Core Tip: Chili peppers, carcinogenic or anti-cancer? Scientists have not yet reached a consensus. Epidemiological surveys, cell/animal experiments conducted on this topic have not been able to provide a clear conclusion. At present, we do not need to be troubled by these controversial research findings to the point of refusing Sichuan cuisine or eating more chili peppers.
Rumor: In the cold winter, spicy food seems to help us fight off the cold. However, reports claim that research has found that chili peppers may lead to stomach cancer, and it's best to refuse this spicy taste. But others say that scientists have discovered that chili peppers are the natural enemy of cancer, and eating more can prevent and treat cancer. So, are chili peppers carcinogenic or anti-cancer?
Chili Peppers and Capsaicin
When we talk about or research whether chili peppers are carcinogenic or have anti-cancer properties, we are actually discussing the relationship between capsaicin, the active ingredient in chili peppers, and cancer. Capsaicin, an alkaloid containing vanillamide, gives chili peppers their spicy flavor. It binds to the vanilloid receptor subtype 1 (VR1) on sensory neurons (this receptor is also activated when the body is exposed to heat stimulation), promoting the release of the neurotransmitter substance P, thereby transmitting information to the brain and giving us a burning sensation when we eat chili peppers. This process also promotes the release of endorphins in the brain, making us feel a sense of pleasure and exhilaration. This is why we feel refreshed and find it irresistible even while we are panting and sweating from the spiciness.
The Tangled Relationship Between Capsaicin and Cancer
Carcinogenic:
In 1994, the *American Journal of Epidemiology* reported on a "case-control" study conducted in Mexico City between 1989 and 1990 by a group of Mexican researchers. The statistical results showed that people who eat red chili peppers have a higher risk of developing stomach cancer than those who do not [1]. Between 1994 and 1996, the same researchers conducted similar "case-control" studies in three regions of Mexico, and this time they measured the capsaicin content of different chili peppers. They concluded that compared to the low-dose capsaicin intake group (consuming 0-29.9 mg of capsaicin per day, equivalent to eating fewer than 3 Mexican red chili peppers per day), the high-dose capsaicin intake group (consuming 90-250 mg of capsaicin per day, equivalent to eating 9-25 Mexican red chili peppers per day) had an increased risk of stomach cancer.
However, both papers used cautious terms like "possible" and "related factor" when discussing the relationship between chili peppers and stomach cancer, and did not explicitly conclude that chili peppers cause cancer.
In 2006, Nuray Erin of Pennsylvania State University and others confirmed that capsaicin reduces the expression of some genes in breast cancer cells, all of which are related to cell growth, proliferation, and cancer progression. Therefore, they suggested that capsaicin enhances the spread of breast cancer cells by reducing the expression of genes associated with apoptosis in mouse breast cancer cells.
In 2010, South Korean scientists shifted everyone's attention back to the relationship between chili peppers and skin cancer. Their research was published in the renowned American academic journal *Cancer Research*. However, they believed that capsaicin is only a co-carcinogen (it is not carcinogenic by itself but can enhance the carcinogenic effect of carcinogens when acting together with them), promoting the induction of skin cancer by 12-O-tetradecanoylphorbol-13-acetate (TPA).
Anti-cancer:
Although the two epidemiological studies mentioned above cannot clearly state that eating more chili peppers leads to stomach cancer, they may have started to worry foodies who can't live without chili peppers at every meal: chili peppers are so irritating to the gastrointestinal tract, they must cause cancer, right? In fact, there is another side to research on capsaicin and gastrointestinal cancers. Cell experiments have shown that gastric cancer cells are more easily induced to apoptosis by capsaicin than normal cells, and capsaicin can also induce apoptosis in human colon cancer cells.
Additionally, we are always advised to eat less spicy food, especially to avoid it when our gastrointestinal function is poor. However, some studies show that capsaicin can protect the gastric mucosa and can treat gastric ulcers by inhibiting gastric acid secretion and increasing gastric mucosal blood flow.
In 2008, the renowned American journal *Apoptosis* published a study from the University of Pittsburgh School of Medicine on capsaicin and "the king of cancers"—pancreatic cancer. The researchers found that capsaicin could induce apoptosis of human pancreatic cancer cells cultured in vitro and had no effect on normal pancreatic cells.
They then conducted in vivo experiments on rats: rats transplanted with human pancreatic tumors were fed capsaicin (2.5 mg/kg body weight, 5 times a week; or 5 mg/kg body weight, 3 times a week). The results showed that capsaicin inhibited the growth of pancreatic tumors, and no side effects were observed. A research group at California State University conducted a study on capsaicin and prostate cancer with a similar experimental design and feeding dosage, and also obtained similar results. Furthermore, in recent years, there have also been reports of capsaicin inducing apoptosis in mouse bladder cancer cells and human liver cancer cells.
Carinogenic or Anti-cancer?
The question of whether chili peppers can treat or cause cancer has been debated in the scientific community. Researchers have not only been unable to draw a clear conclusion on the relationship between capsaicin and cancer, but there are also controversies about its effect on the same type of cancer. For example, regarding prostate cancer, some studies say that capsaicin can induce apoptosis of prostate cancer cells and inhibit the growth of xenografted prostate tumors, but other research results show that capsaicin can promote the proliferation of prostate cancer cells. This tangled relationship between capsaicin and cancer requires more research to clarify.
One point that needs to be clarified is that regardless of whether these studies on the carcinogenicity or anti-cancer properties of capsaicin produce the results we expect, capsaicin promoting cancer cell growth or inducing cancer cell apoptosis does not equate to the chili peppers we eat causing or treating cancer.
This is because, first, although the results of cell and animal experiments can provide ideas and basis for further clinical experiments, there is a big gap between them and clinical experiments. The results of animal experiments may not be reflected in the human body, and other effects on the human body, as well as issues regarding usage and dosage, still need to be resolved. Second, chili peppers contain many other substances. It is unknown whether the capsaicin in the chili peppers we eat produces the same effect as pure capsaicin, and there is currently a lack of pharmacokinetic studies on capsaicin after it enters the human body.
Conclusion: As for whether capsaicin can cause cancer, treat cancer, or act as a co-carcinogen, the scientific community has not yet reached a unified conclusion. Moreover, the results of these cell or animal experiments cannot be directly equated with clinical experiments, and we cannot therefore conclude that eating chili peppers in daily life will cause or treat cancer. Therefore, there is no need to refuse to eat or eat more chili peppers because of these studies.