Heavy chili pepper intake linked to higher esophageal cancer risk
A review found the strongest cancer signal among people eating the most chili peppers, but researchers said the data do not prove causation.
By Lucas Ferreira · Science & Environment Writer
3 min read
People who eat the largest amounts of chili peppers may face a higher risk of esophageal cancer, according to a meta-analysis published in Frontiers in Nutrition. The researchers said the finding points to an association, not proof that chili peppers cause cancer.
The review, reported by SciTechDaily, examined 14 observational studies with more than 11,000 participants, including more than 5,000 people diagnosed with gastrointestinal cancers. The cancers assessed included malignancies of the esophagus, stomach, colon and rectum.
What the review found
Compared with people reporting the lowest chili pepper intake, those in the highest-consumption groups had about a 64% higher risk of gastrointestinal cancers overall, according to the authors, Changchang Chen, Man Zhang, Xutong Zheng and Hongjuan Lang.
The strongest association was with esophageal cancer. People in the highest chili intake category were nearly three times as likely to develop that cancer as those in the lowest category, the review found.
The results were less clear for stomach and colorectal cancers. The researchers did not find a statistically significant increase for either, though stomach cancer showed a higher-risk trend of about 77% among heavier chili consumers.
The authors concluded that the evidence suggests chili pepper may be a risk factor for some gastrointestinal cancers, including esophageal cancer. They also stressed that better studies are needed before dietary advice can be made with confidence.
Why the findings are uncertain
All studies included in the meta-analysis were observational. That type of research can show that two things occur together, but it cannot establish that one causes the other.
Other cancer risk factors could have influenced the results, including smoking, alcohol use, infections, income, broader diet patterns or regional food practices, according to the researchers. The review also found that results differed by geography.
Studies from Asia, Africa and North America generally pointed to higher risks among the heaviest chili pepper consumers, while studies from Europe and South America found no increase or lower risks, according to the review. The researchers said differences in pepper varieties, cooking methods, average intake, genetics and other habits may help explain the split.
Capsaicin remains complex
Chili peppers get their heat from capsaicin, a compound that activates TRPV1 receptors involved in heat and pain sensation. Laboratory studies have produced mixed findings: some suggest capsaicin can reduce inflammation or kill cancer cells under certain conditions, while others suggest it may promote irritation or tumor growth in different settings.
Researchers have proposed that repeated exposure to very spicy foods could irritate the esophageal lining in some people, but that remains a hypothesis. The review did not prove a biological mechanism connecting chili intake to cancer.
A separate umbrella review published in Molecular Nutrition found that spicy foods and capsaicin have been linked to both possible benefits and risks, depending on the disease, population and amount consumed. SciTechDaily reported that some evidence has tied spicy food to lower cardiovascular risk and lower premature death, while findings on digestive cancers remain inconsistent.
The main unanswered question is dose. The researchers said it is not clear whether moderate chili pepper consumption carries the same signal seen among the heaviest consumers, or whether risk rises only above a certain level.
This story draws on original reporting from ScienceDaily.