TPNS 7-8: A Diet In Your Genes?
Wednesday, March 7, 2012 at 08:32AM
Plant Positive

Primitive Nutrition 7:
 A Diet in Your Genes? Part I


As you know by now, the purported superiority of primitive nutrition is premised on the idea that there is particular diet which our hunter gatherer genome requires.


Sometimes it is stated more accurately that our nutritional needs are genetically programmed.  This is true, of course.  We need vitamin C to prevent scurvy, for example, and the reasons for this can be found in our genes.  But nutrition science hasn't needed a Paleo diet idea to figure out what nutrients we need.  And make no mistake, regardless of context, Paleo promoters are not talking about nutrients and nutrients only.  They are devoted to a diet.  Paleo promoters consistently advocate for a specific diet that includes a lot of meat and avoids grains and legumes.


Paleologic is based on the genome.  Amazingly, this line of reasoning has even found its way into a proper nutrition textbook.  That is why I will now take some time to discuss the genome.  Is it possible we have a genome that is so particular about diet?


Thanks to this author, Gary Marcus, we have a very apt term to describe the result of an evolutionary process: kluge.  Sometimes you'll see it spelled differently.  Marcus takes this term from the technology world.


A kluge is an inelegant, jury rigged solution to a problem.


Of course, the results of evolution are often quite beautiful and elegant, but make no mistake, evolution produces Rube Goldberg contraptions.  This is because evolution happens in tiny increments over time, always working from previous inheritance.  In evolution, there is never a complete tear-down or bumper-to-bumper redesign.  No one began a new design for Paleolithic man from a clean sheet of paper.


Evidence of this goes all the way back to the development of eukaryotic cells.  As this paper demonstrates, two billion years has not been enough time for our genome to even integrate fully with itself.


More evidence of our kluge genome comes in the form of genetic material squeezed into it by endogenous retroviruses.  This amounts to about 8% of our genome, compared to the approximately 1.5% of our genome used for protein coding.


Knowing that our genome is a kluge, with evidence of this extending all the way back to our beginnings as eukaryotic cells, we can now appreciate that our genome is the product of a long legacy that extends back not just 10,000 years, and not even two and a half million years, but rather two billion years.


This is a good time to introduce you to some important terms in genetics if you don't know them already.  This will help us understand the Paleo concept on a basic level.


For our purposes, let's call the genotype the total genetic material in someone’s genome.  Usually the term is used in reference to a particular trait that is being discussed.  That trait is the phenotype.  The phenotype is the functional expression of the genome for whatever trait you are considering.


Looked at this way, Paleologic basically says that we have a stone age genotype - that is, we have stone age genes - and therefore we have a stone age phenotype - or that we need stone age food because of all the resulting traits from those genes.


I am not aware of any research into the genome that proves this.  I am not even sure how that would work.  Until such a discovery is proven this idea is pure conjecture.   A major barrier to a discovery proving this is the principle in genetics that genotype and phenotype are not the same thing.  The argument that your genome predetermines complex systems of the body in a purely linear and predictable fashion is not a contemporary view of genetics.  What you see here is a very nice statement of this fact.  Even if one could argue there is indeed a Paleo genotype, it does not follow that we are locked in to a Paleo lifestyle.  As I said, genotype and phenotype are terms normally applied to specific traits, so it is a stretch to even look at it this way.  Nevertheless, this the claim of Paleo-logic.  Our phenotype is supposed to be responsible for us being unable to properly digesting oats, for example, despite all the evidence to the contrary.  I think this is a really tough argument to make based on genetics.  The distinction between genotype and phenotype is yet another flaw in Paleologic that nullifies the idea before we even consider it on a practical level.


The case that we have some sort of Paleo diet phenotype is harder to make when it seems phenotypic variation is a key part of how populations achieve fitness.  How could there be one ideal diet for everyone if variation in phenotype is built into the genome?


Read enough about evolutionary biology and you will find that although it is very fascinating research that has attracted some great minds, it is often quite speculative.  Cordain is well within this speculative tradition with his Paleo diet, although his idea does not seem modern in its specificity and internal consistency, or rather lack thereof.  Let's see where others beside Cordain have stumbled in overextending or corrupting ideas born from evolutionary theory.


The most obvious example is the eugenics movement.  Here you see a respectable-looking academic journal published by the Eugenics Education Society in 1916.


Today we know that in addition to being morally revolting, eugenics was irredeemably flawed scientifically.  I include this slide so you can see how readily accepted it was by the intellectuals of time.


By 1920 evolution had become a tool for constructing a variety of pat explanations for complex human behaviors.  Despite growing evidence that it lacked scientific support, eugenics was too attractive an idea for some to abandon.  Like the appeal to nature, fallacious appeals to genetics and evolution seem to strike a powerful chord in some people.


Of course, the worst abuses of the theory of evolution have been in regard to race and ethnicity.  The racist invoking evolution always thinks he is the more evolved, even as he wallows in base emotions of tribalism and violence.  For the Nazis, their embrace of a hateful ideology turned out to be maladaptive.


The violence of World War II led some to conclude that evolution made us in to inveterate killers.  Cruelty and war were just in our nature.


This, like meat-eating, was argued to be the explanation for our big brains.


Social Darwinism, too, was a concept glibly used to justify all manner of ideologies.  On this slide please notice the last couple sentences, which make clear how this type of thinking is useless as it is inherently vague and speculative.  You've seen already that Paleologic suffers from this same problem of free interpretation.  Paleo ends up just being a rhetorical device for self-validation.


Once again I'll throw up Gary Marcus's book cover.  His book is about evolutionary psychology.  This might be another example of the potential overstretching of the theory of evolution.


Not everyone is in agreement about the value of the conclusions drawn from it.


Here is another example of the speculations you'll find in evolutionary biology.  This author proposes there may be an adaptive advantage to an additional random epigenetic element to the genome beyond the normal background mutation rate.  He can't identify a  molecular mechanism to explain this.  I'm not sure I understand his idea, but what I take from this abstract is that evolutionary biology isn't quite ready yet to tell me what to eat.


He mentions the antagonist pleiotropy hypothesis regarding aging.  Longevity is an issue worth contemplating in regard to the Paleo diet idea.


Normally, when we discuss nutrition it is understood that a healthy diet rewards us with longer life, or at least good health lasting longer into old age.  After all, the Paleo diet is targeted at foods its promoters believe cause Western patterns of chronic disease that take years to develop and harm us.

That's why I found it strange that in his defense of his original 1985 paper about the Paleo diet concept, Paleo nutrition founder S Boyd Eaton seemed aware that post-reproductive lifespan is little effected by the pressures of natural selection.



Think about it.  If evolution is based on the passing on of genes, once a new generation is born and able to carry on, what does it matter how much longer the parents live?  If our genome isn't affected very much after reproduction, then from the diet's very beginning, future claims that it's a way of giving us a longer life were short-circuited.  This wasn't his intent in this quote, as here he argues that contemporary humans are not adapted to so-called novel foods because we wouldn't pay a price for them until we have already passed on our genes.  Unfortunately for him, he can't have it both ways.  The longevity argument for Paleo therefore is off the table.  And if it's off the table, of what practical use is the concept?  This is another serious logical problem for the Paleo promoters.


I'll return to the antagonistic pleiotropy hypothesis of aging now.  Antagonistic pleiotropy is an interesting, albeit speculative, idea that states that traits need not be all good or all bad.  A trait can help your fitness for passing on genes, but it can also hurt you in some other way that may not relate to passing on genes.  In evolution, the gene that improves fitness is the one that matters.  It's an important idea for those who say there is an ideal diet in our genome somewhere.  There really is no reason to think anything is particularly ideal in the genome.  Our genes can work at cross-purposes to our desires in life.


Here I will return to one of the authors in the article Cordain cited in his attempt to find support for his view that nutrition is an immature science.  As I said, I felt the article in question actually undermined his philosophy.  Randolph Nesse seems to be more comfortable with the potential contradictions in our genes that result from our lack of design.  If you pause to read this, first, you will see he recognizes some obvious limits to the genome's impact on health.


 Next, you will see that he understands the primary importance of reproduction in evolution and the potential that creates to undermine our health.  Paleo dieters, is it more important to live according to your imagined genetic requirements, or is it more important for you to have a long and healthy life?  I opt for the latter, so I am more interested in the best objective science for this purpose.


I'm halfway through my thoughts on this idea of having a diet in your genome.  See you in the next video!



 Primitive Nutrition 8:
A Diet in Your Genes? Part II

In the previous video I explained why it is highly unlikely there is a Paleo diet in our genome.  I was just getting going on the topic of longevity.


Here is an example related to longevity of how the speculation found in evolutionary biology can go wrong or be misconstrued.  Read this abstract and you might come away thinking that somehow humans have a longer post-reproductive life span than other primates because we are so well-adapted to eating meat.  This sounds good for the Paleo diet idea, which is why you will see this article wherever people argue against vegetarian diets and for Paleo diets.


But hold on a moment!  It turns out we don't age much differently than other primates after all.


Something else the Paleo promoters are likely to overlook is this comment by one of the authors of the study they like so much.


"Stanford said that modern-day humans 'tend to gorge ourselves with meat and fat.  For example, our ancestors only ate bird eggs in the spring when they were available.  Now we eat them year-round.  They may have hunted one deer a season and eaten it over several months.  We can go to the supermarket and buy as much meat as we want.'"


That doesn't sound like much of an endorsement of the Paleo diet, does it? Once again, speculation about evolution and diet doesn't assure us we will reach the same conclusions.


Lifespan involves interesting issues of antagonistic pleiotropy.  Here is a paper on calorie restriction and aging.  I want you to notice here that the author states that it is unlikely that genes conferring longer lifespan have been positively selected to do so.  We may want long life, but natural selection probably hasn’t done much to help us with that.


This scientist is not convinced that calorie restriction leads to longer life in humans.  We must admit that the evidence for it is lacking, as he says.


Still, it's interesting to consider.  Here is an abstract about lifespan.  If you read this, you could interpret it to mean that your genome is more tuned to fertility  than longevity.  The term somatic maintenance here refers to the turnover of cells not involved in reproduction.


Here this author refers to protein synthesis rather than somatic maintenance but I think the point is the same.  Growth and development are said to be at odds with lifespan, and this is mediated by caloric restriction.


Here is the sort of counterintuitive result  this tradeoff might produce, if it works just this way.  Fewer calories, less body maintenance, but better reproduction.  Once again, perfection in the genome is elusive.  Our genes work at cross purposes.  And once again, even if we grant the Paleo premise of a diet in our genes, the idea may not mean much when we try to figure out how to live a long and healthy life.


Here's another example to show you how our genome might not be the greatest guide for our diet choices.  This is about the so-called Asian flush reaction.  Asians are less able to metabolize alcohol due to a point mutation.  It is believed that this was caused by the adoption of the drinking of hot tea in the East as a way to purify water.  In the West, fermentation of liquids into alcohol was the preferred method of water purification so Europeans generally can now tolerate alcohol better than Asians.  Does this mean alcohol is good for people of European descent?  Not necessarily.  You'd need to look at current scientific research into health outcomes to know that.  No responsible scientist or health official is recommending we drink alcohol on the basis of conjecture about our genes.


It's hardly likely that alcohol could be considered unreservedly healthy and natural for us even if it is well-represented in our genome.  Anything you consume that can inflict this collection of problems can hardly make a claim to have a place in an ideal diet for humans.  I would think that minimally an ideal diet should not induce birth defects, for example.  And yet, if you're of European decent, there alcohol genes are in your genome.  What if there were some meat-adaptive gene in your genome?  Why would you conclude from that, that meat is part of an ideal diet?


Dairy is in a similar situation, and this is one where the Paleo dieters and I might agree, although for different reasons.  Cordain uses an argument based on it's supposed evolutionary discordance to discourage its consumption.  Yet not everyone is lactose intolerant.  Does that mean if you are lactose tolerant milk is engraved in your genes as a healthy food?  Not so fast.


The adaptation for those who tolerate milk well is called lactase persistence.  This is because lactase, the enzyme needed to digest lactose, the sugar in milk, is normally lost after weening because it is no longer needed.  In a neotenous adaptation, the trait of the juvenile phase persists into adulthood because it confers some advantage.  But does this mean it is healthier to eat butter and drink milk throughout life?  Why would we jump to that conclusion?


After all, other mammals lose their lactase production.  Are we fundamentally so different because of a few polymorphisms?


It gets even fuzzier when you see that lactase persistence has evolved differently in different populations.  If we all have a stone age genome that prohibits milk drinking, then why did natural selection find two different paths to put it in the genomes of these populations?  This isn't what you'd expect if our genes were designed.


Lactase persistence is a great example of how our genomes differ.  The only way to decide whether or not to consume dairy is through real empirical research, not by channeling our inner caveman.




I'd like to now talk about the concept of epigenetic expression. Epigenetics basically refers to the role of environment in expressing your genes.  This is important here because it means your genes are not your destiny.   This is understood by most of the Paleo diet promoters, with Mark Sisson coming first to mind.  Of course, he thinks his diet ideas induce epigenetic expression in a uniformly positive way that promotes his ideals of appearance and athletic fitness.  But should it be so simple?  Let's take a look at examples of the impact of epigenetic expression.


Let's return to Randolph Nesse for a really interesting example of the effect of epigenetics.  Here he points out that a childhood spent in a hot climate will affect the number of sweat glands the child eventually has in adulthood.


Mothers exposed to nutritional insufficiency give birth to young who develop the typical disorders of Westen civilization much more easily.  In my Waking to Realities section you will see how this is playing out in parts of the world undergoing rapid changes in their diets with the addition of more meat, fat, and refined carbohydrates.


Notice the use of the word "fitness" in the last sentence.


Once again, this is not the sort of fitness Mark Sisson talks about.  It is fitness in it's true evolutionary meaning.  In evolution, "fitness" does not mean you are athletic.


I like this story as an example of how fitness in evolution may mean quite the opposite of what the phrase "survival of the fittest" usually conjures.  Here, among baboons, the behavior of the most aggressive, dominant males made them unfit for their environment, allowing for the passing on of the genes and culture of the subordinate males.  The subordinate males were fitter within the context of their environment.


But I digress.  Back to epigenetic expression.


Read The Protein Debate and you will see that T Colin Campbell discusses the importance of epigenetic influences.  Here you can see that as far back as 1986 it was known that nutriton in utero could influence the health risks of a baby.  This was all coming into focus shortly after Eaton's original Paleo paper.  Paleo-logic states that the answers to our health needs lie in our stone age genome.  Yet the genetic makeup of an individual was known long ago not to be the full story.   Paleo should never have gotten off the ground.


Look up the effects of epigenetics on nutrition and you will likely find studies about the damage done by a high fat diet, the sort of diet Mark Sisson says is healthy.  Not only does a high-fat diet induce epigenetic havoc in the individual who consumes it...


And not only does it affect the offspring of mothers who eat it...


It can affect offspring through a third generation.


Even fathers can pass the effects of their bad diets along to offspring.  Would an heir to this sort of nutritional legacy be better off eating some imagined historic fatty diet built into his genome, just because that's what a fad diet promoter says?  Or should such a person eat a diet that is best for improving their health given their natural tendencies?


The idea of a hunter gatherer genome is wrong in another big way.  Long before we were hunter gatherers, we were and are primates.  This matters.  I'll show you why in the next video.

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