Look, it’s highly unlikely that giving up booze before running a marathon (or half-marathon, or even a 10K) is going to turn you into Eliud Kipchoge come race day. And while the research isn’t cut and dry in terms of how much it might help you, going sober before a race certainly can’t hurt, says Matthew Barnes, a professor of sport and medicine, and researcher on alcohol and exercise at New Zealand’s Massey University.
“Alcohol is detrimental to pretty much every tissue in the body,” he explains. “You’re likely to reduce any alcohol-related decreases in immune function, hormonal disruptions, altered metabolism, excess energy intake, and altered sleep,” he says.
Of course a beer or two isn’t going to kill you during training; in terms of nutrition, it’s most important to be hydrating and fueling properly.
But “studies have clearly shown the consumption of alcohol immediately before a race can negatively affect motor skills, coordination, balance, and response time,” says McKirven Ceus, M.D., a sports medicine specialist at CareMount Medical. “Chances are, an excessive amount of alcohol consumption closer to race day is likely to negatively impact your performance,” Ceus adds. “So cutting it out completely or reducing your consumption well before the race would be beneficial.”
Besides the obvious fact that no one wants to run—or race—with a hangover, detoxifying your system well before race day can impact you in a number of surprising ways that just might help you nab that PR. Here’s how.
1. You’ll Recover Better
If you tend to finish training runs with a pint, you’re likely to hinder recovery and impair performance, according to a study published in the journal Sports Medicine.
“Alcohol can inhibit recovery in endurance athletes by two primary mechanisms,” explains Alex Harrison, Ph.D., USA Track & Field-certified run coach and sport performance coach for Renaissance Periodization. “First, it’s dehydrating. Dehydration slows recovery and the repair of tissues, slowing any growth of muscle. Second, and perhaps more importantly, lowered sleep quality and quantity as a result of alcohol consumption can decrease testosterone, lower nightly growth hormone concentrations, and increase cortisol, all of which would inhibit tissue repair and make your body composition worse over time.”
2. You’ll Keep Your Blood Sugar Levels Stable
If your blood sugar drops, you’re likely to experience decreased energy output, early fatigue, and an overall decrease in performance—none of which will make getting to the finish line easier or enjoyable.
“Your muscles need glucose to contract, even during low- to moderate-intensity exercise,” says Barnes. “If you don’t have sufficient glucose in your blood stream, you could end up bonking prematurely during exercise.”
The easiest way to make sure your blood sugar levels stay up pre-race? Avoid alcohol.
“Alcohol is high in sugar, so it initially increases your blood sugar,” explains Ceus. “With excessive alcohol consumption, however, a glucose-regulating hormone called insulin is increased, which leads to lower blood glucose levels.”
3. You’ll Sleep Better
A night of drinking may make you pass out cold, but because alcohol disrupts sleep patterns, you likely won’t be getting quality sleep (or enough of it), according to a study published in the journal Alcoholism: Clinical and Experimental Research. And research shows that sleep deprivation in athletes can lead to poor performance in training and competition.
That’s because “disrupted sleep can affect cognitive function, which could affect performance,” says Barnes. “Sleep loss can also lead to symptoms similar to those seen with overtraining, such as impaired immune function.”
Plus, athletes are more likely to experience poorer sleep than the average person, according to a study published in the Scandinavian Journal of Medicine & Science in Sports, which causes them to exert more effort to compensate for that deprivation. Add alcohol to the mix, and you’ll be in rough shape come race day.
4. You’re Less Likely to Gain Weight
Alcohol contains about seven calories per gram, “zero of which go toward effectively fueling exercise,” says Harrison. Sure, most alcohol is sugar and carbs—which you might argue is helpful for an endurance athlete—but alcohol generally provides no micronutrients and no fuel for training in the form of glycogen.
Plus, “alcohol can disrupt other metabolic processes, as its metabolism is prioritized ahead of other macronutrients,” explains Barnes. “That can lead to fat being stored instead of metabolized in both the liver and adipose tissue. And any gain in fat is likely to be detrimental to athletic performance—carrying extra fat is not good for anything.” And decreased fat tends to equal increased speed. “Reduced body fat can improve race pace by 2-3 seconds per mile, per pound of body weight lost,” says Harrison. Cutting out those excess, empty calories in alcohol could be the fastest way to shed some weight pre-race day.
5. You Won’t Get So Dehydrated
The reason you get dehydrated during exercise is because of water loss through sweat. “Alcohol has this diuretic effect, so you urinate more frequently,” says Ceus. As you lose more water, you’re decreasing blood flow to your muscles and losing important electrolytes your body uses for recovery, both of which can increase the risk of muscle cramps and fatigue.
“If you start an event dehydrated, not only will you perform less work for the same heart rate (which is a general reading of how hard your body is working), your gastrointestinal system will be less able to absorb needed fluid,” explains Harrison. “It absorbs fluids when they’re paired with carbohydrates, which is a requirement for optimal performance for any event lasting longer than 75 minutes.”
5. Your Muscles Will Stay Strong
To run strong, you need to be strong. And if alcohol dehydrates you greater than three percent of your body weight, “your muscular strength can still be affected the next day—even if the alcohol is out of your system,” says Harrison. Drink too often, and you’ll be weakening your body, which means you’re not getting the most out of your training plan. Plus, “alcohol can affect the body’s process of building new muscle, known as protein synthesis,” says Ceus.
“One study showed that alcohol decreases the production of human growth hormone,” Ceus adds. “In another study, alcohol consumption in larger doses was shown to have a negative effect on testosterone production. Both testosterone and human growth hormone are important components of the skeletal muscle regeneration and growth system.”
6. You’ll Be Less Stressed
You know what’s stressful on your body? Training for (and running) a race. But using alcohol to relax won’t help.
“In times of stress, cortisol—the stress hormone—aids in allowing the necessary energy to be made available for movement,” says Ceus. “Heavy alcohol consumption, even in small bouts, can actually dampen the production of cortisol, which could potentially impair performance.” And if you’re dehydrated as a result of drinking, your heart has to work harder because of the decreased blood volume, says Harrison. “Decreased blood volume means your heart has to beat faster to get the same amount of oxygen delivered to your muscles when you’re dehydrated”—not ideal when you’re already panting and your muscles need all the oxygen they can get to keep you moving forward.