Alcohol Flush Reaction – can you handle your drink?

You may be able to drink through the night and wake up hungover yet sound, but for many people in the world consuming alcohol has an immediate and negative effect. The question as to whether or not our ancestors consumed alcohol has been met with some debate. The “Drunken Monkey Hypothesis” stems from the idea that primates other than Homo sapiens do consume fermented fruits that contain ethanol and, subsequently, enjoy the effects of alcohol consumption within nature. This has been argued by Dr Robert Dudley of UC Berkley as a potential reason for why humans have an affinity for alcohol and are prone to abuse it.

Within more recent historical evolution, our ability to process alcohol is variable amongst populations. Alcohol flush reaction results in a reddened appearance otherwise known as ‘Asian glow’ or ‘Asian flush’. It occurs more often in people with Asian heritage (40% rates of occurrence in Japanese populations, 26% in Korean populations, and 30% in Chinese/Taiwanese populations). While the reaction does occur in other populations, it is significantly rarer in frequency.

Presence of such a reaction is the result of lacking the chemical enzyme needed to properly process and breakdown alcohol. The enzyme acetaldehyde dehydrogenase converts acetaldehyde (a toxic substance) into acetic acid. This is important as a deficiency in this type of enzyme is associated with an increased risk of esophageal cancer in those who consume alcohol. The Vox video below explains further.

While this area hasn’t been extensively investigated archaeologically, it has been postulated that the reason we see higher rates of Alcohol Flush Reaction within Asian populations is a result of differences in cultural adaptation to water purification. Amongst European populations, it was commonplace to add alcohol to water in order to kill bacteria and avoid contraction of waterborne diseases, such as the case of Victorian London during the time of cholera.

Popular science writer Steven Johnson of Columbia and Brown Universities argues that living in higher density areas as opposed to rural settlements increases the demand for alcohol consumption in order to mitigate the risk of consuming polluted water. In turn, the act of consuming alcohol as a social norm to prevent illness leads to a selection pressure that favours genotypes which produce higher quantities of dehydrogenases (the types of enzymes that are seen in deficient quantities amongst Asian populations).

Interestingly, there is archaeological and DNA evidence to show that there was a significant increase in the frequency of the ADH1B allele in East Asian populations native to the Yangzi basin following the domestication of rice in around 10,000 – 7,000 years ago. The results from this study indicate that the increases in such gene expression is directly linked to the adoption of rice agriculture which varied from region to region with individuals from Tibet showing little to no expression of the gene.

Ultimately, the types of food and drink we can comfortably consume are a result of our own unique and individual evolution and genetic heritage which has been heavily influenced by our ancestors own lifestyle choices and culture. While the role of ‘evolution’ in dietary choices is important, we need to examine it within the context of our own more recent evolutionary history.

References

Bittman, M. (2016). Why Europeans Drank Beer and Asians Drank Tea. [online] Diner’s Journal Blog. Available at: http://dinersjournal.blogs.nytimes.com/2008/07/11/why-europeans-drank-beer-and-asians-drank-tea/?_r=0 [Accessed 21 Mar. 2016].

Blogs.crikey.com.au. (2016). London in the time of cholera –. [online] Available at: http://blogs.crikey.com.au/theurbanist/2010/06/24/london-inthe-time-of-cholera/ [Accessed 21 Mar. 2016].

Dudley, R. 2014. The drunken monkey: Why We Drink and Abuse Alcohol. University of California Press.

Li, H., Mukherjee, N., Soundararajan, U., Tárnok, Z., Barta, C., Khaliq, S., Mohyuddin, A., Kajuna, S., Mehdi, S., Kidd, J. and Kidd, K. (2007).

Geographically Separate Increases in the Frequency of the Derived ADH1B*47His Allele in Eastern and Western Asia. The American Journal of Human Genetics, 81(4), pp.842-846.

Peng, Y., Shi, H., Qi, X., Xiao, C., Zhong, H., Ma, R. and Su, B. (2010). The ADH1B Arg47His polymorphism in East Asian populations and expansion of rice domestication in history. BMC Evol Biol, 10(1), p.15.

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