Capsaicin and Spicy Food

Red is the color most people picture when they think of the Korean table: gochugaru in kimchi, gochujang in stews and rice cakes, fresh and dried chili peppers almost everywhere. Yet chili is a relatively recent arrival. Peppers reached Korea only around the late sixteenth or early seventeenth century and took time to settle into everyday cooking (see chili peppers in Korea). The burn they bring comes mostly from one family of compounds.

What capsaicin is

Capsaicin is the main pungent compound in plants of the genus Capsicum, and it belongs to a group of related molecules called capsaicinoids. It dissolves readily in alcohol and fat but poorly in water. The amount varies widely with pepper variety, growing conditions and which parts of the fruit are used, which is why one bag of gochugaru can be gentle and another fierce.

How heat is perceived

The burn of chili is not a taste in the way sweet or salty is. Capsaicin binds to a receptor called TRPV1 on pain-sensing nerve endings, including those in the mouth. The same receptor responds to physical heat of about 42°C and above, which is why the brain reads chili as something hot, even though the food may be at room temperature. That shared pathway helps explain the sweating, flushing and runny nose that often come with a spicy meal.

Sensitivity is not the same in every animal. Small differences in the receptor make rabbits less responsive to capsaicin and birds largely insensitive to it. In people, laboratory work shows that sustained exposure can desensitize TRPV1. Many regular chili eaters report that their tolerance grows over time, though how much of that is physiology and how much is familiarity is not fully worked out.

What research says

Capsaicin is an active area of laboratory research, much of it in cells and animals. Findings at that stage are not evidence that eating spicy food has the same effects in people.

• Population studies: A 2021 meta-analysis pooled four large observational cohorts, from the United States, China, Italy and Iran, covering about 570,000 people. Regular chili eaters had lower all-cause and cardiovascular mortality than people who rarely or never ate chili. Observational studies like these cannot show cause and effect: chili eaters may differ in many other ways, and the studies varied considerably.
• Digestion: Capsaicin acts on receptors throughout the digestive tract, and its effects on the gut are still being mapped. In a study of functional dyspepsia patients in Korea and Japan, those who ate more spicy food reported more stomach fullness, regardless of their TRPV1 gene variant.

Taken together, spicy food can be part of an enjoyable, varied diet, but there is not enough evidence to eat it as a health measure.

Heartburn and the gut

Spicy food is one of the foods people with reflux most often name as a trigger. The US National Institute of Diabetes and Digestive and Kidney Diseases notes that some people with GERD find certain foods or drinks bring on or worsen symptoms, and lists spicy foods among them. Its suggestions are practical: notice which foods bother you, discuss cutting back with your doctor, and finish eating at least three hours before lying down.

• Know your triggers: Reactions are individual. Some people tolerate a bowl of kimchi-jjigae without trouble; others feel it hours later.
• Mind the meal around the chili: Many very spicy dishes, such as tteokbokki, are also rich and salty. See sodium in Korean food.
• Persistent symptoms: Frequent heartburn, trouble swallowing or ongoing stomach pain deserve a visit to a doctor rather than self-management.

Enjoying heat on your own terms

The Korean table has always had milder dishes alongside the red ones. Baek-kimchi and dongchimi skip chili flakes, gyeran-jjim is soothing, and plain rice and soup give the palate a rest between bites. When cooking at home, start with a smaller amount of gochugaru, taste and build up. Rubbing your eyes after handling fresh chilies is a classic mistake; wash your hands or wear gloves.