 Let's say you really need to find reliable information about the best diet for high blood pressure or heart disease or diabetes. Where do you go? Do you go to a website sponsored by Big Pharma that wants to sell you pills to fix your problem? Or do you want to treat the cause? Welcome to the Nutrition Facts podcast with the latest peer-reviewed research on the best ways to eat healthy and live longer. They don't sell this kind of meth in a back alley. In today's story, we look at the ill effects of an excess of methionine and amino acid that can cause cancerous tumors to grow and our lifespan to shrink. This recent review noting that vegan diets, in part because they tend to be naturally low in methionine, may prove to be a useful nutritional strategy in cancer growth control, also looked at methionine restriction and lifespan extension. It seems that the less methionine there is in body tissues, the longer different animals tend to live. But what are the possible implications for humans? I've talked before about the free radical theory of aging, this concept that aging can be thought of as the oxidation of our bodies, just like rust is the oxidation of metal. And methionine is thought to have a pro-oxidant effect. So the thinking is that lower methionine intake leads to less free radical production of the so-called reactive oxygen species, which slows the rate of DNA damage, which then would slow the rate of DNA mutation, slowing the rate of aging and disease, thereby potentially increasing our lifespan. There are three ways to lower methionine intake. Chloric restriction, they call it dietary restriction here, meaning like you cut your intake of food in half, for example, only eating every other day. That would lower your methionine intake. Or because methionine is found concentrated in certain proteins, you could practice protein restriction across the board, eating a relatively protein-deficient diet. Or the third option is to eat enough food, eat enough protein, and just eat plant proteins because they are relatively low in methionine. Chloric restriction is hard because you walk around starving all the time. Something like every other day eating is never likely to gain much popularity as a pro-long-jevity strategy for humans, so it may be more feasible to achieve moderate methionine restriction in light of the fact that plant-based diets tend to be relatively low in this amino acid. As we've seen, plant products tend to be lower in methionine than animal products. Yes, protein restriction across the board can be performed to avoid the hunger of chloric restriction, but again, methionine restriction could also be performed emphasizing low methionine, high-quality vegetable sources of protein. Among foods containing plant proteins, legumes are especially rich in essential amino acids, offering excellent substitutes for proteins of animal origin. The fact that beans have comparatively low methionine has been classically considered a disadvantage, but given the capacity of methionine restriction to decrease the rate of free radical generation in internal organs, to lower markers of chronic disease, and to increase maximum longevity, ironically converts such a quote-unquote disadvantage into a strong advantage and fits well within the important role of beans in healthy diets like the traditional Mediterranean diet. Interestingly, soy proteins, also especially poor in methionine, is widely considered that soy-containing foods have healthy effects in human beings. Now on a population level, folks could benefit from just lowering their protein intake period. The mean intake of proteins, and thus methionine, of Western human populations is much higher than needed. Therefore, decreasing such levels has a great potential to lower tissue oxidative stress and to increase healthy lifespan in humans while avoiding the possible undesirable effects of caloric restriction. First thing we can recommend is just decreasing the intake of protein, as a large potential to bring about health benefits, but then we can lower methionine even further eating a plant-based diet. The reason plant-based diets are so protective is not known. Yes, vegetables contain thousands of phytochemicals, but separately investigating their possible protective roles would be an impossible task. The idea that the protective effect is not due to any of the individual plant food components, but to a synergistic combined effect is gaining acceptance. However, based on the relationship of excess dietary methionine with toxicity to major vital organs and its likely mechanism of action through increase in free radical generation, the possibility exists that the protective effects of plant-based diets can be due, at least in part, to their lower methionine content. This is not a new idea. It was proposed back in 2009, but is only now gaining increasing acceptance in more mainstream scientific circles. The idea that low methionine content of vegan diets may make methionine restriction feasible as a life extension strategy. In our next story, we learn how plant-based diets may prove to be a useful nutrition strategy because these diets are naturally lower in methionine. In designing an antibiotic, you wouldn't create a drug that destroyed DNA, for example, because that's something that both humans and bacteria share in common. It would kill the bacteria, all right, but it might kill us, too. So many antibiotics work by attacking the bacterial cell wall, something bacteria have that we don't. Anti-fungals can attack the unique cell walls of fungus. Pesticides can work by attacking the special exoskeleton of insects, but fighting cancer is harder because cancer cells are our own cells. So fighting cancer comes down to trying to find and exploit differences between cancer cells and normal cells. Forty years ago, a landmark paper was published showing for the first time that many human cancers have what's called absolute methionine dependency. Meaning you can grow normal cells in a petri dish without giving them the amino acid methionine. Normal cells thrive, but without methionine, cancer cells die. Normal breast cells, for example, grow no matter what, with or without. But leukemia cells, they need that extra-added methionine to grow, or they just flat-line. What does cancer do with the methionine? Tumors generate gaseous sulfur-containing compounds with it that specially-trained diagnostic dogs can actually pick up. There are mole-sniffing dogs that can pick out skin cancer. There are breath-sniffing dogs that can pick out people with lung cancer. Pea-sniffing dogs that can diagnose bladder cancer, and yes, you guessed it, fart-sniffing dogs for colorectal cancer. Doctors can now bring their lab to the lab. Gives a whole new meaning to the term, pet scan. Anyway, methionine dependency is not just present in cancer cell lines in a petri dish. Fresh tumors taken from patients show that many cancers appear to have biochemical defects that makes them methionine-dependent, including some tumors of the colon, breast, ovary, prostate, and skin. Chemo companies are fighting to be the first to come out with methionine-depleting drugs. But since methionine is sourced mainly from food, a better strategy may be to lower methionine levels by lowering methionine intake, eliminating high methionine foods for cancer growth control. Here's the thinking. Look, smoking cessation, consumption of diets, rich in plants, and other lifestyle measures can prevent the majority of cancers. Unfortunately, people don't do them, and as a result, each year hundreds of thousands of Americans develop metastatic cancer. Chemotherapy cures only a few types of metastatic cancer. Unfortunately, the vast majority of common metastatic cancers, like breast, prostate, colon, and lung, are lethal. We therefore desperately need novel treatment strategies for metastatic cancer, and dietary methionine restriction may be one such strategy. So where is methionine found? Particularly chicken and fish. Milk, red meat, and eggs, as less. But if you really want to stick with lower methionine foods, fruits, nuts, veggies, grains, and beans. In other words, methionine restriction may be achieved using a predominantly vegan diet. So why isn't every oncologist doing this? Despite many promising preclinical and clinical studies in recent years, dietary methionine restriction and other dietary approaches to cancer treatment have not yet gained widespread clinical application. Most clinicians and investigators are probably unfamiliar with nutritional approaches to cancer. That's an understatement. Many others may consider amino acid restriction as an old idea, since it's been examined for several decades. However, many good ideas remain latent for decades, if not centuries, before they prove valuable in the clinic. With proper development, dietary methionine restriction, either alone or in combination with other treatments, may prove to have a major impact on patients with cancer. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org slash testimonials. We may share it on our social media to help inspire others To see any graphs, charts, graphics, images, or studies mentioned here, please go to the Nutrition Facts Podcast landing page. There you'll find all the detailed information you need, plus links to all the sources we cite for each of these topics. For a timely text on the pathogens that cause pandemics, you can order the e-book, audiobook, or hard copy of my last book, How to Survive a Pandemic. For recipes, check out my second to last book, my How Not to Diet Cookbook. It's beautifully designed with more than 100 recipes for delicious and nutritious meals. And all the proceeds I receive from the sales of all my books goes to charity. NutritionFacts.org is a non-profit science-based public service where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles. Everything on the website is free, there's no ads, no corporate sponsorship, it's strictly non-commercial. I'm not selling anything, I just put it up as a public service as a labor of love as a tribute to my grandmother, whose own life was saved with evidence-based nutrition.