In 2005, Australian doctors Barry Marshall and Robin Warren won the Nobel Prize for discovering that the bacteria H. pylori causes gastric and peptic ulcers. This work contributed to the development of effective treatments for what was once a chronic ailment. The significance of this research has only grown, as half the world’s population is infected by H. pylori, and H. pylori infections are believed to be the cause of 90% of non-cardia gastric cancers.
While H. pylori can now be readily treated, there are strong motives for finding ways to prevent such infections, as while 80% of people infected with H. pylori are asymptomatic, all people infected with the bacteria develop gastritis—swelling of the stomach lining—which is associated with increased risk of stomach cancer. Thus, most people infected by H. pylori are unaware of their heightened cancer risk.
New research suggests that a high omega-6:omega-3 ratio may contribute to a higher likelihood of Helicobacter pylori infections.
Extensive research has found that high levels of omega-6 fatty acids—found extensively in seed oils and animal proteins—are associated with increased inflammatory response. Meanwhile, the omega-3s DHA and EPA—conventionally found in fatty fish—promote reduction and regulation of inflammatory responses. In recent years, with increased use of seed oils in industrial food production and decreasing seafood consumption, the omega-6 to omega-3 levels in many populations around the world have been rising. This raises the question of how diets high in omega-6s may correlate with the incidence of H. pylori infections and associated gastritis.
A study published in Clinical Nutrition Research in 2024 sought to answer that question. The study, “Does a High Ratio of Dietary Omega-6/Omega-3 Fatty Acids Increase the Risk of Helicobacter pylori Infection? A Case-Control Study,” compared the omega-6:omega-3 ratios of populations with and without H. pylori infections.
After controlling for other risk factors—smoking, as well as increased age and BMI strongly correlate with increased risk of H. pylori—the researchers found that those with high omega-6:omega-3 ratios were twice as likely to be infected with H. pylori.
The study’s authors reviewed previous research which suggests that high levels of omega-3s confer some protection against H. pylori infection and resulting inflammation.
In the paper’s discussion, the authors note that, “Inflammatory substances secreted by H. pylori are advantageous to the bacteria but detrimental to the host. The inflammation disrupts the secretory function of the stomach and damages its tissue.” The implication here is that H. pylori induces inflammation that enables it to better colonize and reproduce in the stomach. Thus, mitigating this inflammation can both reduce injury to the stomach lining—that can result in more serious health consequences—and inhibit growth of H. pylori.
The researchers offer multiple findings from past research which suggest that high omega-3 levels protect against H. pylori, helping to explain the correlation between high omega-6:omega-3 levels and the increased rate of H. pylori infection:
- DHA has been found to decrease “H. pylori growth in vitro in a dose-dependent manner,” inhibit H. pylori colonization, and decrease gastric mucous membrane inflammation.
- It appears that DHA and EPA can block infections of H. pylori “by inhibiting bacterial colonization through futalosine pathway blockade.”
- A study found that omega-3 supplementation appeared to protect the stomach’s mucous membrane from damage caused by H. pylori and other causes.
- Omega-3s have been shown to reduce the expression of interleukin (IL)-8, a proinflammatory cytokine.
It should be noted that the studies cited by the authors are preliminary, and further research is necessary. The authors themselves are also careful to point out that multiple studies have found that omega-3 supplementation is not effective in treating active H. pylori infections.
More research is necessary to understand how DHA and EPA interact with H. pylori and the human digestive tract, and how a lower ratio of omega-6 to omega-3 in the diet potentially reduces the likelihood of H. pylori infection. We thank the study’s authors for their efforts in attempting to answer these questions and look forward to reviewing future research on the topic.