By Brigitte Spurgeon | Board-Certified Functional Genomics Practitioner | Doctor of Orthomolecular Nutrigenomics

What your DNA is trying to tell you about your digestive health and gut health SNPs

You’ve cleaned up your diet. You’ve cut out gluten, dairy, maybe even coffee. The probiotics, the digestive enzymes, the elimination protocols. You’ve tried them all. And yet your gut still isn’t cooperating. The answer may lie in your gut health SNPs. The bloating returns, the brain fog lingers, the inflammation quietly persists.

I’m about to share a truth you can anchor to: your unresolved symptoms don’t mean your body is broken or that you have failed. Your body is speaking to you. And that in itself is reason for hope.

In my clinical experience, the women who struggle most with stubborn gut symptoms are often doing many things right. What’s missing isn’t effort. It’s the layer of information that explains why their body responds differently than someone else’s doing the exact same protocol. That layer is your genetics.

Your microbiome isn’t just shaped by what you eat. It’s shaped by what your genes allow your body to do with what you eat. And until we understand that, we’re guessing.

THE MISSING PIECE IN MOST GUT PROTOCOLS

Most gut health approaches treat the microbiome as though every body starts from the same place. Take a probiotic. Add fermented foods. Eat more fiber. These are reasonable starting points, but they don’t account for your genetics. You may carry single nucleotide polymorphisms, or SNPs (pronounced “snips”), that fundamentally alter how your body processes histamine, absorbs B vitamins, clears toxins, or feeds your beneficial bacteria.

A SNP is a variation in a single position in your DNA sequence. These variations are incredibly common. We all carry them. But certain combinations can quietly undermine gut healing at the cellular level. They don’t cause disease on their own. What they do is create vulnerabilities that, in the right conditions, become the root cause of the symptoms you can’t explain.

Here are six of the most clinically relevant gut health SNPs I assess, and what they mean for your healing process.

FUT2: ARE YOUR GUT BACTERIA GETTING FED?

FUT2 is one of the first SNPs I look at when a client tells me her probiotics “don’t seem to do anything.” This gene controls your secretor status: whether or not your gut lining produces the compounds that your beneficial bacteria, particularly Bifidobacterium, need to survive and thrive.

Roughly 20% of people are non-secretors, meaning they carry two non-functional copies of the FUT2 gene. In these women, the gut mucosa is less fucosylated. In plain terms, the environment that Bifidobacterium depends on simply isn’t there. You can take the most excellent probiotic on the market, and if FUT2 variants mean your gut can’t support colonization, the benefit will be minimal.

What this looks like clinically: poor Bifidobacterium colonization, reduced microbial diversity, a higher susceptibility to gut infections, and difficulty sustaining improvements from probiotic supplementation.

What actually helps: strain-specific probiotics chosen for non-secretors, prebiotic fibers that feed the strains most compatible with your terrain (resistant starch and inulin are particularly valuable here), and understanding that your microbial rebuilding phase needs more time and more targeted support than a general protocol would suggest.

There’s one more piece of the FUT2 picture that most practitioners miss entirely, and it matters deeply for the women I work with. FUT2 non-secretors have a well-documented association with impaired B12 absorption. The mechanism is direct: FUT2 influences the fucosylated glycans on the gut mucosa that are involved in binding and absorbing the intrinsic factor-B12 complex in the ileum. When that mucosal environment is compromised, B12 uptake at the intestinal level is reduced. This happens even when diet is adequate and intrinsic factor is functioning normally. This means a non-secretor can be eating plenty of B12-rich foods, taking an oral supplement, and still running low.

I see this pattern regularly in my perimenopausal clients who present with fatigue, brain fog, low mood, and cognitive sluggishness. These symptoms are easily attributed to hormonal changes. The real driver may be chronically suboptimal B12 that standard oral supplementation can’t fully correct. For these women, sublingual B12 is my preferred recommendation. It bypasses the ileal absorption mechanism altogether, absorbing directly through the oral mucosa and delivering reliably regardless of what FUT2 is or isn’t doing in the gut.

PEMT: THE FAT METABOLISM GENE THAT AFFECTS MORE THAN YOUR WAISTLINE

If you’ve been eating well, exercising consistently, and still struggling to shift body fat, PEMT may be part of your answer. This is one of the patterns I see most often in my perimenopausal clients, and it’s one of the least talked about in gut health conversations.

PEMT stands for phosphatidylethanolamine N-methyltransferase. It’s the gene responsible for your body’s ability to produce phosphatidylcholine (PC) internally. Phosphatidylcholine is not a supplement term worth skipping over. It’s a structural fat found in every cell membrane in your body. It also makes up a primary component of the mucus layer that lines and protects your gut wall. Bile production depends on it too. Bile is how your body emulsifies and absorbs dietary fats, fat-soluble vitamins, and hormones.

Here’s what makes PEMT particularly relevant for women in their 40s and 50s: estrogen upregulates PEMT expression. While estrogen levels are healthy, many women with PEMT variants compensate without knowing it. As estrogen declines through perimenopause, that compensation disappears. PEMT activity drops and phosphatidylcholine production falls. Suddenly a woman who managed fine for decades begins struggling with fat metabolism, sluggish bile flow, and a gut lining that’s losing structural integrity.

What this looks like clinically:

– Difficulty losing body fat despite doing the right things

– Bloating or discomfort after fatty meals

– Poor absorption of fat-soluble vitamins like A, D, E, and K

– A gut lining that’s more reactive and harder to repair than it should be

What actually helps: I address PEMT more simply than most protocols suggest. Eggs are my first recommendation. Egg yolks are one of the richest dietary sources of choline and phosphatidylcholine, and for women with PEMT variants, making eggs a daily staple is genuinely therapeutic. If you’ve been avoiding egg yolks out of outdated cholesterol concerns, this is your clinical permission to bring them back.

Beyond food, I supplement with phosphatidylcholine directly or with sunflower lecithin, which is a well-tolerated and effective PC source. The other nutrients commonly associated with this pathway are usually addressed through other SNPs in a comprehensive protocol, so there’s no need to overcomplicate it. Food first. Targeted supplementation second. That’s the PEMT approach that works in my clinic.

DAO AND HNMT: WHEN FERMENTED FOODS MAKE YOU FEEL WORSE

This is one of the most common clinical puzzles I encounter. A woman starts doing everything she’s been told is good for her gut: sauerkraut, kimchi, kefir, kombucha. Instead of feeling better, she feels worse. More anxious. More inflamed. Headaches. Heart palpitations. Flushing. Insomnia.

The instinct is to blame the food. The real answer is usually her histamine pathway genes: DAO and HNMT.

Histamine is a compound found naturally in fermented and aged foods, and it’s also produced by your own immune cells. Your body manages histamine through two main enzymes: DAO (diamine oxidase), which breaks down histamine from food in the gut, and HNMT (histamine N-methyltransferase), which clears histamine from your body’s tissues and brain. When either of these enzymes is genetically impaired, histamine accumulates, and the symptoms that follow look a lot like what my clients often mistake for hormone imbalance, anxiety, or autoimmune flares.

The SNPs in the AOC1 gene (which encodes the DAO enzyme) reduce enzyme activity, meaning histamine from food isn’t broken down efficiently in the gut. The HNMT Thr105Ile variant produces a less stable enzyme that degrades more quickly in cells, leaving histamine to accumulate in tissues, including the brain.

What this looks like clinically:

– Reactions to fermented foods, wine, aged cheese, and leftovers

– Histamine-driven anxiety and insomnia

– Skin flushing and gut motility issues

– Symptoms that look hormonal but don’t resolve with hormonal interventions

What actually helps: a low-histamine approach during the microbiome rebuilding phase, DAO enzyme support before meals, and methylation support: specifically B6 (as P5P), copper, and vitamin C, which are the cofactors DAO depends on to function. The fermented foods can come later, once the enzyme pathways are better supported.

MTHFR: THE METHYLATION GENE THAT TOUCHES EVERYTHING

If there’s one SNP my clients have heard of, it’s MTHFR. And while it has become something of a buzzword in integrative health circles, the clinical reality is more nuanced and more significant than most people realize.

MTHFR, methylenetetrahydrofolate reductase, is the gene that controls a critical step in your methylation cycle. Methylation is a biochemical process that happens over a billion times per second in your body. It’s involved in detoxification, DNA repair, neurotransmitter production, hormone regulation, and immune function. When MTHFR variants impair this process, the effects ripple through every system, including the gut.

In the context of gut health, here’s what matters: the MTHFR C677T and A1298C variants reduce the body’s ability to convert folate into its active form, methylfolate. This impairs the production of SAMe (S-adenosylmethionine), the body’s primary methyl donor. HNMT, the histamine-clearing enzyme we just discussed, depends on SAMe to function. So MTHFR variants can compound histamine issues and impair the gut lining’s ability to repair itself. They also significantly reduce detoxification capacity.

In my clinical work, I pay close attention to MTHFR status before any pathogen-clearing protocol. Women with compound heterozygous MTHFR variants often experience more intense detox reactions. Not because the protocol is wrong, but because their Phase 1 and Phase 2 liver detoxification pathways are under-resourced. Before we clear candida, heavy metals, or parasites, we make sure methylation is supported.

What actually helps: active, bioavailable forms of folate and B12 (not folic acid, not cyanocobalamin), alongside B6 as P5P, magnesium, and riboflavin. I want to be specific here: the right form of folate and B12 for you depends on your full SNP picture, not just MTHFR in isolation. Compound heterozygous patterns are worth understanding in full. A slow COMT alongside MTHFR, in particular, can mean that pushing methylation too hard creates its own set of problems: anxiety, irritability, sleep disruption. This is precisely why I don’t recommend a blanket supplement protocol for MTHFR. The support needs to match your specific variant combination, and that requires looking at the full map, not a single gene.

TNF-ALPHA AND IL-6: YOUR INFLAMMATORY THERMOSTAT

Some women have guts that inflame easily and calm down slowly. Others move through gut healing protocols with minimal reaction. A significant part of that difference comes down to cytokine gene variants, specifically TNF-alpha and IL-6. These two genes regulate how aggressively your immune system mounts an inflammatory response.

TNF-alpha (tumor necrosis factor alpha) and IL-6 (interleukin-6) are inflammatory signaling molecules. Certain SNPs in these genes create a tendency toward heightened immune activation, meaning the same gut insult that causes mild bloating in one woman can trigger significant systemic inflammation in another. In the context of gut healing, this matters enormously for two phases of your protocol:

– The initial gut barrier restoration phase, where inflammation needs to be reduced before rebuilding can begin

– The pathogen-clearing phase, where die-off reactions can be more severe and prolonged

What this looks like clinically:

– Heightened reactivity to foods, supplements, and protocols

– A gut that seems to stay inflamed even when dietary triggers are removed

– Difficulty tolerating the pathogen-clearing phase without significant fatigue or immune symptoms

What actually helps: curcumin, omega-3 fatty acids, and quercetin are among the most clinically meaningful anti-inflammatory supports for these variants. But the sequence matters. Inflammation has to come down before you can effectively rebuild or clear. This is one of the reasons I don’t rush clients through the early phases of a gut protocol, no matter how eager they are to get to the “detox” stage.

WHAT THIS MEANS FOR YOUR GUT HEALING JOURNEY

Here’s what I want you to take from this: your gut symptoms are not random, and they are not your fault. They are the downstream expression of genetic patterns working in the background your entire life. Stress, environmental exposures, hormonal shifts, and the cumulative burden that lands so heavily on women in their 40s and beyond all amplify those patterns.

The reason gut protocols fail so often is not that the protocols are wrong. It’s that they’re not built around the person following them. Two women can do everything identically and have completely different outcomes, because their FUT2 status is different, their DAO activity is different, their methylation capacity is different. The protocol that heals one woman can make another one worse.

This is why understanding your gut health SNPs is central to how I practice nutrigenomics. Not as an add-on to gut health. As the foundation of it. When I know your SNP profile, I can sequence your protocol correctly, choose the right strains and supplements for your specific terrain, modify the phases that need more support, and anticipate where your body will push back.

Your DNA is not your destiny. But it is your map. And working without it is like trying to navigate a new city without knowing which roads are closed.

If you’re ready to stop guessing and start working with the biology that is actually yours, a Nutrigenomics Report is where we begin. This is the work I do with my 1-on-1 clients. I run a thorough analysis of the SNPs most relevant to your symptoms, then translate that into a protocol that fits how your body actually works.

You can learn more and book a discovery call at brigittespurgeon.com.

*Brigitte Spurgeon, BCFGP, DON*

*Doctor of Orthomolecular Nutrigenomics*

*Board Certified Functional Genomics Practitioner*

Brigitte Spurgeon is not a medical doctor. This article is for educational purposes only and does not constitute medical advice. Nothing in this article is intended to diagnose or treat any medical condition.