inflammation & autoimmunity

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HNMT

Are You Genetically Vulnerable to High Brain Histamine, Migraines, or ADHD? (HNMT)

Written by Jasmine Foster, BSc, BEd on August 19th, 2019

Do you struggle with the symptoms of ADHD? Do you frequently have migraines? Poorly functioning histamine-degrading enzymes may cause either or both. Let’s dive into your HNMT gene and find out if you’re vulnerable.

Histamine in the Brain

Histamine is vitally important for brain function: it wakes you up, suppresses appetite, and lets you know when you’re thirsty. Brain histamine may also make you feel more curious and motivated. It keeps you alert, helps you prepare for stressful situations, and promotes the formation of memories [R, R, R].

However, too much brain histamine can cause serious problems. In this post, we’ll explore histamine-N-methyltransferase (HNMT), which breaks down histamine in the brain, and how low HNMT activity can impact your health.

How Does the HNMT Gene Cause Problems?

HNMT codes for histamine-N-methyltransferase, the second major enzyme (after DAO) that breaks down histamine. HNMT is found throughout the body and (perhaps most importantly) in the brain. It deactivates histamine by adding a methyl group [R, R].

Variations in the HNMT gene have been associated with chronic hives and eczema as well as neurological symptoms [R, R].

It’s plausible that the HNMT enzyme may be decreased in these conditions, and increasing it may help.

HNMT is the major histamine-degrading enzyme in the brain and much of the body.

Histamine and Migraines

Migraine is a condition that causes excruciating headaches, nausea, intense fatigue, sensitivity to light and sound, and inability to move without pain [R, R].

One possible villain behind these often disabling events is excess brain histamine. In fact, researchers have known for decades that they can induce a headache just by giving a person enough histamine by mouth; we also know that people who get migraines are more susceptible to histamine headaches than people who don’t [R, R, R].

Furthermore, some antihistamines are currently under investigation as future migraine medications. Drugs that activate the H3 histamine receptor may have the most potential [R].

The ‘T’ allele at rs11558538 is associated with decreased HNMT activity and increased risk of migraines [R].

Excess brain histamine may cause migraines; people who tend to get migraines are also more sensitive to the effects of histamine in the brain.

Histamine and ADHD

HNMT, as the primary histamine-degrading enzyme in the brain, appears to be linked to ADHD symptoms, but researchers aren’t sure exactly how [R].

In one interesting study, increased brain histamine worsened behavioral symptoms in children with ADHD. The children with the AA genotype at rs1050891 were more likely to have worse symptoms when they were exposed to artificial food colorings and additives (sunset yellow, carmoisine, tartrazine, ponceau 4R, quinoline yellow, Allura red AC, and sodium benzoate) that raise brain histamine [R].

The ‘T’ allele at rs11558538 is associated with decreased HNMT activity, but the link between this variant and ADHD is not clear [R].

Therefore, cases where brain histamine levels are higher, increasing HNMT may help ADHD.

Certain variations in the HNMT gene make children with ADHD more sensitive to the effects of high brain histamine and a variety of food additives.

Your Histamine Gene Results for Brain Histamine

Important SNPs

HNMT rs1050891:

‘G’ = Normal breakdown of histamine
‘A’ = Reduced breakdown of histamine, higher brain histamine

HNMT rs11558538:

‘C’ = Normal breakdown of histamine
‘T’ = Reduced breakdown of histamine, higher brain histamine

SNP Table

variant	genotype	frequency	risk allele
rs1050891
rs11558538

Recommendations

To Increase HNMT Activity

S-adenosyl-L-methionine, also known as SAM-e, occurs naturally in your body and donates methyl groups during the methylation processes. Histamine N-methyltransferase (HMNT) inactivates histamine by methylating it; therefore, SAM-e might help HMNT work more efficiently [R, R, R, R].

To Prevent Histamine Release

People who are susceptible to migraine may benefit the most from a diet low in histamine and histamine-releasing agents. For a complete explanation of how the low histamine diet works and whether you should try it, check out this post [R, R].

If you’re looking for a supplement that targets histamine in the brain, you might want to try theanine, an amino acid found in green and black tea. Theanine crosses the blood-brain barrier (BBB), which means that it may be more effective at targeting brain histamine than other natural antihistamines [R, R, R, R].

Most of the strategies for managing histamine intolerance prevent histamine from being either produced (histidine decarboxylase inhibitors) or released (mast cell stabilizers). Over on SelfHacked, we’ve compiled a comprehensive list of supplements and lifestyle options that can help; check out this post to see them all.

It’s also a good idea to reduce the amount of histamine you consume in your food. This post explains how to make the most of a low-histamine diet. For a dive into which foods are high and low in histamine, check out this post. Also, remember to speak with your physician before starting on any new supplement regimen.

Jasmine Foster

BSc, BEd

Jasmine received her BS from McGill University and her BEd from Vancouver Island University.

Jasmine loves helping people understand their brains and bodies, a passion that grew out of her dual background in biology and education. From the chem lab to the classroom, everyone has the right to learn and make informed decisions about their health.

Disclaimer

The information on this website has not been evaluated by the Food & Drug Administration or any other official medical body. This information is presented for educational purposes only, and may not be used to diagnose or treat any illness or disease.

Also keep in mind that the “Risk Score” presented in this post is based only on a select number of SNPs, and therefore only represents a small portion of your total risk as an individual. Furthermore, these analyses are based primarily on associational studies, which do not necessarily imply causation. Finally, many other (non-genetic) factors can also play a significant role in the development of a disease or health condition — therefore, carrying any of the risk-associated genotypes discussed in this post does not necessarily mean you are at increased risk of developing a major health condition.

Always consult your doctor before acting on any information or recommendations discussed in this post — especially if you are pregnant, nursing, taking medication, or have been officially diagnosed with a medical condition.

More inflammation & autoimmunity blogs

How to Combat Histamine Intolerance Through Genetics (DAO) Are You Genetically Vulnerable to High Brain Histamine, Migraines, or ADHD? (HNMT) How to Tell if You’re Lectin Sensitive Using Your Genetic Data (CNR1) Are You Sensitive to Lectins? (MTHFR) Fight Oxidative Stress, Inflammation, and Brain Fog (PARP1) Is This Gene Causing Your Autoimmune Problems? (PTPN22)

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Histamine in the Brain How Does the HNMT Gene Cause Problems? Your Histamine Gene Results for Brain Histamine

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Are You Genetically Vulnerable to High Brain Histamine, Migraines, or ADHD? (HNMT)

Histamine in the Brain

How Does the HNMT Gene Cause Problems?

Histamine and Migraines

Histamine and ADHD

Your Histamine Gene Results for Brain Histamine

Important SNPs

SNP Table

Recommendations

To Increase HNMT Activity

To Prevent Histamine Release

Disclaimer

More inflammation & autoimmunity blogs

More headaches & migraines blogs

More mental health blogs

Content

Unlock Personalized Results And So Much More!

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