Jiroemon Kimura, the oldest man ever (Image: YouTube/Screenshot)

Professor S. Jay Olshansky once told Gizmodo, “In the world of aging sciences, if you want to live a long life, choose long-lived parents.” So genetic markers linked to longevity are interesting as hell. But if you’ve got the wrong genes, then the wrong moves might do you in.

A team of researchers from universities in the United States wanted to figure out the role of genetics in human lifespan, specifically relating to growth hormone. The researchers’ work shows two main things: first, that a mutation in men’s DNA relating to growth hormone might lead to a longer lifespan. And secondly, that treating older people with growth hormone might be dangerous if they don’t have the variation.

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Gil Atzmon, the study’s principal investigator from Albert Einstein College of Medicine and the University of Haifa in Israel, was most excited by how a slight change in DNA could have such a big impact. Delete a few base pairs, “and you still have a functional protein that now makes people live longer,” he said. “I think this is phenomenal.”

This is complex, so I’m going to take it slow and possibly oversimplify things. Basically, there’s one system in question, the “IGF-1/GH axis.” Each of these are genes that code for different molecules in your body.

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Researchers have already had a hunch that IGF-1 can regulate height at the expense of longevity, like the case in dogs. More IGF-1 means taller but shorter lifespan and less IGF-1 means shorter but longer lifespan. This should make sense—it’s akin to the way big dogs live shorter lives than small dogs.

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The researchers studied 800 men and women from across four populations and found something surprising. Indeed, the IGF-1 levels were lower in the centenarians, but many of the men were also taller. The data showed the researchers that there’s more than just IGF-1 at play.

Centenarian males were often missing a specific snippet of DNA in their GHR gene. These people seem to be more sensitive to growth hormone and grow taller. So, even though their IGF-1 levels were lower (they lived longer), they still grew taller from their special GH gene. The people with this mutation seemed to live ten years longer, on average.

And the study really was huge. The replication across the four different populations “makes our result more accurate and globally translated.”

Atzmon himself admitted that all this is pretty complex. But it’s definitely new, important evidence pointing to the role that this IGF-1/GH axis plays in simultaneously determining your height and your lifespan, explained Andrzej Bartke, Professor of Physiology and Internal Medicine at Southern Illinois University School of Medicine, in a conversation with Gizmodo.

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But we’re not at some level of life-hacking clarity. “Clearly more research is needed to understand exactly why this type of GH receptor favors extreme longevity, why the effect was seen only in men and why the results in people studied by these investigators differ from some of the previous findings in different groups of human subjects with the same type of receptors,” said Bartke.

There’s a catch to all this. Their results seemed to show that folks who don’t have the GH variation might actually be sensitive to growth hormone therapy. “This is a stark reminder that administering growth hormone as an intervention to slow aging—which is still being done in the anti-aging medicine industry — is not warranted by the scientific literature,” Olshansky told Gizmodo. “In fact, could actually be harmful.”

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So, you’re still going to die one day. But as to when, that answer probably doesn’t reside in what you eat (or in young blood) nearly as much as it does in what your DNA looks like.