buzzed drinkingMany people figure a few drinks over a few hours won’t put them over the legal limit. But the amount of alcohol it takes to raise your Blood Alcohol Content (BAC) can vary. Studies show blood alcohol level may be influenced by a variety of factors, such as age, weight, and gender. In addition, someone who chronically consumes significant amounts of ethanol can develop a tolerance. They will show fewer signs and look less impaired at a higher blood alcohol level than someone who does not consume ethanol as often.


Ethanol: What Happens in Your Stomach, Small Intestine and Liver

Ethanol is absorbed through the stomach and small intestine, with the small intestine being most efficient. Between the stomach and the small intestine is a valve called the pyloric valve.

Your body breaks down ethanol primarily via your liver. Through a complex metabolic process, the liver first converts alcohol into acetaldehyde, a highly toxic substance. The acetaldehyde is converted by the liver into acetate, a harmless substance, which is then turned into carbon dioxide and water, then excreted.


Factors that Affect Alcohol impairment

What and whether you eat matters

Eating low-fat or fat-free healthier foods can alter how drunk you get. According to the National Institute on Alcohol Abuse and Alcoholism, foods with a higher fat content take more time to leave the stomach and can slow the rate at which your body absorbs the alcohol from your digestive tract. If you eat a big meal consisting of fried or fatty food this valve closes to keep the food in the stomach for digestion. The high fat content can cause the valve to remain closed for up to six hours.


Gastric bypass surgery; an unexpected side effect

The normal surface area of the stomach is a couple of square feet. Because surgery reduces the stomach to the size of a walnut, alcohol will transfer faster to the small intestine, where it is quickly absorbed.  Stanford University researchers conducted a study in which they gave 5 ounces of red wine to 19 post-operative gastric bypass patients and 17 controls. They were told to consume the drink in 15 minutes. The surgery patients reached peak blood-alcohol level of 0.08 percent while the control group reached only 0.05 percent, according to Medical News Today.


Your body fat percentage makes a difference

Size matters when it comes absorbing alcohol. A larger person has more body fluids, which dilute the alcohol. Because women generally have more body fat, they proportionally have less body water than men – less water means a more concentrated blood alcohol. The percentage of your body fat to muscle mass (BMI) plays a role too. Because alcohol is more soluble in water than in fat, a 150-pound person with more lean muscle mass (who has less fat) will be less affected by the same number of drinks as a 150-pound person with more body fat.

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Some evidence indicates women may metabolize alcohol slightly differently. There are small amounts of the enzyme ADH, which is responsible for breaking down alcohol in the liver and the lining of the stomach. Some research suggests that the ADH levels (link to NIH article) are lower in women and that this might contribute to their higher blood alcohol levels.


Older adults get drunk faster

A report was published in the March issue of the Journal of Studies on Alcohol and Drugs, discussing the role of age and intoxication. The older you get, the more easily you become intoxicated, thanks to a number of physical changes in your body. Two such changes are the decrease in the metabolism of alcohol in your digestive tract and a decrease in body water. Sara Jo Nixon, now a professor in the department of psychiatry, division of addiction medicine, and director of the Neurocognitive Laboratory at the University of Florida in Gainesville recently told ABC News, “Older adults thought they were fine when they weren’t. You really can’t rely on asking, ‘Are you alright to drive,’ even with lower amounts of alcohol. This may be particularly true for older adults.”


You mixed your drink with soda

Carbonated beverages raise alcohol levels faster, because the gas (CO2) irritates the stomach lining, causing alcohol to be absorbed faster. Blood alcohol levels also spike faster if mixed with diet soda compared to regular soda, according to a small study recently published in the journal Alcoholism: Clinical and Experimental Research. In two different sessions, study participants drank the equivalent of three to four mixed drinks in a short period of time. When they drank vodka mixed with regular soda, their peak blood alcohol level measured 0.077, just under the legal limit of 0.08. But when they drank vodka mixed with diet soda? Their blood alcohol measured 0.091.

The most accurate way researchers and law enforcement officials determine BAC is by drawing blood and testing it using methods such as gas chromatography and mass spectrometry.


Additional Resources

Visit our online Volatiles Screening and Quantitation resource within our Toxicology community to learn more about Blood Alcohol testing by gas chromatography. You can also view the resources below for more information on this topic.