In 2007, I stood backstage at a wellness conference, about to speak to a large audience, more nervous than I had been in years.
Sitting in the front row was Professor T. Colin Campbell of Cornell University, one of the most rigorous nutrition scientists alive, whose decades of NIH-funded research had just been published in a New York Times bestselling book I had not yet read. He had come to hear me speak because he had heard I was a scientist too. We shared a Cornell connection. And I had not had time to read The China Study between the moment I learned he would be there and the moment I walked onto that stage.
I went out and gave my talk anyway.
What happened backstage afterward changed my life.
Five Minutes That Reshaped Everything
Within literally five minutes of meeting him, I understood I was in the presence of a scientist who had spent decades asking the right questions, designing rigorous experiments, and following the data wherever it led, including places that made powerful industries very uncomfortable.
I did read his book right after. Heavy-handed with the highlighter, like a college student cramming for midterms all over again.
His central finding, distilled simply: if you consume more than approximately 10% of your calories from protein, you turn on cancer-promoting genes. His initial hypothesis was built on large bodies of epidemiological data from human populations across different settings, from rural to urban, where increasing protein consumption correlated reliably with rising rates of cancer. He and his colleagues then demonstrated this same dynamic repeatedly in controlled laboratory studies in mice, turning cancer promotion on or off by using protein as the switch. The protein they used was casein, the dominant protein in dairy, which Professor Campbell considers the most harmful of animal proteins. This of course set off certain dominant industries to undermine his findings.
We did not have the full molecular explanation at the time. We did not yet have the language of mTOR or IGF-1 or autophagy in the way longevity science uses those terms today. But what I understood immediately was this: here was a source of real, trustworthy, rigorous information about diet. The kind I had been looking for.
That day I decided to become a vegan, or as Professor Campbell prefers to say, plant-based. I did not know how I was going to do it, as I was about to leave on a speaking tour for several weeks. But I knew.
Professor Campbell signed my copy of The China Study with a warm inscription saying he appreciated my work. I was so touched. For many months, I would call him with questions which he would patiently answer. I started sharing his book with everyone I could, supporting his research as much as possible, even as he faced significant backlash, including political pressure from the very industries his data challenged. He discusses that backlash honestly in The China Study. It is not a comfortable book for people who profit from the status quo.
That began a journey of being vegan until just a few years ago, a journey that reshaped not just my diet but my entire scientific framework for thinking about what we put in our bodies and why.
The Evolution: From Vegan to Pragmatic Plant-Forward
I stayed vegan for many years. And I am not vegan anymore, which I say with full transparency, because intellectual honesty matters more to me than ideological consistency.
The shift came pragmatically. I started eating collagen, which is not vegan, because the science on collagen loss after menopause is compelling and the biological need is real. I started eating eggs occasionally when traveling because protein options were limited and I still enjoyed the taste.
Then I noticed something. Every time I ate eggs, I got constipated, nothing too serious but consistent. My body, accustomed to a very plant-forward diet, was clearly signaling something. My microbiome, fed on fiber and plant diversity for years, did not welcome eggs the way it would have in another context. And to me, that is data. I pay attention to my body the way I pay attention to research: carefully, and without dismissing signals I do not want to hear.
So I do not eat eggs often. Not because someone told me not to. Because my own biology told me.
I do eat collagen peptides now. I have added creatine because the research on creatine and cognitive function in plant-based eaters is genuinely compelling, and protein and creatine deficiency are real issues for people who do not eat meat. I use plant-based protein that derives primarily from soy, a complete protein with all essential amino acids, because I believe in getting protein from plants and because the science supports it, including the bioflavonoids in soy that offer meaningful benefits for women as we become elders.
I am a scientist. Scientists update their views when the evidence warrants it. My diet has evolved. The underlying principle has not.
What mTOR Explains That Campbell Saw Coming
Here is where the science catches up with what Campbell observed empirically thirty years ago.
Inside every cell in your body, a protein called mTOR (the mechanistic Target of Rapamycin) acts as the master regulator of one of the most fundamental decisions biology makes: grow, or repair.
When mTOR is activated, your cells build proteins, multiply, and expand. Muscle grows. The body is in construction mode. When mTOR is suppressed, during fasting, during caloric restriction, during low protein intake, something completely different happens. Autophagy activates, the cellular cleanup process that breaks down damaged proteins and dysfunctional organelles and recycles them. DNA repair programs ramp up. Senescent cells, the zombie cells that have stopped dividing but refuse to die, get cleared. The maintenance backlog gets addressed.
You cannot do both simultaneously. Growth and repair are competing programs running on shared cellular resources. mTOR is the switch that decides which one gets priority.
Now here is what David Sinclair’s lab at Harvard has documented: your cells sustain approximately 10,000 DNA damage events per cell per day. Oxidative stress, replication errors, metabolic byproducts, UV exposure. Every single day. The repair machinery, SIRT1, PARP enzymes, the homologous recombination pathway, is sophisticated and powerful. But it needs a window in which mTOR is not signaling “keep building.” Without that window, the DNA damage accumulates faster than it can be repaired. That accumulation is biological aging.
What Campbell observed in his laboratory, that protein above 10% of calories turns on cancer promotion, maps almost perfectly onto this mechanism. High protein intake raises blood amino acids, especially leucine. Leucine directly activates mTOR. mTOR activates IGF-1 (insulin-like growth factor 1), which creates a permissive growth environment in which already-mutated cells receive “grow” signals rather than being cleared.
Interestingly, leucine is the dominant amino acid in whey protein, which is known to be the most effective for hypertrophy and thus a favorite choice of bodybuilders. Yes, leucine grows muscles. It also feeds cancer promotion. Therein lies the rub.
Campbell was seeing the downstream consequences of chronically activated mTOR before the longevity field had named the mechanism. He was thirty years ahead of the conversation.
The Influencer Problem
Open any fitness influencer’s feed right now and you will find some version of the same advice: eat 0.7 grams of protein per pound of body weight. Spread it across five meals. Never miss a protein window.
I want to be direct about something: the people giving this advice are almost universally either selling protein supplements, sponsored by protein brands, or building an identity around a body that requires extreme protein loading for competitive athletic performance. Their recommendations are optimized for maximum muscle hypertrophy in athletes training fifteen or more hours per week. That is a completely different goal than aging well, maintaining cognitive function into your eighties, and keeping your cancer risk as low as possible.
Five protein meals a day means mTOR is being stimulated approximately every three hours, around the clock. There is no meaningful window in which autophagy can establish itself, DNA repair can run its full program, or the cellular economy can shift from building to maintenance.
The same daily protein quantity delivered in a time-restricted window, say within six to eight hours, produces mTOR activation followed by a genuine repair period. The fasting window that follows allows mTOR to fall, autophagy to activate, and the DNA damage from the day to get addressed. Timing may matter as much as quantity. Almost nobody in the protein influencer space is talking about this.
Said simply, our cells are mutating daily, and we need to give the body enough of a pause from protein consumption to do what it already knows how to do: identify and clear those mutations before they get out of hand. The repair machinery is not broken. It is just waiting for a window that five protein meals a day never opens.
And while we are here: do not mistake the protein demands of someone training five or more hours a day with the ambition to win a bodybuilding competition for your own. Your goal of getting to the gym most days of the week, moving well, and feeling strong in your body is genuinely commendable. It is also a completely different biological situation, and it does not require you to eat like a competitive athlete. The recommendations were not made for you. They were made for someone whose entire life is organized around extreme muscle hypertrophy, and marketed outward to everyone else.
Is this making sense to you?
Plant Protein Changes the Equation
This is not a simple “protein is bad” argument, and Campbell’s work was never that simple either.
The primary trigger for mTOR activation from dietary protein is leucine, found in dramatically higher concentrations in animal proteins than plant proteins. Whey, dairy, and red meat are among the highest leucine sources in the food supply. Pea protein, rice protein, hemp, soy, and legumes have significantly lower leucine concentrations. The same gram-quantity of protein from plant versus animal sources produces a meaningfully different mTOR activation signal.
This is why Campbell’s most dramatic findings centered on casein specifically. It is also why a plant-forward diet at moderate total protein levels threads the needle between maintaining muscle and protecting longevity in a way that a high animal-protein diet cannot.
Chart 11.2 from The China Study by T. Colin Campbell, PhD and Thomas M. Campbell II, MD. Reprinted for educational purposes.
The protein content is nearly identical, 33 grams from plants, 34 from animals. Everything else is not. Beta-carotene, vitamin C, folate, fiber, magnesium, calcium: plants deliver these in quantities that animal foods simply cannot match. The protein was never the problem. The protein was always there.
A plant forward diet matters more than most people realize, because fiber and plant diversity are not just about nutrition in the conventional sense. They are the primary currency of your gut microbiome. Professor Tim Spector, British epidemiologist and co-founder of ZOE, helped popularize a finding from the American Gut Project that has since been widely replicated: people who consume 30 or more different plant types per week have measurably more diverse and resilient gut microbiomes than those eating 10 or fewer. The 2024 BIOME randomized controlled trial confirmed it further, showing that a diet high in plant variety directly boosts the beneficial microbes associated with improved metabolic and immune health.
Thirty plants a week sounds ambitious until you realize that herbs, spices, nuts, seeds, whole grains, fruits, and vegetables all count. Two tablespoons of mixed seeds on your morning yogurt is already four or five plants. And I use coconut yogurt. A stir-fry with six vegetables is six more. The number becomes achievable quickly, and what you are building as you achieve it is exactly the microbial ecosystem that produces the short-chain fatty acids your gut, brain, and immune system depend on. You are also, incidentally, getting plenty of protein.
Valter Longo at USC, whose laboratory has produced some of the most rigorous longevity research in the field, recommends approximately 0.31 to 0.36 grams of protein per pound of body weight (0.68 to 0.80 grams per kilogram of body weight) daily for healthy adults, primarily from plant sources. That is roughly half what the bodybuilding influencers recommend. At that level, from plant sources, time-restricted, you support muscle maintenance without chronically activating the growth pathways that accelerate biological aging.
What I Do Now
I am a plant-forward vegetarian. I eat protein primarily from soy-based plant protein, legumes, mushrooms, plant yogurts, and seeds. I use collagen peptides because the post-menopausal collagen loss data is compelling and I am not willing to ignore it. I supplement with creatine because I am a long-term plant-based eater and postmenopausal, which means the cognitive benefits are real and my deficiency risk is doubled.
I eat in a time-restricted window, generally sixteen or more hours of fasting on weekdays, because I want the repair programs to run. I do not eat five protein meals a day. I do not chase a gram target designed for a competitive bodybuilder.
My most recent GlycanAge biological age test showed my biological age twelve years younger than my chronological age. This is after two significant hits that are known to accelerate biological aging: going through menopause, and losing my life partner of thirty years.
Have questions for me?
I am not telling you this to impress you. I am telling you because the protocol matters and the data is real. And because I spent years confused about protein, vegetarianism, and what rigorous nutrition science actually says. That five-minute backstage conversation with one of the world’s most rigorous nutrition scientists pointed me in a direction I have never fully left, not because I am immune to confusion. I am not. The influencers reach me too, and there are moments when I find myself questioning what I know. But those moments of uncertainty send me back to the primary literature, back to the mechanisms, back to the logic on which the body actually thrives. That is what a scientific education is for.
T. Colin Campbell was right. The mechanism is clearer now than it was in 2007. The influencers have gotten louder. And the void of honest, science-based voices, particularly women’s voices, in the longevity conversation has only grown.
That is the void I am here to fill.
This article is for educational purposes only and does not constitute medical advice. Individual protein needs vary based on age, activity level, health status, and goals. Consult a qualified healthcare provider before making significant dietary changes.