Vitamin U, S-methylmethionine supplement
500 mg per capsule, 60 capsules. Made in the USA, third-party tested.
$49
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Vitamin U is S-methylmethionine, a sulfur-containing compound found in raw cabbage and other cruciferous vegetables. People take it to support the stomach's protective lining, and that is what almost all of the research on it looks at.
It is not actually a vitamin. The name comes from a 1949 study at Stanford in which peptic ulcer patients drank fresh raw cabbage juice, and the U stood for ulcer. (Cheney, 1949)
How does Vitamin U (S-methylmethionine) work in the body?
Your stomach lining is a maintenance job, not a fixed structure. It rebuilds itself constantly, and it can fall behind when something is wearing it down faster than usual.
Plenty of things do that. H. pylori infection is the most common cause of long-term stomach inflammation worldwide, and it can sit there quietly for years. Anti-inflammatory painkillers are next, and for some people a daily low-dose aspirin is enough to irritate the lining on its own. After that come alcohol, bile flowing back up from the small intestine, severe physical stress, and autoimmune gastritis, where the immune system attacks the lining cells directly. (Cleveland Clinic)
Some of those need a doctor rather than a supplement, and autoimmune and H. pylori gastritis both belong firmly in that category. But the underlying situation they create is the same one: a barrier being worn down faster than the cells beneath it can rebuild it. That is the gap S-methylmethionine is studied for, supporting the barrier that protects the stomach wall and supporting the cells that keep rebuilding it. If you want the practical version of that question, we cover who should and shouldn't take Vitamin U separately.
Three things appear to be going on.
It signals the stomach to produce more mucus
Your stomach produces acid strong enough to break down meat. The only thing standing between that acid and the cells of your stomach wall is a layer of gel, a few tenths of a millimetre thick, built from proteins called mucins.
That layer is not permanent. The cells underneath it secrete new mucus continuously, because the acid is continuously wearing it away. In a healthy stomach the two rates match and the barrier holds.
When they stop matching, the layer thins. Acid reaches cells it was never meant to reach, those cells become inflamed, and inflamed cells produce less mucus than healthy ones. That is the part people underestimate. It is self-reinforcing. A thinner barrier means more irritation, and more irritation means a thinner barrier, which is why a stomach that has become inflamed often stays that way long after whatever started it has gone.
S-methylmethionine appears to act on the production side of that balance. Rather than neutralising acid or coating the stomach the way an antacid does, it signals the cells that build the barrier to build more of it. Laboratory studies have measured increased mucus secretion in stomach cells and increased activity in the genes that produce mucins. There is a fuller walkthrough in how Vitamin U actually works in the body.
An antacid changes what the barrier is up against. This works on the barrier itself.
It acts as a methyl donor
Methylation sounds technical, but the idea is simple. Your body is constantly attaching small carbon tags to molecules to switch processes on and off: genes, hormones, maintenance signals. It needs a supply of those tags.
S-methylmethionine carries a spare one and can hand it over. This is the same general chemistry as SAMe, which is covered below.
It supports the body's own antioxidant defences
Oxidative stress is one of the ways the stomach lining gets worn down, and the body has its own defence against it built around a molecule called glutathione. S-methylmethionine appears to support that system rather than acting as an antioxidant itself. (Bakhrushina et al., 2026)
That is a different job from thickening the mucus layer, and the compound appears to do both.
The chemistry behind S-methylmethionine
Methionine is an amino acid, one of the building blocks your body uses to assemble proteins. You eat it every day in eggs, fish, nuts and seeds.
S-methylmethionine is methionine with one extra methyl group attached to its sulfur atom. A methyl group is small: one carbon, three hydrogens. That single addition changes the charge on the sulfur and turns the molecule into something that can pass that methyl group along to other reactions. It is the reason the compound behaves differently from the amino acid it is built from.
Plants make it themselves and use it to move sulfur from the roots up to the leaves and into developing seeds.
You will also see it written as methylmethionine sulfonium chloride, or MMSC. Same compound, different naming convention.
What foods contain Vitamin U?
Raw cabbage is the best-known source, at roughly 53 to 104 mg per 100 g depending on the variety and how fresh it is. Broccoli, kale, celery, asparagus and spinach all contain smaller amounts.
The catch is heat. S-methylmethionine breaks down when you cook it, which is why the historical research used raw juice rather than cooked cabbage. It is also why the amounts studied are hard to reach through diet. Getting to 500 mg means drinking close to a litre of raw cabbage juice, every day, which is the comparison we go through in Vitamin U supplements versus cabbage juice.
That is the actual reason supplements exist for this compound. Not because the vegetable is inadequate, but because the quantity is impractical.
Who can benefit from Vitamin U (S-methylmethionine)?
The research focuses on people who already have issues with their stomach lining. Three situations come up most often.
Anti-inflammatory painkillers are the clearest example. Ibuprofen, aspirin and naproxen work by suppressing prostaglandins, and prostaglandins are part of what tells the stomach to keep its mucus barrier topped up. The strongest study in the whole S-methylmethionine literature is a double-blind randomised trial in 172 patients whose stomach bleeding was brought on by these drugs. (Salim, 1993) If you are already on acid-reducing medication, we look at how the two interact in can you take Vitamin U with PPIs.
Alcohol is the second. In animal studies, the mucosal layer was better preserved and showed less oxidative damage when S-methylmethionine was given beforehand. (Watanabe et al., 1996)
Ongoing low-grade discomfort is the third. Patients taking 300 mg a day for six months reported less bloating, early fullness and queasiness, with better quality of life scores at the end of the six months. (Drozdov et al., 2023)
Stress and infection run through the older Soviet and Ukrainian clinical literature, usually as part of combination treatment rather than on its own. The specific question of Vitamin U and H. pylori has its own article, because it comes up constantly and the honest answer has caveats.
None of this replaces medical care. If you have been diagnosed with something, or you suspect an infection, that is a conversation for your doctor first.
Is Vitamin U the same as SAMe?
They are related and they are not interchangeable.
Both come from methionine and both act as methyl donors. SAMe is the body's own primary methyl donor and is usually taken for mood and joint support. S-methylmethionine is a plant compound, and the research on it sits almost entirely in the gut. For how it compares to the other compounds people consider for stomach support, see our roundup of stomach lining supplements.
How much Vitamin U (S-methylmethionine) do people take?
Published human studies span 300 mg to 2,000 mg a day.
The low end comes from the six-month study above at 300 mg. The high end comes from the 1993 trial, which used 500 mg four times daily in a hospital setting. Our own S-methylmethionine capsules contain 500 mg each.
Most people take it with food. On an empty stomach it is more likely to cause mild queasiness. The full breakdown is in the Vitamin U dosage guide, and if you are wondering about timelines, how long Vitamin U takes to work covers what the studies measured and when.
Is Vitamin U (S-methylmethionine) safe?
No serious adverse effects have been reported in any published human study at the doses studied, and that record covers trials from the 1940s through 2023 across the United States, Russia, Ukraine and Japan. The animal safety work is consistent with it.
Mild stomach upset is the side effect that comes up, usually when taken without food. Headache and changes in bowel habits are mentioned occasionally, and the Vitamin U side effects article goes through what each study actually reported.
If you are pregnant or breastfeeding, taking prescription medication, or managing a diagnosed condition, talk to your doctor before starting. That is not a formality. It is a supplement with real biological activity, and interactions are worth checking.
Vitamin U in Japan and Eastern Europe
Outside North America, this is not just a supplement.
In Japan it has been a prescription medicine since June 1960, sold as Cabagin U Kowa Tablets 25 mg and prescribed for gastric ulcer, duodenal ulcer and gastritis at 25 to 75 mg three times daily. It carries an official government drug price, the same as any other listed medicine there. A separate lower-dose version sits on pharmacy shelves without a prescription. (Japanese drug listing)
In Ukraine it is sold as Doctovit, a Vitamin U and B5 supplement, and it runs through the Ukrainian clinical literature as something doctors recommend alongside standard treatment for erosive stomach conditions.
It never went through drug approval in the United States for a straightforward reason. The compound is old and cannot be patented, so no pharmaceutical company has ever had a commercial reason to fund the trials registration would require. The barrier was financial, not scientific.
That is why it sits in the supplement aisle here and in a doctor's prescription pad in Osaka.
Where to read the research
Every study named on this page, plus roughly twenty more, is summarised in plain English in our Global Vitamin U Research Database. It is the most complete English-language collection of S-methylmethionine research we have been able to assemble, including the Japanese and Soviet clinical work that has never been translated properly.
This article is for educational purposes and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. Consult your healthcare provider before starting any supplement.
*This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.