Could eating a lot of chili peppers affect your cancer risk? Scientists have been debating that question for years and the answer is far from simple. Although chili peppers contain compounds that have shown anti-inflammatory and even anti-cancer effects in laboratory experiments, some studies in humans have linked very high consumption with an increased risk of certain cancers of the digestive tract.
A great review published in Frontiers in nutrition examined the available evidence and found that people who ate the most chili peppers were more likely to develop certain gastrointestinal cancers, especially esophageal cancer. At the same time, the researchers emphasized that the evidence does not prove that chili 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 esophagus, 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 when they have already advanced, scientists continue to look for dietary and lifestyle factors that may influence risk.
Billions of people eat chili peppers every day and they are an essential ingredient in the cuisines of Asia, Latin America, Africa and many other parts of the world. Its characteristic heat comes from capsaicin, a natural compound that activates nerve receptors sensitive to heat and pain.
Capsaicin has attracted considerable scientific interest. Laboratory studies have suggested that it can 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 tumor growth or contribute to tissue irritation. That conflicting evidence has made it difficult to pin down its overall effect on cancer.
What the analysis found
To better understand the relationship, the researchers combined data from 14 observational studies involving more than 11,000 participants, including more than 5,000 people diagnosed with gastrointestinal cancers.
Compared to people who consumed the least chili peppers, those with the highest consumption were about 64% more likely to develop gastrointestinal cancers overall.
The strongest association involved esophageal cancer. People in the highest consumption group were almost three times more likely to develop this cancer than those in the lowest consumption group.
The picture was less clear for other digestive cancers. The researchers found no statistically significant increase in the risk of stomach or colorectal cancer. Although stomach cancer showed a trend toward a higher risk, about 77% higher among heavy chili consumers, the difference did not reach statistical significance.
Based on their findings, the researchers concluded that the evidence “suggests that chili pepper is a risk factor for certain gastrointestinal cancers (e.g., AE).”
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 higher chili consumption. In contrast, studies from Europe and South America found no increased risk or even lower risks.
The researchers believe that several factors could explain these differences. Average chili consumption varies dramatically around the world, and cooking methods, pepper varieties, genetics, smoking, alcohol consumption, and other dietary habits can influence results. The researchers noted that “geographic regions influence the risk of gastrointestinal 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 esophagus appears more affected than other parts of the digestive tract.
Capsaicin activates receptors called 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 lining of the esophagus in susceptible people. Differences in how quickly cells are repaired and replaced throughout the digestive tract may also influence tissue response over time. These ideas remain hypotheses and have not been tested.
The bigger picture
Although these findings may seem worrying, they should be interpreted with caution.
All studies included in the review were observational. That means the researchers were able to identify associations, but they couldn’t determine whether the chili peppers themselves caused an increased risk of cancer. Other factors could also contribute, such as smoking, alcohol consumption, socioeconomic differences, infections, or general dietary patterns.
Since the review was published, broader analyzes have continued to paint a mixed picture. An overview that examined multiple systematic reviews concluded that spicy foods and capsaicin appear to have both potential health benefits and possible risks, depending on the disease being studied, the amount consumed, and the population involved. Some evidence links spicy food to lower risks of cardiovascular disease and premature death, while studies on digestive cancers remain inconsistent.
For now, researchers say one of the biggest unanswered questions is dosage. It is not yet clear whether moderate chili consumption carries the same risks seen among more frequent consumers, or whether there is a threshold above which the risk begins to increase.
Future studies that follow people for many years will be needed to determine whether chili peppers themselves play a direct role in cancer development or whether the observed associations are driven by other environmental and lifestyle factors.