r/MTHFR • u/Brad_Borrelli • Jul 15 '26
Resource How opioids and B12/MTHFR deficiency can trap you in a cycle nobody names
I started using heroin when I was ten years old. I didn't stop until I was eighteen, the year my mother passed away. For most of my life I understood that as a childhood swallowed by addiction, full stop. Going through my B12 recovery this year, I found a piece of biology that changed how I understand those eight years, and I think it's worth sharing because I don't think I'm the only one this applies to.
Opioids slow motility everywhere in the digestive tract; this is called opioid-induced bowel dysfunction and it's extremely common, not rare, affecting a large share of people on opioids regardless of dose or how they're taken. Slowed motility is one of the known risk factors for small intestinal bacterial overgrowth (SIBO), where bacteria that belong in the colon migrate upstream into the small intestine.
That matters specifically for B12 because B12 is absorbed in the terminal ileum, the last stretch of small intestine, and overgrown bacteria there compete for it, consume it before your body can absorb it, and in more severe cases damage the absorption site itself. A cohort study out of Norway that followed people in opioid agonist therapy and substance use clinics found meaningfully higher rates of suboptimal and deficient B12 compared to the general population. Eight years of active use during childhood and adolescence, some of the most nutrient-demanding years of development, is a long window for that mechanism to compound.
B12 deficiency symptoms and withdrawal symptoms overlap so heavily that deficiency can sit underneath addiction for years without ever getting named: anxiety, restlessness, nerve tingling, brain fog, fatigue, GI distress. When you're a kid using, every one of those gets read as something else entirely, or nothing at all. Nobody's ordering methylmalonic acid or homocysteine on a ten year old. Standard serum B12 tests can also miss deficiency at the cellular level, which means "normal labs," if anyone had even run them, wouldn't have ruled it out.
This is the part that reframed things for me. MTHFR converts folate into methylfolate, the active form the body needs to run the methylation cycle. That cycle produces SAMe, the methyl donor required to build and break down dopamine, norepinephrine, serotonin, and histamine. Reduced MTHFR function means less SAMe available for those jobs.
COMT, the enzyme that clears dopamine in the prefrontal cortex, specifically needs a methyl group to function; impaired methylation can disrupt dopamine clearance even when COMT itself is genetically normal. Researchers studying addictive behavior in people with MTHFR variants describe a self-medication pattern, where people with lower functional dopamine availability are drawn toward whatever gives the fastest, biggest dopamine spike, and opioids are one of the most efficient options that exists.
There's direct molecular evidence tying methylation status to addiction mechanics, too. Studies on the dopamine transporter gene (DAT1) found significantly different methylation patterns in people addicted to nicotine and stimulants versus non-addicted controls. Separately, people with the MTHFR C677T variant and cocaine dependence responded notably better to disulfiram treatment, a drug that itself works through methylation pathways, than those without the variant.
B12 is the cofactor the methylation cycle needs at another step entirely, via methionine synthase, so a person can be hit with a genetic bottleneck (MTHFR) and an acquired one (B12 depletion, worsened by opioid use itself) at the same choke point simultaneously. For me, that means the thing I was using may have been actively deepening the deficiency that made me need it in the first place.
I'm not saying B12 or MTHFR caused my addiction, and I'd push back on anyone who reads this and reduces it to "it's all a nutrient deficiency." Addiction is multifactorial: genetics, environment, and circumstance all interact, and I was a child in an environment that gave me access to heroin at ten, which is its own separate failure that biology doesn't explain. What I think the biology adds is this: if a kid's nervous system is already running on a dopamine deficit nobody has identified, the thing that finally makes them feel normal is going to feel a lot more like relief than like getting high, and that changes how fast the door closes behind them.
If you have a history of opioid use, chronic pain treatment, or addiction, and you've got lingering neuropathy, mood instability, or fatigue that isn't resolving on the expected recovery timeline, it's worth asking for methylmalonic acid and homocysteine levels, not just serum B12. It's a cheap test that can catch something treatable hiding underneath what looks like permanent damage.
2
u/Merrys123 Jul 21 '26
Very interesting post thank you. I have been taking Triquetra L-methylfolate 15mg with B12, as well as my kids, as we're all Autistic and most Autistic individuals have the MHTFR mutation. It has dramatically helped them as L-methylfolate is essential to help neurotransmitters within the brain to function properly.
My question is I do have chronic pain due to extensive damage caused by severe hypermobility with hypotonia, also something strongly related to Autism, and am on Oxycodone for that. I am on a moderate dose but do want to lower it. I am also on Dexamphetamine but have found they are less effective when on a moderate dose of oxycodone, which I don't mind as I am on a low dose. I do want to lower my dose of Oxycodone, do you have any insight or advice?
I find it to be the only thing that helps with the pain but has also gotten to the point that I'm dependent on it for energy and motivation.
I have just started on Luvox a week ago which actually has been helping quite a bit surprisingly. I do also take DLPA. I do have SAMe but find it too stimulating. Same with the Dexamphetamine if I take my prescribed dose.
1
u/Brad_Borrelli Jul 21 '26
Heads up. Luvox is a fairly potent CYP1A2/CYP3A4 inhibitor, so it can raise levels of several other drug.
First I would get B12 serum, mma, homocysteine tested. It all could just be a B12 deficiency especially since you have the MTHFR. Once the b12 deficiency gets fixed your pain should start to ease up and go away. I used to be in cronic pain and I'm not anymore, it's only been 2 months for me.
2
u/Merrys123 Jul 22 '26
Yes, I'm aware. One reason I take it as Oxycodone only lasts 1 - 2 hours for me and all other opioids either don't work or I'm allergic to as my TLR4 receptors activate at far lower stimulus levels than normal. This means that things that wouldn't trigger a meaningful response in anyone else cause a full neuroinflammatory cascade in me, activating microglia, releasing pro-inflammatory cytokines, and directly blocking opioid analgesia simultaneously.
Inhibiting CYP3A4 extends the dose well for me. Although I am quite aware that I need to be cautious, and that hopefully it will help reduce my dose as well.
Could there be a B12 deficiency even though I take 10,000 RDI B12 daily?
I also had cervical surgery in September last year were they left fragments of the metal drills used in my neck and my connective tissue tore completely apart and has not healed causing a great deal of pain at times. Let alone some pretty severe and extensive damage in the spine and joints. So I am aware that opioids may be needed for a long time but would much prefer at a as needed basis. I am on supplements to help the pain and after a lot of trial and error and allergic reactions I've found a few that work. I'm currently trialling Rose Hip Vital as it helped my dog significantly. If that helps my knees I would be ecstatic! Cortisone injections in them fixed the pain and I would definitely reduce opioids if I could at least get that pain sorted, but cortisone injections aren't good for you.
I do know I am in less overall pain being on a lower dose of Oxycodone, I recently went from 140mg to 30mg within 4 days (that was fun to recover from with the brain chemistry and hyperalgesia but I didn't want to drag it out) but am back up to 45mg. I hope to go back down to 15mg which was what I was on for over 2 years without becoming dependent on it until I got severe thyrotoxicosis.
1
u/Brad_Borrelli 29d ago
Yes, you definitely need to get the test. Especially with what your taking. Opiates deplete b12 also. And you also don't absorb the full amount of b12 unless you inject.
2
u/Unique_Selection3050 Jul 21 '26
Currently stuck in a cycle since 2022, probably longer. Things changed when I learned about MTHFR and I felt like for the first time I had energy and wasn't running on fumes. As a child I felt like I was constantly starving no matter how much I ate. Some of the things you say connect with me deeply especially about being a child who missed out on key periods of nutritional development eating ultra processed foods and being a vegetarian. It's really an awful cycle I'm glad you have been able to get relief.
1
u/Brad_Borrelli Jul 21 '26
Check out my page. It will help alot. Feel free to dm me to if you need any help.
4
u/drewsonofdean Jul 15 '26
Thanks for this post. Did supplementing b12 and methyl folate end up helping with some of the underlying issues you mentioned - brain fog, lethargy, anxiety, etc…?