What drinks should I avoid when running?

October 2, 2025 •

3 min read

Research indicates that even mild dehydration can negatively impact an athlete's physical and mental performance. To ensure optimal comfort and endurance, it is essential to understand what drinks should I avoid when running and why they hinder your efforts.

Quick Summary

Certain beverages like alcohol, sugary sodas, caffeinated drinks, and high-fat dairy can impair performance and cause dehydration or stomach upset. Proper hydration choices are key.

Key Points

Alcohol causes dehydration: Acting as a diuretic, alcohol increases fluid loss and impairs athletic performance, with effects lasting up to 72 hours.
Sugary drinks lead to energy crashes: Sodas and juices provide a short-lived sugar rush followed by fatigue, and do not provide proper hydration.
Carbonated drinks cause GI distress: The fizz in sodas and seltzers can cause uncomfortable bloating, gas, and stomach pain during a run.
High-fat dairy slows you down: Beverages like full-fat milk are hard to digest before a run, leaving you feeling sluggish.
Artificial sweeteners can upset your stomach: Sugar alcohols like Sorbitol, found in some diet drinks, can have a laxative effect and cause bloating.

The Dangers of Dehydrating Drinks

Proper hydration is the cornerstone of any successful run. However, some beverages actively work against this goal. Alcohol and excess caffeine are the two most prominent culprits when it comes to dehydration and performance-killing effects. Alcohol, a known diuretic, increases urine production and causes your body to lose essential fluids and electrolytes at a faster rate. This can lead to muscle cramps, fatigue, and impaired athletic ability. The effects of alcohol can linger in the body for up to 72 hours, significantly impacting recovery and subsequent performance. It also negatively affects your body's ability to regulate temperature, which is especially critical during a long run or a race.

Excessive caffeine, while sometimes used for a pre-run boost, also acts as a diuretic, accelerating fluid loss. While a small amount of coffee is tolerated by some runners, overdoing it can lead to dehydration, increased heart rate, and jitteriness. For endurance events, this can be counterproductive and leave you feeling depleted.

Sugary Drinks and Energy Crashes

Many runners fall into the trap of thinking sugary sodas or fruit juices are a good source of quick energy. The reality is far from it. These drinks, packed with simple sugars and often high-fructose corn syrup, cause a rapid spike in blood sugar followed by an inevitable crash.

Why to avoid:

Energy Fluctuations: The immediate sugar rush is followed by fatigue and headaches, making your run feel much harder than it should.
Lack of Hydration: Sugary drinks do not effectively hydrate the body. The high sugar concentration pulls fluid from your body into your digestive tract, hindering true hydration.
Empty Calories: They provide calories with little to no nutritional value, which is not what your body needs to fuel sustained performance.

Why Carbonated Beverages Cause GI Distress

Fizzy drinks, including soda and seltzer, are another type of beverage to leave off your pre-run menu. The carbonation can cause significant gastrointestinal discomfort, such as bloating, gas, and abdominal pain. This happens because the gas in the drink can linger in your stomach, causing bubbles and a feeling of fullness that can make running uncomfortable. For a runner, any kind of stomach upset can derail a training session or race.

The Problem with High-Fat and Artificially Sweetened Drinks

Drinks like full-fat milk, coconut milk, and those with artificial sweeteners also pose problems for runners.

High-Fat Beverages

Slow Digestion: High-fat drinks like coconut milk or full-fat dairy take a long time to digest. This can leave you feeling heavy and sluggish, diverting energy away from your muscles and towards your digestive system. While chocolate milk is popular for post-run recovery, consuming it right before or during a run is not recommended for many athletes.

Artificially Sweetened Drinks

GI Issues: Many 'diet' or sugar-free drinks contain sugar alcohols like Sorbitol. The body has difficulty absorbing these, which can lead to bloating, gas, and a laxative effect. This is the last thing any runner wants to experience mid-route.

Comparison: Drinks to Avoid vs. Runner-Friendly Drinks


Feature	Drinks to Avoid (Alcohol, Soda)	Runner-Friendly Drinks (Water, Sports Drink)
Hydration	Poor. Causes dehydration due to diuretic effects or high sugar content.	Excellent. Replenishes fluids and maintains proper hydration.
Energy	Causes energy spikes and crashes due to simple sugars.	Provides steady energy and electrolytes for sustained performance.
GI Comfort	High risk of bloating, gas, and stomach cramps.	Low risk of GI distress when consumed correctly.
Recovery	Hinders muscle repair and glycogen replenishment.	Supports muscle recovery and restores electrolyte balance.
Overall Impact	Negative on endurance, speed, and recovery.	Positive on performance, comfort, and recovery.

Conclusion: The Hydration Bottom Line

Making smart hydration choices is a critical part of a runner's success. Avoiding dehydrating and sugary beverages, as well as those that cause GI discomfort, can make a noticeable difference in your training and race-day performance. Stick to water for most runs, and consider a purpose-formulated sports drink for longer, more intense efforts to replenish electrolytes and carbohydrates effectively. Your body will thank you, and your running will undoubtedly improve. For more information on sports nutrition, consider exploring the resources from reputable health organizations like KidsHealth, which offers valuable guides for athletes at all levels.

Frequently Asked Questions

Alcohol acts as a diuretic, causing dehydration and increasing fluid loss. It also negatively impacts energy metabolism, slows muscle recovery, and can impair your balance and coordination, making it a poor choice before any athletic activity.

While some runners find a small amount of caffeine can boost performance, excessive amounts should be avoided. Caffeine is a diuretic and can lead to dehydration and jitters if overconsumed. It is best to experiment in training to see how your body reacts.

Sodas are high in sugar, which causes a rapid energy spike followed by a crash, and carbonation, which can cause bloating and gas. Both can lead to stomach discomfort and a significant drop in performance.

Many fruit juices are loaded with sugar and lack the fiber of whole fruit. This can lead to the same energy crash as soda and does not provide effective hydration for your run.

Full-fat milk and other dairy products are typically high in fat and take longer to digest, which can cause stomach discomfort and a sluggish feeling. While low-fat chocolate milk can be a good recovery drink, it's generally best to avoid dairy right before a run.

Most energy drinks are loaded with both high levels of sugar and caffeine or other stimulants. This combination can overstimulate your system, cause GI issues, and lead to a significant energy crash, which is not ideal for endurance.

For most runs, water is your best choice. For runs longer than 45-60 minutes or in hot conditions, a sports drink with a moderate concentration of carbohydrates and electrolytes (like sodium and potassium) is beneficial for sustained performance and hydration.