The health-promoting effects of alcohol
The BIO230 class is currently discussing the control of microorganisms in the environment, and one chemical method that we pay close attention to in class is the use of ethanol. Ethanol is powerful disinfectant, and is commonly used to reduce or eliminate microorganisms on inanimate surfaces. Its mode of action is to denature nucleic acids in microbes, and when used appropriately it is an effective bacteriocidal compound. A similar compound, isopropanol, is also frequently used as a topical antiseptic and wound cleanser, and has a similar mode of action.
My long-standing interest in alcohol prompted my immediate attraction to this report in the biomedical literature (with the intriguing title Alcohol Consumption as Self-Medication against Blood-Borne Parasites in the Fruit Fly), which I came across via the science blog io9.com. Researchers at Emory University in Atlanta, Georgia, started from an interesting premise: the fruit fly Drosophila melanogaster, which of course feeds on fruit, also ingests yeasts on rotting fruits, which can then ferment the sugars in the fruit to produce ethanol. The flies consequently have developed a high tolerance to the biological effects of ethanol. The researchers then wanted to see whether ethanol then might offer the fly some matter of protection against invading organisms.
Fruit flies are susceptible to any number of pathogens and parasites, and indeed this year’s Nobel Prize for Medicine or Physiology recognized work characterizing the way that fruit flies are able to resist infections using aspects of the immune system that are shared with humans. This report looked at something a bit more scary; fruit flies are also susceptible to attack by parasitic wasps that lay their eggs into the body of the fly. The developing wasp larvae then use the fly as a source of food, and ultimately kill the fly as they grow. The premise that the researchers at Emory proposed was that ethanol, produced by the action of yeasts acting on the fruit eaten by the flies, might be able to inhibit attack by these parasitic wasps.
With this premise in play, they examined the frequency of egg laying by wasps into fruit fly larvae, and found that alcohol would reduce the ability of the larvae to be parasitized in the first place. Additionally, for fruit fly larvae that had already been infected by wasps, consumption of alcohol increased the death of wasp larvae and led to survival of the flies. Furthermore, larvae which have been infected appeared to seek out alcohol-containing foods, suggesting that they were actively striving to eliminate the parasites. The article concludes that the ability of Drosophila to resist the effects of alcohol puts the organism in a unique position to use alcohol as a curative compound, and perhaps this ability might extend to other organisms.
With that fabulous premise in mind, I thought perhaps it might be beneficial to work to cure myself with some wine. However, for most ailments of humans, this might not be terribly effective. As we will discuss in class, ethanol has its most significant bacteriocidal effects when used at a concentration of approximately 70%, and at levels below 45% it is not very good as a disinfectant. Unfortunately, even at these measly levels, a blood alcohol level of only 0.4% is close to toxic for the human body, consequently even a whole bottle of wine might not have very much effect on that bacterial infection.
So, unless you are infected by parasitic wasp larvae, don’t count on that drink to make you feel better!