FoundMyFitness - #097 The Science of Protein and Its Role in Longevity, Cancer, Aging, and Building Muscle

Episode Date: November 27, 2024

Discover my premium podcast, The Aliquot Download my "How to Train According to the Experts" guide Protein is far more than a building block for muscle—it's essential for metabolic health, insulin sensitivity, and preventing conditions like type 2 diabetes and sarcopenia. But how much do we truly need? And could too much protein, especially from meat, actually be harmful? This episode challenges the conventional RDA of 0.8 g/kg, presenting research that supports higher intakes of 1.2–2 g/kg for maintaining muscle, improving body composition, and promoting longevity. We also confront myths around protein timing and the so-called "anabolic window." Lastly, we address concerns about protein's links to cancer, heart disease, and kidney function, showing how exercise can redirect growth factors like IGF-1 to promote repair while mitigating risks.  Timestamps: (00:00) Download my "How to Train" guide (00:51) Introduction (03:32) Why muscle matters (05:57) Why do we lose muscle? (07:31) How to negate anabolic resistance (08:24) Why it's never too late to build muscle (09:05) Requirements for overweight & obese individuals (09:52) Exposing the flaws of the RDA (11:12) Optimal intake when resistance training (11:55) What to do when losing weight (13:08) Does protein harm healthy kidneys? (14:59) How important is distribution? (17:11) Debunking the "anabolic window" (18:48) Benefits of pre-sleep intake (20:20) Timing & distribution takeaways (21:01) What are the best sources? (24:05) Animal vs. plant protein (26:27) Protein supplements (whey, casein, & collagen) (27:57) Does high intake accelerate aging? (31:32) Why exercise changes the story (34:02) What we can learn from athletes (34:36) Does high intake accelerate atherosclerosis? (36:51) 8 key takeaways Show notes and transcript are available by clicking here Watch this episode on YouTube

Welcome to today's episode, which promises to be exceptional for anyone aiming to maximize their training outcomes. We are going deep into the science of protein, a crucial element in achieving your fitness goals. Accompanying this episode is a new Found My Fitness Guide titled How to Train According to the Experts. This comprehensive guide not only encompasses everything you'll learn today, but also tackles key questions on how to best train, eat, and supplement for optimal results. It synthesizes the best advice. on training, nutrition, and supplementation from the world's leading experts featured across nearly 100 episodes of this show. I highly encourage you to download this free guide at how to

train guide.com. Once again, that's how to train guide.com. Now let's proceed with the episode on the science of protein. Beyond its well-known role as the building block of muscle, Protein is fundamental to our metabolism, insulin sensitivity, and the prevention of diseases such as type 2 diabetes and circophenia. But how much dietary protein do we really need? And could too much protein, especially from meat, actually be harmful? Today, we'll discuss why maintaining and even building muscle is critical for everyone, not just athletes. You'll discover how protein intake, coupled with resistance training, drives muscle repair and growth, enhancing athletic performance, improving metabolic health,

and promoting longevity by acting as a defense against age-related frailty. You'll learn about optimal protein amounts based on age, activity level, and goals, whether you want to actively gain muscle, maintain it, or just improve body composition. We will critically examine current protein recommendations, challenging the adequacy of the RDA of 0.8 grams per kilogram body weight. Drawing on the latest research, we discuss why higher intakes, ranging from 1.2 to 1.6 grams per kilogram, are more beneficial for general health and why up to 2 grams or higher may be best for body recomposition. Addressing the contentious links between high protein diets and health risks, we will analyze evidence surrounding proteins association with cancer, heart disease,

and kidney function. We'll explore how lifestyle factors, particularly physical activity, profoundly influence these risks. Specifically, we'll uncover how exercise modulates growth factors like IGF1, diverting them towards muscle and brain tissue where they support repair and growth, while potentially mitigating their pro-cancer effects in other tissues. We dissect the differences between animal and plant proteins in stimulating muscle protein synthesis. We'll provide practical strategies for vegetarians and vegans to meet their protein needs effectively through increased total intake, diversified sources, and the use of plant-based protein concentrates. We'll also dispel myths around protein intake timing. You'll learn how distributing protein

evenly across males can maximize muscle protein synthesis and why the so-called post-exercise anabolic window may not be as narrow as once thought. Additionally, we highlight the pivotal role of the amino acid leucine in activating muscle building pathways and how this impacts protein quality considerations. By the end of this episode, you'll be equipped with all of the evidence-based insights you need to better navigate common misconceptions and ultimately harness protein for muscle maintenance, performance, and a frailty-free future. So let's get into it. How much muscle we have tells us more about how we are aging than body weight or BMI ever could. Here's a startling fact. After the age of 50, the average person loses about 1% of their muscle mass every single

year and it's not just muscle mass strength plummets even faster dropping around 3% annually by the time you reach 75 if you're not engaging in regular strength training you could be losing up to 4% of your strength every year so what can we do about this exercise both before you need it building muscle reserve but also in old age to slow and reverse the decline while resistance training is the most important factor for building and maintaining muscle mass and strength. Protein intake plays an important role too. A meta-analysis from Dr. Stewart Phillips and colleagues highlights the importance of protein intake by showing that people who engage in resistance training and supplemented with additional protein taking their total daily protein intake up to 1.6 grams per kilogram

body weight, increase their muscle mass by 27 percent and their strength by 10 percent more than those who did resistance training without additional protein supplementation. So these people were getting around 1.2 grams of protein per kilogram body weight. So dialing in that protein intake matters for both muscle mass and strength when combined with the resistance training. Skeletal muscle makes up around 30 to 40 percent of our lean body mass. More muscle doesn't just mean more strength. It means better metabolism, enhanced insulin sensitivity, and a pretty good defense against

type 2 diabetes. It also dramatically decreases frailty and the risk for sarcopenia, one of the main risk factors for falls and fractures in older adults. Research has shown that individuals who suffer from a fragility fracture are twice as likely to die compared to those without such fractures. And between 22 to 58% of people with the hip fracture pass away within just 12 months after the injury. In old age, falling and breaking a hip can literally be a death sentence. A better body composition dramatically improves quality of life and reduces disability risk. Having a higher muscle mass can decrease the risk of early death by 30%, whereas having a high fat mass can increase that risk by 56%. So what explains our

greater susceptibility to lose muscle mass as we get older? There are a few factors that play a role in this, but a big player here is a phenomenon called anabolic resistance. So as we age, our muscles become less responsive to amino acids, meaning they don't trigger muscle protein synthesis in response to protein intake as effectively. So for older individuals, the same amount of protein results in a smaller increase in muscle protein synthesis compared to younger people. Some studies have shown that an older person requires almost twice as much protein for the same response. For example, around 0.24 grams of protein per kilogram body weight or 0.1 grams per pound. That's 20 grams of protein for about an 80 kilogram man, maximally stimulates muscle protein synthesis and someone young. But

this dose is higher for older adults who need about 0.4 grams of protein per kilogram or 0.18 grams per pound of protein per dose. An older adult man weighing about 80 kilograms would need about 32 grams of protein to maximally stimulate muscle protein synthesis. By the way, for anyone taking notes, this suggests that the optimal amount of protein per dose is between 20 and as high as 35 grams of protein depending on your personal level of anabolic resistance. So this means a few things. The first is that if you're older, you need a higher total daily protein intake to maintain or increase muscle mass. It also means that you need a higher dose of protein at each meal to stimulate muscle protein synthesis. But anabolic resistance is not inevitable

or only due to aging, as some might suggest. In fact, physical inactivity may actually be the biggest contributor. Reducing physical activity worsens anabolic resistance. For example, taking fewer steps for just two weeks causes anabolic resistance in older adults and reduces their insulin sensitivity. Imagine what decades of inactivity can do. That's the bad news. But the good news is that exercise makes muscle more sensitive to protein and essentially negates anabolic resistance. When older adults exercise before protein intake, their muscle anabolic response is identical to that of a younger adult. So how do I interpret this? Active older adults probably don't experience as much anabolic resistance as inactive people,

and therefore it might not be such an issue for people that are physically active. The most effective way to combat anabolic resistance as we age is through regular physical activity combined with a higher daily protein intake, ideally around 1.6 grams per kilogram body weight. We do not have to be frail in old age. We can build muscle into our 40s, 50s, 60s, and even our 70s and beyond, and we can definitely increase muscle strength and power output at this age. In one study that recruited adults aged 90 years and older, eight weeks of high intensity strength training produced a 174% increase in muscle strength. Muscle strength and size increased even in the ninth decade of life, and age when most people wouldn't even think twice about touching a weight.

So let's talk about the optimal protein intake. The optimal amount of protein will not be the same for everyone. Some people want to build muscle mass. Some people want to maintain it and others want to improve their body composition by building muscle and losing fat. Each of these goals requires a more tailored approach. The first thing to know is that it's generally agreed upon that protein needs should be calculated based on a lean body mass or an adjusted body weight, reflecting a healthy body fat percentage. So, for example, 12 to 15% for men and around 20% for women. This prevents unrealistic targets, especially for those who are overweight or obese. So when I refer to protein intake in grams per kilogram of body weight per day, what I'm ideally referring to is your ideal or

goal body weight. Let's address one thing up front. The recommended dietary allowance or the RDA for protein of 0.8 grams per kilogram per day is thought by many to be too low. This is because the RDA was derived from nitrogen balance studies, which have limitations due to incomplete collection and inaccurate estimates of amino acid losses. The optimal range for daily protein intake is closer to 1.2 to 1.6 grams per kilogram body weight per day, or roughly 0.54 to 0.72 grams per pound. This is based on alternative methods like stable isotope studies, which consistently show that higher intakes are necessary to maintain a positive protein balance, far above the 0.8 grams per kilogram often cited. So aiming for at least 1.2 grams and up to 1.6 grams is what we're talking about,

for optimal protein intake. There's good evidence to suggest this. For example, older adults consuming at least 1.2 grams of protein per kilogram body weight per day prevented age-related losses in lean mass when compared to consuming the RDA of 0.8 grams per kilogram body weight. Older women were also 30% less likely to experience frailty when consuming protein above the RDA. So what is the optimal protein intake for building muscle while resistance? training. For people engaged in resistance training, a protein intake of 1.6 grams per kilogram body weight per day has been shown to maximize gains in lean body mass with a 27% increase in muscle mass over even a 1.2 gram per kilogram intake. That's a lot and it really just serves to really

underscore how low the RDA really is when you're talking about 0.8 grams per kilogram body weight. By the way, for an excellent discussion of the protein RDA and much more, see my interview with Dr. Stewart Phillips in episode 76 of the Found My Fitness podcast. There are special circumstances where even a higher protein intake might offer some marginal benefit. The first example is people undergoing body recomposition, where they are in an energy deficit to lose fat mass while preserving or even increasing muscle mass. So let's talk a little bit more about body recomposition and weight loss. A higher protein intake tends to improve satiety. It helps you feel fuller for longer and may help prevent overeating. For people who want to lose weight, this is a major benefit.

Eating more protein is also essential during weight loss to prevent the loss of lean body mass. When you eat a higher protein calorie restricted diet, more weight loss comes from fat mass than muscle mass. But remember, resistance training is also important to prevent the loss of lean mass. High protein diets may also cause a slight increase in the metabolic rate due to the thermic effect of food, helping you burn a few more calories throughout the day. The second example where a higher protein intake above 1.6 grams per kilogram may be beneficial is with professional athletes where extremely marginal improvements in muscle protein synthesis gives them an edge on competition.

So in this scenario, this is where up to 2.2 grams of protein per kilogram per day or one gram per pound may provide marginal benefits. Despite common misconceptions of very high protein intake is not harmful to kidney health in people without pre-existing kidney conditions. Research consistently shows that high protein diets are safe for most people and any concerns over kidney damage are largely unfounded. So let's talk about this myth. Early interpretations of certain studies suggested that excessive protein intake might overwork the kidneys. While protein restriction can slow the progression of kidney disease in some individuals, we now know this does not imply that a healthy people should limit their protein

consumption. Higher protein diets do induce changes in kidney function, but they do not overburdened the kidneys. The observed increase in markers in kidney function is a normal adaptive response to eliminate urea and other waste products generated during protein metabolism. This is entirely normal for individuals with healthy renal function. So current evidence does not support an association between higher protein intake and kidney disease among healthy adults or those at risk, such as individuals with obesity, hypertension, or even diabetes. Moreover, research and athletes has shown that consuming protein intakes as high as 3.2 to 4.5 grams per kilogram of body weight per day for up to one year does not cause any adverse changes

in kidney function and is considered safe. This intake is four to six times higher than the RDA for protein. And emerging research even suggests that higher protein intake may actually be beneficial for people with chronic kidney disease. Some studies have found that consuming protein at levels above the RDA is associated with reduced mortality risk in this population, challenging the traditional approach of protein restriction. The bottom line, we can finally put to rest the myth that high protein diets harm healthy kidneys. It's time to tackle another important aspect of protein intake, and that's how often and when we should consume it.

We'll tackle two key points. First, how we consume our daily protein intake, whether we should spread it evenly across three to four meals or load it up into one or two meals. Second, and related, does protein have to be consumed within a critical anabolic window or timed with our workouts? In short, the answer to both of these is that factors are less important overall than you might expect.

Emerging evidence reveals that the body can effectively utilize even very large protein doses. This challenges the notion that protein must be meticulously spread over multiple meals to maximize muscle protein synthesis. Even though an even daily protein distribution is ideal, this doesn't mean that consuming the same total amount of protein in fewer high protein meals is ineffective. Protein distribution is important, but not vital. When you eat a larger dose of protein, it takes longer to digest, but your body will eventually use it. This is contrary. to what some people think happens when you consume more than 20 to 25 grams of protein in a single meal. They think that the excess protein will just be excreted by the body and otherwise wasted.

In fact, a study by Dr. Luke Van Loon and colleagues found that consuming 100 grams of protein after exercise led to a more robust and prolonged anabolic response than did 25 grams of protein, but had negligible effects on amino acid oxidation. The conclusion from this study was, quote, the magnitude and duration of the anabolic response to protein has no upper limit in humans and has been severely underestimated, end quote. This dispels a few myths about how the body can use only 20 to 25 grams of protein at once. As a practical takeaway, a more evenly distributed pattern of protein intake throughout the

day is probably what we should be striving for. But evidence like this highlights why more and more experts seem to be aligning on the simple fact that the vast majority of us, athletes or not, should be thinking about protein intake from the standpoint of total daily intake with less overall focus on factors like timing or the per meal intake. Another question that people have regarding protein timing is whether protein needs to be consumed immediately after exercise to enhance the effects of training. This idea is known as the anabolic window. The anabolic window is a period after exercise typically lasting from 30 minutes to two hours during which the body is primed to absorb and utilize nutrients, particularly protein

and carbohydrates for muscle repair and growth. It occurs because the body's ability to synthesize protein and replenish glycogen stores is heightened, aided by exercise-induced hormonal changes like increased insulin levels. Consuming 20 to 40 grams of high-quality protein, often paired with carbohydrates, can enhance muscle recovery and growth during the anabolic window. Or so, what was once thought. Recent scientific evidence reveals that muscle protein synthesis remains significantly elevated for a full 24 hours following exercise, effectively debunking the notion of a very narrow anabolic window lasting only a few hours. Furthermore, supplementing with protein before exercise has the same effects on body composition and strength compared to supplementing with protein

immediately after exercise. In other words, there are no meaningful differences between pre- and post-exercise protein ingestion. This means that you're free to choose when you want to consume protein in relation to exercise so long as your total daily intake of protein is adequately high to support optimal muscle protein synthesis. Of course, there is definitely no downside to consuming protein immediately after a workout, especially for people interested in achieving marginal gains in strength or muscle mass. To wrap up our discussion on protein timing and distribution, I want to bring up one more strategy to help with muscle building that relates to protein distribution and timing. pre-sleep protein. There's two ways to look at this. One way is through the lens of time-restricted

eating, and the other is through the lens of actively optimizing for muscle protein synthesis on training days. It's been shown in studies by Dr. Luke Van Loon and colleagues that protein consumed before bed is digested and absorbed overnight. It also increases overnight muscle protein synthesis rates and improves net protein balance in people who had performed resistance training earlier in the day to enhance muscle recovery. The benefit The benefits of pre-sleep protein have also been shown during chronic resistance exercise training. Consuming about 30 grams of protein before bed every night while resistance training appears to increase muscle mass and muscle strength.

Another thing about pre-sleep protein is that it does not seem to reduce appetite or diminish the muscle protein synthesis response at breakfast the next morning, which may have been a concern for some people. Overall, I think pre-sleep protein is just one way to increase total daily protein intake. If you don't like going to bed hungry, having a low calorie protein shake on training days may have the benefit of potentially enhancing your muscle gain on those training days. But don't use this as an excuse to go wild. We should still be mindful about the fall and insulin sensitivity that happens as we get close

to our habitual bedtime. And this is particularly true if you're not actively training. So let's summarize some key points about protein timing and distribution. First, while it's not necessary to consume protein immediately after a workout, there's no harm in doing so. For those who exercise fasted, having a protein-rich meal right after may be beneficial. Ultimately, total daily protein intake is the most crucial factor. Second, evenly distributing protein across meals is ideal, but your body can use even large protein meals. And finally, consuming protein before bed isn't essential, but it can be a helpful strategy.

to boost total daily intake or support muscle recovery, especially in those who are actively training. All this talk about protein lacks context unless we discuss the best sources of protein, particularly when it comes to stimulating muscle protein synthesis. Is animal protein better than plant protein? What about weigh protein compared to casing protein? A high-quality protein can be efficiently digested and utilized to maximize muscle protein synthesis. Several factors influence a protein's digestibility, including,

whether it's a whole food source, an animal-based or plant-based protein source, the presence of other nutrients like fiber, which are mainly present in plant foods, and the amino acid composition of the protein. When it comes to the amino acid composition, leucine is of particular importance for protein quality. The main anabolic component of protein is the branch chain amino acid leucine, which is a potent stimulator of muscle protein synthesis. Lusine stimulates muscle protein synthesis by activating the mTOR pathway, which is our body's central regulator of cell growth and metabolism. In fact, lucine appears to be more critical than the total protein content of food or supplement in determining the muscle protein anabolic response.

This concept is referred to as the lucine threshold or the lucine trigger hypothesis, which suggests that a specific amount of lusine must be consumed to activate muscle protein synthesis. Essentially, lusine acts as a switch kick-starting the muscle protein building process. About 0.25 grams of protein per kilogram body weight in a single meal provides a saturating dose of leucine and amino acids to stimulate muscle protein synthesis for up to six hours. That's about 2 to 3 grams of leucine, which can be obtained by consuming 20 grams of a high-quality protein like weight protein. Even though leucine might be the most important amino acid for stimulating muscle,

muscle protein synthesis, all of the amino acids are required to allow the process of muscle protein synthesis to sustain for four to six hours. Losing is the signal, but we also need to have all of the building blocks to build and repair muscle protein. Exercise lowers that loosing threshold because it makes muscle more sensitive to amino acids. This means a lower dose of leucine and therefore a lower dose of protein is needed to reach the loosing threshold and stimulate muscle protein synthesis after exercise. Aging does reduce the sensitivity of lusing and other amino acids. It takes a larger dose of protein or lucine to stimulate the same muscle protein synthesis response for someone who is older compared to a younger adult. But again, older adults who routinely exercise can

help overcome this since exercise increases sensitivity to leucine. If you're consuming a variety of plant-based and animal-based food sources and or supplementing with whey protein, you probably don't have to worry about consuming enough lucine at each meal or throughout the day. Focusing on whole foods is the best way to ensure you're getting enough lucine, but of course if you're concerned, adding weight or branch chain amino acid supplement to your diet is another way to get additional leucine. Now let's talk about the difference between protein from animal and plant-based sources. Animal versus plant protein.

Whether your loyalties are towards a plant-based diet or a meat-inclusive diet from a standpoint of just focusing on optimizing for muscle protein synthesis, an animal source protein is better. It is also easier for most people to obtain protein from an animal-based food source for a few reason. For one, animal protein sources have a greater protein density. Plant-based foods contain less protein per gram than most animal-based foods. For example, getting 20 grams of protein from potatoes means you need to consume more than a kilogram of potatoes. But just 70 grams of meat like chicken or beef contain 20 grams of protein. Second, plant-based foods have a lower digestibility than animal-based foods, largely due to the presence of a food matrix consisting of

fiber. Fiber can slightly reduce the body's ability to extract and utilize protein found in plants. It also slows the digestion process. Sprouting and fermenting can overcome some of this and improve the digestibility and absorption of plant protein. Third, plant proteins are often deficient, in one or more of the essential amino acids. For example, lysine, methanine, and most importantly, leucine. Remember, that essential amino acids are needed to be consumed in the diet to build complete proteins in the body. A lower essential amino acid content means that most plant proteins are incomplete proteins and stimulate a lower anabolic response compared to animal-based protein. If you're eating plant-based, you do have options. Protein needs can be met on plant-based diets,

by supplementing with plant-based protein isolates and concentrates, by consuming a larger quantity of protein each day to compensate for a lower protein quality, and also by diversifying the intake of a variety of plant-based sources of protein, so creating complementary proteins that have the right amino acid profile. Despite the lower anabolic potential of plant-based protein sources, studies generally support the idea that as long as the total daily protein intake is high enough, a vegetarian or a vegan diet can support daily muscle protein synthesis and gains in muscle size and strength as much as a diet containing animal-based protein. But because plant protein is lower in quality, you'll have to consume more food overall to reach your daily protein intake. But whole foods aren't

the only source of protein. Many people choose to obtain their protein through protein supplements or protein powder, and there's a good reason to think that this is a fairly sensible practice. Way protein is one of the most popular protein supplements, in part because it's an extremely high-quality protein source. Way is a rich source of the essential amino acids cysteine and the branch chain amino acids, leucine, isolucine, and valine. Way also contains several bioactive peptides. The leucing content of way is what makes it stand out. The leucing content in Way is 50 to 75% higher than other protein sources. Compared to the other component of milk protein like casein, way protein is more rapidly digested and stimulates muscle protein synthesis more effectively

at rest and after exercise, making it a go-to protein source for many athletes. The slower digestion of casein compared to weight isn't necessarily a downside because this means casing provides a prolonged release of amino acids that can be helpful for sustaining the muscle protein synthesis response for a longer period of time. Way and casing protein are both much higher quality protein sources than collagen, which has a lower quality amino acid profile. It's rich in glycine and prylene, but lacks essential amino acids like leucine. Furthermore, collagen does not significantly enhance muscle protein synthesis or muscle connective protein synthesis at rest or after exercise,

making it a suboptimal protein choice for those engaged in resistance training and wanting to improve skeletal muscle protein synthesis. It should be clear from our discussion thus far that dietary protein, especially when optimized to suit your individual goals and needs, has an array of health benefits for nearly everyone. It's performance enhancing, anti-aging from the standpoint of frailty prevention, and can help you lose weight. However, this might come as a surprise to many, but there is a school of thought within the aging community that too much dietary protein increases cancer risk and contributes to accelerated aging. Yet today, many athletes consume a high protein diet, and the fact of the matter is being an athlete, even a recreational one, is one of the best things we can do to age well.

This is both intuitively and scientifically obvious. do we reconcile these facts? Let's get into it. Some researchers argue that a high protein intake, especially for meat, accelerates aging and even raises the risk of cancer and early death. This idea stems largely from laboratory studies showing that restricting protein intake extends lifespan in animals and observational data linking high animal protein diets to a higher mortality rate. Supporting this idea, one study found that middle-aged adults consuming high protein diets where 20% of their calories came from protein were 75% more likely to die from any cause and four times more likely to die from cancer. This is a pretty shocking statistic and animal evidence

corroborates some of this at the mechanistic level. However, there is more to this story. In another major study, middle-aged adults consuming high-protein diets did show increased mortality rates, but only if they had other unhealthy lifestyle factors like obesity, smoking, heavy drinking or being sedentary. Among healthy people, this association disappeared. So does a high animal protein diet really pose a health risk? Or is it more about what unhealthy lifestyle factors exist in someone's life? This is where it gets interesting. Protein, particularly from animal sources, spikes levels of a hormone called IGF1, which can help build muscle, support brain health, it enhances muscle repair. But high IGF1 levels also come with potential downsides like

promoting the survival of pre-cancerous cells and potentially allowing them to form cancer. Numerous studies have found an association between elevated IGF-1 levels and an increased risk of various cancers. So, should we cut protein drastically to lower IGF-1 levels? Not necessarily. Lowering IGF-1 too much can come with its own set of risks. For example, calorie restriction which significantly drops IGF-1 has been linked to brain matter loss and non-human primates. This raises questions about whether low IGF1 might have tradeoffs in terms of brain health. So is it better to significantly cut protein intake and avoid these risks, or is there a balance to be struck that gives us the best of both worlds?

Muscle strength, muscle repair, cognitive health, and protection against cancer. A recent meta-analysis by Dr. Walter Longo and colleagues highlighted this idea showing a U-shaped relationship between IGF-1 levels and mortality. Both very high and very low IGF1 were linked. to higher death rates. What was the optimal range? It was actually around 120 to 160 nanograms per milliliter. And to reach this IGF1 sweet spot, researchers estimated a daily protein intake of around 50 to 80 grams, which is not very much protein. Not to mention this study did not specifically look at healthy, physically active people. And that's a critical piece to the puzzle because

a strong response to exercise requires IGF1. So it raises a philosophize. question, are these recommendations aimed at healthy, physically active individuals, or are they tailored to people maintaining a largely sedentary lifestyle? Physical activity fundamentally changes how IGF1 behaves in the body. Exercise lowers IGF1 in the bloodstream, redirecting it to where it can be beneficial, like the muscle, and notably the brain. Here's why that's important. When you exercise, whether it's cardiovascular exercise or strength training or high-intensity interval training, it stimulates muscle fibers and increases IGF-1 receptor density in the muscle cells. This makes muscle tissue more sensitive to IGF-1, potentially enhancing its uptake.

While this precise mechanism is still being explored in research, what's clear is that exercise increases the ability of IGF-1 to cross the blood-brain barrier. Once in the brain, IGF-1 plays a crucial role. role in promoting neurogenesis. That's the growth of new brain cells, especially in regions of the brain like the hippocampus, which is important for learning and memory. Exercise doesn't stop there. Exercise, particularly intensive exercise, also raises levels of proteins that bind to IGF1 and reduce its bioavailability to damage cells that could potentially form cancer cells. Exercise alone causes more amino acids to be taken up into skeletal muscle, which also has the effect of reducing

circulating IGF1. In fact, when protein is consumed after exercise, IGF1 levels do not increase in the ensuing 24 hours like they do when protein is eaten without exercising beforehand. So by channeling how IGF1 is used and making it less available to potentially stimulate cancer cells, exercise acts as a protective shield. Regular physical activity has long been shown to strongly reduce the risk of many types of cancer, and this may just be one crucial mechanism that accounts for that fact. Furthermore, exercise enhances the immune system's ability to find and destroy cancer cells. It lowers chronic inflammation, which is a known risk factor for cancer, and it improves insulin sensitivity, which can further influence IGF1 levels. So in short,

higher IGF1 levels are inherently dangerous. It's the context that matters. Exercise and a healthy lifestyle changed the story entirely, showing us that IGF1 can be a powerful ally for health, strength and also longevity when guided by an active balanced lifestyle. This brings us to another important question. If protein truly is inherently pro-aging, wouldn't we expect a population with a higher protein intake, athletes, for example, to experience reduced life expectancy? But this doesn't appear to be the case, and in fact, the opposite is true. Athletes, who we can reasonably expect generally consume higher protein amounts and are known to have elevated IGF-1 levels, consistently show longer lifespans and a better health metric. On average, they live two to eight years longer than the

general population. They also die less of cancer and cardiovascular diseases. Let's circle back to the amino acid lucine, whether we're talking about optimizing muscle protein synthesis or controversies in the aging fields surrounding IGF1 and mTOR. Lucine is at the heart of it. Lucine is the critical signal driving robust activation of mTOR. Animal protein has a lot of lucine and whether you consider that a good thing or not actually depends on your views of IGF1 and mTOR. MTOR plays key roles in skeletal muscle growth by driving muscle protein synthesis and recovery, but this brings us to another area where mTOR pathway has also sparked controversy, its potential connection to athorosclerosis.

A study from early 2024 suggested that a high protein intake could accelerate the development of athrosis, which is the hardening and stiffening of arteries. The study suggested that lucine, which activates mTOR and muscle tissue to drive muscle growth, might also activate mTOR in the vascular system, promoting plaque buildup through immune cell activation. The important thing to remember is that exercise causes leucine to be taken up by muscle, where it activates mTOR in muscle to build and repair muscle, rather than spending time in the bloodstream, triggering mTOR in the vascular system. This is yet another example of how being physically active versus sedentary changes the entire equation.

It's a different game for people who exercise regularly. Okay, so I hope it's clear by now that the evidence suggesting high protein diets are harmful to health is not particularly strong. When it comes to some observational data suggesting a potential link between high protein intake and risks like cancer, this risk primarily applies to sedentary individuals with other unhealthy lifestyle factors like obesity. For physically active people, it's a different story. Exercise ensures that protein and leucine are directed toward muscle growth and repair, keeping mTOR activation where it's beneficial in the muscles rather than in peripheral tissues. This explains why athletes, despite consuming more protein, enjoy better health and longer lifespans than the general population.

The bottom line is that for active individuals, higher protein intake supports performance, longevity, and health. All right, everyone, that just about does it for our discussion on the science of protein. To wrap up, I want to provide eight of the most important takeaways. Number one, for most adults, a protein intake in the range of 1.2 to 1.6 grams per kilogram of body weight per day should be consumed to support overall health. Older adults, athletes and people who want to lose weight while sustaining lean body mass should consume 1.6 grams per kilogram per day or more.

Protein needs should be calculated based on lean body mass or an adjusted body weight that reflects a healthy body fat percentage. This is typically around 12 to 15% for men and 20% for women. This means that if you're not at your ideal weight, you should determine your protein requirements using the target weight you're aiming to achieve. Number two, when it comes to protein timing, the so-called anabolic window after exercise isn't as narrow as once to believe. Consuming protein either before or after a workout is effective, but also just focusing on total daily protein intake is what is most important for optimizing resistance training gains. Number three, it is ideal to try and distribute your protein intake evenly across the day.

Aim for around three to four protein rich meals, each containing around 20 to 25 grams of high. quality protein to stimulate muscle protein synthesis. For older adults, increasing each meal's protein content to 20 to 30 grams may be advantageous due to their higher protein needs and anabolic resistance. But remember that total daily protein intake is much more important than how protein is distributed throughout the day. Number four, consuming protein before bed, a practice known as pre-sleep protein intake. This can be particularly beneficial for older adults and athletes.

This strategy enhances overnight muscle protein synthesis in aids and muscle recovery. It contributes to better muscle health and performance. Number five, for those considering protein supplementation, high-quality sources like whey and casein proteins are excellent options. Way protein is rapidly digested and effective at stimulating muscle protein synthesis, making it a great choice post-exercise or even before bed to provide additional boost of amino acids. K-cine protein digest more slowly, providing a prolonged release. of amino acids. Even if you're meeting your protein needs through diet alone, supplementation

can offer targeted benefits such as supporting recovery during sleep or after very intense exercise. Number six, animal proteins are generally superior to plant proteins for maximizing muscle protein synthesis due to their higher protein density, better digestibility, and complete essential amino acid profiles, particularly their leucine content. However, vegetarians and vegans can still meet their protein needs by consuming larger quantities of plant-based proteins, diversifying their protein sources, and incorporating plant-based protein isolates and concentrates to ensure they get all their essential amino acids. Number seven, concerns about high protein intake harming healthy kidneys are largely unfounded

for individuals without pre-existing kidney issues. And finally, number eight, despite some schools of thought in the longevity field that higher protein intakes may reduce longevity or promote cancer growth, the available evidence in humans just isn't convincing enough. Exercise positively influences how the body uses amino acids and growth factors like IGF1 and proteins like MTOR, directing them towards the muscle and brain health where they're most beneficial. That brings us to the end of this special episode on all things protein. I sincerely hope that you learned a few new things and have a greater understanding of the incredibly important role that protein plays in promoting physical health.

Thank you so much for joining me in today's episode. I hope you enjoyed our deep dive into the science of protein and that you learned something valuable. If you found this episode helpful, please share it with anyone who might benefit. Remember, you can download my free guide, How to Train According to the experts at how to train guide.com. This comprehensive resource distills the most effective training, nutrition, and supplementation strategies from world-leading experts I've interviewed on the podcast. It dives into optimizing protein intake for muscle growth and recovery, effective resistance training techniques, and aerobic exercise protocols all designed to help you maximize your results,

no matter your fitness level. This guide tackles key questions like, what are the core principles of resistance training for strength, hypertrophy, and body composition? Is training to failure necessary for maximizing muscle growth? Are training zones effective for monitoring intensity during aerobic exercise? How can you structure high intensity interval training? to optimize aerobic fitness? What's the ideal weekly volume and intensity for aerobic exercise?

Does protein timing and distribution impact training adaptations? How safe and effective is creatine supplementation? You can get the training guide at how to train guide.com. Thanks for listening and I'll catch you in the next episode.