"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,
may prove to be a useful nutritional strategy
in cancer growth control,
also looked at methionine restriction and life-span 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,
caloric 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, but just eat plant protein,
because they are relatively low in methionine.
Caloric 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-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 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 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 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 “disadvantage” into a strong advantage
and 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.
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 life span 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 has 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
will 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 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 "The low-methionine content of vegan diets"
"may make methionine restriction feasible as a life extension strategy."