Garlic supplements and stomach cancer risk over 22 years in people
What it found
Taking garlic supplements for about seven years was linked to fewer deaths from stomach cancer over 22 years in people living in a high-risk area of China.
Garlic did not clearly reduce the number of new stomach cancer cases.
What they found
Studies in people
Fewer stomach cancer deaths
People who took garlic supplements had fewer deaths from stomach cancer over 22.3 years compared with those taking dummy pills. This protective effect only became clear about 12 years after the trial started.
New stomach cancer cases
Garlic supplements did not lead to a clear reduction in the number of new stomach cancer cases. Any possible benefit was too small to rule out chance.
Effects appeared slowly
During the first several years of the trial, garlic showed almost no effect on stomach cancer rates. Benefits only emerged later and lasted through the end of the follow-up period.
Other cancers and heart disease
The researchers found no link between garlic supplements and deaths from other types of cancer or from heart disease.
What the authors conclude
- They report that taking garlic supplements for over seven years led to fewer deaths from stomach cancer across more than 22 years of follow-up.
- They note that garlic did not significantly lower the number of new stomach cancer cases.
- The authors call for further large trials to confirm these benefits and check for any risks before recommending garlic supplements widely.
How it was done
Stomach cancer causes many deaths worldwide, especially in parts of rural China. Earlier research suggested that diets rich in garlic might protect against stomach cancer in people at high risk.
Researchers followed 3365 adults in China for 22.3 years. Participants took garlic extract and oil capsules, vitamin capsules, or dummy pills twice daily for 7.3 years. Some also received two weeks of treatment for a common stomach infection.
What it can’t tell you
- This trial studied people in a rural Chinese area with very high stomach cancer rates and low nutrient intake.
- It cannot show whether garlic would have the same effects in well-nourished populations or areas where stomach cancer is rare.
- The study used a specific mix of aged garlic extract and garlic oil, so it cannot tell us if eating fresh garlic or taking different garlic products would work the same way.
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 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error