Garlic supplements and stomach cancer in a Chinese trial
What it found
In a 22 year trial in China, people who took garlic supplements for 7.3 years had fewer deaths from stomach cancer.
The result for new stomach cancer cases was not statistically significant.
What they found
Studies in people
Stomach cancer deaths
Garlic supplementation was linked to a statistically significant reduction in deaths from stomach cancer over 22.3 years. The effect became apparent after about 12 years.
New stomach cancer cases
Garlic supplementation was linked to fewer new cases of stomach cancer, but this result was not statistically significant. The effect only appeared after 14.7 years.
Other causes of death
No statistically significant links were found between garlic supplementation and other cancers or heart and blood vessel disease.
Timing of effects
The effects of garlic on stomach cancer deaths became visible after about 12 years. For new cases, effects were negligible during the first part of the trial and only appeared later.
What the authors conclude
“Garlic supplementation also yielded a statistically significant decrease in gastric cancer mortality and a promising, but not statistically significant, decrease in gastric cancer incidence.”
Also in their conclusions
- They conclude that garlic supplementation for seven years was associated with a statistically significant reduced risk of death due to gastric cancer for more than 22 years.
- They say that further large scale intervention trials are warranted to confirm the preventive effects of vitamin and garlic supplementation.
- They advise that before major public health campaigns are launched, more trials are needed to identify possible risks from nutritional regimens.
How it was done
The authors wanted to see whether Helicobacter pylori treatment, vitamin supplements, or garlic supplements could prevent stomach cancer, and whether any effects would last with longer follow-up.
They followed 3365 residents of Linqu County, China, a high risk area for stomach cancer, for 22.3 years. Participants took garlic extract and garlic oil capsules, or placebo, twice daily for 7.3 years.
What it can’t tell you
- The trial cannot show whether the effects would be the same in well nourished people or in populations with low rates of stomach cancer.
- It cannot separate the effects of the different components of the garlic supplement or show whether a higher dose would work better.
- It cannot rule out that other changes in diet or lifestyle after the trial ended affected the results.
Who paid
- Conflicts
- Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organization for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
- Authors work at
- Peking University Cancer Hospital and Institute, China; International Epidemiology Institute, USA; Vanderbilt University Medical Center, USA
The paper
- Title
- Effects of Helicobacter pylori treatment and vitamin and garlic supplementation on gastric cancer incidence and mortality: follow-up of a randomized intervention trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Li WQ, Zhang JY, Ma JL, et al (2019). Effects of Helicobacter pylori treatment and vitamin and garlic supplementation on gastric cancer incidence and mortality: follow-up of a randomized intervention trial. BMJ (Clinical research ed.). doi:10.1136/bmj.l5016Free full textPubMed 31511230DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error