On pages 58 - 60, Dr. Moalem talks about the alcohol flush response. After drinking alcohol, the body needs to detoxify it so it can extract calories. There are three main enzymes that take part in the breaking down of alcohol. The first of which is alcohol dehydrogenase which converts the alcohol into acetaldehyde, a by-product of alcohol that is 30 times as toxic. The second enzyme, acetaldehyde dehydrogenase, breaks down the acetaldehyde into acetate. The third enzyme converts the acetate into fat, carbon dioxide, and water.
Many people of Asian descent have a variation of the enzyme acetaldehyde dehydrogenase called ALDH2*2. This is less effective in converting acetaldehyde into acetate, and creates a buildup of acetaldehyde, which could cause a flushing response, dizziness, and extreme nausea. Europeans do not have the variation. Dr. Moalem also stated that this may have occurred because Europeans used fermentation to purify their water and Asians boiled their water and made tea to ferment their water. Relating this to Big Idea 1: The process of evolution drives the diversity and unity of life, research the prevalence of ALDH2*2, or another variation of acetaldehyde dehydrogenase in other areas of the world. With this information, how do the people in that society react to alcohol? Why might this variation have occurred (think back to how said society purified their water)?
(Posted by Sriya Potham, spotham4@students.d125.org)
According to “Effects of Worldwide Population Subdivision on ALDH2 Linkage Disequilibrium”, an article published in Genome Research, Africans have similar alleles on their ALDH2 compared to Asians yet very rarely do they experience the Alcohol Flush Reaction that is common amongst Asians. Africans, like Europeans do not have the variation of acetaldehyde dehydrogenase called ALDH2*2 that many Asians have and as a result do not have as intense of a reaction to alcohol if any response.
ReplyDeleteThis variation may have occurred as Europeans with traits that allowed them to drink alcohol without experiencing a buildup of acetaldehyde and the following flushed reaction may have been a selective advantage in a society that used fermentation to purify water. Those who couldn’t drink alcohol without the reaction may have resorted to drinking unpurified water and may have had a higher chance of getting sick through waterborne pathogens. This would not have been the case in Asia where having the alcohol flush reaction trait was not selected against as pure water was consumed through tea rather than alcohol.
This relates to Big Idea 1: the process of evolution drives the diversity and unity of life. People with the ALDH2*2 trait living in Asia would not have been selected against as water was mainly purified through boiling and drunk in the form of tea while people living in Europe may have been selected against if they had the ALDH2*2 trait. This would be because many European people purified water through fermentation and those who would not be able to drink alcohol comfortably would have resorted to drink unpurified liquids resulting in a higher chance of infection and a reduced chance to survive and reproduce.
-Chris Yao
(chyao4@students.d125.org)