or sort of corollary evidence that people who have kidney failure are put on lower or protein diets. And that tends to prolong their kidney function and prolong their survival. And that's true. But that doesn't reverse cause mean what the protein caused their kidney failure. So I think it's sort of a self-fulfilling prophecy using, you know, diagnostic or prognostic criteria in reverse and getting a reverse causality. But, you know, I'm, I'm agnostic on that. At this point, I don't think it's a causative agent. I think you're far more likely to suffer from renal issues if you have diabetes as an example or hypertension. And a lot of other lifestyle factors too, but, you know, there's a row group of even nephrologists who would, would back me up on protein not being a causative agent. So maybe things will change, but it's, it's taking a long time. Well, great. Thank you for that. And so before I get to the final question, and this is for those who are interested in either finding you on social media or contacting you to learn more about your work, where is the best place for them to do that? Sure. Yeah. So I am on social media and much to my colleague's surprise and she's a grin sometimes. Whitey father. But I do think it's a good place to have some some good interactions. So I am Mac, Ken, prof, M-A-C-K-I-N-P-R-R-F on Twitter and Instagram. I don't do as much Instagram as they do on Twitter. And I'm also on Facebook as well as smp.phd. So you can find me on all of those. And I'm on LinkedIn as well, Stuart Phillips McMaster. And yeah, I try and reply to people, I try and get back to people as much as I can. It's sort of a like a little sideline hobby, not a, not a main vocation. So apologies if I don't get back to you right away. But, but I have, I have financial social media. I enjoy the interactions and I find it mostly productive. Sometimes it gets a little nasty. I think that happens on everybody's social media can occasionally. Yeah. Well, thank you. That's perfect. And so that brings me to my final question. And it's simply if you could provide us with a few nuggets or any recommendations for people that could have a positive impact on their health, what would that be? Yeah, you know, I mean, I would be remiss is, you know, as a kinesaeologist, if I let everybody go without saying, I know it's not nutrition, but be as physically active as you can as often as you can. And wherever and whenever you can. I think that that really is a cornerstone foundation of activity. And for many nutrition standpoint, you know, one of the things that when I used to spend a lot of time working with athletes, we should teach people how to shop at the grocery store. And the message is really, stay around the outside of the grocery store and eat real and whole foods and as many varieties and as abundance as you can. So produce down one side meat and down the other and usually dairy and then probably baked goods around. It's the it's the stuff in between in the aisles, the the processed and hyper palatable foods that if you wanted to at least in my opinion to pick something to really squabble nutritionally over, that would be it. I think we've done ourselves a real disservice in creating super tasty, but not particularly good for your foods that tend to, you know, inhabit those middle aisles, but I don't think you can go too wrong, stick into the outside. And if you choose not to eat meat and dairy, that's fine. I have no issues with that. I'm a big believer in vegan and vegetarian lifestyles is a very healthy way to eat. So, yeah. And enjoy food. I think sometimes we talk too much about nutrition, right? And it should be we should be able to sit down and enjoy a meal with friends, family and that to me is that's a that's you know, and there's the other part, right? The socialization and everything else like that. And I think that physical activity and eating right and everything is, and it's a hard combination to beat for sure. Yeah, well, thank you for that. I absolutely agree. And those are some wise words and a wonderful message to leave us with. So, thank you so much for your time today, Dr. Phillips. It's been an absolute honor to speak with you. Well, it's my pleasure. Thanks for having me on the show and particularly inaugural episode. I really appreciate that. Hopefully I can live up to the billing. 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