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Thread: Optimizing diet for different goals? page

  1. #1
    gsudre's Avatar
    gsudre is offline Junior Member
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    Optimizing diet for different goals?

    Primal Fuel
    Hello,

    I've been part of a long and healthy debate with a vegan friend about the benefits of the Paleo diet. His last question stumped me, and I was wondering if anyone in the forum could provide a few insights. Please disregard his remarks about cholesterol and heart disease, since apparently he hasn't read the many posts in the Paleo-sphere about that. I'm looking for comments mostly on the genetic/evolutionary perspective of his questions, and also on the link between IGF-1, cancer, and meat consumption, which always comes up when we talk about these issues.

    I'm summarizing his main question below to make it easier, but I'll also attach the full length e-mail below.

    Thanks,

    Gustavo

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    Summarized version:

    [...] This basically seems to suggest that looking at what our ancestors ate to determine that diet is "optimal" for us today is of very limited value, since our objective function (a long and healthy life) wasn't the same one that evolution was optimizing when tuning our body for the food available to our ancestors. Our ancestors' objective function could be summarized as "tune the body to a diet that helps you grow fast, be strong, and have lots of kids", regardless of the impact on health in old age. [...] These early-life survival and reproduction advantages of meat eating would remain, regardless of whether in the long-run (after one's reproductive years) meat is deleterious to human health via cancer (e.g. IGF-1 is boosted by meat protein, and thereby promotes growth, but also cancer later in life), or heart disease (through increased arterial plaques from higher cholesterol). [...] how does a Paleo Diet proponent back up the idea that eating that our paleolithic ancestors ate will be undeniably "optimal" for us now too, when "optimal" from our genes perspective during paleolithic times was defined as the diet which promoted reproductive fitness, while "optimal" from our modern perspective is that diet which promotes health and longevity?

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    Full question:

    Can you fill me in on how Paleo proponents address the issue that if we have an optimal diet shaped by our evolutionary past, the function that natural selection was optimizing was evolutionary fitness, which equates to the ability to successfully pass on one's genes. Post-reproductive fitness, and hence the ability to live healthily to a ripe old age, would not have mattered, since there is little (if any) value to our genes if we continue living after we've sired our offspring. The "grandmother hypothesis" (that the older generation helps their adult children with childraising sufficiently to benefit their shared genes, and would therefore be selected for) has very weak scientific support, and would exert relatively little selection pressure even if it does exist.

    So any diet that was optimal for our ancestors would "very happily" (excuse my anthropomophizing) trade off a long and healthy life after 40 years of age for an increase in the ability to grow quickly, survive in violent environment, and have lots of kids.

    A clear parallel to this idea of sacrificing long-term health for early life survival is seen in the gene for sickle-cell anemia ( Sickle-cell disease - Wikipedia, the free encyclopedia). Carrying the gene for sickle-cell anemia reduces one's life expectancy to about 42 years, but it remains in our genome, particularly in people whose ancestors lived in the tropics, because carrying the gene protected our ancestors against malaria infection, and thereby allowing carriers to reproduce more effectively than those who didn't carry the gene, and are therefore more likely to die off from malaria before reproducing. So the sickly-cell gene helps us during youth to reproduce, at the expense of shortening our life.

    Animal protein seems like an possible example of this idea in the area of diet. We likely have evolved away from our (mostly) herbivorous primate ancestors to better digest and assimilate meat because it provided a good source of calories, not to mention an amino acid profile that closely matches our needs for building muscle quickly - two things that would help us survive famine and grow rapidly, so we could effectively propagate our genes.

    These early-life survival and reproduction advantages of meat eating would remain, regardless of whether in the long-run (after one's reproductive years) meat is deleterious to human health via cancer (e.g. IGF-1 is boosted by meat protein, and thereby promotes growth, but also cancer later in life), or heart disease (through increased arterial plaques from higher cholesterol).

    Further, there would be no selection pressure during our ancestral past to "fix" our genome to correct for these late-life problems.

    Of course, the same argument could be made that our genes have evolving to varying degrees to handle other "new" fuel sources like tubers, legume, grains and dairy in order to improve reproductive fitness, independent of, or perhaps even at the expense of, post-reproductive health and longevity. So they might not be good for our long-term health either, despite the fact that we've been eating all of them for a relatively long time.

    This basically seems to suggest that looking at what our ancestors ate to determine that diet is "optimal" for us today is of very limited value, since our objective function (a long and healthy life) wasn't the same one that evolution was optimizing when tuning our body for the food available to our ancestors. Our ancestors' objective function could be summarized as "tune the body to a diet that helps you grow fast, be strong, and have lots of kids", regardless of the impact on health in old age.

    This seems to leave us with nutrition science as the only way to determine what diet best promotes the outcome we're interested in - long-term health and longevity. And to me it appears that nutrition science pretty definitively point away from a diet that is high in animal protein and animal fats, and towards a whole-food, plant-based diet if one wants to avoid the diseases that kill us most often when we get older - heart disease and cancer.

    So how does a Paleo Diet proponent back up the idea that eating that our paleolithic ancestors ate will be undeniably "optimal" for us now too, when "optimal" from our genes perspective during paleolithic times was defined as the diet which promoted reproductive fitness, while "optimal" from our modern perspective is that diet which promotes health and longevity?

    Can you point me to a source that addresses this issue head-on?

  2. #2
    picklepete's Avatar
    picklepete is offline Senior Member
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    The notion that there's a conflict between performance/fertility and lifespan may have some truth to it, like the difference between white giant and brown dwarf stars.

    It's probably true that evolution doesn't much care what happens to us after age 40, but it's far from settled which diet corresponds to which life path. I think it's a fair point that a perfect H-G recreation is not necessarily what we need today and research has its place, but when guessing at the ideal diet I suspect H-G hits closer to the mark than SAD or vegan which are both radical departures from historical precedent and feature demonstrable deficiencies and/or toxicities. The only real disagreement here is the validity of the anti-SFA/cholesterol evidence.

    I think the Jaminets found a correlation between 100+ lifespans and a lowish protein intake of 10-15% but by no means vegetarian (they regard plant protein as allergenic). Their Perfect Health Diet blog has some great longevity articles and links. The book approaches human fuel as an engineering problem and arrives at a sort of preindustrial Pacific diet via scientific evidence with no ideology or sentimentality.
    34//6'3"/180

    Lots of: urban hiking, cycling, sprinting
    Lots of: fresh meat, seafood, eggs, organs, tubers, starch fruits, vegetables, meat fat, dairy fat, oil fruits
    Some: cured meat, dairy protein, sweet fruits, rice, pulses, tree nuts, oil seeds
    Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, refined oils, peanuts

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