Drinking alcohol produces a complex set of effects on a number of body systems.
(a) On which system are the main acute effects most likely to lead to sudden death, and why?
(b) Name some possible causes of death from drinking alcohol.
(a) The main acute effects are on the nervous system, causing mood changes and impairment of judgement and reaction time, etc.
(b) Possible causes of death are a fatal traffic accident due to poor judgement; other accident due to uninhibited behaviour; inhalation of vomit; heart or lung failure; liver cirrhosis; suicide due to depression. You may be able to think of others.
Explain two different ways whereby some individuals could have higher levels of acetaldehyde in their system than others, after drinking identical alcoholic drinks.
(a) Acetaldehyde is produced from ethanol more rapidly in some individuals than in others.
(b) Acetaldehyde is converted into acetic acid more slowly in some individuals than in others.
If the reaction catalysed by ALDH to form acetic acid is faster than the production of acetaldehyde (catalysed by ADH), how will this affect the drinker?
There will be no build-up of acetaldehyde because it will metabolise to acetic acid as soon as it is made. So, the drinker will not experience the flushing, increased heart rate, dizziness or nausea associated with a build-up of acetaldehyde.
The proportion of fat per body weight increases with age. How might this affect older drinkers?
The increased proportion of fat to muscle in older people will result in a decrease in total body water. As ethanol is water-soluble, the same amount of ethanol will be dissolved in a smaller amount of water, resulting in a higher BAC in an older person than a younger. Unless the body responds by making more enzymes, this will result in higher levels of intoxication after smaller amounts of ethanol.
(a) Why is it impossible to be precise about what is a safe drinking limit? (b) Why in particular are pregnant women advised to avoid drinking any alcohol at all?
(a) People inherit genes that direct production of ethanol-metabolising enzymes, and will therefore process ethanol at different rates. People also vary greatly in weight and in their muscle to fat ratios. It is therefore impossible to do more than give very broad guidelines on what might be a safe level of drinking.
(b) Pregnant women are advised to abstain from drinking alcohol because of the risk of fetal alcohol syndrome (FAS). No safe limit has been identified for this because the mechanisms by which alcohol consumption causes FAS in some individuals are poorly understood.