Brain Chemistry & ADHD, Decoded
- Nikki Drummond, CCN
- Oct 19
- 7 min read
Every ADHD evaluation starts the same way: check the boxes, circle the symptoms, tally the score. But behavior is only the signal. Beneath every hyperactive child and forgetful adult lies a biochemical story—one that can be measured, mapped, and modified.
As a clinical nutritionist, my work goes far beyond what my clients eat day to day. Nutrition is just the entry point — but to truly improve quality of life, I aim to uncover why the symptoms exist in the first place. That’s where functional testing comes in.
I use a range of data-driven tools to trace imbalances back to their biochemical roots. One of my favorites — and the reason many clients call me “Neuro-Nikki” — is the Urine Neurotransmitter Test. This is a simple urine test that's easy for adults and kids to collect from the comfort of home. The test is only $249 and reveals the full story behind focus, mood, and motivation. The results often surprise both parents and adults who’ve lived with the ADHD label for years. Their brains aren’t broken — their chemistry is simply playing the right notes in the wrong key.
🧠 Behavior vs. Biochemistry
The Dopamine Pathway—Drive, Reward, and the Energy Economy
Dopamine is the neurotransmitter most people associate with ADHD. It fuels motivation, curiosity, and the satisfying click of finishing a task. On a urine neurotransmitter panel, I look at both dopamine levels and its primary metabolite homovanillic acid (HVA).
When dopamine production is low and HVA is low, I know the brain’s reward circuitry is simply under-supplied—usually due to insufficient precursors like tyrosine, iron, and/or vitamin B6 (National Institutes of Health [NIH], 2022).
But when dopamine is normal or high and HVA is very high, it means the brain is burning through dopamine too quickly. That pattern often matches the “can’t stop, won’t focus” presentation—busy, impulsive, exhausted by noon.
Mitochondrial sluggishness and oxidative stress can also raise HVA, as dopamine oxidizes into reactive intermediates that damage the very neurons trying to make it (Paul et al., 2021). Supporting mitochondrial nutrients—CoQ10, riboflavin, magnesium—helps stabilize both energy and focus.
Serotonin and 5-HIAA—Calm in the Midst of Chaos
Serotonin is the brain’s “soothing soundtrack.” It regulates mood, sleep, and emotional flexibility—the ability to move through frustration without crumbling.
Urine testing measures 5-HIAA (5-hydroxyindoleacetic acid), serotonin’s primary metabolite. Low 5-HIAA tells me the person isn’t synthesizing or recycling serotonin efficiently—often due to low dietary tryptophan (protein), inadequate B6, or an inflamed gut that’s diverting tryptophan down another pathway (Herbert et al., 2023). High 5-HIAA, on the other hand, can mean serotonin is breaking down too rapidly under the influence of high cortisol or histamine stress. Either way, the brain loses its internal brake pedal.
The Tryptophan Fork—When Inflammation Steals Serotonin
Tryptophan, the amino acid precursor to serotonin, has two possible fates:
1️⃣ toward serotonin → 5-HIAA, producing calm and emotional stability, or
2️⃣ toward the kynurenine pathway, producing metabolites like quinolinic acid that are neuro-excitatory and inflammatory.
Inflammatory cytokines and stress hormones push tryptophan down that second route (Brown & Stevens, 2020). On a urine test, this looks like low 5-HIAA with elevated kynurenine—a pattern I call the inflammatory hijack. In children, it often appears as “wired and tired”: anxious, sleepless, emotionally volatile. In adults, it feels like burnout—the gas pedal pressed to the floor but no traction left.
Nutritionally, the solution isn’t simply “add tryptophan.” It’s about cooling the inflammation: improving gut integrity, balancing omega-3/omega-6 ratios, and using antioxidants like N-acetyl cysteine (NAC) to redirect traffic back toward serotonin synthesis (Gonzalez et al., 2022).
Glutamate and GABA—The Brain’s Gas and Brake Pedals
If dopamine sets the melody and serotonin keeps rhythm, glutamate and GABA control the tempo. Glutamate excites; GABA calms. In a balanced brain, they alternate like inhaling and exhaling. In ADHD, especially in clients with high stress or processed-food diets, glutamate often dominates. Elevated glutamate with low GABA feels like internal noise: chatter, impulsivity, sensory overload. Depleted glutamate and GABA together, however, feel flat—foggy focus, low drive.
Supporting GABA pathways through magnesium, taurine, L-theanine, and nervous-system regulation practices (slow breathing, HRV training) restores the brake pedal without sedation (Wu et al., 2021).
Histamine—The Overlooked Accelerator
Histamine doesn’t just make your nose itch; it’s a potent neurotransmitter that controls alertness and energy. High histamine increases dopamine turnover and can heighten anxiety or impulsivity (Kaplan et al., 2019). With kids, I often see high histamine paired with high HVA and low 5-HIAA—a sign that the brain’s accelerator is stuck and the brakes are worn. Lowering dietary histamine load (reducing strawberries, fermented foods, leftovers, aged cheese) and supporting DAO enzyme activity often calm both gut and focus.
The Gut–Brain Factory: Where Neurotransmitters Are Born
About 90 percent of serotonin is produced in the gut (Gershon & Tack, 2021), and many dopamine and GABA precursors are processed there too. When I look at a neurotransmitter test that shows widespread depletion—low dopamine, low 5-HIAA, low GABA—the first place I investigate isn’t the brain. It’s the microbiome.
When Dysbiosis Disrupts the Assembly Line
Dysbiosis—an imbalance of gut microbes—creates three domino effects that derail focus and mood:
Inflammation → Signal Confusion Opportunistic bacteria release lipopolysaccharides (LPS) that inflame the intestinal lining. That inflammation triggers immune cytokines which cross-talk with the brain and divert tryptophan away from serotonin into the kynurenine pathway (O’Mahony et al., 2020).
Malabsorption → Missing Raw Materials Even a “perfect” diet can fail if the gut wall is inflamed. Amino acids, iron, B-vitamins, and magnesium—the substrates for neurotransmitters—can’t be absorbed efficiently. The result is biochemical malnutrition hiding beneath “healthy” meals.
Loss of Microbial Diversity → Under-staffed Factory Beneficial species such as Bifidobacterium longum (a natural GABA producer) and Lactobacillus rhamnosus (serotonin modulator) dwindle, leaving fewer microbes to convert dietary compounds into brain-supportive metabolites.
Malnutrition by Malabsorption
This is one of the biggest blind spots in ADHD care. I routinely see children and adults eating “healthy” foods yet showing neurotransmitter depletions because their guts can’t utilize what they consume.
Low protein = low amino acids = low dopamine/serotonin.
Low B-vitamins = poor methylation = sluggish neurotransmitter synthesis.
Low magnesium = hyper-excitable neurons = low GABA.
When we repair the gut barrier and repopulate beneficial microbes, follow-up testing often shows normalization of 5-HIAA, dopamine, and GABA within months.
The NeuroFit Nutrition Reset Plan: Supporting the Blueprint
"Heal the gut, feed the brain, and neurotransmitters start normalizing on their own."
A Real-World Turning Point
One 13-year-old girl came to me after years of restlessness, poor sleep, and “ADHD” that didn’t respond to medication. Her results showed low 5-HIAA, high kynurenine, and elevated glutamate—classic signs of inflammation diverting serotonin and overstimulating the brain.
We began by calming the gut: eliminating high-histamine foods, increasing protein at breakfast, adding magnesium glycinate, zinc, and a probiotic blend rich in Bifidobacterium longum. Within six weeks her sleep normalized; within three months her teachers reported she could stay on task. Her follow-up neurotransmitter test told the same story her behavior did—chemistry restored balance.
The Bigger Picture: ADHD as a Nutrient-Delivery Problem
ADHD isn’t just a neurotransmitter imbalance; it’s a delivery problem. If the gut can’t absorb or the cells can’t utilize nutrients, neurotransmitters can’t form. That’s why “eat better” advice often fails and why stimulant medication can provide short-term focus but not long-term repair. Restoring the gut-brain axis is what rebuilds sustainable attention, mood, and motivation.
When we measure the chemistry, we stop blaming the behavior. Evaluation of urine neurotransmitter levels offers a biochemical snapshot of how dopamine, serotonin, GABA, histamine, and their metabolites (5-HIAA, kynurenine, glutamate) are performing. For me, that snapshot is the foundation of NeuroFit Nutrition—an approach that translates lab data into actionable nutrition, lifestyle, and gut-healing steps.
If you’ve ever been told, “This is just how your brain works,” know this: chemistry can change. Your focus can be rebuilt. And the story of ADHD can evolve—from a lifelong label to a measurable, modifiable map.
With love & science,
Nikki
If you suspect your neurotransmitters or gut might be off — if the patterns in this article sound a little too familiar — start by mapping your chemistry.
My Brain Map Assessment begins with a Urine Neurotransmitter Test (collected from home), which measures key brain chemicals like dopamine, serotonin, GABA, and histamine, along with their metabolites. From there, we connect the dots between your symptoms, nutrition, and gut health to create a personalized NeuroFit plan for balance and focus.
References
Brown, L., & Stevens, R. (2020). Tryptophan metabolism and inflammatory signaling in neurodevelopmental disorders. Frontiers in Immunology, 11, 585–597. https://doi.org/10.3389/fimmu.2020.00585
Gershon, M. D., & Tack, J. (2021). The serotonin signaling system: From gut to brain. Gastroenterology, 160(6), 2044–2060. https://doi.org/10.1053/j.gastro.2020.12.076
Gonzalez, A., Lopez, E., & Martin, P. (2022). Antioxidant modulation of the kynurenine pathway and implications for ADHD. Journal of Nutritional Biochemistry, 99, 108888.
Herbert, B., Nguyen, T., & Lee, S. (2023). 5-HIAA as a biomarker for serotonin metabolism under stress conditions. Neuroscience Letters, 813, 136191.
Kaplan, J. M., Vaughn, K., & Moore, D. (2019). Histamine modulation of dopamine pathways in attention disorders. Neurochemical Research, 44(5), 1102–1113.
National Institutes of Health. (2022). Role of vitamin B6, iron, and tyrosine in dopamine synthesis. NIH Office of Dietary Supplements.
O’Mahony, S. M., Clarke, G., & Cryan, J. F. (2020). Microbiota and inflammation in the gut-brain axis. Nature Reviews Gastroenterology & Hepatology, 17(2), 77–92.
Paul, B. D., Zhu, H., & Snyder, S. H. (2021). Dopamine oxidation and mitochondrial dysfunction in neuropsychiatric disorders. Nature Communications, 12, 3148.
Wu, T., Chen, Y., & Zhang, X. (2021). Magnesium and taurine modulation of GABAergic signaling in ADHD models. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 111, 110345.
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