Sweat Science & Sports Drinks
Staying hydrated is a crucial aspect of health. As we learned in Hydration 101, we talked about the what, where, and how of general hydration. We learned that the body goes through a lot of water each day. And those that are active and sweating lost even more water by way of sweating.
Sweat is not “pain leaving the body.” It’s also not “fat crying.” The purpose of sweating is to cool the body. Bodies need to maintain tight internal temperature control. A few degrees too hot or too cold can be dangerous. When sweat evaporates from the skin, it creates a cooling effect. Everyone has a different sweat rate depending on their genetics, training level, and body size.
Sweating is not a sign of weakness and it has nothing to do with the number of calories burned. Actually, those who are more fit tend to sweat sooner and heavier than those that are not.
While we need to sweat to maintain our internal temperature, we also need to maintain fluid balance- particularly during exercise. For people who are heavy sweaters, training over an hour, and/or training in hot weather, sports drinks can play an important role in exercise.
But beyond using them for exercise, sports drinks are not superior to water for hydration. Since they’re typically used for sport, many people get the impression that there’s something “magical” about them and that they hydrate better than water. They’re not magic – they are a science designed to fuel and hydrate sweaty bodies in motion.
They contain the necessary nutrients to keep active people hydrated and moving during long bouts of exercise and/or in hot temperatures. But for someone who is not exercising long periods and/or in hot weather, they have little to no benefit beyond other hydration options.
Additionally, more is not always better when it comes to sports drinks. While many come conveniently packaged anywhere from 20 – 128 oz, the body only benefits from small doses during exercise (typically 6-8 oz at a time). However, because they taste so good and “refreshing,” it can be easy to consume more than needed.
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Role of sports drinks
Sports drinks (such as Gatorade and Powerade) are a tasty tool designed to support the maintenance of hydration and energy during exercise. Three main ingredients support the process:
- Energy: Sports drinks contain easily digestible blends of sugar (namely glucose and fructose) in amounts the body can tolerate (and absorb) during times of sustained increased heart rate, such as during running, cycling, or swimming.
- Maintain hydration: Sports drinks have sodium, which helps the body hold on to water.
- Hydrate: Sports drinks contain fluid to replace what’s lost during sweating.
To understand the role of sports drinks, it’s essential to understand more about the human body. Sports drinks are a tool designed to be used in small, frequent doses over a long period, ideally during physical activity. They’re especially valuable for those exercising over an hour and who lose fluid by way of sweat.
Principle 1: Sweat is not just water.
The average person sweats .8 – 1.5 liters of fluid every hour of exercise, and it’s not uncommon for an athlete to sweat 3 liters or more per hour. We know athletic performance goes down a lot when a body is 2% dehydrated (or a 3.5 lb loss for a 180 lb person OR a 2.5 lbs for a 120 lb person).
Sweat contains a lot of sodium as well as chloride, potassium, calcium, and magnesium. These minerals are called “electrolytes” and support muscle contraction as well as fluid balance in the body. They’re also the reason some people who sweat a lot might have a white crust on their skin – those are the electrolytes (mostly sodium).
While the number of minerals lost can vary, 1 liter of sweat can contain upwards of 900 mg of sodium – that’s almost 50% of daily sodium needs. Sports Drinks contain a modest amount of sodium to increase thirst and to help replace some of what’s lost. And having sugar in the drink increases the rate of absorption of the sodium and fluid.
Side note: This is also why eating well after sport is so important! Fruits, vegetables, whole grains, and protein contain many of the electrolytes lost during physical activity.
Principle 2: Exercise changes digestion.
There’s a large body of science behind sports drinks formulation, and much of it has to do figuring out how to fuel a body during physical activity. As heart rate increases with physical activity, the body’s ability to digest and absorb nutrients decreases.
The 6-8 oz serving of sports drinks provides around 8-12 grams of sugar – the amount of fuel most bodies can absorb within a 15-20 minute period without causing an upset stomach. Higher doses of sugar can cause nausea, vomiting, and diarrhea. Lower amounts fail to give the body enough energy. This is why it’s important not to water down or over concentrate sports drinks – it changes how the nutrients are absorbed and nourish the athlete.
Additionally, because absorption is limited, it’s important not to use sports drinks exclusively to hydrate during sport. It’s best to alternate water and sports drink every 15 minutes, but individual tolerance may vary.
Are sports drinks required?
While the principles of hydration are important, sports drinks are not “required” for hydration and/or fueling exercise. Sports drinks are valuable for
- Those who exercise/train over an hour to fuel activity and maintain hydration
- Those who exercise/train in high temperatures to maintain hydration
- Those who are heavy sweaters to maintain hydration
Those training over two hours, especially in the heat, sports drinks may not be enough. They may need to add supplemental foods to replace the glucose, sodium, and other electrolytes lost during sport.
For those training for less than an hour, eating and hydrating properly before and after with water is enough to fuel the activity.
While sports drinks are designed to be used during physical activity, they can be used before or after to help people fuel up for their sport and/or rehydrate and refuel.
The goal of nutrition before exercise is to give the body the fuel it needs to move. Because once someone is exercising, the body can’t replace the fluid and fuel that the body uses as fast as it’s lost. If you go into exercise undernourished and/or dehydrated, it’s not realistic to think you can correct it while exercising. It’s better to go into exercise fueled and hydrated to perform best.
The body operates best when fueled and hydrated with a balanced meal or snack 2-3 hours before training, with enough carbohydrates to fuel their activity. For most people, carbohydrate needs 2-3 hours before sport can range from 45 – 90 grams (depending on genetics, age, sex, and physical activity).
To put that in food equivalencies, 45 grams of carbohydrate would be like having 2 slices of bread + fruit (along with your meat and veggies). And 90 grams is TWICE that amount of carbohydrate, which isn’t within everyone’s stomach capacity.
A 20 oz sports drink provides the equivalent energy as about two slices of white bread. But since sports drinks are exclusively sugar, they don’t give as much nutrient value as an alternative beverage such as milk (which also provides protein, calcium, potassium, and magnesium).
Additionally, sports drinks are also a tool that can be used for a quick burst of energy that won’t upset the stomach within an hour of physical activity. But note that because all of the energy is coming from sugar, the energy is quickly used and won’t provide the same sustained fuel as having real food – but not everyone can tolerate that.
Finally, sodium is another important player in sports drinks to help maintain hydration. Most people get plenty of sodium in their day since it’s added to most meals and snacks in the form of table salt. While most Americans get too much sodium (from salt), those who are exercising more than an hour and/or in hot temperatures benefit from the sodium in salt to help them maintain fluid balances during exercise.
After training, the name of the game is to replenish lost fuel and fluids and help the muscles repair. Rehydrating is crucial. Most people are dehydrated after exercise because it’s so hard to keep up with losses during training. It’s not uncommon for people to weigh less after exercise than they did before. This is not an indication of body fat lost – it’s how much fluid is gone. That weight should be restored by rehydrating for health and performance.
Glucose (which comes from carbohydrates) is the primary fuel source lost. Having glucose, along with protein within an hour of exercise, maximizes muscle recovery. A balanced meal with protein, carbohydrate (from grains and veggies/fruits), as well as fat is a great option for recovery because it contains not only the macronutrients the body needs but also the nutrients lost.
But for those struggling with low appetite and/or can’t find a carbohydrate source, sports drinks may be helpful to replace lost fuel until they’re ready for real food. But as mentioned before, because sports drinks are exclusively sugar (with small amounts of electrolytes), they don’t provide as much nutrient value as other foods.
If real foods aren’t appetizing, a blend of milk + frozen fruit is also a great way to rehydrate, refuel, and get the nutrients needed. Other options include a glass of milk with a peanut butter sandwich OR water along with a turkey sandwich with tomato and cheese OR crackers and hummus with some fruit.
But isn’t sugar bad?
For some people, the fact that sports drinks have sugar terrifies them. Yes, it’s true that sports drinks have sugar, but as we learned in the carbohydrates module, sugar is just a type of carbohydrate. In sports drinks, the presence of sugar has two purposes:
- Easily digestible form of readily available fuel in a small volume
- Helps facilitate the absorption of electrolytes and fluid
Without sugar, sports drinks wouldn’t be as effective at fueling and hydration. If you’re getting stuck on the fear of sugar, consider the chemistry of the energy separate from the concept of sugar.
Sports drinks provide energy in the form of sugar. A 20 oz Gatorade offers 140 calories. Those calories come from 36 grams of carbohydrate, mostly in the form of sugar. But forget the word sugar for a moment. In terms of carbohydrate (the overarching nutrient), this is the same as having 9 teaspoons of sugar OR 1 small box of raisins OR 2 slices of bread OR ~ ¾ cup of cooked rice or pasta OR 1 KIND bar OR 1 cup cooked oats OR 2 ½ cups of strawberries OR 1 ⅓ medium banana OR 2 large apples OR 6 cups of broccoli.
All of these could be options for fueling and refueling to get the same amount of carbohydrate, but not all of these foods provide the same nutrients, satisfaction, or volume of food. And what you use to fuel changes depending on whether you need fuel before, during, or after a workout. Can you imagine trying to eat 2 ½ cups of strawberries or 6 cups of broccoli to fuel mid-run? Yikes, probably not a good idea. The point is depending on where you are in your day and how you want to feel, you may choose a different food to meet your nutrient needs.
Tips for choosing a sports drinks
Sports drinks are not required for anyone and everyone exercising or training. But they are a convenient tool for heavy sweaters, those training over an hour, and/or those training in hot weather to balance hydration. Most sports drinks provide electrolytes (typically from sodium) and are mixed with water to hydrate. In general, they have similar amounts of sugar and calories, because the ratio of sugar, fluid, and electrolytes is reasonably well standardized to hydrate during physical activity without upsetting stomachs (which is why it’s not ideal to water them down or over concentrate them – it can reduce their effectiveness). But note some drinks can have caffeine and/or protein in them. These are sport-specific additions and not right for everyone.
There are many options for sports drinks. The most common and readily available at most major retailers are Gatorade and Powerade. But there are other brands, including Scratch Labs and Hammer products. (Nuun is another popular product, but it does not have sugar and, as such, doesn’t provide energy. It’s designed to be taken with another glucose source while training and/or in addition to meal/snack before/after training).
Hydrating for training is a unique topic with lots of variables to consider. Every active body needs to be fueled and hydrated to perform its best. Sports drinks are a valuable and convenient tool to simplify the process, but they’re not required across the board. It is possible to do it with real food, but sports drinks are particularly valuable during exercise, to stay energized and fueled.
Belval LN, Hosokawa Y, Casa DJ, et al. Practical Hydration Solutions for Sports. Nutrients. 2019;11(7):1550. Published 2019 Jul 9. doi:10.3390/nu11071550
Michael N. Sawka, PhD, Samuel N. Cheuvront, PhD, RD, Robert Carter, Iii, PhD, MPH, Human Water Needs, Nutrition Reviews, Volume 63, Issue suppl_1, June 2005, Pages S30–S39, https://doi.org/10.1111/j.1753-4887.2005.tb00152.x
Nuccio RP, Barnes KA, Carter JM, Baker LB. Fluid Balance in Team Sport Athletes and the Effect of Hypohydration on Cognitive, Technical, and Physical Performance. Sports Med. 2017;47(10):1951-1982. doi:10.1007/s40279-017-0738-7
Popkin, B. M., D’Anci, K. E., & Rosenberg, I. H. (2010). Water, hydration, and health. Nutrition reviews, 68(8), 439–458. https://doi.org/10.1111/j.1753-4887.2010.00304.x
Ronald J Maughan, Phillip Watson, Philip AA Cordery, Neil P Walsh, Samuel J Oliver, Alberto Dolci, Nidia Rodriguez-Sanchez, Stuart DR Galloway, A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index, The American Journal of Clinical Nutrition, Volume 103, Issue 3, March 2016, Pages 717–723, https://doi.org/10.3945/ajcn.115.114769
Meet The Author: Rebecca Toutant, MA, RDN, LDN, CDE
Rebecca is a registered dietitian, personal trainer, and certified diabetes educator living and working in the Boston area.
Learn more about Rebecca and her background here: Fuel 4 Fitness – Rebecca Toutant