Garlic vegetable intake lowers risk of gastric cancer

Greater dietary intake of allium vegetables, particularly garlic, provides a protective benefit against the development of gastric cancer (GC), suggests a study. This association is independent from vitamin or garlic supplementation.

“Our study provides prospective evidence corroborating the potential inverse association of garlic vegetable intake with the risk of developing GC and, therefore, holds public health implications for dietary recommendations,” the researchers said.

This prospective study sought to determine whether allium vegetable intake would change the risk of GC occurrence and whether such associations would be modified by vitamin supplementation, garlic supplementation, and Helicobacter pylori (H. pylori) treatment.

The researchers included a total of 3,229 participants with information on the intake of allium vegetables (eg, garlic vegetables and scallions), obtained through structed questionnaires in 1994. They then examined the associations of total and individual allium vegetable intake with the risk of GC.

Some 144 incident cases of GC have been identified during follow-up. An association was noted between garlic vegetable intake and a lower risk of incident GC (odds ratio [OR], 0.83 per 1 kg/y increment, 95 percent confidence interval [CI], 0.70‒0.98; p_trend=0.02). [Am J Clin Nutr 2023;117:22-32]

Notably, the inverse relationship of total allium vegetable and garlic vegetable intake with GC risk was more pronounced among individuals receiving placebo for vitamin or garlic supplementation. This suggested the potential effect modifications of nutritional supplementation on allium vegetable intake and the risk of developing GC.

Analyses of the combined prevalence of dysplasia or GC revealed similar results.

Case-control studies in the past also explored the interaction of allium and garlic vegetable intake with the risk of GC, and a pooled analysis of these studies supported their inverse relationship. [Am J Clin Nutr 2000;72:1047-1052; Mol Nutr Food Res 2015;59:171-179; Nutr Res Pract 2021;15:773-788; Oncol Lett 2022;23:125; Nutr Cancer 2015;67:1-11; Br J Cancer 2022;126:1755-1764]

In an analysis based on the Netherlands Cohort study, the findings showed an inverse association between onion intake and the risk of GC, particularly noncardia GC. In contrast, a previous prospective study on garlic and GC found no significant difference in GC risk between categories of garlic intake. [Gastroenterology 1996;110:12-20; Int J Cancer 2018;143:1047-1053]

Allium vegetables are rich in organosulfur compounds (OSCs), especially allyl sulfur, and flavonoids, which promote antibacterial and antioxidant activities. [Cancer Prev Res (Phila) 2015;8:181-189; Int J Mol Sci 2020;21:6451; Food Chem 2019;276:680-691; Molecules 2019;24:4006; Nutrients 2020;12:872; Semin Cancer Biol 2021;73:219-264; Environ Health Perspect 2001;109:893-902]

“The antioxidant components were shown to inhibit the transition from atrophic to metaplastic mucosa caused by N-nitroso compounds, impede cancer cell progression and angiogenesis, and induce its apoptosis,” the researchers said. “Moreover, OSCs may suppress the growth of H. pylori.” [Am J Chin Med 1998;26:353-364; Nutr Cancer 1997;27:118-121]

However, the current study did not observe significant findings for scallions which, along with onions, contain very limited allicin relative to garlic vegetables. [Sci Total Environ 2020;725138387]

“Studies are warranted to elucidate the effect of allicin on the observed discrepant associations with garlic vegetables and scallions and to examine other possible mechanisms,” the researchers said.