Ethanol is a small molecule that has a strong affinity for water. It is absorbed efficiently and rapidly after consumption. Regardless of how it is consumed and in what form of spirits, the effect of alcohol on the central nervous system is closely correlated with the circulating concentrations of alcohol in the blood. This allows enforcement authorities to set certain tolerable (legal) limits of blood alcohol concentrations (BAC) as a surrogate limit for alcoholic intoxication (Singapore's legal limit is 0.08%, or 80 milligrams of alcohol per 100 millitres of blood). As the alcohol in the blood equilibrates very rapidly with the alveolar concentrations, breath alcohol concentrations (BrAC) are often used by the traffic police as an alternative to measuring blood alcohol concentrations. In Singapore, the BrAC limit is 35 micrograms of alcohol per 100 millilitres of breath. See Singapore Traffic Police.It is therefore of some interest to the public to know how much alcohol one can drink without exceeding the BrAC limits.
The peak (maximum) BrAC after consuming alcohol depends on a number of factors:
a] the total amount of alcohol consumed (not the volume of beverage). Obviously the larger the quantum of alcohol, the higher the BAC will be.
b] the rate of absorption of the alcohol. The rate will be faster if the stomach is empty, and if the concentrations are high but not too high. Higher concentrations of spirit (alcohol) will produce a greater concentration gradient to drive the absorption. However, if the concentrations are too high, there may be slower gastric emptying of stomach contents into the small intestines where absorption of the alcohol is faster and more complete. Men theoretically therefore absorb more alcohol then women.
c] the amount of first pass metabolism in the linings of the stomach. There is some controvery about how important this actually is. Women are said to have less alcohol dehydrogenase expressed in the stomach walls and therefore have less first pass metabolism. The less metabolism, the greater the absorption.
d] the 'volume of the body' into which the alcohol is distributed. Pharmacokinetically this is referred to as the volume of distribution. Men have a higher water content in their body compared to women, and since alcohol is distributed primarily into body water, men will weight for weight, develop lower BrACs.
e] the rate of elimination of alcohol. The ADH genetic polymorphims have been discussed elsewhere. If consumed quickly, the rate of elimination will not affect the BrAC much, but if the consumption is protracted over a period of time, long enough for elimination to occur, the rate of elimination may have a significant effect on the BrAC.
Based on the above understanding, it is a reasonable expectation (assuming that the amount of alcohol consumed is exactly the same) that a muscular Chinese man sipping several glasses of wine over the course of a 4-course meal will produce substantially lower BrACs compared to an Indian lady quaffing down a series of stiff drinks on an empty stomach.
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b] Around 20% concentration of alcohol in beverages is rapidly absorbed compared to 3-8%. However, above 40% concentrations such as spirits or whisky can retard absorption. Aerated beverages also increases absorption compared to a non-aerated beverage. Thus, Vodka Coke can promote absorption as compared to a Screw Driver (Vodka & orange juice)
ReplyDeletec] There are other metabolizers of ethanol such as CYP2E1 that can be induced by smoking, excessive drinking, intake of medication, etc. Though it can sound unrealistic but it may be possible for a female who drinks excessive and smokes to metabolize ethanol as fast as a male who of similar size, does not drink and does not smoke.
d] Women also has lower lean body mass that enables them to reach peak concentrations faster. Due to the lower metabolism of alcohol, they tend to contain the concentrations for longer time periods compared to their counter parts.
e] There are many studies conducted on alcohol dehydrogenase (ADH). It is suggested that the beta subunits of ADH class I, ADH1B (formerly named ADH2), is responsible for the vast difference in metabolism of ethanol (though there are many other ADH such as ADH7 that needs to be in consideration). A well described single nucleotide polymorphism by Hurley et al. (2002) in ADH1B exon 3 at position 3240 distinguishes the ADH1B*1 (β1 subunit) and ADH1B*2 (β2 subunit) allele. A study conducted by Yin et. al. (1984) demonstrated that the Vmax for ethanol oxidation of β2/β2 is about 5 – 40 times higher than that of β1/β1 in vitro conditions. Further more, studies such as Teng et al. (1979) states that the allele β1 and β2 can be seen mostly in Indians and Chinese respectively. Thus, it would seem that a Indians tend to metabolize ethanol slower than Chinese.
These are based on my understanding and it is not complete. Do correct me if I were to misinterpret some details. Thanks.
References:
1) Alex Paton. (2005). ABC of alcohol. British Medical Journal. Vol. 330: 85-87.
2) Hurley, T.D., Edenberg, H.J. and Li, T.-K. (2002) The Pharmacogenomics of alcoholism. Pharmacogenomics: the Search for Individualized Therapies, Wiley-VCH, Weinheim, Germany, pp. 417–441.
3) Yin S.J., Bosron W.F., Magnes L.J., et. al. (1984). Human liver alcohol dehydrogenase: purification and kinetic characterization of the beta 2 beta 2, beta 2 beta 1, alpha beta 2, and beta 2 gamma 1 "Oriental" isoenzymes. Biochemistry. Vol. 23(24): 5847-5853.
4) Teng YS, Jehan S Lie-Ijo LE, (1979). Human alcohol dehydrogenase ADH2 and ADH3 polymorphisms in ethnic Chinese and Indians of West Malaysia. Hum. Genet Vol. 53: 87–90.
Cool.Nicely done. Any idea why aerated beverages make a difference? I've not read that before.
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