Your Gut Runs 70% of Your Immune System. Here’s What’s Steering It.

Two people can eat the exact same lunch and one of them feels completely fine while the other is bloated for the rest of the afternoon. It’s easy to blame the food. But your gut isn’t just a tube that processes whatever goes in — it’s a genetically wired system that decides how much stomach acid you make, how your gut lining holds up under stress, and how your body reacts to specific compounds like gluten and histamine.

That’s a bigger deal than it sounds like, too. Your gut makes up roughly 70% of your immune system and has a direct line to your brain. When it’s off, the ripple effects go well beyond digestion.

The Report Decoder series

This is one in a series where we take the massive, genuinely complicated health reports that services like SelfDecode generate from a DNA sample, and translate them into something you can actually read in five minutes. No spreadsheets of gene variants, no clinical percentiles — just what the report is actually telling you, and why it matters. Explore the rest of the series here.

Today’s topic: the Gut Health, Digestion & IBS report, which looks at your genetic predisposition across bowel health, stomach acid production, gut infections, gut inflammation, food intolerance, and the makeup of your gut microbiome.

The part that surprised us: some gut conditions are more genetic than you’d think

Digestive issues get written off as “just diet” more than almost anything else. The genetics tell a different story for several of the most common conditions — the heritability numbers are surprisingly high.

Worth noting: IBD itself is still rare — only about 3 in 1,000 people worldwide have it — so even a high genetic tendency toward it doesn’t mean it’s likely to happen. The heritability number describes how much genetics explains the *differences between people*, not your personal odds of developing the condition.

How the report actually sorts your results

Instead of drowning you in raw data, a report like this sorts each trait or condition into one of three lanes based on your genetic tendency relative to most people:

• More likely — your genetics lean toward a higher tendency for this
• Typical — your genetics land in the ordinary range
• Less likely — your genetics lean toward a lower tendency

It covers a wide range: bowel conditions like IBS, bloating, and hemorrhoids; stomach issues like acid reflux and peptic ulcers; susceptibility to specific gut infections; inflammatory conditions like Crohn’s disease and gastritis; food intolerances like gluten and alcohol sensitivity; and the diversity of your gut microbiome itself.

The detail everyone should know before reading any genetic report

Here’s the part that doesn’t get said often enough: a “More Likely” result does not mean you’re headed for a diagnosis.

Even someone with a meaningfully elevated genetic tendency toward a rare condition is still, in absolute terms, unlikely to develop it — because the condition itself is rare across the whole population to begin with. A shift from “typical” to “elevated” on a rare condition can still land you at very low overall odds.

Where results like this tend to be more genuinely useful is the reverse case: if you’ve already been dealing with unexplained bloating, discomfort, or a food that never seems to sit right, seeing a “More Likely” tag next to a matching trait — higher gluten sensitivity, for instance, or a genetic lean toward lower gut microbiome diversity — can be a real clue about where to start, rather than eliminating entire food groups on a guess.

What a personalized version looks like

Everything above is the general picture. A personalized Gut Health, Digestion & IBS report swaps out the general statistics for your actual results — pulled from your own DNA — across 65 individual markers, grouped into 7 categories: Bowel Health, Stomach Health & Acid Production, Gut Infections, Gut Inflammation, Food Intolerance, Gut Microbiome, and Gut Health Genes, covering genes like FUT2, MUC1, and NOD2.

It also comes with a prioritized list of 50 diet, supplement, and lifestyle recommendations, ranked by how much evidence supports them and how relevant they are to your specific results — rather than a generic “eat more probiotics” list that ignores your biology entirely.