Epigenetics is one of those buzzwords that you might not have heard before, and if you have, chances are that it was in the context of a snake oil pitch for how you can miraculously control your body's genes. It's not a brand new science, but it's one whose popularity and interest level has exploded over the past decade and a half or so. When a relatively new science bursts onto the public scene like this, it's often because it comes with the promise for incredible new cures or powers. And that's just what we see with epigenetics: bold claims that you can change your behavior a bit, and tweak your body's genes to be just the way you want them; and then, you can even pass these traits along to your children. Sound too good to be true? Well if it didn't, it wouldn't be on Skeptoid.
Normally we'd start off an episode like this with a basic, layman's definition of epigenetics, but even searching for this is where you hit the first stumbling block. Even geneticists don't agree on any given definition. Some talk about whether a trait is passed on from a parent to an offspring; others focus on whether a trait is expressed or not in a given individual. Even the most fundamental definition requires a bit of background knowledge: it's a change in phenotype without a change in genotype. We discussed these terms in episode #546 about the genetics of race. Your genotype is your genetic fingerprint, the actual data encoded in your genes; while your phenotype is the broader picture that includes all your observable traits, not just those that come from your genes but also those that come from your environmental influences. Think of identical twins that were raised separately in the most different possible environments: one is fat, one is skinny; one is strong, one is weak; one is smart, one is dumb; two identical genotypes, but displaying phenotypes that are barely recognizable. Epigenetics is the science of how outside influences can actually change which genes are expressed and which are repressed, and then possibly even passing these new phenotypical expressions on to offspring. Might the respective children of these twins display some of these non-genetic traits?
Think about that oversimplified question for a moment, and it becomes easy to see how epigenetics could easily be oversold and used to sell miracle cures. The suggestion that behavior can control gene expression might seem to mean that we can do something simple like change our diet, and overcome genetic tendencies toward disease. Or maybe we can live longer if we eat some supplement that activates a longevity gene or represses an aging gene. It's this kind of promise that makes epigenetics a magnet for snake oil authors and pitchmen.
In fact, epigenetics is not only incredibly complicated, there's very little about it that's concrete or proven. To understand why, let's have a quick look at how it works. As you may know, DNA consists of incredibly long strands of the four bases we call G, C, T, and A. Specific sequences of these bases are genes; a gene can consist of just a few, or a huge number. These genes are all strung out along our DNA. Now, messenger RNA (mRNA) is able to fit and connect to your DNA based on these genes, and where it is and isn't able to connect tells your body what to do. Tells it to produce blue eyes, grow red hair, whatever is in your genes.
Correction: More knowledgeable sources than me have pointed out that mRNA is synthesized in place along the DNA, lest the above be misconstrued to mean that it's flying around looking for a place to land. –BD
Now here is where epigenetics comes into the picture. epi-, meaning above, refers to factors that can enhance or inhibit the availability of certain genes. Two of the most commonly discussed factors are methylation and histones (although there are others we know about, and probably more still that we don't). Methylation is when a methyl molecule decides to bind to a gene, thus putting itself in the way, and making it either easier or harder for the mRNA to access. Histones are little chunks of protein that DNA likes to wind around, and when a gene is tucked away inside these windings, it can't be accessed either. Such factors as this can differ even among identical twins, and even from cell to cell in the same person. Thus, an identical genetic code can produce a person (or any other organism) that expresses different genetic traits.
Fueling the fire of epigenetics woo is the fact that these epigenetic factors can be influenced in any number of ways over our lifetimes and by environmental pressures. Age is among the most powerful influencers, as our epigenetic factors do change over time. Exposure to certain drugs, diseases, and environmental chemicals can change them as well. There is some evidence that diet and sleep patterns and where we live can influence the factors. Even things like abuse suffered in early life appears to be able to influence epigenetic factors.
Now, none of this so far is all that new. We've known about the expression and repression of genes for a long time, but it's really only been since around the year 2000 that a lot of attention has been paid to the changes that these factors can produce. As the science of epigenetics has risen from obscurity to a rapidly growing field of research, so has — unfortunately — the practice of hawking magical cures that leverage popular headlines claiming that behavior can result in predictable (and desirable) genetic traits.
Let's have a look at some examples. Here is a snip from the publisher's description of the 2014 book Epigenetics: The Death of the Genetic Theory of Disease Transmission:
New Age spiritualist Deepak Chopra writes:
The 2017 book Younger: A Breakthrough Program to Reset Your Genes, Reverse Aging, and Turn Back the Clock 10 Years promises an even simpler and more magically easy solution to a complicated problem:
...as easy as that. What do you want to change in your body? Epigenetics makes it possible to change your diet or make some other lifestyle change — practice yoga or meditate or avoid gluten or whatever — and you can make fundamental genetic changes to your body. Turn off those fat genes, reverse aging, blast your muscles, eliminate baldness — just about any change you can think of, someone somewhere is selling the snake-oil idea that epigenetics gives you miraculous control over your own body.
All such claims are nonsense. All such claims are nonsense. All such claims are nonsense.
By no means is it even remotely clear that there are any behavioral changes that will produce a predictable epigenetic effect in everyone. No evidence is consistent with such a conclusion. We don't even have good evidence that one day we will find such cause-and-effect relationships.
To understand this better, we can look at the evidence that some epigenetic effects appear to be heritable. The way this is presented in the snake-oil books is that if I eat a lot of kale, it will turn off my cancer genes, and I won't get cancer — but moreover, the heritability of epigenetic effects means that my children will also have those same factors that repress their cancer genes — the inheritance of a non-genetic trait. Sounds amazing, and it's no surprise that it sells books. It also bears almost no resemblance at all to anything that's actually true about epigenetic inheritance.
Outrageous claims about this even come from academia. In a 2017 article in Gizmodo, a professor of biology made this assertion:
What he was referring to was a widely promoted study published in 2015 claiming that a higher risk of developing PTSD, depression, and anxiety was inherited by the children of Holocaust sufferers who experienced those conditions, and the reason they concluded was epigenetic inheritance. Immediately, the study was comprehensively debunked from all sides. The sample size studied was uselessly small, and it failed to control for other social factors that might have been conducive to stress, such as your parents having been in the Holocaust. But, like most headline-grabbing studies, it was the original flawed research that entered the public awareness, and not the subsequent finding that it was wrong.
Some researchers believe that the causal relationship actually goes in the other direction: that it is your genes that govern the epigenetic factors. Thus it is expected that certain epigenetic effects would be inherited: let's say my genes make me really stressed when I'm a child, the stress triggers some epigenetic repression or expression of some other trait, and that trait also appears in my offspring. It's not the epigenetic effects that are ultimately responsible for that heritability, but my actual genome itself, which is passed on to my offspring, thus triggering a similar history of epigenetic effects in them. True? We don't know. What we do know is that everything is actually ferociously more complicated than my podcast-friendly, oversimplified examples.
When we move from humans to other organisms such as plants, we do find a much stronger body of evidence that acquired epigenetic changes — meaning something that happened to one plant and not to others, changing its gene expression — gets passed along to that plant's offspring, even though they were never exposed to whatever environmental pressure caused the change in its parent.
But let us repeat: this stuff is really complicated. Here is what an actual example of epigenetic inheritance reads like, this one from a 2007 article in the Annals of Botany:
Unfortunately for the authors trying to sell miracle-cure books, examples of real-world epigenetics do not read like "do yoga and your kids will be smarter". In fact there is not a single such statement — tying a specific change in our behavior to a specific desirable physical outcome — that is true. It is purely a matter of opportunistic authors grasping at a sciencey-sounding concept that's in the news, and leveraging it to separate you from your money. Epigenetics is indeed one of those rare fields of study that truly does incite genuine excitement in those who study it, but it is absolutely not — yet, anyway — anything that you should be looking at to miraculously solve a complicated problem.
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