Episode 125 | Apr 10, 2025

The Longevity Molecule You’ve Never Heard Of, With Leslie Kenny

Can you really reverse your biological age—and feel better than you did in your 30s? This week on Health Coach Talk, Dr. Sandi sits down with Leslie Kenny, Oxford-based CEO of Oxford Healthspan and co-founder of the Oxford Longevity Project, to explore the science of longevity, immune modulation, and one intriguing compound that’s making waves in the wellness world: spermidine.

“You can take spermidine, but if you’re not sleeping well, if you’re eating ultra-processed food, if you’re super stressed out, you’re not going to get the full benefit. It’s like putting a Ferrari engine into a junker body—you’ve got to take care of the whole system. And that’s really where health coaches come in. They help people change their lifestyle so they can actually see the results.”

Leslie Kenny

Leslie’s health journey is nothing short of extraordinary. At 39, she was diagnosed with lupus, rheumatoid arthritis, and Hashimoto’s and told she had five years to live. Fertility treatments had failed, and she was advised to suppress her immune system and accept a limited future. Instead, Leslie took a different route—changing her diet, addressing stress, and seeking out immune-supportive therapies. Within months, her markers for autoimmune disease disappeared. Two decades later, she’s biologically 21 and still uncovering new ways to support healthspan and longevity through lifestyle and nutrition.

In this conversation with Dr. Sandi, Leslie explains what spermidine is, why it’s often misunderstood, and how it supports autophagy, immune regulation, and cellular renewal. The episode touches on everything from mitochondrial health and hair growth to hormone balance and gut function—showcasing why this polyamine found in food (and not just semen, despite the name) is being called an “anti-aging vitamin.” She also discusses how health coaches can help clients integrate spermidine-rich foods into their diets and assess whether supplementation might be appropriate.

Health coaches will especially appreciate how Leslie frames the importance of lifestyle in achieving longevity. Her story reinforces the power of taking charge of one’s health, and how health coaches can be vital allies in that journey—asking the right questions, identifying triggers, and helping clients embrace small shifts with lasting impact. Her experience is a powerful reminder that even the most serious diagnoses can become turning points toward transformation when clients are supported and informed.

Watch The Episode

Listen Now

Transcript

Dr. Sandi: What if a client asks you, if you’re a health coach, what is spermidine? What do you know about it? Well, we’re going to talk about spermidine on the podcast today because my guest is Leslie Kenny. Let me tell you about Leslie. She is an Oxford-based CEO and patient advocate faced with a life-altering diagnosis in her late 30s with lupus, rheumatoid arthritis, and Hashimoto’s thyroiditis. Told she had just five years to live and would never have children, Leslie refused to accept this fate.

Through eliminating inflammatory triggers and supporting her body’s natural healing, she transformed her health, becoming autoimmune disease free and naturally conceiving at 43. Now 59, she has a biological age of 21. Empowered by her journey, Leslie founded Oxford Healthspan and launched Primeadine, a plant-derived spermidine supplement after discovering the compound’s anti-aging potential. Spermidine activates autophagy and targets key aging pathways, earning it the nickname anti-aging vitamin. Leslie also co-founded a non-profit organization called Oxford Longevity Project alongside Oxford University scientists and doctors. Both are part of Leslie’s mission to educate the public on improving health span and longevity through actionable methods. So, I know you are going to enjoy this episode of “Health Coach Talk.” Welcome, Leslie.

Leslie: Thank you very much, Sandi.

Dr. Sandi: Let’s begin with your health journey. You have a fascinating story. So, I’d love for you to share that and how you successfully reversed biological age. I’m really curious about that.

Leslie: Well, to start with, I should mention that I actually had a very poor biological age when I was in my 30s. So, at age 39, I was diagnosed with multiple autoimmune conditions, rheumatoid arthritis, and lupus. I also had Hashimoto’s, but for some reason, that didn’t get diagnosed until a few years later when they discovered I had almost no thyroid left. And I was only 39, and I was one of those women who had waited to have children. And I’d spent a few years doing the usual IUIs and I’d done IVF. And I was on my fifth IVF round, and I was using donor eggs. I was listening to my IVF specialist who said, “Your eggs are too old. You need to get donor eggs.” It was right before embryo transfer that I noticed pain in my hands and went to the doctor to just check it out, thinking, well, it feels like something you’d get if you were older and had arthritis. But I’m obviously young, and it must be something else.

When I got the call from the doctor’s office saying, “Your results are back, and we need you to come in to go over the test results,” I knew that something wasn’t quite right. And the doctor said the right answer is to suppress your overreactive immune system, and you’ll have to make some lifestyle changes. That means avoiding large groups of people where you might be more likely to get an infection because now the immune system on immune suppressants will be very low. So, the cinema, parties, church, and definitely avoid small children because they carry germs like crazy and you don’t want to be around them.

So, that was the lifestyle advice I was given by my doctor. I did think about this. And could the doctor be wrong? And I was really very angry that she was messing up my plans right before embryo transfer. Really? You have to give me this terrible news and tell me I’ve got to inject myself with another drug. I’ve just been doing this. How is this going to mess up my embryo transfer? Because as you probably know and your listeners will know, if you’ve ever advised women who are going through this process, there is a lot to tee up physiologically in the woman’s body and the person who’s the donor. And so she was really scuppering my plans. And I called her on and said, “Hey, wait a second. I am your client. You’re the expert. Give me the answer. Give me the right answer, because that’s what I’m paying you for.”

And I think a lot of Americans might feel like, “That’s what the doctor’s for. Fix me,” like I’m taking a car to a mechanic, “Fix me. I’m going to pay you. Make it happen.” And I said, “This is my fifth IVF. A lot is riding on this. Do you understand? You have to fix this.” And she said, “I wouldn’t do it. Even if you’re successful, you’ve only got a good five years left.” And that was a shock. I really didn’t understand how that could be possible because I was only 39, but this was the same age at which my own father had passed away. And when we’re young, we feel immortal. And when somebody stops you and taps you on the shoulder and says, “Actually, there are no more chairs in the game of musical chairs for you, you need to step off,” it’s really quite shocking.

So, I decided… I of course asked her, “Is there anything I can do to change my situation?” And she said, “Not really. No.” “What about diet?” “No, no, there’s really nothing.” And I left thinking, “Well, she might believe that, but I think Americans also can be quite bolshie.” We’re independent thinkers. And I thought, “She might say that, but I don’t believe it.” I feel like I can make myself just a little bit better. She might say I can’t, but I’m going to say she’s wrong. And so I left the appointment thinking, “I’ll just try anything. I’ll be open to absolutely everything.” And I went to the patient bulletin boards. This is before ChatGPT. This was in 2004, so patient bulletin boards were a great place to get resources. And talking to a lot of lupus patients, I didn’t know much about lupus, they told me about a treatment that could actually reset my immune system. It was called intravenous immunoglobulin. It was a transfusion of antibodies from anywhere between 3,000 and 10,000 donors. And I liked philosophically the idea of bringing my body back into balance because IVIG is not just there to give you antibodies. It’s an immune modulator.

This made more sense to me. Both of my grandparents went to medical school in Japan at the University of Kyoto. So, maybe it’s my half-Taiwanese, Japanese background that is making me feel like this is the right way, restore the body to balance, and it has an innate wisdom to heal itself. So, I did that. At the same time, I removed all of the triggers to my immune system. And in particular, these were dietary things. So, I got rid of dairy, gluten, eggs, went on a very low-sugar diet, fixed my sleep, got rid of stress, quit my job. I just thought, “I’ve got to throw the kitchen sink at this.” And did yoga, was walking through the Rockies. I was living in Boulder, Colorado at the time. I did Mayan uterine massage. I tinctured my own herbs. I was doing everything, and I was open to all of it.

But the one thing I could not continue with was the immune suppressants. And after my second transfusion, I just thought, “I don’t think I can do this. I don’t feel right whenever I inject myself.” And I decided to stop. But I’d had the two transfusions, and I had also really reformed my lifestyle. And I went back to get tested again. And I’ll never forget my doctor’s face when she came in with the folder, opened it up, looked at the folder and just said, “Well, look at that. You don’t have lupus or RA.”

Dr. Sandi: Wow.

Leslie: What? So, our doctors are infallible? How is that even possible? She was wrong. Am I glad that I listened to myself as opposed to just believing there was nothing I could do? Yeah. Very, very pleased. And it’s a message I try to give to other people. You and your body are much more powerful. You’ve got to start listening to the messages that it’s sending you on the regular, right? If we feel a little niggle, that niggle, it’s from a nerve that’s saying there’s something not quite right. If we’re tired, that’s a message. We get these messages 24/7, but so many times we override them. We give our power sometimes to our doctors. Not all patients do this, but there are many to do. I don’t know what’s right. I don’t know what I feel. My doctor will tell me. My doctor will diagnose. My doctor will tell me what to do.

But we patients are a lot smarter and capable than that. It needs to be a partnership with our doctors. I’ve always said that health coaches are the bridge between that patient and the doctor, right? Because health coaches can get curious. What is this patient doing that could be causing…? What’s the root cause? Doctors have no time to explore and look for the root cause, but coaches can ask all the questions, put the puzzle pieces together, get a wrap around image of what this patient’s day is like and think, “Oh, right. So, they’ve got this terrible eczema, but they’re not showering before they put the eczema cream on. They need to shower first before they do that.” Something small that a doctor would never have the time to get to the bottom of.

Dr. Sandi: Well, first of all, that story was so moving and it really shows that you became empowered to take charge of your health. And the worst thing in someone is that, “Whatever you say, Doc, I’m in your hands.” Those people fare the worst. And what you did was focus on all the lifestyle factors, and that’s the zone of health coaches. So, absolutely. They are the bridge between you and your doctor. They have the time. They are curious. They ask the right questions so that you can take charge and you can say, “Yes, this makes sense.” Most people have that aha moment where they realize some of the things that were triggers and go back and start to self-correct and you reversed your biological age.

Leslie: Well, so that came later. So, for the last 20 years, I’ll be 60 in June, which is really exciting and I did a biological age test on the fly. Somebody said, “Hey, Leslie, you need to have this test done.” I was like, “I’m so tired of doing all this work. Okay, but if you really want me to go ahead, let’s see what it’s like.” I was quite afraid of looking at the results for about a week. I just didn’t open the results, but the GlycanAge, biological age test came back at 20 and I didn’t really get that. But I think the only way I can explain that is, for the last 20 years, I have done everything I can to keep inflammation at bay. That has been my raison d’etre. So, I try to limit sugar or if I’m going to have it, have something, healthy fats, some protein beforehand just to slow the sugar spike. I try to optimize things so that I have as little inflammation as possible. And that’s the only reason I can think of for getting such a good result.

But what is also nice is that I’m living proof that 60 is the new 20. So, we can actually get better with age because at age 39, I might’ve chronologically been 39, but I was biologically so much older. So, even if you’re a patient with a terrible prognosis, which I was, you can affect change with working with your body’s inner wisdom, with patients, some time, it can be done. And of course, health coaches play a big role too in being the cheer leader and the private detective at your side, helping you figure out your own health puzzle.

Dr. Sandi: That’s right. As someone once told me, they are your wingmen and also your fertility journey. Can you share that?

Leslie: Of course. Yeah. So, that was a happy ending. So, needless to say, that fifth IVF with donor eggs failed. And actually the embryologist said to me, he was from the CU Boulder, he said, “I don’t know why you use donor eggs. Your eggs are much better than these.” I was like, “You’ve got to be kidding me.” But he said that. And he also said that Asian women tend to not respond to the fertility drugs the way that other ethnicities do, that we produce fewer but higher quality eggs. So, that was interesting. I, however, was really finished with this whole fertility thing. I was like, “I need to have a baby. I really don’t want to pin my hopes on another cycle,” so just forget this.

So, adopted a little girl from China and then moved back to the UK. And once I was in England, I had this little girl, and I could see what all the other mothers were doing. And they might have three or four kids. They’d have a dog. They’d have a gardening allotment. They were leading scout troops and I was still so, so tired and put everything into Dr. Google at the time, all my symptoms, and it just kept coming back. And I went to see NHS doctor, said, “You’re fine.” Went to see a specialist in London. They said, “You’re fine.” Found somebody on the patient bulletin boards again. Everyone said, “This man, Dr. Barry Durrant-Peatfield is a genius when it comes to the thyroid.” And he had so many testimonials that I went to see him and he said, “Wow, your cortisol levels are shot and your hands are so cold. They’re icy. Your pulse is around 50. That’s not normal.” I said, “Well, all the doctors say that’s an athletic pulse or your heart is not strong.” And he diagnosed me with hypothyroidism, but suspected that because I had so little thyroid tissue left, that it had come under attack. And as a result, I was unable to produce very much. He said, “As soon as you take this thyroid hormone,” which was Armour Thyroid, so desiccated pig’s thyroid, “As soon as you take this, your hormones are going to be perfect again and so you better take precautions,” I thought, “if you don’t want any more children.” I said, “You’ve got to be kidding me. I’ve been trying for eight years, nothing has worked.” And about two weeks later, I fell pregnant. It was that quick.

Dr. Sandi: Amazing.

Leslie: Two weeks after I started his protocol, it was so fast. That was what I needed was a thyroid hormone.

Dr. Sandi: Wow. It’s such an inspiring story. So, thank you for sharing that.

Leslie: You’re welcome.

Dr. Sandi: So, let’s turn to something that I have now become a part of my supplement regimen, which is spermidine. Can you talk about what this is, what it isn’t, because most people think, “Sperm, what?” In fact, when I first heard that, I think I heard it from Dave Asprey. I was like, “What’s he talking about?” So, can you talk about that and its benefits? Any risks? Who should be taking it? Should we all be taking this?

Leslie: Sure. So, spermidine is a naturally occurring compound, a molecule that we make in our tissues and our gut biome, and we get it from all plants that we eat as food. So, it’s ubiquitous. The body recognizes it very well in its plant form. It’s also very present in semen. And because Antonie van Leeuwenhoek, the Dutch biologist who first identified the crystals that it was made up of. He identified it in his own semen. He called it first spermine and then later it was called spermidine. So, that’s where the name comes from. But if a woman had identified it, she would have called it something else because it is in copious quantities in breast milk. And that is because it helps with cell turnover and growth, and babies need to grow very quickly. So, that is one of the reasons why we get it from breast milk.

But the reason that I became interested in it was because of my background as a rheumatoid arthritis patient. So, I live in Oxford, England. This is home of the University of Oxford. And as you do on the school playground, I began speaking to other parents who were scientists and asking them what they do. And through that and through some work fundraising for different startups and regenerative medicine at Oxford, I was introduced to a team in the Kennedy Institute of Rheumatology that were using spermidine to rejuvenate the immune systems of mice.

So, their experiment was giving them the flu vaccine. So, every year, at least here in the UK, the National Health Service spends a huge amount of money and time getting older people basically over the age of 60 into the clinics so that they get a flu vaccine. But those don’t tend to work very well in older individuals because while their antibodies may shoot right up, initially, they tend to drop down very quickly. It’s as if their immune cells don’t remember what they have seen. Like remembering a telephone number. When we’re young, so easy. I can do 10 numbers, right? My best friend’s got a seven-digit number. But when you get older, it’s like, “I think I can do three numbers.” And it happens to our immune cells that they get this kind of amnesia.

So, the experiment that Professor Katja Simon, an immunologist, and Dr. Ghada Alsaleh, a rheumatologist, did was they took these mice. They took young mice and they took older mice, and they gave them both the flu vaccine. They saw that reaction with young people and old people, antibodies go up, but with young people, it’s sustained and old people, it doesn’t. Then they did another experiment with the same cohorts of old and young mice, and they gave them spermidine together with the flu vaccine. Antibodies went up, but with the older mice, they performed better on the antibodies and they sustained better. Why? The older mice did better than the younger mice? That’s not supposed to happen. Are we going to get better with age?

And in fact, the thought is that the reason why those older mice, once their immune cells were rejuvenated, why they did better was they actually had more experience. They’d been around the block more times than these young mice, so they’d been exposed to more pathogens and had an antibody recipe book, “Oh, I know what I’m supposed to do with this one. Yeah, I saw that back in ’25 or I saw that in 1976. This is how we get rid of it.” So, when I heard about this, I was very excited because the rheumatology aspect is to do with the immune system, obviously.

So, here they are rejuvenating elderly immune cells, but it appears that spermidine also helps with autoimmune patients as well, helping with modulation of the immune system. And with the immune cells, what it does, we’ve heard of senolytics. These are compounds that actually get rid of senescent or zombie cells that the body is saying, “Don’t reproduce anymore because you’re making too many mistakes. Sit in that corner and just be quiet.” So, senolytics get rid of those. What spermidine does, it’s a xenomorphic. That means that it modulates senescent cells. And that I think is more powerful because some populations of cells like the cardiomyocytes that modulate the rhythm of the heart, we don’t have a lot of those. And even at age 25, we only replace 1% of all those cells a year. So that means it takes us a hundred years to replace all of them. Well, guess what? By the time we’re 60, you’re replacing half a percent.

So, those cardiomyocytes, we need to maintain. We can’t afford to use a senolytic to get rid of them. We need to modulate them, and reform them, and rejuvenate them. And that’s where spermidine’s power comes in. So, there are so many other papers. Some are preclinical, quite a lot are preclinical, but polyamines, spermidine is a polyamine like spermine. Another one is putrescine. These polyamines have something like 13,000 papers published on them over the years. They are very well known in science, but until we realize that they had these extra powers to rejuvenate and renew through a process called autophagy, people didn’t think very much of them. Now, because autophagy was the subject of the 2016 Nobel Prize in Medicine or Physiology, everybody’s, “Oh, great, autophagy activators. These are good things.” They mimic the benefits of fasting. How do I get more in my diet? I don’t want to fast.

Dr. Sandi: Wow. So, it sounds like this is wonderful for anti-aging. And I’ve also heard it’s great for hair growth. What other benefits does it have?

Leslie: Well, it inhibits 9 of the 12 hallmarks of aging. These are everything from stem cell dysfunction, mitochondrial dysfunction, telomere shortening, inflammation, gut dysbiosis. For instance, with the gut, when mother’s milk hits the lining of the gut, those immune receptors that line the gut are being primed for food, and they are being told to have an appropriate immune response to food. That’s why babies that are not breastfed tend to have more allergies, because they didn’t get that priming. So, very good for gut dysbiosis. I’ve already mentioned autophagy. Very good for misfolded proteins in the cell. So, that’s all the cellular stuff.

In terms of neurological issues, autophagy is really helpful for getting rid of waste in the brain. So, for conditions like Alzheimer’s, dementia, it could be very useful. For heart disease, very helpful as well. It can be helpful with bone tissue, with helping to rebuild bone. Obviously, we know we lose bone as women, so that’s one thing. Hormones are another area. There’s only one human trial that was done with wheat germ derived spermidine that also had spermine in it. It was done up in Canada, and they had both been in women. They could see after only 30 days of supplementation with 5 milligrams, a relatively high dose, that they had the cortisol levels. Testosterone had gone up in the men by 50%. DHEA, pregnenolone, went up in both groups, both cohorts. Those are the precursors to the reproductive hormones. And progesterone, testosterone, and estrogen had gone up in the women as well.

So, that’s quite interesting as we get older. I always say, get this from your food first if you can. Yes, I make a food-derived supplement, but again, the body recognizes the foods we eat. So, try to get it from legumes, from soy. One of the big sources of spermidine is in long-fermented soy. It’s a Japanese dish called… Doesn’t smell great, doesn’t taste great, but it’s so good for you. A little bit like chicken liver. Your mom’s telling you, “Have this chicken liver, so good for you.” Chicken liver also has spermidine. So, the livers of poultry have it, but not of other animals. So, if you’re on the carnivore diet, just make sure you get some chicken liver. Mushrooms, beans. I know a lot of people say, “Oh, I can’t eat beans,” but they are full of spermidine. So, these are good places to get it too.

And in terms of ages, when you’re young, you should have sufficient ability to make it in your tissues and your gut biome. Unless you have a very specific condition. For instance, you have been exposed to multiple courses of broad spectrum antibiotics, which may have wiped out the colonies of beneficial bacteria that makes spermidine, then you should be capable of making it. I’d say late 20s, this is when it starts to diminish, and it’s like vitamin C. We don’t store it in our body. We are constantly excreting it, so we need to constantly replenish it. And that’s, again, another reason to get more plants into your diet. Cheese is another source, long fermented cheeses. Have it as well. Parmesan is a good type. Cheddar but not American cheddar. You need British cheddar because it’s fermented longer.

Dr. Sandi: And these are all ways that health coaches can support clients by having perhaps print out a list. These are the foods that are high in spermidine. I think the benefits that you’re describing are really unknown. I think most people would not… They’re going to know vitamin C, but they’re not going to know spermidine. So, you have…

Leslie: I do. So, my company, Oxford Healthspan, works together with the Japan Autophagy Consortium. So, it was a Japanese researcher, Professor Yoshinori Ohsumi, who won the 2016 Nobel Prize for his research on autophagy. And he’s senior advisor to the consortium. We’re the only non-Japanese company there, and we source all of our food-derived spermidine from Japan. One is a gluten-free version. So, I did that specifically for other autoimmune patients who couldn’t take the lectins in wheat. We get that one from a special strain of chlorella from Okinawa. And then we have one that is a wheat-derived version with a prebiotic fiber to help feed the bacteria in your gut that can make spermidine too. We also get that from Japan. And they don’t use the American wheat, which is interesting because of glyphosate. So, it’s one of the reasons why we source it from Japan.

But, yeah, we have standards that we have to meet in Japan. Japan has very strict regulations on food imports. They do import a lot of food themselves. But unlike some countries like the United States, they actually have labs at the ports. And they’re constantly testing the food that comes through to make sure it meets their standards. So, for instance, you may have heard from Dave Asprey that coffee that comes to Japan and doesn’t meet standards on mycotoxins gets sent back to the United States. Well, it gets sent back. And the companies who own it say, “Well, who’s going to accept this? Let’s try the U.S. because their regulations are lower,” which is a bit of a shame.

Dr. Sandi: That’s so scary. Yeah, yeah.

Leslie: But, yeah, so with food-derived spermidine, a couple of other cases where health coaches might find it beneficial is if somebody has recently had any kind of a virus and have noticed hair shedding. With any kind of virus, the body will use spermidine to activate a process called virophagy. That is basically the sequestration or the bagging up of viruses and the disposal of them. And another time is when you have a baby and you’re breastfeeding. You will lose a lot because you’ve been giving your spermidine in utero to the baby. And then once you start breastfeeding, your body makes that decision. The next generation is more important than this person. So, it takes all the spermidine from you and gives it to the baby. And again, women notice hair shedding then. And you mentioned hair. It’s good for hair. There have been studies that show that it keeps the hair follicle in the growth phase of the hair life cycle, which means you can grow it longer but that’s also the only phase of the hair life cycle that pigment is made. And one other thing we can see with this molecule is it increases tyrosine, and tyrosine will help with melanin production as well. So, we think that’s possibly why some people get good results with their hair. If they’re just starting to go gray, they often see some results, but you know, I’m not talking about this is the only reason, but it’s part of the puzzle.

Dr. Sandi: Yeah. Incredible. So, Leslie, first of all, can you share the name of the product? Where can people find it? And then I want to share that we have for our listeners a very special discount code. It is SANDI15.

Lesliei: So, your listeners can find it at oxfordhealthspan.com. And the product is Primeadine, and you can take it as a capsule. You can take it as a powder. You can take it as a gluten-free tablet. So, those are all the ways that you can add it to your diet or to your smoothies.

Dr. Sandi: That’s fantastic. And where can people find you personally?

Leslie: You can find some of my work on lesliesnewprime.com. New prime because I think… Well, I’m still 59. It’s a prime number. I feel like I’m just entering my prime. And then I also do work for a nonprofit called the Oxford Longevity Project. That’s oxfordlongevityproject.org. And you can see interviews that we’ve done on everything from ketones to NAD. We talk about a lot of different things. We have other speakers who come into this conference at the University of Oxford. So, that’s free for the public to take a look at.

Dr. Sandi: Fabulous. And we have actually a lot of house coaches from FMCA who are in the UK. And we need many, many more. So, this has been absolutely fascinating, Leslie. Thank you so much for being our guest today from across the pond.

Leslie: Thank you very much for having me, Sandi. Thank you.