Transcript: Methionine Restriction as a Life Extension Strategy
This recent review, (noting that vegan diets, in part because they tend to be naturally low in methionine, an amino acid and thus a “building block” of protein), may prove to be a useful nutritional strategy in controlling cancer growth) 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, the 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 creation of so-called reactive oxygen- and fewer free radicals would slow the rate of DNA damage, which slows 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. The first is caloric restriction—they call it dietary restriction here, meaning you cut your intake of food in half, for example, by only eating every other meal. 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. The third option is eat enough food, eat enough protein, but just eat plant proteins that are relatively low in methionine.
Caloric restriction is hard, because you walk around starving all the time. Something like every-other-meal eating is never likely to gain much popularity as a pro-longevity 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 have low levels of methionine. As we've seen, plant proteins tend to be lower in methionine than animal proteins.
Yes, protein restriction across the board can be performed to avoid the hunger of caloric 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 comparably 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, this “disadvantage” is actually a strong advantage. And it fits well with the important role of beans in healthy diets like the traditional Mediterranean diet. Interestingly, soy protein is also especially poor in methionine, and it is widely considered that soy-containing foods have healthy effects in human beings.
On a population-wide 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 life span in humans while avoiding the possible undesirable effects of caloric restriction.” We're eating around double the protein we need, so the first thing doctors can recommend is just that decreasing the intake of protein has a large potential to bring health benefits.We can also get our methionine even lower by eating a plant-based diet.
The reason why 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 synergic “combined effect” is gaining acceptance. However, based on the relationship of excess dietary methionine to vital organ toxicity, as well as its likely mechanism of action through increases 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. Therefore, "The low-methionine content of vegan diets may make methionine restriction feasible as a life extension strategy"
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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