Does caffeine help you drink?

It was my brother who told me that drinking coffee while drinking alcohol was a good idea - it would lessen the effects of intoxication. I launched into an ethanol fuelled discussion of how physiologically implausible that sounded to me, but we were celebrating a great occasion, and so I don't think I got much beyond slurring something about cyclic AMP before we instead had some of Arizona's finest porter. But I recall that exchange fairly well, a few years later.

It's with the fact that I'm taking on my brother that I write this - here's a man who can, and has when I was younger, beat me up, so I'll be diplomatic about it. Energy Drink-Cocktails have been in vogue for the last little bit, so Ferreira and colleagues decided to perform a small experiment of the effects of Redbull® and vodka. They took 26 subjects, all Brazilian males, and were put on treatment of one of two doses of vodka (a lesser and greater amount), modulated with and without Red Bull. There were a total of 3 treatments at least 7 days apart, and the whole thing was double blinded throughout - meaning neither researchers nor subjects knew whether they were getting alcohol, or the alcohol mixed with the energy drink. They also standardized the subjects on calories in a novel way - they used a big mac as a pre-drinking caloric unit. Who knew McDonalds was a research tool?

The graph most worth reproducing is the one that shows absolutely no effect on breath alcohol concentrations. I've included it to the right. I'm not fond of breath measurements (blood is better), but that aside, the effect is pretty clear: there is none. Co-drinking caffeine does not appear to modulate your BAC. Already, one urban myth dead.

But even if it doesn't effect your BAC, perhaps it effects how intoxicated you are, or your performance while intoxication. They tested this, by examining motor co-ordination and visual reaction time. In both cases, there was no effect of energy-drink on performance. Having a Red Bull® does not improve your ability to function while intoxicated. The popular myth of co-administered caffeine appears well and truly dead. But this raises the question, why did such a persistent myth get started?

There's no good figure for this (basically a page of tables), but at the same time they asked their subjects a variety of questions about wellbeing, and how they felt at the time. It covered the field from tiredness, tremor, to speech impairment and so on. Now, right now, these menus are basically a laundry list, and some of the results can easily show up as positivity spuriously. With that in mind, they found that individuals felt they had significantly better motor co-ordination than they in-fact had. Remember, they were double blinded, so they didn't know what they had just drank. The expectation bias should be weak in this instance - something about the energy drink makes us /feel/ illusory confidence in our motor skills. Perhaps it prevents us from feeling how poor our skills have become, or perhaps it bolsters confidence in the skills. It's hard to divine which, from the data.

Aside from the problem of multiple tests on that, I've got one other criticism of the study, and that's how they standardized their subjects. I've long suspected that self-reported alcohol consumption is not a reliable indicator of true alcohol (or other drugs) consumption. There's a stigma attached to excessive drug consumption, and so people are likely to under-report their use. There needs to be a better way to gauge participant alcohol consumption.

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Ferreira, S., de Mello, M., Pompeia, S., & de Souza-Formigoni, M. (2006). Effects of Energy Drink Ingestion on Alcohol Intoxication Alcoholism: Clinical and Experimental Research, 30 (4), 598-605 DOI: 10.1111/j.1530-0277.2006.00070.x