Alcohol Does Dehydrate You. Here’s What to Do About It
Does Alcohol Dehydrate You?
If you’ve heard that alcohol dehydrates you, then you’ve heard correctly. Alcohol removes water and important nutrients from your body, making those dreaded hangovers longer and worse.
And while the non-alcoholic fluids in beer, wine, and liquor are inherently hydrating, they’re not necessarily hydrating enough to offset the effects of alcohol-induced dehydration.
But that doesn’t mean you shouldn’t enjoy an adult beverage or two from time to time. Here’s what you need to know about how alcohol dehydrates the body and how to drink responsibly.
Alcohol and your body: What happens
Alcohol consumption affects your body in a number of ways.
If you’ve ever heard the term, “breaking the seal,” you know that alcohol has a diuretic effect on the body, meaning it causes you to urinate more frequently. The process is called diuresis, which on its own causes dehydration .
In fact, 10 grams of alcohol makes you produce 100 mL (3.38 fl. oz.) of urine .
For reference, a standard drink—12 ounces of beer, 5 ounces of wine, 1.5 ounces of liquor—has 14 grams of alcohol, according to the National Institute on Alcohol Abuse and Alcoholism .
In other words, the alcohol alone in one standard drink can make your body produce a little less than half a cup of pee.
Part of what causes you to urinate more while drinking alcohol is that alcohol inhibits the release of an anti-diuretic hormone (also called vasopressin) . The result: Party time means more potty time later.
But prolific pee production isn’t the only way alcohol dehydrates you. Alcohol delays stomach emptying, which can cause vomiting, a sure way to become dehydrated .
Excessive drinking can also lead to a buildup of a toxic substance called acetaldehyde. When your body can’t get rid of acetaldehyde quickly enough, you may experience a vomiting hangover—throwing up after a night of drinking .
How much alcohol does it take to dehydrate you?
Even just one drink can lead to dehydration. But, as Lindsey Pfau, M.S., R.D., points out, just one beer, for example, also has a lot of non-alcoholic fluids, which will help lessen the dehydrating effects of one beer.
But once you introduce alcohol into your system, you urinate more, and the mechanism that normally prevents excessive urination—anti-diuretic hormone—is inhibited, causing dehydration.
Do some types of alcohol dehydrate you more than others?
It’s possible that some alcoholic drinks may be more dehydrating than others, but more research is needed, Pfau says.
A 2016 study published in the American Journal of Clinical Nutrition assigned a beverage hydration index (BHI) to various drinks that would determine hydration status after ingestion.
Drinks that contained electrolytes—milk and oral rehydration solutions, for example—were more hydrating after two hours compared to water.  In other words, subjects peed less relative to their fluid intake two hours after consuming these drinks compared to water.
One lager beer seemed to be just as hydrating as water after two hours, but Pfau points out, that could be because beer contains a lot of non-alcoholic fluids—it has high water content—and contains calories, which could delay gastric emptying.
Based on this thinking, Pfau says a 1.5-ounce spirit and a 5-ounce glass of wine could be worse compared with a 12-ounce lager beer, but it’s not entirely clear. (It’s worth noting that grams of alcohol and ABV are basically the same thing, explains Megan Stoutz, M.S., R.D.. Grams measures alcohol by weight, while ABV measures alcohol by volume.)
“Stronger alcohol might provoke more dehydration, but it truly has not been studied enough to know for sure,” she says, pointing to a 2017 study published in Nutrients. That paper summarizes that research into whether stronger alcohol is linked with increased dehydration is inconclusive. .
Mixed drinks are tricky. A vodka with soda is likely more hydrating than just a shot of vodka because you’re consuming more fluids from the soda.
And there’s dark liquor. Alcohols like whiskey and brandy have high levels of congeners, including tannins and acetaldehyde. These might lead to dehydration more quickly, according to a 2010 study  .
Can you prevent dehydration while drinking alcohol?
While being hydrated is important, Pfau points out that if you aren’t properly hydrated prior to drinking, your body’s water content is already low, which means you will urinate less than you would otherwise.
“Interestingly, your hydration status before drinking alcohol will have little to do with your ending hydration status,” she says. “I certainly do not promote being dehydrated, but if you are already dehydrated prior to consumption of alcohol, you won't urinate quite as much. What you do before drinking has less to do with hydration status as what you do after [drinking] to rehydrate and recover.”
That said, being dehydrated before drinking alcohol could cause your blood alcohol concentration to increase more quickly. In other words, you’ll get drunk faster.
“Essentially, when you’re dehydrated, you’ll feel alcohol’s effects sooner and for longer,” Pfau says.
Stoutz emphasizes the importance of hydrating before and during drinking, which can minimize how dehydrated you become.
“You can’t entirely prevent it, but if you go into drinking well-hydrated, you are less likely to feel the negative effects of dehydration,” she says.
- Don’t drink on an empty stomach. Without vitamin-rich foods in your stomach, alcohol is absorbed more quickly, which means you get drunk and dehydrated more quickly, and could end up with a worse hangover.
- Hydrate before you drink. Make sure you’re well hydrated before your night out on the town. As Pfau explains, your body needs water for its normal functions regardless of whether you’re drinking alcohol. A good way to check your hydration status is your urine: It should be a pale yellow color.
- Trade off between water and alcohol. Once you start drinking alcohol, make sure water is getting some love, too. For every alcoholic drink you have, drink a 16-ounce glass of water.
- Avoid dark liquors. Alcohols like whiskey and brandy have high levels of congeners, including tannins and acetaldehyde, which might dehydrate you more quickly.
How to rehydrate after drinking alcohol
After a night of drinking it’s important to make sure you rehydrate. Stoutz says the best way to hydrate is to alternate alcohol and water while you’re drinking.
“If you’ve gone the whole night and realize you didn’t have any water, you can’t ‘catch up’ with plain water,” she says.
In those cases, try rehydrating with an electrolyte solution. (Ahem—here’s a good one.)
Electrolytes are minerals—sodium, calcium, potassium, chloride, phosphate, and magnesium—in the body that help balance the amount of water in the body, balance the body’s acid and base levels, move nutrients to cells, removes waste from cells, and helps muscles and the brain work properly.
Electrolytes are found in common foods, including salt, bananas, and watermelon, and can also be consumed from electrolyte-specific drinks or mixes.
“An electrolyte solution will help you absorb more [fluids],” Stoutz says.
Milk is also a good choice to help you rehydrate, assuming your hangover hasn’t put you off dairy. The same 2016 study from the American Journal of Clinical Nutrition found that milk was more hydrating than water, sports drinks, coffee, tea, and a handful of other common beverages .
“The best beverages to rehydrate with should include electrolytes like sodium and potassium, as well as calories from carbs, proteins or fats to help the fluids be absorbed into the cells,” Pfau says.
She goes on to explain these nutrients also help you retain fluids, while chugging a bunch of water will cause much of it to pass through your system without properly rehydrating you.
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 Mayo Clinic Staff, “Hangovers,” Mayo Clinic, Dec 16, 2017. https://www.mayoclinic.org/diseases-conditions/hangovers/symptoms-causes/syc-20373012
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