Effects of Eating and Smoking
on DUI Breath Alcohol Tests

The delaying effects of food on alcohol absorption - and thus on any attempts to use retrograde extrapolation in guessing earlier blood alcohol levels in a drunk driving case - have been documented. In A. W. Jones, "Concentration-Time Profiles of Ethanol in Capillary Blood After Ingestion of Beer", 31 Journal of the Forensic Science Society 429 (1991), groups of subjects were given both light and regular beer on an empty stomach, during a normal lunch, and one to two hours after a meal.

The results of blood-alcohol testing showed lower peak blood-alcohol concentration (BAC) with light beer on an empty stomach than with regular beer; the same was true for beer consumed after a meal. Peak concentrations for the two types of beer taken during a meal were similar, but the regular beer produced a slower rate of elimination.

Peak BACs for both kinds of beer were lower with a full stomach, and those peaks were reached earlier. This confirmed earlier studies indicating that some of the ingested alcohol is trapped by food in the stomach, forming a so-called bound pool which is not absorbed immediately. The untrapped "free pool" of alcohol, on the other hand, is absorbed as if in an empty stomach, causing a peak BAC to be reached quickly. The bound pool of alcohol continues to be slowly absorbed, creating a slowly dropping level of blood-alcohol concentration.

See also Jones and Neri, "Evaluation of Blood-Ethanol Profiles After Consumption of Alcohol Together with a Large Meal", 24(3) Canadian Society of Forensic Science Journal 165 (1991), for a study with similar results. After extensive experimentation involving ingestion of alcohol by 16 DUI police officers, the researchers concluded that "[t]he results presented in this paper emphasize the need for caution when engaging in retrograde extrapolation."

Studies of the effects of eating on DUI breath alcohol tests have also been conducted by scientists at the Southern California Research Institute. Conducted under a contract with the Highway Safety Research Institute, the results are contained in a final report entitled "Methods for Estimating Expected Blood Alcohol Concentration", DOT HS-805-563 (U.S. Department of Transportation, National Highway Traffic Safety Administration, Wash., D.C. 20590). Among the findings:

The limited literature on alcohol and food effects provides considerable evidence that food delays gastric emptying, and that it is the delay which slows the rate of alcohol absorption. In turn, it is the slower absorption process which underlies the lower BACs associated with food intake.

If a drinker wishes to hold his or her BAC at a low to moderate level, what are the guidelines for food consumption? What is the best time to eat in relation to alcohol intake? What type of food is best? How much food is it necessary to eat to insure the desired effect? The data from this study indicate that the following are appropriate responses to these questions.

In brief summary of the study findings, when food is eaten in close proximity to drinking alcohol, it can substantially reduce the BAC from the level that would be reached if the alcohol were consumed on an empty stomach. Protein has the largest effect, and carbohydrates also are very effective.

Fatty foods are relatively ineffective in any quantity, and for the purposes of limiting BAC, it would be best to restrict the fat content of meals to a minimum, choosing instead foods which are largely protein and carbohydrates. Finally, a large amount of these latter types of food will be more effective than a small amount.

The findings regarding time of food intake show an inverse relationship; the greatest reduction in BAG was found at one-half hour, the shortest interval between eating and drinking which was examined. At an interval as long as two hours, the laboratory data show that the food exerted an effect. At four hours there was no effect of the food (as would be expected inasmuch as that period of time allows the food to pass through the stomach). Note that the findings regarding time of food intake are from pilot data only. This variable was not examined in the larger experiment in which the single interval of one-half hour between food intake and alcohol consumption was used.

The findings concerning the amount of food are fairly straight forward. A full meal will offer more protection than a snack, but even small amounts of food will have some effects on the BAC. In the laboratory 1000 calorie meals, which were either high in protein content or high in carbohydrate content, were followed by a 40% reduction in BAG. Certainly a change of that magnitude has practical significance to the individual.

Type of food is a more complex issue than the other variables of interest, but the data provide the basis for some recommendations. The person who expects to be drinking and would prefer to offset the alcohol to some extent by eating can be advised to consume a typical, full meal. For example, a meal which contains bread, meat, potatoes, and vegetables would be ideal. Such foods are largely protein and carbohydrates with a smaller proportion of the food being fats, and that kind of basic menu can be recommended. There is no evidence in these data to suggest that any specific, special foods should be eaten.

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