Garlic

• Antibacterial activity vs Helicobacter pylori — garlic and its sulfur compounds (notably allicin and derived organosulfur compounds) inhibit H. pylori growth in many in vitro studies and some animal models. Since H. pylori is a leading cause of chronic gastritis, this antibacterial action provides a plausible mechanism for benefit. Oxford Academic Frontiers
• Anti-inflammatory and antioxidant effects — garlic contains multiple antioxidants and anti-inflammatory constituents (S-allyl cysteine, other organosulfur compounds) that can reduce mucosal inflammation and oxidative damage in the stomach lining in preclinical work. These properties support a second, non-antibacterial route by which garlic might reduce gastritis symptoms or mucosal injury. MDPI Frontiers
• Clinical signal in long-term prevention trials — large long-term randomized studies in a high-risk Chinese population (the Shandong Intervention Trial) found that long-term garlic supplementation (with aged garlic extract + steam-distilled garlic oil) was associated with a reduction in gastric-cancer mortality over decades (more about the study below). Those results are encouraging but do not prove garlic cures gastritis. They do show potential long-term protective effects in a population with high gastric cancer risk. BMJ Europe PMC

Summary: biological mechanisms (antibacterial + anti-inflammatory) are well supported in lab and animal studies; human data are mixed — there are signals for long-term benefits in specific trial settings, but garlic is not a proven standalone cure for gastritis in clinical practice.

• Dietary garlic (food) — many studies simply assess habitual garlic intake (raw or cooked) as part of diet surveys. No standardized “food” dose is validated for treating gastritis. Dietary use is reasonable for general health unless you have contraindications (see warnings). Frontiers
• Aged garlic extract (AGE) and garlic oil supplements — clinical trial dosing (Shandong Intervention Trial): participants received two capsules each containing 200 mg aged garlic extract and 1 mg steam-distilled garlic oil, twice daily (so 4 capsules/day total), for roughly 7.3 years in the trial. That is one of the clearest, documented human supplement regimens from a randomized trial. That trial tested long-term supplementation for cancer prevention, not short-term gastritis symptom relief. Europe PMC BMJ
• Typical supplement labeling / standardization: commercial garlic supplements vary (raw garlic powder, aged garlic extract, garlic oil, enteric-coated tablets). Trials that report biological effects usually use standardized extracts (e.g., defined amounts of S-allyl-cysteine or allicin derivatives). If you want a supplement that corresponds to trials, look for aged garlic extract formulations with manufacturer data on active constituents. The NIH/NCCIH and trial reports give more context. NCCIH Oxford Academic

Practical, evidence-informed instructions (summary):

• For research-style supplementation (as used in the major trial): aged garlic extract + garlic oil capsules, two 200 mg AGE + 1 mg oil capsules twice daily (the trial’s format), taken long-term under medical supervision. Europe PMC
• For everyday use (if you have mild gastritis and no contraindications): moderate dietary garlic (cooked or raw) is common culturally; if trying supplements, start with a lower dose and discuss with your clinician — don’t replace standard H. pylori eradication therapy or other prescribed treatments. NCCIH

Major randomized intervention (large, long follow-up):

• The Shandong Intervention Trial — randomized, placebo-controlled factorial trial (Linqu County, Shandong, China). Participants received 7.3 years of garlic supplementation (aged garlic extract + steam-distilled garlic oil: 2×(200 mg AGE + 1 mg oil) daily) and were followed long term; results showed reduced gastric-cancer mortality over decades but mixed results for incidence. Important for long-term outcomes, not for short-term gastritis cure. BMJ Europe PMC

Human follow-up / long-term analyses from the same program:

• JNCI & BMJ follow-up papers describing 14–22 year outcomes from that trial (reporting effects on cancer incidence/mortality). Oxford Academic BMJ

Laboratory / microbiology evidence (mechanistic):

• In vitro studies showing inhibitory effect of garlic extracts on H. pylori isolates (lab MIC data). These explain the antibacterial plausibility. Example: FEMS Study on inhibition of H. pylori by aqueous garlic extract. Oxford Academic

Systematic reviews / reviews of bioactivity:

• Recent reviews summarizing bioactive compounds, antimicrobial, anti-inflammatory and antioxidant effects of garlic (Frontiers review 2024; MDPI review). These give a modern view of mechanisms and therapeutic potential. Frontiers MDPI

Recent cautionary epidemiology (important new finding — 2025):

• Sci Rep 2025 (Wu J et al.) — a case-control study from Gansu Province, China, examined garlic intake and atrophic gastritis risk stratified by H. pylori infection status. The paper reported an association between frequent garlic intake and increased atrophic gastritis risk in people who were currently or previously infected with H. pylori (no significant effect in never-infected individuals). This is a new, important caution and shows the relationship is complex — garlic might not be uniformly beneficial for all patients with gastritis. Nature European Medical Journal

Other useful resources / authorities:

• NCCIH (NIH) — authoritative safety/summary page on garlic (benefits, typical adverse effects, interactions). Useful for practical safety guidance. NCCIH