Past, Present, and Future of “Biological Aging” with Dr. Fitzgerald
How Much Should We Eat For Optimal Health & Longevity?
Plus my thoughts on combining with Younger You epinutrient targets
About a month ago, I podcasted with Valter Longo, PhD, a highly respected scientist and director of the Longevity Institute at the University of Southern California. Of course, our conversation hit on protein, something he thinks we should be consuming in limited amounts when young and slightly more as we age. I posted the following quote from him on our social media channels: “We’ve shown in our study that a high protein diet is associated with a 75% increase in overall mortality risk.” Unsurprisingly, this quote generated a massive response on my platform and elsewhere, from confusion to agreement to disregard. There has been much dialogue in the longevity space around protein needs and safe consumption. A number of scientists challenge Longo’s ideas and counter-propose that, in fact, a much higher protein intake is essential for robust muscle mass, which is vital for one’s healthspan, which in turn favorably influences one’s lifespan.
As I’ve talked about elsewhere, I am very physically active and have in the past year taken up resistance training as a part of my longevity plan (and for my sanity – but that’s another blog). I also follow the epinutrient targets we devised for our research study and spell out in the book Younger You. By some standards, the Younger You (YY) protein targets are fairly low, although I am clear in the book that we need more protein as we age and more if we’re building muscle. Of all of the macro and micronutrient targets of the Younger You program, protein is the one variable I have thought about tweaking. Let’s take a look at the research and I’ll share my conclusions – along with what I’ll personally be undertaking – at the end of this blog.
Varying Recommendations
Research around optimizing protein consumption, or how much we should eat, is one of the most controversial topics in nutrition, which also makes it a very confusing topic for individuals trying to do, or in this case eat, the right thing for their health.
The Recommended Daily Allowance (RDA) for protein is 0.8 grams per kilogram of body weight. Dr. Valter Longo recommends keeping protein intake low, around 0.7 – 0.8 grams per kilogram of body weight, and slightly increasing that amount (to 1 gram per kilogram) if you’re over age 65. Younger You targets from our study are a minimum of 0.66 grams per kilogram of body weight under 60 and 1.0-1.2 grams per kilogram for those over 60 – but this is specifically for animal protein, when vegetarian sources are added in (from nuts, seeds, etc.) our numbers are higher. And then you have the ‘Carnivore Camp’ folks swinging upwards of 2.2 grams and more per kilogram body weight. So, what gives?
From a functional medicine standpoint, we understand that the RDA was created to stave off malnutrition. As such, the recommendations have little to do with health optimization (although, interestingly, the protein RDA is comparable to Longo’s). That said, it can be a useful starting place to consider what optimal might be. And in the case of the RDA for protein specifically, Rhonda Patrick’s recent podcast with Stuart Phillips (muscle protein synthesis expert, weight lifter and aging and longevity researcher) did a fantastic job explaining how the RDA for protein was calculated and the various issues surrounding that calculation. Phillips believes the average individual needs anywhere between 1.2 – 1.6 grams of protein per kilogram of body weight and up to 2.2 g/kg for older folks. For those looking to increase muscle mass, protein requirements range from 1.2 g/kg body weight up to 2.2 g/kg body weight (here’s another study with similar recommendations: 1.6-2.2 g/kg body weight) in both men and women. These numbers are actually pretty consistent among scientists. And this is because there is an upper limit to how much protein our body can actually use. Ingested protein is broken down into constituent amino acids and either used in the body or further broken down into the nitrogenous waste product urea, which is eliminated in the urine.
What We Know
We know that we lose muscle mass at quite a clip as we age. We also know that sarcopenia, the loss of muscle mass and strength, has repeatedly been linked to an increased risk of morbidity and mortality. We know that frailty, characterized by weakness and decreased strength, leads to falls. It is currently estimated that one-third of individuals over age 65 fall each year — and that these falls quickly and dramatically increase the risk of morbidity and mortality (in fact, older people who can sit on the floor and get up live longer. Try it now — can you do it?). We also know that the older you get, the more protein you need to ingest to maintain muscle mass and inhibit sarcopenia. Why? We’re not as efficient at breaking down, absorbing and using protein as we age. We can help offset this loss of efficiency with increased intake.
Thus, we know that the amount of lean muscle mass you have is a critical component of healthspan and lifespan — and to build and maintain muscle mass you need to consume adequate amounts of protein in the context of a healthy diet along with a commitment to regular resistance training. Both items are extremely important, especially as we age.
What Can’t be Overlooked
While we know that epidemiological data is fraught with confounding variables and is not the gold standard when it comes to showing causality, I don’t think we can discount the fact that lower protein diets, in the context of healthy diets, have demonstrated improved health outcomes in multiple healthy older populations (including centenarians). These findings, along with his own research, inform Longo’s thinking (more on this here, here and here). However, there was a positive association found between the “oldest old” in a Sardinian population (age range 90-101) who modestly increased their consumption of meat (primarily from sheep/goat and chicken) and improved functionality in activities of daily living.
Furthermore, in the well-done CALERIE study, caloric restriction was shown to significantly slow biological aging as measured by the DNA methylation DunedinPACE of Aging Clock. In this study, while protein intake wasn’t tracked during the entire two-year intervention, the initial phase-in diets, at 25% daily caloric restriction, were modest at best in protein intake (ranging from 15% to 30% of total caloric intake), far below the higher recommendations of the so-called “carnivore camp” or those interested in building muscle.
Two studies currently being written for peer-reviewed publication suggest that vegan diets — well recognized to be lower in protein — may outperform an omnivore diet when it comes to slowing the DunedinPACE clock.
However, let’s circle back to the original Longo paper that generated an outpouring of comments. Quoted from the abstract:
Respondents aged 50-65 reporting high protein intake had a 75% increase in overall mortality and a 4-fold increase in cancer death risk during the following 18 years.
This study has been roundly challenged by some, and interestingly, Longo himself was an author of a JAMA Network 2016 paper which found NO association with protein intake and higher mortality, including cardiovascular disease, when there were NO unhealthy lifestyle factors (ie: smoking, heavy alcohol intake, overweight or obese and physical inactivity). However, in those individuals with risk factors, animal protein intake was associated, albeit very weakly, with higher mortality, especially CV mortality; and replacing animal protein with plant protein reduced this risk.
Other studies corroborate this study, at least in part: In older Chinese adults, higher protein intake was associated with lower all-cause mortality. Interestingly, in this study, men did better with animal-based protein and women with plant-based protein. A 2020 meta-analysis conducted by Walter Willett and colleagues and published in BMJ similarly reported that higher total protein intake was associated with a lower risk of all-cause mortality and intake of plant protein was associated with a lower risk of all-cause and cardiovascular disease mortality.
A variable that may have a role in the difference between animal and vegetable proteins on cardiovascular disease may be trimethylamine oxide (TMAO). Stay tuned for an upcoming post on TMAO, a compound produced by our microbiome in the presence of animal protein and associated with atherosclerosis. In the meantime, if you’re curious or concerned, check out this 2022 Nature paper on resolution of TMAO after short term ingestion of 55ml of raw garlic juice. And if you have Younger You, read my thoughts on pages 220-221.
It makes mechanistic sense that controlling for the unhealthy diet and lifestyle variables could improve protein tolerance and the associated health benefits. Maintaining tight metabolic control (i.e. good carbohydrate tolerance, no insulin resistance or dysglycemia) may significantly change the behavior of protein in the body. Recall we worked through a similar dance with fats, where they became the villain macronutrients, but in this case, it was the fat/simple carb combination that created the heart disease/diabetes/obesity epidemic that we now see globally. Fats alone are NOT associated with heart disease or heart disease-associated mortality.
What Seems to be True
It doesn’t currently strike me as likely that protein intake alone promotes the chronic diseases of aging the way we once thought, and if it does, it may be in conjunction with other disease-promoting diet and lifestyle habits, similar to fats. In those individuals with risk factors, probably replacing at least some animal protein with good quality plant protein is smart.
The question then becomes, “but is it associated with longevity?”
As I discuss above, if increased protein consumption is needed to generate and sustain muscle mass and muscle mass is needed to prevent early morbidity and mortality due to loss of strength, sarcopenia, and frailty, then increased protein consumption does seem to be associated with increased lifespan, and more importantly, healthspan.
How Much Protein I Consume and Why: Embrace the Uncertainty!
As I have fully embraced maintaining robust muscle mass as I age, it’s logical that I need to ingest sufficient “ingredients” to make muscle – protein. But what is my magic grams-per-kilogram body weight protein need? The research I mentioned above pretty clearly suggests I should be somewhere in the neighborhood of 1.2-2.2 grams per kilogram of body weight. But how will I respond to this leap up in protein? I expect muscle mass to increase, but will biological age also increase, as I believe Longo would suspect?
My Plan
I am shooting for around 2.2 grams of protein per kilogram of body weight on days I am engaged in resistance training (3-4 mornings per week). And given the above research, my protein choices will continue to include both high-quality animal and plant-based choices. While I’ll need to drop calories elsewhere (it’s a lot of protein!), I still want to consume those YY target epinutrients I believe to be most essential: e.g. the veggie quantity and type, shiitake and other mushrooms, Himalayan Tartary buckwheat, eggs, liver, seeds, turmeric, green tea, EPA/DHA (supplements). I think anyone looking to dramatically increase protein intake needs to think carefully about what their other macronutrient and micronutrient targets will be and whether supplementation will be required. It’s not as simple as it’s described to be: “just consume 150-200 grams of protein per day and eat healthy other stuff” (coming from a recent Twitter post I read authored by a famous scientist/weightlifter guy). Consuming a lot of protein is… a lot of food! On the other days, when I do cardio (riding my bike), I will follow the classic YY target nutrient goals with a lower protein intake of around 0.8 g/kg body weight. This pulsed, high protein 4 days on/3 days off plan will average out to be about 1.6g/kg body weight per day.
Tracking success (or failure): I have committed to the above plan with my resistance training coach joining me on the journey (Kevin Cleary, Athlete Factory). At baseline, I looked at standard labs plus a bio age clock, along with a bioimpedance analysis (BIA) of current muscle mass and fat mass, and of course, a subjective assessment of quality of life and symptoms.
It should be no surprise I am bullish on the macro and micro epinutrient targets of the YY program – both because of what we identified with regard to bio age reduction (as measured by the original Horvath DNA methylation clock) in our original study, what we are seeing now, in our current cohorts, and of course what I am experiencing personally and have observed in my patients. Thus, I think it is important to maintain them as much as possible as a part of a logical longevity plan, even as protein targets are tweaked. I also want to stress again that, if people adopt a very high protein diet without carefully thinking through their other macronutrient and micronutrient needs, deficiencies will likely result. This is something we’ve observed in clinic practice whenever a dietary trend emerges (think keto, paleo, time-restricted eating and fasting) As I stated earlier, it’s not as easy as it looks.
Final Thoughts
Much like any topic in nutrition, information is constantly evolving. What is known to be true today will certainly evolve tomorrow. As my laboratory mentor and dear colleague Richard Lord, PhD said to me almost daily during my training, we need to “embrace the uncertainty” in science, and nutritional biochemistry especially. For me, this keeps it real, and keeps me excited to explore, tuck into new research, and integrate new knowledge. All we can do is look at the current body of evidence, integrate it with what we know clinically, form a reasonable hypothesis, and test it.
I think we can conclude that, in the context of a healthy diet and lifestyle, protein (animal and plant sources) is probably not a villain macronutrient. And that higher protein intake for older adults (along with resistance training) is essential, and higher protein intake for younger adults (also with resistance training) is likely smart. Phillips’ recommendations of 1.2 – 1.6 grams of protein per kilogram of body weight for younger adults and 1.5- 2.2 grams per kilogram of body weight for older folks make sense to me.
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This blog was crafted by Kara Fitzgerald, along with Tish Campbell, PhD, MScN. Tish is a health educator and researcher interested in health optimization and longevity. She teaches in the Functional Nutrition Program at PCC in Portland, Oregon and sees clients in her own functional nutrition clinical practice. She is currently finishing up a functional nutrition residency with Dr. Kara Fitzgerald’s clinic in Sandy Hook, CT.
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Very interesting! thank you
Can I ask how you think or take into account the fact that most of the plant protein we consume is not whole protein and lacks one of the essential amino acids?
The reason I’m asking is that I find it very hard to get to these levels of WHOLE protein consumption, but could this high target taking into account that a lot of the protein we will consume [e.g. from a slice of WW bread] will not be counted as whole protein?
Dr Fitzgerald, you are an inspiration. At 56 years old ( But 53.7 according to your BASA score), I am training for the World Offroad Triathlon Xterra Championships in Italy September.
As Dr Sims suggested, I will increase Resistance training & Protein intake.
I will now take my InBody scan of %Skeletal Muscle mass etc. and measure progress.
Thank you so much! Looking forward to your Younger You Practitioners Course!!
@https://www.instagram.com/liveyounglizl/
I am a bit confused. In the Younger You book, according to page 96, I should be aiming for .66g of animal protein per kg of bodyweight. When I do the math – 55kg x .66g = 36.3g of animal protein. However on page 99 I’m told I should be aiming for 170g of animal protein daily. It’s quite a big difference, so I’m keen to get to the bottom of this. Any help appreciated.
Hi Nadine, thanks for your question. It seems the confusion is arising because the recommendation of 0.66g/kg protein refers to the pure protein content of foods. On page 99, the reference to animal protein is really intended to mean animal meat. The amount of protein in 1 oz of chicken, for example, is about 8g. The calculations on page 96 allow for more precise protein calculation since body weight is factored in. Those on page 99 are set for “average” weights and intake requirements.
Hope this helps!
You might also like this write up on protein from Dr. Fitzgerald: https://www.drkarafitzgerald.com/2022/10/06/the-protein-magic-formula/