You avoid trigger foods, yet migraines still strike after eating. Here's the biological reason.

Your MTHFR gene codes for an enzyme that sits at the center of your body’s methylation cycle. This cycle is responsible for converting dietary folate and B12 into their active forms, and for producing compounds like SAM (S-adenosylmethionine) that control dozens of downstream processes, including the production and regulation of neurotransmitters and the control of vascular tone.

The MTHFR C677T variant, carried by roughly 40% of people with European ancestry, reduces this enzyme’s efficiency by 40 to 70%. That means your cells are struggling to convert dietary folate and B12 into usable methyl donors. Even if you eat plenty of vegetables and take a B vitamin supplement, your brain and blood vessels are running on reduced methylation capacity. You have functional folate and B12 deficiency at the cellular level, even though your standard bloodwork looks normal.

This directly impacts migraine. Your trigeminal nerve and blood vessels depend on methylation to regulate neurotransmitter balance and vascular tone. When methylation is impaired, serotonin and dopamine become harder to produce and clear. Nitric oxide, which controls blood vessel flexibility, becomes dysregulated. And histamine, which accumulates from food, becomes harder to break down efficiently.

Your AOC1 gene codes for an enzyme called diamine oxidase (DAO). This enzyme’s job is to break down histamine that enters your body from food. Aged cheese, fermented foods, cured meats, certain fish, tomatoes, and spinach all contain histamine. Once you eat them, DAO is supposed to neutralize this histamine before it reaches your bloodstream and brain.

Variants in the AOC1 gene, present in roughly 30 to 40% of people, reduce DAO enzyme activity. Your body accumulates histamine from food because you cannot break it down as quickly as your body produces it. This histamine then crosses into your brain, where it acts on histamine receptors in the trigeminal system and brain stem, triggering vasodilation and neuronal sensitization.

You notice that aged foods, fermented foods, and leftovers (histamine rises as food ages) are especially likely to trigger your migraines. One person’s aged cheddar is another person’s trigger. That’s because their DAO is working fine; yours isn’t.

Your COMT gene codes for catechol-O-methyltransferase, an enzyme that breaks down dopamine, norepinephrine, and other catecholamine neurotransmitters. This enzyme controls how long these powerful signaling molecules remain active in your brain. It’s like the volume knob on your pain and sensory response system.

The COMT Val158Met variant, carried by roughly 25% of people as homozygous slow, significantly slows the clearance of dopamine and norepinephrine. Neurotransmitters linger in your synapses longer, amplifying pain signaling and sensory sensitivity in your trigeminal nerve. Your brain becomes hypersensitive to normal stimuli. The pain and vascular response systems are essentially turned up too loud.

This is why you may be exquisitely sensitive to caffeine, why stress hits you harder, and why the release of dopamine after a meal (especially after eating foods high in tyrosine, like meats and aged cheeses) can push you toward a migraine. Your brain can’t clear these signals fast enough, and the buildup triggers the migraine cascade.

Your MAOA gene codes for monoamine oxidase A, an enzyme that breaks down serotonin, dopamine, and norepinephrine in the brain and gut. This enzyme is crucial for preventing the buildup of these powerful neurotransmitters. When MAOA is working well, these signals stay balanced. When it’s not, they accumulate.

Variants in MAOA, present in roughly 30 to 40% of the population depending on ancestry, can reduce enzyme activity. This leads to accumulation of serotonin and dopamine, which initially seems beneficial but actually creates a state of neuronal overstimulation and poor signal-to-noise ratio. Your brain becomes oversensitive to stimuli, and the migraine threshold drops.

You may notice that after eating foods high in serotonin or dopamine precursors (chocolate, nuts, fermented foods, high-protein meals), you’re more prone to migraines. The sudden spike in these neurotransmitters, combined with your impaired ability to break them down, triggers the migraine cascade.

Your NOS3 gene codes for endothelial nitric oxide synthase, an enzyme that produces nitric oxide in the lining of your blood vessels. Nitric oxide is a signaling molecule that tells your blood vessels when to relax and dilate, and when to constrict. It’s the foundation of healthy vascular tone.

The NOS3 Glu298Asp variant, carried by roughly 30 to 40% of people, reduces nitric oxide production in your cerebral blood vessels. Your brain’s blood vessels cannot regulate their tone properly, becoming more prone to the vasoconstriction and vasodilation cycles that define migraine. Compounds in food that normally cause mild vascular shifts can trigger the dramatic vascular changes that underlie migraine with aura and migraine pain.

You may notice that your migraines come with visual symptoms, that they’re more likely during hormonal shifts (when vascular tone is already unstable), or that they follow foods that cause vascular stress, like high-sodium foods, foods high in histamine, or foods containing phenolic compounds. Your blood vessels are simply more reactive than other people’s.

Your SLC6A4 gene codes for the serotonin transporter, a protein that reabsorbs serotonin from synapses after it’s been released. This recycling process is how your brain regulates serotonin levels and prevents both depletion and overstimulation. It’s the critical control point for serotonin signaling stability.

The SLC6A4 5-HTTLPR short allele variant, carried by roughly 40% of people, reduces the expression of the serotonin transporter. Your brain cannot reabsorb serotonin efficiently, leading to alternating periods of depletion and overstimulation as food-derived serotonin precursors (like tryptophan from meats and nuts, or direct serotonin from chocolate and fermented foods) create spikes and crashes. These fluctuations in serotonin are a core driver of migraine pathophysiology.

You may notice that your migraines follow meals rich in serotonin or tryptophan, or that they’re worse during low-serotonin periods (certain parts of your cycle, early morning). Serotonin dysregulation is your Achilles heel, and food compounds that affect serotonin directly affect your migraine threshold.