The belief that mixing different types of liquor is inherently worse than consuming a single spirit is common, often cited as the cause of severe next-day symptoms. This perception suggests a chemical incompatibility between spirits like vodka and tequila. However, the body does not fundamentally change how it processes the primary substance in any alcoholic beverage. Negative outcomes relate instead to the body’s consistent detoxification mechanism, the specific byproducts in each spirit, and consumption patterns when switching drinks.
How the Body Processes Ethanol
Regardless of the spirit consumed, the intoxicating component is always ethanol. Once ethanol enters the bloodstream, the liver begins a two-step detoxification process using specialized enzymes. The primary enzyme, alcohol dehydrogenase (ADH), first converts ethanol into acetaldehyde, a compound highly toxic to the body.
A second enzyme, aldehyde dehydrogenase (ALDH), then rapidly converts acetaldehyde into acetate, a harmless substance the body can easily eliminate. The speed of this entire process is consistent across individuals, averaging a reduction in Blood Alcohol Concentration (BAC) of about 0.015% per hour. Since the liver’s capacity is fixed, the rate of intoxication depends entirely on the total volume of pure ethanol consumed and the speed of consumption, not the spirit’s source.
Congeners and Hangover Severity
While the core alcohol molecule is identical across all spirits, the chemical differences between vodka and tequila are due to compounds known as congeners. Congeners are biologically active byproducts of fermentation and aging, including substances like methanol, acetone, and fusel oils. These compounds contribute to the severity of hangover symptoms because they add to the toxic load the liver must process alongside ethanol.
Vodka, being highly distilled and filtered, is one of the lowest congener spirits available. Tequila, by contrast, generally contains higher levels of congeners. This is particularly true for aged varieties, such as Reposado or Añejo, which are rested in oak barrels. The barrel aging process introduces additional compounds, including wood tannins and acetaldehydes, which increase the total congener content compared to unaged Blanco (silver) tequila.
When a person switches from low-congener vodka to higher-congener tequila, they increase the concentration of these byproducts entering their system. The negative feeling from mixing these two spirits is often a result of adding a high-congener spirit to the total intake. This leads to a more intense hangover than if the person had consumed only the low-congener vodka. The severity is less about a chemical reaction between the two liquids and more about the cumulative effect of the total congener load.
The Impact of Consumption Patterns
For many people, the behavioral aspect of mixing spirits is a greater contributor to negative outcomes than the chemical content. Switching between different types of drinks, such as moving from a vodka cocktail to a tequila shot, often disrupts a person’s ability to accurately track their total alcohol intake. This lack of self-monitoring can lead to consuming a higher volume of ethanol over a shorter period.
The psychological effect of “mixing” can encourage faster and less inhibited drinking behavior. The pace of consumption is a direct determinant of the Blood Alcohol Concentration spike, meaning that drinking quickly increases intoxication and subsequent sickness. The danger lies in the total quantity of alcohol consumed, not the specific combination of spirits reacting poorly within the stomach. Focusing on the number of standard drinks consumed and maintaining a slow, consistent pace is more important than worrying about the order or type of liquor.