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What Accounts for Variations in Height?

Genetics account for only about 10% in variation in height. So what accounts for the other 90%?

It’s nice to be tall. Tall people are more likely to get hired, get promoted and are paid better than their shorter counterparts. They can reach things from high shelves, have unobstructed views at parades, and are consistently rated as being more attractive than others. Overall seems like a sweet deal.

If you are short, you get depressed when some points out that a study in the New England Journal of Medicine suggested that shorter people are at higher risk for heart disease. However, you might find some solace from a study published in PLOS one that found that shorter people lived longer or another study that suggested that taller people are at increased risk for cancer. When it comes to whether it is better to be tall or short, there is a lot of medical research on the subject, and one half contradicts the other half.

These studies get a lot of media play because they are instinctively popular. We are obsessed with height as a society. After all, we invented high-heeled shoes to defy genetics and punish our ankles.

But every time a report claims that taller is better (or that shorter is better), headline writers seem to consistently forget that six months ago they were claiming the opposite.

It’s worth noting that the cardiovascular study in the New England Journal of Medicine didn’t actually measure people’s height. It tested them for 180 genetic markers and combined them into a gene score. But these 180 genetic markers only account for about 10% in variation in height.

So what accounts for the other 90%?

Well, you’ve probably noticed that you’re taller than your parents and you’re almost certainly taller than your grandparents. Go back a few hundred years and you’ll find that humans were downright diminutive by today’s standards. That has nothing to do with genetics.

What most people don’t realize is that most aspects of health and medicine are not strictly genetic or environmental, but are really the result of a complex interplay between the two. In generations past, widespread malnutrition lead to stunted growth. With the triumph of agriculture in the 20th century, food shortages (at least for middle income families in North America) are a thing of the past. It was access to adequate nutrition that unlocked the genetic potential for taller stature.

That’s not to say genetics don’t matter, but they are not the most important factors when it comes to predicting heart disease risk. It turns out that most cardiovascular disease can be explained by four simple lifestyle factors. If you don’t smoke, eat a healthy diet, maintain a normal body weight, and exercise regularly you can reduce 80% of your cardiovascular risk. Factor in blood pressure, diabetes, cholesterol, and alcohol consumption and you account for much of the rest.

So how do we place this NEJM paper in that all too critical context? There may be a genetic advantage to being taller (if you’re willing to disregard the many other studies that say the opposite), but the relative contribution of your genes is fairly minimal. One researcher summed it up nicely for the BBC, “If you’re 6ft 1in, you still need to stop smoking.”

It turns out, your risk of heart disease and death is not locked in your genes. Most of it is a consequence of our bad lifestyle choices and is something we have the power to change. It’s worth remembering what Zeus says at the beginning of Homer’s Odyssey, “See now, how men lay blame upon us gods for what is after all nothing but their own folly…”


@DrLabos

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