Back to our regularly scheduled program. We left off at a bit of a cliffhanger last time. And as with any cliffhanger, we need to follow with a recap. Here’s what we’ve done so far…
…We noticed that smoking, which is the number one predictor of heart disease, causes a microbial shift. Not only that, but a specific one.
…We noticed that plant fiber consumption, or the lack of it, causes a shift as well. The same one we see in smoking.
…And we realized that both plant fiber consumption and smoking are both considered to be not only related to overall health, but they are also both correlated to heart disease. Which is just a little too convenient.
…Along the way, we noticed that transplanting the microbiota from healthy people to people with metabolic syndrome restored insulin sensitivity. And it was due to the same microbial shift that we see in plants & smoking. And we also noticed that smoking seems to be related to some other conditions that have a strong microbial connection. And that smoking introduces pathogenic, gram-negative bacteria directly into smokers. And that nicotine probably doesn’t explain any of this. That was all very interesting.
Finally, we presented a pretty solid base of research on the microbiome/brain connection. And we surmised that, since we established a pretty good microbiome/heart disease link, then if there were some kind of brain factor closely correlated to heart disease, it too would be under suspicion of having a microbial link. Turns out: low IQ is the second strongest predictor of heart disease. And then, lo and behold, we were handed a hot-off-the-presses rodent study showing that the feeding of prebiotic, fermentable fiber leads to changes in the brain.
OK. That should catch us up. Now where were we? Oh right: IQ. Could microbiota, and its primary modulator (fiber), really have an impact on IQ?
I think I know what most people were thinking last time: “Yeah, ok. Cute. But let’s be honest: dumb people do dumb things. If you have a low IQ, you’re probably less cognizant of the fact that cigarettes, ho ho’s, big macs, and spending all day on the recliner are slowly going to kill you.”
That’s certainly one explanation. And it’s an intuitive one. It’s the explanation that is widely cited in most of the reports by the epidemiologists themselves. But it’s not the only one. In fact, it didn’t even seem to be the most emphasized one by the epidemiologists in these reports. Here’s the explanation that got the most attention. I’ll quote from the NYT report:
“I.Q. is a marker of lifetime insults, physiological insults. We know kids with poor diets, kids who have repeated infections, have a lower I.Q., so it could be an I.Q. is capturing something about lifelong misery.”
“It may also be that a high I.Q. is associated with better overall neurological and physiological “wiring,’’ meaning all the body systems, from brain to heart to liver to kidneys, function at a more efficient level.”
So, we now have the two possible explanations of the IQ/Heart disease correlation, from the researchers themselves.
The Bad Behavior theory: Heart disease and low IQ track closely together because low IQ can cause heart disease. People with low IQs are more likely to engage in unhealthy behaviors because they don’t know that they’re hurting themselves when they smoke, consume an unhealthy diet, don’t exercise, etc.
The Bad Wiring theory: Heart disease and IQ track closely together because a low IQ is caused by all of the same things that cause heart disease — a series of physiological insults from the environment, poor diet, toxins, infections, etc.
There isn’t much to say of the Bad Behavior theory, other than that it is plausible, but by no means a sure thing. If you ask me, there is a whiff of condescension and misunderstanding about health-based decision making. To quote again from the NYT article:
It may be that people with low I.Q. have a more difficult time understanding complex health messages and don’t fully understand the long-term health effects of an unhealthy lifestyle.
But are these messages so complex? The idea that you should not eat unhealthy food? Sit on the couch all day? Smoke cigarettes? Or are these decisions more about basic willpower? Don’t we all know smart people who engage in these types of behaviors? Is understanding how or why they are “bad” even relevant? After all, even most children understand the basic “badness” of these types of things by a certain age, and they know you should avoid them without knowing the why or the how. And yet we’re to believe that adults could have a difficult time making the same basic connection? I’m willing to bet the average person, of average intelligence, doesn’t truly understand the why’s and how’s of unhealthy behaviors. We just know you aren’t supposed engage in them or our health will suffer. And yet many of us continue to do so — not because we lack basic intelligence, but because these activities challenge a fundamental part of human nature.
So color me skeptical. But alas, it isn’t something we can outright disprove. We’ll have to let this stand as one plausible explanation. For now.
Which brings us to the Bad Wiring theory. The idea that IQ is a reflection of overall “wiring” — that all the different physiological assaults that lead to heart disease can also, separately, lead to worse cognitive performance — is an intriguing but not so controversial idea. I think most people wouldn’t be too surprised to hear that an accumulation of negative health factors throughout life will lead to a deterioration in overall functioning, and that brain functioning would be a reflection of that deterioration.
But when viewed within the context of our investigation here — that heart disease may have microbial origins — then things become much more interesting.
You see, if heart disease has a microbial origin, then all of the “physiological assaults” that contribute to it — smoking, diet, infections, toxins, etc. — must share some sort of microbial mechanism themselves. In fact, we’ve shown here how smoking and diet (fiber, specifically) do so.
But if those same set of physiological assaults also contribute to worsened cognitive performance, then isn’t it reasonable to conclude that the same microbial mechanism is at play in that effect? What are the chances that they would all share a completely different mechanism?
In other words, with the Bad Wiring theory, the epidemiologists have essentially made the case for us.
So that’s where we find ourselves now — still two possibilities. If IQ is simply a predictor of unhealthy behavior, then that’s that. Our investigation has hit a dead end. Fun while it lasted.
Or….it could be the other thing.
So, what now? Do we just all place some bets and wait a couple of decades to see how it all shakes out? Not quite.
First, it turns out that IQ can do a lot more than predict just cardiovascular-related death. It can predict all death. That would suggest that something other than the inability to make good, “healthy” decisions is at work in the IQ connection. But it gets better.
In 2005, researchers set out to see if reaction time had the same predictive association with mortality. Reaction time can be understood as a cognitive subset of IQ. Reaction time is inversely correlated with cognitive ability. People with higher cognitive ability have shorter and less variable reaction times.
And here’s what the researchers found: reaction time did have the same correlation, and not only that, but when reaction time was factored out, the IQ correlation no longer held up.
Then, in a study by the same researchers who discovered that IQ was the second strongest predictor of heart disease, it was found that reaction time was, in fact, the critical element — reaction time was found to be the second strongest predictor in heart disease.
And finally, in a study published just a few weeks ago, those same researchers, wanting to eliminate confounding variables that can be involved in tests of intelligence (knowledge, education, culture), sought to replicate the effect using an even simpler reaction time test designed to be a raw measure of neuropsychological functioning — of one’s “wiring,” if you will. The effect, again, was replicated.
In other words, the IQ correlation is really a reaction time correlation.
With all this in hand, let’s now ask ourselves the million dollar question: what does reaction time have to do with understanding “complex” messages about health and avoiding behaviors that would lead to heart disease? NOTHING. That’s what.
And what would something like the speed with which your brain can react to something indicate about, say, your overall…”wiring”? Oh, maybe everything?
Bad Wiring: We have a winner.
OK. This is all a little too heavy for me. Someone get me a stiff drink. FOS, Psyllium, and Raw Potato Starch. On the rocks.