Could eating many chilli peppers affect your risk of cancer? Scientists have been debating that question for years, and the answer remains far from simple. While chilli peppers contain compounds that have shown anti-inflammatory and even anticancer effects in laboratory experiments, some human studies have linked very high consumption to a greater risk of certain cancers of the digestive tract.
A large review published in Frontiers in Nutrition examined the available evidence and found that people who consumed the most chilli peppers were more likely to develop certain gastrointestinal cancers, especially oesophageal cancer. At the same time, researchers emphasised that the evidence does not prove chilli peppers cause cancer and that more rigorous studies are still needed.
A Closer Look at Chili Peppers and Cancer Risk
Gastrointestinal cancers include cancers of the oesophagus, stomach, and colon or rectum. Together, they account for millions of new cancer diagnoses worldwide each year and remain among the leading causes of cancer-related deaths. Because these cancers are often discovered after they have already advanced, scientists continue searching for dietary and lifestyle factors that might influence risk.
Chilli peppers are eaten every day by billions of people and are an essential ingredient in cuisines across Asia, Latin America, Africa, and many other parts of the world. Their signature heat comes from capsaicin, a natural compound that activates heat- and pain-sensing nerve receptors.
Capsaicin has attracted considerable scientific interest. Laboratory studies have suggested it may reduce inflammation, influence metabolism, and even kill certain cancer cells under specific conditions. However, other experiments have found that under different circumstances it could promote tumour growth or contribute to tissue irritation. That conflicting evidence has made its overall effect on cancer difficult to pin down.
What the Analysis Found
To better understand the relationship, researchers combined data from 14 observational studies involving more than 11,000 participants, including over 5,000 people diagnosed with gastrointestinal cancers.
Compared with people who consumed the least chilli peppers, those with the highest intake were about 64% more likely to develop gastrointestinal cancers overall.
The strongest association involved oesophageal cancer. People in the highest consumption group were nearly three times more likely to develop this cancer than those in the lowest intake group.
The picture was less clear for other digestive cancers. Researchers did not observe a statistically significant increase in the risk of stomach or colorectal cancer. Although stomach cancer showed a trend toward higher risk, about 77% higher among heavy chilli pepper consumers, the difference did not reach statistical significance.
Based on their findings, the researchers concluded that the evidence “suggests that chilli pepper is a risk factor for certain GI cancers (e.g., EC).”
Why Results Differ Around the World
The findings also varied by region.
Studies from Asia, Africa, and North America generally found higher cancer risks among people with the greatest chilli pepper consumption. By contrast, studies from Europe and South America found either no increased risk or reduced risks.
Researchers believe several factors could explain these differences. Average chilli pepper intake varies dramatically around the world, and cooking methods, pepper varieties, genetics, smoking, alcohol use, and other dietary habits may all influence the results. The researchers noted that “geographical regions influence the risk of GI cancers”, suggesting that regional differences should be considered when making dietary recommendations.
Why the Esophagus May Be Especially Vulnerable
Scientists have proposed several explanations for why the oesophagus appears more strongly affected than other parts of the digestive tract.
Capsaicin activates receptors known as TRPV1 receptors, producing the familiar burning sensation associated with spicy foods. Some researchers suspect that repeated exposure to extremely spicy foods could contribute to chronic irritation of the oesophageal lining in susceptible individuals. Differences in how quickly cells are repaired and replaced throughout the digestive tract may also influence how tissues respond over time. These ideas remain hypotheses and have not been proven.
The Bigger Picture
Although these findings may sound concerning, they should be interpreted with caution.
Every study included in the review was observational. That means the researchers could identify associations, but they could not determine whether chilli peppers themselves caused the higher cancer risk. Other factors, such as smoking, alcohol consumption, socioeconomic differences, infections, or overall dietary patterns, could also contribute.
Since the review was published, broader analyses have continued to show mixed results. An umbrella review of several systematic reviews found that spicy foods and capsaicin may have both health benefits and risks, depending on the disease being studied, the amount eaten, and the people involved. Some evidence links spicy food to lower risks of cardiovascular disease and premature death, while studies of digestive cancers remain inconsistent.
For now, researchers say one of the most significant unanswered questions is dose. It is still unclear whether moderate chilli pepper consumption carries the same risks observed among the heaviest consumers or whether there is a threshold above which risk begins to increase.
Future studies that follow people over many years will be needed to determine whether chilli peppers themselves play a direct role in cancer development or whether the observed associations are driven by other lifestyle and environmental factors.
