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Mysterious enzyme defect: Why do some Japanese react so strongly to alcohol?
Alcohol is often seen as an integral part of social situations in many parts of the world, but for some people, enjoying it can be a painful experience. In Japan in particular, nearly half of adults have a condition known as "Asian flush," a cascading physiological response to alcohol that is being studied intensively by scientists.
The physiological effects of alcohol go beyond flushing and can also cause breathing difficulties and asthma symptoms, and the root cause of these reactions appears to be a metabolic defect in the body's enzymes.
In 1973, Breslin et al. conducted a study and found that 11 participants with a history of asthma experienced asthma symptoms such as chest tightness after drinking certain alcoholic beverages. Subsequent studies further revealed that these reactions did not appear to be caused by the alcohol itself, but rather by certain non-alcoholic allergens or other compounds.
A 1986 study showed that 9 out of 18 participants showed red wine-induced asthma symptoms, and the intensity of these symptoms was positively correlated with the sulfur dioxide content in the red wine. This means that many of these reactions are actually caused by the chemical components rather than the alcohol itself.
Alcohol-induced allergic reactions have been extensively studied especially in Asian populations, especially the Japanese. Many Japanese people have a mutation in an enzyme called ALDH2 that prevents them from metabolizing acetaldehyde efficiently. The variant, which is common in more than half of Japanese adults, makes them more susceptible to a variety of adverse reactions after drinking, including facial flushing, rapid heartbeat and increased asthma.
These physiological reactions usually occur within 1 to 30 minutes after drinking. Some people may even experience severe allergic reactions due to the inability to properly metabolize acetaldehyde, ranging from moderate wheezing to fatal cardiovascular collapse.
The impact of the ALDH2 variant is not limited to Japan. The variation of this gene also exists in other East Asian populations, but the degree of variation varies, resulting in different ethnic groups having different tolerance to alcohol. For example, the mutation rate in the Han Chinese is close to 30%, while it is about 28% in Koreans. This means that the alcohol responses in these groups will be significantly different from those in the Japanese population.
For non-Asian populations, although there is a lack of research on ALDH2 mutations, some Western statistics show that about 5% of adults also experience alcohol-induced allergic symptoms. According to surveys, this group of people may have other genetic abnormalities, which cause them to accumulate acetaldehyde after drinking, leading to allergic reactions.
The most effective treatment recommended by the medical community for alcohol-induced asthma symptoms is to avoid alcohol completely. According to research, individuals who experience an allergic reaction to alcohol tend to spontaneously reduce their alcohol consumption, thereby reducing the associated physical discomfort.
In addition, the use of H1 antihistamines before drinking alcohol was able to prevent these adverse reactions, which was confirmed in the human population, especially in Japanese participants.
While many alcohol-induced breathing symptoms are ultimately attributed to genetic defects, this also makes each person's reaction after drinking unique and closely related to their ethnic background. Japan's mainstream culture is highly accepting of alcohol, but the differences in academic reactions to alcohol still need further discussion.
When making a clinical diagnosis of an alcohol allergic reaction, doctors often use questionnaires for initial screening. Such questionnaires help understand if a particular alcohol triggers a reaction, and further skin testing or genetic testing may then be done to confirm the allergen.
With such a wide variety of alcohol responses, is it possible to find more effective ways to help these people overcome alcohol-related health problems and social barriers in the future?
