Alcohol (when used commonly refers to ethanol) is consumed widely around the world for numerous reasons. Its properties have been both praised and demonized. In humans it generally acts as a depressant with, conversely, mild stimulating effects of some parts of the brain. At low levels of consumption alcohol has minimal effects on a person; at higher levels it leads to disorientation, coma, and death. Most alcohol that is consumed is removed from the body via the liver, which breaks alcohol down before removal. However, alcohol can readily cross any cell membrane. Ethanol is widely used as a solvent and disinfectant. It is used as a solvent because it breaks down many proteins and other molecules, such as lipids, which form the main structure of cell walls. It is used as a disinfectant for the same reasons — it breaks down bacteria and many viruses.

When consumed, alcohol has similar effects on cells in the body. It can break down the lipids and proteins that form the walls of cells. Body tissue left in alcohol will dissolve over time (this is one reason why alcohol is sometimes used as a marinade or tenderizer for meat). Most of the time, the concentration of alcohol in the body is too low to do much, if any, damage to cells; however, over time as alcohol continues to be consumed it can have lasting effects on the body. This is one of the effects that leads to sclerosis of the liver; eventually the toxicity and solvent effects of alcohol are too much for the liver. In the brain, alcohol easily crosses the blood brain barrier, which serves to protect the brain from harmful substances (it also keeps out many good ones), and directly affects the neurotransmitters and receptors of neurons. At high enough concentrations (or over time) alcohol can weaken the blood brain barrier by damaging the tight junctions of blood vessels in the brain that form the barrier.

At high concentrations alcohol acts as a vasoconstrictor, increasing blood pressure. Over time, high blood pressure can severely affect the brain leading to stroke and other disorders such as vascular dementia. Volatile (rapid changes in) blood pressure (such as could hypothetically occur secondary to frequent binge drinking) has also been linked to Parkinson’s disease. On the other hand, a recent study found lower rates of Parkinson’s disease in people who had consumed alcohol versus abstainers (Paganini-Hill, 2001). The etiology of this effect is unknown.

Alcohol intake can also lead to vitamin deficiency, which can severely damage the brain (e.g., Korsakoff’s Syndrome), resulting in memory loss, emotional disturbance, gait problems, and ataxia. Additionally, alcohol is physiologically and psychologically addictive. So, does all of this mean that we should not drink alcohol? There certainly are good arguments against its consumption that possibly outweigh any possible positive health benefits it might have. However, if abstinence is not desired then drinking in moderation should certainly be encouraged.

Reference

Annlia Paganini-Hill (2001). Risk Factors for Parkinson’s Disease: The Leisure World Cohort Study Neuroepidemiology, 20 (2), 118-124 DOI: 10.1159/000054770