 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, 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, outward 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, but 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-longjevity 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, and it's 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. We're eating twice as much protein as we need, so 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.