Doomed by Your Genes?

One of the most inspiring collaborations in the history of medicine was the Human Genome Project. Taking place from 1998 to 2003, it was an enormous international effort to create a map of all the genes in human DNA. With this map in hand, we would surely be able to navigate our way through all the protein and enzymatic pathways that make a human tick. The fervent hope was that by matching up ailments with genetic variations, we would soon discover the root of all diseases.

It was not to be. Although a few genes were found to be associated with disease, the connection was rarely clean. Finding a one-to-one link between genes and disease was the exception, not the rule. Since then, we’ve discovered that the wealth of microbial species in our gut contain a hundred times more genes than our own surprisingly paltry DNA. Genetically, we are mostly microbe! The Human Genome Project, by missing our microbiota, captured only a tiny sliver of our total genetic toolkit.

Tiny microbes turn out to play an outsized role in our health. Friendly microbes provide us with protection against the other far nastier microbes blanketing the planet. They even help us digest our food and provide us with nutrients that feed and heal the cells lining our guts. If you take care of them, they will reward you with a long healthy life. If you don’t, all hell can break loose.

A poorly balanced microbiota is called dysbiotic. Instead of a bustling cosmopolitan bacterial society, a dysbiotic gut is more like an autocracy where a handful of species take over with few counterbalancing microbes. Without pushback from a diverse microbiota, even mild-seeming commensals can become marauding pathogens. When that happens, the mucus layer in the gut starts to get eaten away, and the gut lining can become porous, letting bacteria enter the bloodstream where they get pumped to every organ in the body. That bodily infection leads to an immune response that, over time, can develop into chronic systemic inflammation.

The collateral damage from inflammation is astonishing. It is a scorched earth campaign that can save you – or kill you trying. Inflammation is at the root of almost all chronic diseases, from Alzheimer’s and Parkinson’s to diabetes, heart disease, obesity, autoimmunity, allergies and pretty much all the scourges of mankind. Most of our problems – as well as the probable solutions – come from our microbiota, not our genes. Our lives are at the mercy of our bacterial overlords. We can only fight them for about 100 years before they take us back.

An interesting question is: do our genes affect our microbiota? Is there a human trait that could make you the perfect bacterial host, or is it all the luck of the draw, the microbes you happen to bump in to as you move through life? Recent research from Eran Segal of the Weizmann Institute in Israel has given us the answer to this nature vs. nurture question. It turns out that our human genes account for a puny 2% of our microbial composition.

It’s a little humbling to know our contribution is so meager, but it’s actually a boon. We can’t control our genome – it’s the parental gift we can’t return – but we can control our diet.

Here’s the takeaway: A poor diet leads to an unbalanced, dysbiotic microbiota that can lead to systemic inflammation – the root of most chronic diseases. That’s the bad news. The good news is that we hold the reins. A proper diet rebalances the microbiota, which can protect you from chronic illness. Our genes may not hold much sway over disease, but our will-power definitely does. No more excuses, no more blaming your parents. This one is up to you.

 

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