Monoamine oxidase (MAO) is the enzyme your body uses to break down neurotransmitters like serotonin, norepinephrine, and dopamine after they’ve done their job. Increasing MAO activity speeds up this cleanup process, which can matter if low MAO levels are contributing to problems like impulsivity, emotional reactivity, or difficulty regulating behavior. While most health content focuses on blocking MAO (that’s what a class of antidepressants does), there are evidence-based ways to support and increase the enzyme’s activity through nutrition, hormonal balance, and lifestyle factors.
What MAO Does in Your Brain
MAO exists in two forms. MAO-A has a stronger preference for serotonin and norepinephrine, while MAO-B primarily handles a stimulant-like compound called phenylethylamine. Dopamine is broken down by both forms, though MAO-B plays a larger role in the human brain specifically. Both versions sit on the surface of mitochondria, the energy-producing structures inside your cells, where they chemically deactivate neurotransmitters through a process called oxidative deamination.
When MAO is absent or severely reduced, neurotransmitter levels climb dramatically. Animal studies show that eliminating MAO-A alone causes serotonin levels to double and norepinephrine to rise by about 30%. Knocking out both forms simultaneously pushes serotonin to seven times its normal level and dopamine to twice normal. These aren’t subtle shifts, and they have real behavioral consequences.
Why Someone Would Want Higher MAO
Low MAO activity is consistently linked to a cluster of behavioral traits: sensation-seeking, poor impulse control, risk-taking, and emotional volatility. Research on platelet MAO-B activity (a common proxy for brain levels) shows a robust correlation between low readings and behavioral disinhibition, including traits central to ADHD.
The most extreme example is Brunner syndrome, a rare genetic condition where MAO-A is virtually absent. Affected individuals show borderline intellectual disability, impulsive aggression, sleep disturbances, and a high tendency toward violent or antisocial behavior, often triggered by minor stressors. While Brunner syndrome is exceptionally rare, the genetic variant associated with lower MAO-A activity (the 3R variant) is not. It has been linked to higher impulsive aggression, poorer stress responses, lower cognitive functioning, and more severe symptoms in conditions like autism.
If you recognize yourself in traits like chronic impulsivity, emotional overreactivity, or difficulty winding down, supporting healthy MAO activity is a reasonable goal.
Riboflavin: The Essential Cofactor
MAO cannot function without a molecule called FAD, which is made from riboflavin (vitamin B2). FAD is physically attached to the MAO enzyme, and without it, the enzyme is inactive. This isn’t a minor relationship. When neuronal cells are grown in a riboflavin-free environment, MAO activity drops significantly. Adding riboflavin back restores it, but the recovery requires building entirely new enzyme molecules from scratch rather than simply reactivating old ones.
This means riboflavin deficiency doesn’t just slow MAO down temporarily. It reduces the total amount of working enzyme in your cells. Good dietary sources include eggs, dairy, lean meats, almonds, mushrooms, and fortified grains. The recommended daily intake is 1.1 to 1.3 mg for adults, though many people fall short, particularly those who avoid dairy or eat a restricted diet.
Iron’s Role in MAO Production
Iron deficiency reduces the amount of functional MAO your body can make. In patients with iron-deficiency anemia, platelet MAO activity is significantly lower than in healthy controls, and the amount of active enzyme drops by roughly 48%. The enzyme that is present also becomes less stable and more vulnerable to degradation.
Researchers believe iron is needed either for building the MAO protein itself or for the process that attaches the FAD cofactor to it. Either way, the practical takeaway is the same: if your iron stores are low, your MAO activity is likely compromised. This is especially relevant for premenopausal women, vegetarians, and frequent blood donors, all groups at higher risk for iron deficiency. A simple blood test for ferritin can tell you where you stand.
Stress Hormones Activate MAO Genes
Cortisol, your primary stress hormone, directly increases MAO-A gene expression. Cell studies show that glucocorticoids (the class of hormones cortisol belongs to) boost both the genetic transcription and the catalytic activity of MAO-A through multiple pathways. The cortisol receptor physically binds to the MAO-A gene promoter and also works through intermediary proteins to ramp up production.
Androgens activate the same gene through a similar mechanism. This means that both stress hormones and sex hormones serve as natural signals for your body to produce more MAO-A. Chronically low cortisol, which can result from prolonged burnout or adrenal fatigue patterns, could theoretically reduce MAO-A expression. On the other hand, chronic high cortisol has its own serious downsides, so the goal is healthy, responsive cortisol rhythms rather than artificially elevated stress.
Practical ways to support normal cortisol patterns include consistent sleep schedules, regular exercise (particularly morning exercise, which reinforces the natural cortisol awakening response), and managing chronic psychological stress rather than suppressing it.
Dietary Fat and MAO Activity
The type of fat you eat may influence brain MAO levels. In animal research, rats fed diets based on lard (primarily saturated and monounsaturated fat) had higher neuronal MAO activity than those fed soybean oil-based diets (high in polyunsaturated omega-6 fat). The lard-fed group showed about 38% higher maximum enzyme activity. While this is a single animal study and shouldn’t be treated as definitive dietary advice, it does suggest that the fatty acid composition of your diet can influence MAO function at the cellular level, likely through changes in mitochondrial membrane composition where MAO enzymes are anchored.
Epigenetic Switches That Control MAO
Your MAO genes can be turned up or down through epigenetic modifications, chemical tags on DNA that control whether a gene is actively read or silenced. The most studied of these is methylation. When the MAO-A gene promoter is heavily methylated, the gene is less active, producing less enzyme. Brain imaging studies in humans have confirmed that higher MAO-A gene methylation corresponds to lower MAO-A activity in the brain.
The encouraging finding is that DNA methylation is reversible. Environmental factors can remove methyl tags and reactivate silenced genes. While the specific lifestyle interventions that reduce MAO-A promoter methylation haven’t been mapped out in clinical trials, the broader epigenetics literature points to exercise, adequate nutrition (particularly folate, B12, and other methyl-donor nutrients), and reduced chronic stress as general influences on DNA methylation patterns. Early life stress in particular has been shown to increase MAO-A methylation in animal models, suggesting that the behavioral effects of childhood adversity may partly operate through reduced MAO production.
The Tradeoff: Too Much MAO Has Costs
Before aggressively pursuing higher MAO activity, it’s worth understanding the other side of the equation. Every time MAO breaks down a neurotransmitter, it produces hydrogen peroxide as a byproduct. This is a reactive oxygen species that can damage cells, particularly neurons. Excessive MAO activity, especially MAO-B, has been implicated in the oxidative stress that contributes to neurodegenerative conditions. This is actually why MAO-B inhibitors are used as a treatment in Parkinson’s disease: they reduce dopamine breakdown and the associated oxidative damage in aging brains.
The goal isn’t to maximize MAO activity but to normalize it. If you suspect your levels are low due to nutritional deficiencies, genetic variants, or other factors, correcting those root causes is a different proposition than pushing the enzyme beyond its healthy range. MAO activity exists on a spectrum, and both extremes carry risks.
How MAO Levels Are Measured
In research settings, MAO activity is most commonly measured through platelet testing. Platelets in your blood contain MAO-B, and their activity level has been used as a peripheral marker for brain MAO function for decades. The standard approach uses a substrate called kynuramine and measures how quickly platelets break it down. Whole blood assays are sometimes preferred over platelet-rich plasma because isolating platelets can inadvertently select for subpopulations with higher or lower enzyme activity, skewing results.
Brain MAO activity can also be measured directly using PET imaging with specialized radioactive tracers, though this is limited to research facilities. Neither test is routinely available in clinical medicine, which means most people will need to work from indirect clues: nutritional status, genetic testing for MAO variants (available through some consumer genomics services), and behavioral patterns associated with low MAO activity.