Hydration Supplements for Optimal Performance

During the 2024 Summer Olympics, sports fans around the world gathered to cheer on the premier athletes from their respective countries. As the competition grows over time, much research and attention has shifted to optimizing electrolyte, supplement, and fluid intake to perform at the top of their abilities. With the growing interest in the Sports Pharmacy specialty¹, there remains an unmet need for those engaged in sport and exercise for advice regarding the optimal timing, composition, and consumption of various hydration supplements. As one of the most accessible healthcare professionals,² pharmacists are perfectly positioned to fulfill this role. Not only that, but these topics also benefit users of all ages: children, elderly, those with certain conditions (diarrhea, SIADH, emesis, kidney dysfunction), medications (diuretics, beta-blockers, some anticonvulsants), or anyone dehydrated. 

Great news, though! The increased demand for sports pharmacists hasn’t gone unnoticed. There are a few organizations across the country already addressing this unmet need (below), allowing many pharmacy students, fellows/residents, and practicing pharmacists to join! Personally, I’m involved with the United States Sports Pharmacy Group (USSPG), and I highly recommend anyone with an interest in sports pharmacy to sign up and participate.

• USSPG
• Drug Free Sport
• USC Mann School of Pharmacy and Pharmaceutical Sciences Certificate Program
• Sports Pharmacy Network
• Baptist Health Clinical Wellness Pharmacists
• World Anti-Doping Agency

As we dive into the nuances of the use of hydration supplements for optimal performance, keep in mind that all patients require personalized attention and needs, as there is no one-size-fits all. Most of the recommendations are summarized from a variety of primary literature studies, including wide ranges for fluid intake, electrolyte needs, and more. Always consult with a healthcare professional for specific recommendations! 

Hydration Pharmacology

Electrolytes play a key function in restoring the proper ratio of total body water to total body weight (TBW). From a larger perspective, hydration can be referred to as a balance between water and electrolyte intake/elimination. There are three main intrinsic factors that play a role in the overall regulation of electrolytes and hydration: kidneys, antidiuretic hormone (ADH), and thirst sensation. 

An average adult’s TBW ranges between 55-60% water.³  ⅔ of the water is the intracellular fluid, and the remaining ⅓ is the extracellular fluid. The main electrolytes found in the intracellular fluid include:

• Positively charged: potassium, magnesium, and calcium
• Negatively charged: phosphate and sulfate

The main electrolytes found in the extracellular fluid include: 

• Positively charged: sodium
• Negatively charged: chloride and bicarbonate

Fun Fact: Do you know the recommended amount of water you should consume each day, according to the literature?

a. 8 cups a day for everyone
b. 13 cups a day for men and 9 cups for women
c. 15.5 cups a day for men and 11.5 cups for women
d. Whatever my doctor says

According to the U.S. National Academies of Sciences, Engineering, and Medicine,⁴ C is the recommended answer, but about 20% of daily fluid intake usually comes from food, so the difference is actually B! In reality, the answer truly depends on activity levels, age, medications, medical conditions, etc., but there are a few ways to gauge if you’re on the right track: thirst sensation, temperature, and urine color. Once you feel thirsty = you are already dehydrated (~2% total body weight loss)!

Sodium:⁵

• Purpose: Nerve impulses, muscle contraction/relaxation, water balance
• Normal Values: 135-145mEq/L
• Goal: 1500-2300 mg/day
• Supplement: High sweat rates (>1.2L/hour), >2% TBW lost during exercise, exercise duration >2 hours, cramping
• Dose: 300-600 mg/hour (adjust as needed)
  • Average sweat sodium content = 1 g/L
  • Average sports drink = 230-690 mg/L

Potassium:^6,7 

• Purpose: Regulates heartbeat and fluids, ensures proper function of muscles/nerves
• Normal Values: 3.5-5 mEq/L
• Goal: 2,600 mg/day (women); 3,400 mg/day (men)
• Supplement: Inadequate diet, certain illness/medications (not sweat)
• Dose: Varies (goal Na:K <1)
  • Average sweat potassium content = 0.2 g/L
  • Average sports drink = 45-80 mg/L

Magnesium:⁸ 

• Purpose: Cellular metabolism & neuromuscular, CV, immune, and hormonal functions
• Normal Values: 1.7-2.2 mg/dL
• Goal: 400-420 mg (men); 310-320 mg (women)
• Supplement: Inadequate diet, autoimmune/chronic diseases, deficiency (not sweat)
• Dose: Depends on sex, age, and indication
  • Average sweat magnesium content = 18 mg/L
  • Average sports drink = 0 mg/L

Calcium:⁹

• Purpose: Growth, maintenance, bone tissue repair, muscle contraction or conduction
• Normal Values: 8.6-10.3 mg/dL
• Goal: 1,000-1,200 mg
• Supplement: Deficiency, disordered eating, amenorrhea, risk of early osteoporosis
• Dose: 1500 mg elemental
  • Average sweat calcium content = 60 mg/L
  • Average sports drink = 0 mg

Chloride:¹⁰

• Purpose: Acid-base balance, muscular/nervous activity, fluid/solute movement
• Normal Values: 96-106 mEq/L
• Goal/Supplement/Dose: Pairs with Na⁺

Phosphate:¹¹ 

• Purpose: DNA creation, 85% in bone/teeth formation, cell membranes, muscle function
• Normal Values: 2.5-4.5 mg/dL
• Goal: 700 mg
• Supplement/Dose: Pairs w/ Ca²⁺
  • Average sweat phosphate content = 3-6 mg/L
  • Average sports drink = 0 mg

Sulfate:¹¹ 

• Purpose: Structural component proteins, gene expression, and DNA repair
• Goal: No RDA
• Dose:  Normal amounts obtained through diet/body stores
  • Average sweat sulfate content = 0 mg/L
  • Average sports drink = 0 mg 

Fun Fact: You Can Drink Too Much Water!

• Kidneys can remove ~24 L/day (1 L/hour)
• Too much too quickly → hyponatremia and/or cell swelling in the brain
• Symptoms: headache, nausea, confusion, dizziness, muscle weakness, coma, death

Marketed Hydration Supplements

• Sports Drinks
• Powders
• Tablets, Capsules, and Gummies
• Electrolyte Replenishers Children
• Oral Rehydration Therapy

Hydration boils down to the tonicity of the fluid, or composition of the electrolytes that affects the movement of water. There are three types: hypotonic, isotonic, and hypertonic. The lower number of particles (carbohydrates, caffeine, etc.) in the fluid reflects more of a hypotonic solution, with higher number of particles suggestive more of a hypertonic solution. The tonicity of the solution can affect the absorption rate of electrolytes throughout the body. For reference, the normal blood osmolality of the blood is 280-290mOsm/kg. 

• Hypotonic:
  • Rapid rehydration
  • Indications: Pre-hydration, shorter workouts, long rides, hot weather
    • When you need to rehydrate quickly and effectively, not to replenish carbohydrates (energy)
• Isotonic:
  • Carbohydrates + rehydration
  • Indications: Shorter duration or high-intensity workouts
    • When you need to rehydrate carbohydrates during endurance exercise
    • Provides energy as your workout while replacing fluids and electrolytes lost through sweat
  • Trade-off: 
    • More carbs → more energy to cross the gut wall vs. hypotonic drinks  → slower energy/electrolyte release
  • Caution: Can be full of sugar, sweeteners, and additives that may upset the stomach
• Hypertonic:
  • Recovery/preparation for carbohydrates (energy)
  • Indications: After intense or sustained exercise or extra carbohydrates leading up to a race (some endurance athletes use before/during)
  • Can cause dehydration as the body moves water from the bloodstream into the intestine to dilute the fluids before it can absorb them

Before comparing various sports drinks and showing which ones are stronger than others, it’s important to remember how to read specific hydration labels based on your preferences/needs. In addition to tonicity, one must consider the ideal proportion of electrolytes to mimic that of sweat. Specifically, this ratio, in mg, is about 250:50:5:15 (Na:K:Mg:Ca) for 8oz (~250mL) of fluid. In other words, for a 1 liter of a sports drink, the composition must contain, in mg, 1000:200:20:60 of Na:K:Mg:Ca (x4). 

Step 1: Determine your ideal use for a sports drink (rapid rehydration, carbohydrate + fluids, or carbohydrate loading for energy pre-or-post workout). This will determine the ideal tonicity of the fluid (hypotonic, isotonic, or hypertonic, respectively) which you will compare to that of normal blood osmolality (280-290 mOsm/kg). 

For example, according to this chart, Hammer Head, Gatorade G 01 Prime, and HerbaLife Hydrate contain osmolalities closer to that of normal blood osmolality, and should be most commonly used by athletes looking to replace both carbohydrates (energy) with fluids in a relative amount of time. 

Osmolalities <280-290 mOsm/kg, such as Shaklee Performance and Cytomax, are preferred for rapid rehydration, as the lower osmolality will absorb faster into the bloodstream due to osmosis. 

Gatorade G 02 Perform, Powerade, Accelerade, and Coconut contain larger amounts of particles, increasing the tonicity and slowing the rehydration process. However, these drinks can be used in the pre or post-workout setting for those looking to replenish carbohydrates or other particles, such as caffeine, in certain formulations. 

Step 2: After determining your ideal tonicity/indication, it’s important to understand the nuances between the primary sugar source. The best resource to compare is a Glycemic Index (GI) scale or chart. Foods lower on the GI index don’t spike blood glucose as rapidly and are slower absorbing into the bloodstream. On the other hand, foods higher on the GI index spike glucose faster and are rapidly absorbed into the bloodstream. As a result, for athletes looking for a quick burst of carbohydrates (energy) during performance, maltodextrin or pure glucose are the preferred carbohydrate sources. 

• Maltodextrin = Highest GI index (110)
• Glucose = High (100)
• Sucrose = Medium (65)
• High-Fructose Corn Syrup (HFCS) = Medium (56)
• Fructose = Lower (25)

Step 3: Next, study the amount and composition of sodium and potassium, as these are lost in higher amounts of sweat vs. magnesium, calcium, and phosphorus. Chloride is usually formulated with sodium for simplicity, so we are not as concerned with separate supplementation. To determine your individual sweat amount, performing a simple sweat test, such as with a Gx Sweat Patch, can help determine if you need to supplement more fluids/electrolytes vs. others. You can then predict how many electrolytes to replenish given the duration, intensity, and conditions of the workout. Keep in mind that the ideal ratio for a 8-ounce (250 mL) bottle is 250:50:5:15 of Na:K:Mg:Ca (in mg). 

Important Notes:

• There is no place for protein and fat in a sports drink, as they would require digestion and negatively affect the osmolality, especially if rapid rehydration is the goal. 
• Energy drinks are NOT sports drinks, as they usually contain caffeine, other stimulants, few electrolytes, and inadequate water = hypertonic. 

Other Sports Drink Recommendations for Reference¹²

• American College of Sports Medicine: 
  • Consume 20 oz (1 standard bottle) 2-3 hours before exercise
  • Consume 10 oz (½ standard bottle) 20 minutes before exercise
  • Consume 20 oz (1 standard bottle) per pound of body weight lost during exercise after
• Texas A&M:
  • Endurance athletes should consume 16 oz with 4-8% carbohydrates and electrolytes 1-2 hours before event
  • If event >1 hour = consume 20-40 oz (1-2 standard bottles) per hour of a sports drink containing carbohydrates and 500-700 mg Na per hour
• Precautions: 
  • Not to rehydrate children with vomiting/diarrhea (improper balance carbohydrates and electrolytes)
• Side Effects: 
  • Salty taste → Glycine can neutralize
  • Tooth decay (artificial dyes) → 3-11x faster than soft-drinks

Hydration Powders/Tablets/Capsules

Commercial gels, although can be effective for rapid rehydration of electrolytes and/or carbohydrates with an easier formulation, require the athlete to “play biochemist” while running in order to be sure there is enough water to effect a hypotonic reaction for absorption. However, there are some newer formulations (Science in Sport and Maurten) which are designed to be absorbed rapidly without supplemental water/fluids. These are typically preferred for endurance athletes for convenience during the event. Many also contain flavorings to mask the salty/bitter taste, and should be kept out of reach from children. 

Comparing hydration powders, tablets, and capsules is similar to that of sports drinks regarding the composition/amount of electrolytes. Keep in mind the goal ratios (Na:K:Mg:Ca):

• 32 oz (1000 mL): 1000:200:20:60
• 8 oz (250 mL): 250:50:5:15

Another key consideration is that none of these products are FDA approved (vs. traditional medicines). However, supplement companies are responsible for having evidence that their products are safe, and the label claims are truthful and not misleading. As a result, it’s best to search for products that are third-party tested for accuracy and safety. One of the most popular third-party testers is the National Sanitation Foundation (NSF). 

Bolded are the remaining hydration supplements that meet the proper composition of the most crucial electrolytes and are NSF certified. At this point, it’s more personal preference regarding carbohydrate content, calories, caffeine, sweeteners, and price. Certain sweeteners, such as xylitol and pure cane sugar, can upset the gut and increase calories, respectively. 

Electrolyte Replenishments Children

These are typically indicated in children who are dehydrated <1 day from recurrent vomiting or episodes of diarrhea. The dose depends on age and weight, but higher fluid requirements may be necessary due to the increased proportion of TBW. Additionally, freezer pops may be used for those >1 year old as often as the child desires. However, it’s important to keep these out of reach of children and away from the heat, and they have no use for those with intestinal blockage. Side effects may include allergic reactions, hypernatremia (dizziness, seizures, twitching), and vomiting. The main interactions include salty foods and fruit juices. 

In pediatric patients, 60 mEq/L is the preferred sodium amount for optimal H2O absorption. The normal child osmolality is 275-290 mOsm/kg H2O, so all three of the formulations mentioned are beneficial as a hypotonic solution for rapid rehydration. 

Oral Rehydration Therapy

Oral rehydration therapy contains water, sugar, and electrolytes, usually for cholera-related diarrhea. The World Health Organization (WHO) has created packets to be mixed with ~32 ounces of water as soon as the child/adult becomes ill (not boiled). An alternative is 8 teaspoons of table sugar + ½ teaspoon of salt + ½ teaspoon of baking soda. In an emergency, 1 tablespoon of sugar + ½ teaspoon of salt in ~32 ounces of water can be used. These are not to be stored in damp places or heat and are not used in those with intestinal blockage. 

Conclusion

Choosing the optimal hydration supplement is a nuanced topic depending on your individual sweat rates, indications, and type of athletic event. Nonetheless, following key principles such as isotonicity, electrolyte composition, and route of administration will help narrow down the options. There is no one-size-fits-all approach, but hopefully this guide helps you identify what traits to look for when analyzing a product to determine the most ideal fit for you!

I created a PowerPoint presentation of this topic for one of my APPE rotations at The Ohio State Student Health Center, where we also serviced all the student athletes regarding proper management of specific medications for optimal athletic performance. Attached is a copy of the presentation to review many of these topics. Feel free to share with anyone who may benefit and/or connect if you have any questions! Thank you!

Definitions

• Hydration Supplement: Any product intended to correct electrolyte imbalances
• Electrolytes: Electrically-charged minerals found throughout the body (blood, urine, tissues) responsible for water distribution, muscle contraction/expansion, nerve transmission, O₂ delivery, HR, acid-base, etc. 
• SIADH: Syndrome of inappropriate antidiuretic hormone secretion
• HR: Heart Rate
• RDA: Recommended daily allowance

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Jordan Fortunato

Medical Information/Medical Affairs Postdoctoral Fellow | Incyte

St. Joseph’s University

Strava

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References

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