Mastic gum is a resin harvested from the Pistacia lentiscus tree that has shown antibacterial activity against H. pylori in laboratory testing, and it's one of the most talked-about natural options in gastritis communities for that reason. S-methylmethionine (SMM), also known as Vitamin U, is the compound found in cabbage and other crucifers that has been studied since the 1940s for supporting the gastric mucosal lining. Both compounds come up constantly in comparisons of natural gastritis support, but they're not actually aimed at the same target. This comparison lays out what the research shows for each.
What is mastic gum?
Mastic gum is a resin harvested from the Pistacia lentiscus tree, grown almost exclusively on the Greek island of Chios, with a folk-medicine history for stomach complaints going back centuries. The modern research interest started with a 1998 letter in the New England Journal of Medicine reporting that mastic gum killed H. pylori in laboratory testing, including strains resistant to the antibiotic metronidazole. (1)
Follow-up research has been more mixed than that initial finding suggested. A later in vitro and in vivo study found mastic gum extract reduced H. pylori colonization roughly 30-fold in infected mice, but did not reduce the chronic inflammatory activity of the gastritis itself. (2) A randomized pilot study testing whether mastic gum could actually eradicate H. pylori in humans found it did not meet its primary endpoint for statistical significance, even though it showed some benefit when added to standard treatment. (3) Separately, a randomized, double-blind, placebo-controlled trial of 148 patients with functional dyspepsia found that 350 mg of mastic gum taken three times daily for three weeks significantly improved stomach pain, pain related to anxiety, and heartburn compared to placebo. (4) That's a genuinely positive result, but for symptom relief in functional dyspepsia, not for eradicating H. pylori or structurally repairing the gastric lining.
What is S-methylmethionine?
S-methylmethionine (SMM), also known as Vitamin U, is the compound found in cabbage juice and other crucifers responsible for cabbage juice's long folk history as a stomach remedy. It was first studied scientifically in the late 1940s by Garnett Cheney, a physician at Stanford, who investigated why fresh cabbage juice seemed to help peptic ulcer patients heal faster than standard treatment of the era. His 1949 trial found that patients drinking roughly a litre of fresh cabbage juice daily healed their ulcers in an average of 7.3 days, compared to 42 days on standard treatment. (5) Follow-up trials through the early 1950s were consistent enough with that result that by 1952 Cheney had isolated and named the active compound Vitamin U, U for ulcer, which is why the name is tied specifically to ulcer healing rather than general stomach discomfort. (6)
That research history carried SMM into modern pharmaceutical use. The mechanism centers on stimulating mucin secretion, the protective mucus layer that physically coats and shields the stomach wall from acid, along with general cytoprotective activity against irritants like alcohol and NSAIDs. (7) It's licensed as a prescription drug in Ukraine (Doctovit) and sold as an over-the-counter stomach medicine in Japan (Cabagin), both in continuous clinical use for decades.
More recently, a 2023 clinical trial followed 37 chronic gastritis patients taking 300 mg/day for six months, tracking symptoms with the same validated tools used in gastroenterology practice: the GSRS symptom questionnaire and the SF-36 quality of life survey. By month three, overall dyspeptic symptom severity had dropped significantly, and the SF-36 data specifically showed improvement in the bodily pain subscale, not just general wellbeing. (8) By month six, the average symptom score had fallen from 15 points before treatment to 5.5. Full details, including how this dose compares to pharmaceutical doses used elsewhere, are in the dosage guide and the Global Vitamin U Research Database.
How do their mechanisms differ?
Mastic gum's best-documented mechanism is antibacterial: laboratory evidence that it can kill H. pylori directly, plus a separate line of evidence for general dyspepsia symptom relief through a mechanism that isn't fully characterized. SMM's mechanism is about mucosal support: stimulating mucin production and supporting the structural integrity of the stomach lining over sustained use, the same territory covered in more depth in how to repair the stomach lining naturally. One is aimed primarily at a bacterial target and general symptom relief; the other is aimed primarily at the tissue itself. These aren't competing claims on the same territory. They're addressing different parts of the gastritis picture.
Where the research is stronger for each
Mastic gum's strongest evidence is the in vitro antibacterial data against H. pylori and the functional dyspepsia symptom trial. Its weakest point is that the human eradication studies (actually clearing an H. pylori infection in real patients, not just in a test tube) have not reached statistical significance. The lab result is real. Translating it into "mastic gum cures your H. pylori" is not supported by the human trial data currently available.
SMM's strongest evidence is the Cheney ulcer-healing trials and the Drozdov chronic gastritis trial, which showed sustained six-month symptom improvement, including a documented reduction in bodily pain specifically, not just general dyspepsia scores. Its weakest point is that it doesn't have a dedicated antibacterial trial the way mastic gum does; if H. pylori eradication itself is your primary concern, that's a conversation for antibiotic-based treatment with your doctor, not a supplement comparison.
Which should I try first?
If short-term dyspepsia symptom relief (stomach pain, heartburn, discomfort) over a few weeks is the main concern, mastic gum's three-week functional dyspepsia trial is a direct match for that specific use case. SMM's evidence isn't limited to structural repair either: the Drozdov trial documented improvement in bodily pain and overall symptom severity as well, tracked over a longer three-to-six-month window rather than three weeks. If the priority is longer-term structural mucosal support alongside that symptom relief, SMM's research base, spanning both the original ulcer-healing trials and the modern chronic gastritis trial, maps more directly onto that.
Neither compound is a substitute for confirmed H. pylori treatment, which requires antibiotics under medical supervision. If you test positive for H. pylori, that's the conversation to have with a doctor first, regardless of which supplement you're also considering.
Safety and side effects
Both compounds have shown favorable safety records in the available research, though the depth of that research differs.
Mastic gum has not been associated with significant adverse effects in the published trials, including the 148-patient functional dyspepsia RCT, which ran for three weeks at 350 mg three times daily without notable safety concerns. (4) The human safety data available is comparatively limited in duration; the longest published trial runs three weeks, shorter than the multi-month trials available for SMM.
SMM's safety data spans a longer duration: the Drozdov trial ran six months at 300 mg/day with no serious adverse effects reported, and a 2025 pharmacological review described its toxicity profile as low across a broad range of organ systems. The most commonly reported mild effect is gastrointestinal discomfort when taken on an empty stomach, addressed by taking it with food. See the side effects guide for the full breakdown of what's documented about SMM specifically.
Can you take mastic gum and Vitamin U together?
No published research has tested the combination, and there's no known mechanism suggesting a conflict between them. They act on different aspects of the gastritis picture (antibacterial and dyspepsia symptoms versus mucosal structure) rather than competing for the same pathway. As with any supplement combination, mention it to your doctor if you're also on other medications.
Summary
Mastic gum's H. pylori finding is one of the more interesting results in this research area, and it's a reasonable option for someone whose priority is general dyspepsia symptom relief backed by a specific randomized trial. Its human eradication data hasn't caught up to the laboratory result yet, and its safety research is comparatively short in duration.
SMM and mastic gum aren't really answering the same question. Mastic gum is closer to an antibacterial and short-term general symptom-relief compound; SMM is closer to a mucosal-support compound with its own documented symptom and pain relief, studied over months rather than weeks, alongside pharmaceutical use in two countries spanning more than 70 years and a research history that goes back to the original ulcer trials the compound is named after. If the goal is longer-term structural support for the stomach lining, backed by that range of evidence, Vitamin U is built around exactly that research base.
For how these two compare to zinc carnosine, DGL, and L-glutamine as well, see 5 stomach lining repair supplements that actually work.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any new supplement, especially if you have a health condition or take medications.
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.
References:
1. Huwez FU, Thirlwell D, Cockayne A, Ala'Aldeen DA. Mastic gum kills Helicobacter pylori. N Engl J Med. 1998;339(26):1946. link
2. Paraschos S, et al. In vitro and in vivo activities of Chios mastic gum extracts and constituents against Helicobacter pylori. Antimicrob Agents Chemother. 2007. https://pmc.ncbi.nlm.nih.gov/articles/PMC1797732/
3. Dabos KJ, et al. The effect of mastic gum on Helicobacter pylori: A randomized pilot study. Phytomedicine. 2010. https://pubmed.ncbi.nlm.nih.gov/19879118/
4. Dabos KJ, et al. Is Chios mastic gum effective in the treatment of functional dyspepsia? A prospective randomised double-blind placebo controlled trial. J Ethnopharmacol. 2010. link
5. Cheney G. Rapid Healing of Peptic Ulcers in Patients Receiving Fresh Cabbage Juice. California Medicine. 1949;70(1):10-15. https://pmc.ncbi.nlm.nih.gov/articles/PMC1643665/
6. Cheney G. Vitamin U Therapy of Peptic Ulcer. California Medicine. 1952. https://pubmed.ncbi.nlm.nih.gov/13009468/
7. Watanabe T, et al. Augmentative Effects of L-Cysteine and Methylmethionine Sulfonium Chloride on Mucin Secretion in Rabbit Gastric Mucous Cells. 2000. https://pubmed.ncbi.nlm.nih.gov/10719747/
8. Drozdov VN, et al. Effect of 6-Month S-Methylmethionine Intake on the Quality of Life and Dyspepsia Symptoms in Patients with Chronic Gastritis. 2023. https://pubmed.ncbi.nlm.nih.gov/37346023/
*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.