Vitamin B12 is one of the most essential nutrients for brain health. It supports the production of key neurotransmitters, helps build and protect nerve fibres, and plays a central role in the biochemical processes that keep the brain functioning at its best.
Unfortunately, studies show that many children with ADHD have lower levels of vitamin B12 than their peers. In one study of five different B vitamins, only B9 and B12 were significantly lower in children with ADHD, while B1, B2, and B6 showed no difference.
Scientists believe this could be due to dietary patterns common in ADHD, genetic differences in B12 metabolism, gut microbiome changes, or — more likely — some combination of all three. Whatever the cause, B12 deficiency has real consequences for attention, learning, and brain development.
B12 affects ADHD primarily in three ways: neurotransmitter synthesis, myelin formation, and methylation.
Curious about whether B12 supplementation might help? Read this article here.
1. B12 Supports Dopamine Production
Dopamine and norepinephrine are the primary neurotransmitters disrupted in ADHD. They regulate attention, motivation, and impulse control. B12 plays an important role in their production through a biochemical process called one-carbon metabolism.
This metabolic pathway is responsible for producing the methyl groups needed to create dopamine, serotonin, and other monoamine neurotransmitters. When B12 is low, it’s more difficult for the brain to create and use those neurotransmitters.
Specifically, B12 helps by:
- Enabling the conversion of homocysteine to methionine, a critical step in neurotransmitter synthesis
- Supporting the production of SAMe (S-adenosylmethionine), the body’s primary methyl donor
- Working alongside folate (B9) to regulate the enzymes that build dopamine and serotonin precursors
The basal ganglia is particularly vulnerable to B12 and folate deficiency. The Basal ganglia is a group of structures in the brain that affect movement, reward, attention, emotional regulation, and habits. Having a B12 or B9 deficiency, then, can make those processes more difficult.
2. B12 Builds and Protects Myelin
Myelin is the protective sheath that wraps around nerve fibres, allowing signals to travel quickly and efficiently across the brain. Think of it like the insulation around an electrical wire: without it, signals slow down, cross-wire, or fail to transmit efficiently.
B12 is essential for myelin formation. Deficiency, especially during development, can impair myelination in the brain responsible for attention, impulse control, and executive function. This is why it’s important to have adequate B12 levels during growing years. The brain is still actively myelinating through adolescence, and disruptions to this process during critical windows can have lasting effects.
Your brain continues to create myelin as you age, though, like everything, it slows down. However, again B12 is crucial to create myelin, which can impact your cognitive health as you age.
Continued below…
3. B12 Regulates Methylation and Gene Expression
B12 and folate are the two key drivers of methylation — a process that controls how genes are switched on and off throughout the body, including in the brain. Methylation affects:
- DNA synthesis and repair
- Neurotransmitter production and breakdown
- Neuroinflammation and oxidative stress
- Long-term changes in brain structure and behaviour
When methylation is disrupted, as it can be when B12 is low, it affects not just our bodies but also how we feel in the world. Research has linked methylation dysfunction to ADHD, depression, autism spectrum disorder, and schizophrenia.
Some children also carry variants in the MTHFR gene that impair their ability to process folate and activate B12 efficiently. These variants can cause mild elevations in homocysteine and reduced neurotransmitter synthesis. However, these polymorphisms are very common and do not occur more frequently in ADHD.
If you have an MTHFR polymorphism, it’s typically recommended that you eat or supplement extra folate or folic acid. Contrary to popular belief, your body does process it—it is simply less efficient and may require more than normal to process it effectively. Methylated folate or B12 is also an option; however, it can cause negative reactions in some people with specific polymorphisms. Always discuss with a physician prior to taking supplements.
4. Specific ADHD – B12 Research
- In one study, B12 levels correlated positively with IQ scores in children with ADHD, meaning children with higher B12 tended to perform better cognitively.
- Another study found that B12 deficiency affected social functioning in kids with ADHD.
- A 2024 systematic review found that low B12 levels are connected with ADHD.
- A Swedish randomised controlled trial found that children with ADHD on psychostimulant medication had significantly lower abundance of the gut bacteria responsible for B12 synthesis, suggesting that kids with less manageable ADHD might have issues creating B12.
- This 2020 study found no connection with ADHD symptom severity and B12 deficiency.
Supporting B12 Levels
Diet: The richest dietary sources of B12 are animal products: eggs, meat, fish, shellfish, dairy, and poultry. For people who eat a restricted diet or follow a plant-based diet, getting adequate B12 through food alone is very difficult, and supplementation may be necessary. A natural way to supplement is through eating nutritional yeast.
Testing: If your child has ADHD — especially alongside learning difficulties, a restricted diet, or multiple comorbid diagnoses — it is worth asking their healthcare provider about testing serum B12 and folate. Some practitioners also test homocysteine and active B12 (holotranscobalamin) for a more sensitive picture of B12 function. You may also consider genetic testing or gut microbiome testing.
Supplements: B12 supplementation should only be considered under the guidance of a trained medical professional. For more information on B12 supplementation and ADHD, read this article.
This article summarizes the research from the aforementioned studies and the author’s knowledge. It is for educational purposes only. Nothing in this article constitutes medical advice.
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