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August 2010

Electrolytes: Understanding Replacement Options

 

electrolytes

BY SHAWN H. DOLAN, Ph.D, R.D., C.S.S.D.

Electrolytes are some of the most complex and misunderstood nutrients, which can make answering client questions about replacement options a challenge for many fitness professionals. For example, clients may ask why electrolytes are important, which specific electrolytes need to be replaced, as well as what options there are for replacing electrolytes before, during and after exercise. The following article explores this topic with the goal of helping fitness professionals feel better equipped to answer client questions and address concerns related to electrolytes. 

Why are electrolytes important for physically active people?

Electrolytes are positively or negatively charged ions that conduct electrical activity. In the human body electrolytes must be present in proper concentrations to maintain fluid balance, muscle contraction and neural activity. The kidneys work to maintain electrolyte balance by conserving or excreting electrolytes. Water follows the movement of electrolytes, particularly sodium and chloride, meaning that water is drawn to locations where electrolytes are most concentrated. Therefore, electrolytes play a critical role in maintaining equilibrium of water throughout the body, particularly during exercise when electrolytes and water can be lost through sweating.

Do all electrolytes play an equally important role with regard to physical activity?

Electrolytes lost in high concentrations through sweat include sodium and chloride, while electrolytes lost in low concentrations include potassium, magnesium and calcium. Keep in mind that all electrolytes work together to maintain fluid balance in the body at rest and during physical activity, so be sure to educate your clients on all electrolytes, rather than focusing on only one or two. Table 1 lists common food sources, deficiency symptoms, and recommended intakes of electrolytes.

food sources

Table 1. Deficiency Symptoms, Food Sources and Recommended Intakes of Various Electrolytes
Nutrient Deficiency Symptoms Food Sources Recommended Intake*
Sodium

Muscle cramps

Loss of appetite

Dizziness

Dill pickle

Tomato juice, sauce, soup

Table salt (1 tsp = 2300 mg sodium)

1500 mg

1300 mg for people over 50

1200 mg for people over 70

Chloride

Changes in pH

Irregular heartbeat

Table salt

Some fruits and vegetables (tomatoes, lettuce, olives)

2300 mg

2000 mg for people over 50

1800 mg for people over 70
Potassium

Muscle weakness

Muscle paralysis

Mental confusion

Potato with skin

Plain yogurt

Banana
4700 mg
Magnesium

Muscle cramps

Nausea

Confusion

Halibut

Pumpkin seeds

Spinach

320 mg for women

420 mg for men
Calcium

Osteporosis, osteopenia

Muscle spasms

Dairy (yogurt, milk, ricotta)

Collard greens, spinach, kale

Sardines

1000 mg

1200 mg for people over 50
*Recommended intake is based on Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997) and Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2004). These reports may be accessed via www.nap.edu. Copyright 2004 by the National Academies of Sciences.

 

One commonly held myth is that muscle cramping in active individuals is due to the loss of potassium; however, the amount of potassium in sweat is likely too low for this to be the culprit. Muscle cramping due to electrolyte imbalance is more likely associated with the loss of high amounts of sodium through sweat. Therefore, replacing sodium is important to maintain electrolyte balance for physically active individuals who experience high losses of sodium through sweating. 

How much electrolytes are lost through sweating? Should they be consumed before, during or after exercise?

Electrolyte losses vary greatly among active individuals depending on total sweat losses and sweat electrolyte concentration. Individual sweat rate (and therefore sweat loss) also varies between individuals and is determined by length and intensity of exercise, body composition, clothing and environment. Some individuals are considered salty sweaters, meaning the sodium concentration of their sweat is higher than average. This amount is typically determined by genetic predisposition, diet, sweat rate and heat acclimatization. It is important to note that dehydration can increase the sweat concentration of sodium and potassium. A general rule of thumb is to never begin a workout session thirsty or dehydrated. One way to assess hydration status prior to a workout is by looking at urine color. Ideally, urine color should be pale yellow. In addition, as individuals become more acclimatized to a hot environment, they adapt by improving their ability to reabsorb (or hold on to) sodium and chloride, resulting in decreased loss of electrolytes via sweat.

When is it important to replace electrolytes?

Before Exercise

Currently there is no recommendation for electrolyte intake before exercise. However, salty sweaters, indicated by skin and clothing covered in salt residue during and/or after exercise, should eat a salty snack or drink a sports drink instead of water for pre-exercise hydration.

This is particularly important when heavy sweating is anticipated during exercise due to extended duration (> 60–90 minutes), increased intensity, or high ambient temperature and humidity.

hydrate drink

During Exercise

A sports drink that includes both carbohydrates and electrolytes is recommended for exercise sessions lasting longer than 60–90 minutes. The sodium in a sports drink helps the body absorb and retain the fluid and utilize the carbohydrate. Replacing specific amounts of sodium during exercise is more important when a client is a salty sweater and/or exercise lasts longer than two to three hours. In these situations an endurance-specific sports drink with higher amounts of electrolytes is recommended.

After Exercise

Drinking plain water after high-intensity or long-duration exercise is not always effective for rehydration. For water to be retained it needs to be consumed with foods that contain sodium and other minerals. Recovery foods and beverages containing plentiful amounts of sodium include mixed nuts, baked potato chips, pretzels, pickles and crackers. If foods containing sodium are not readily available, a sports drink or bar can be used to replace electrolytes. 

What are the options for taking in electrolytes?

There are many commercially available products targeted at replacing electrolytes lost through exercise, including food, sports drink, sports gel, and sports candy/gummies. Some of the sports drinks provide fluid and electrolyte intake with a low amount of carbohydrate, while others supply carbohydrate to meet recommended amounts in addition to the fluid and electrolytes. Some of the products are ready-to-drink formulas available in a bottle, while others are powder mixes sold in bulk or individual servings that are added to water. A newer option is offered in a portable electrolyte tablet form that is dissolved in water.

The following categories are designed to help navigate the variety of electrolyte replacement options:

A. Electrolytes + No/Very Low Calories (< 10 calories per 8-ounce serving)

zym

This category includes most of the newer portable hydration tablets and electrolyte capsules, which provide no calories. Products in this category that do provide carbohydrate are often flavored with alternative sweeteners (e.g., sucralose, acesulfame potassium, sorbitol and stevia). The electrolyte-specific capsules are useful during longer-duration exercise sessions and competitions in a hot environment, particularly for individuals who have a high sodium sweat concentration and high sweat losses. These products are typically taken along with a traditional sports drink to increase overall electrolyte consumption.

Examples: Nuun Active Hydration, Zym Endurance Tablet, Elixir, Powerbar Electrolyte Sticks, Thermolytes, Thermotabs, Lava Salts, Endurolytes, Sportaktive Portable Electrolyte Mix

B. Electrolytes + Calories (10–80 calories per 8-ounce serving)

clif shot

This category includes familiar sports drinks, as well as some new options designed to provide fewer calories. Most of the products contain a 4–8% carbohydrate solution and include ingredients such as glucose, glucose polymers, sucrose, maltodextrin and fructose. These products provide appropriate amounts of carbohydrates and electrolytes to prevent glycogen depletion and maintain fluid balance when exercise sessions and competitions last 45–120 minutes.

Examples: Accelerade, Accelerade Hydro, Clif Shot Electrolyte Replacement, Cytomax, G2, Gatorade, Powerade

C. Endurance-specific electrolytes + Calories (10–80 calories per 8-ounce serving)

Luna

This category includes products for individuals participating in exercise sessions and competitions lasting longer than 120–180 minutes. These products are designed to help offset higher sweat losses and may prevent muscle cramping.

Examples: First Endurance Electrolyte Fuel System (EFS), Gatorade Endurance Formula, Luna Electrolyte Splash, Hammer Motor Tabs, Powerbar Endurance Sports Drink

Once a product is chosen, it is important to determine the appropriate amount to consume. Table 2 includes detailed information regarding the composition and calorie content of different replacement options. All values of nutrients are given per 8 ounces of fluid (1 cup or ~250 ml). As a reference, most standard water bottles that fit in bike cages hold approximately 16 ounces of fluid (2 cups). Always check the label on premixed drinks for the serving size and nutrient amounts.

Table 2. Description and Purpose of Electrolyte-replacement Options
Electrolyte Option Sodium (mg) Potassium (mg) Other Nutrients Purpose
A. Electrolytes + No/Very Low Calories

Portable hydration tablets

(< 10 calories)

125–180 23–50

Calcium

Chloride

Magnesium

Manganese

Vitamin C, B (5, 6, 12)

• Additional electrolyte replacement for salty sweaters and heavy sweaters

• Additional electrolyte replacement in hot and/or humid conditions

• Electrolyte replacement for individuals trying to achieve weight loss

• Some products serve as a flavored alternative to plain water

Electrolyte capsules

(0 calories)

40–150

25–43

Calcium

Chloride

Magnesium

Manganese

Selenium

Vitamin B-6

Zinc

 

B. Electrolytes + Calories (10–80 calories)
  60–120 15–43

Amino acids

Calcium

Magnesium

Vitamin C, E

• Electrolyte and carbohydrate replacement during exercise sessions lasting 45–120 minutes including continuous and intermittent types of activities

C. Endurance specific electrolytes + Calories (10 – 80 calories)
  180–250 10–107

Amino acids

Calcium

Chloride

Choline

Folate

Iron

Magnesium

Vitamin A, C, E, B

• Electrolyte and carbohydrate replacement during exercise sessions lasting longer than 120 minutes

• Electrolyte and carbohydrate replacement during exercise sessions lasting longer than 120 minutes

*All amounts are per 8-ounce serving

 

Putting it all Together: Case Study

Carrie is training for her first marathon. As part of her training she runs three times per week, including two short runs during the week (20–60 minutes) and one long run on the weekend (one to four hours). Carrie considers herself a “heavy sweater” and a “salty sweater” because her clothes are drenched with fluids and caked with salt after a long run. She doesn’t experience muscle cramps during short runs, but frequently experiences calf cramps during or after long runs. What recommendations would you give to Carrie to help her meet her fluid and electrolyte recommendations and avoid muscle cramps?

carrie

Short runs during the week (20–60 minutes): Electrolyte replacement is not likely to be necessary during Carrie’s short runs because the length is less than one hour. Though Carrie considers herself a “salty sweater,” she isn’t experiencing muscle cramps during the short runs so sports drinks should not be necessary. She should take in 16–24 ounces of water two to three hours before her run so she starts off well hydrated. Based on her sweat rate, Carrie should drink adequate fluid during the short runs to make sure she loses no more than 2% of her body weight (130 lb x 0.01 = 2.6 lb). Electrolytes lost during short runs are easily replaced by the minerals/electrolytes found in Carrie’s regular diet.

Long runs on the weekend (one to four hours): Electrolytes are important before, during and after Carrie’s long runs because she is a “salty sweater” and has a history of muscle cramps. She should take in 16–24 ounces of an electrolyte-replacement drink with or without calories, two to three hours before her run. During a long run lasting one to two hours, she should consume an electrolyte-replacement drink with or without calories. For long runs lasting longer than two hours, Carrie should consume an electrolyte-replacement drink with calories to prevent glycogen depletion. For long runs lasting longer than three hours, Carrie should choose an endurance-specific sports drink in order to consume the necessary extra electrolytes. The amount of the electrolyte-replacement drink consumed during Carrie’s long runs should be based on her sweat rate to prevent her from losing more than 2% of her body weight. To promote rehydration and glycogen replenishment after long runs, Carrie should drink an electrolyte replacement drink with calories or drink water along with eating salty, high-carbohydrate foods.

Summary

It is important for fitness professionals to understand the role electrolytes play in maintaining fluid balance before, during and after exercise. Furthermore, the ability to navigate electrolyte replacement recommendations and options is necessary to educate and answer client questions related to hydration and performance. This is especially true as more commercial sports nutrition products become available to consumers.

References

Burke, L.M. and Deakin, V. (2006). Clinical Sports Nutrition. 3rd ed. Australia: McGraw-Hill.

Dunford, M. (2006). Sports Nutrition: A Practice Manual for Professionals, 4th ed. USA: American Dietetic Association.

Food and Nutrition Board, Institute of Medicine. (1997). Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington D.C.: National Academy Press.

Food and Nutrition Board, Institute of Medicine. (2004). Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington D.C.: National Academy Press.

Murray, R. and Kenney, W.L. (2008). Sodium balance and exercise. Current Sports Med Reports Suppl, 7, 4, S1–S2.

Sallis, R.E. (2008). Fluid balance and dysnatremias in athletes. Current Sports Med Reports Suppl, 7, 4, S14–S19.

Sawka, M.N., et al. (2007). ACSM position stand on exercise and fluid replacement. Medicine & Science in Sports & Exercise, 39, 2, 377–390.

_______________________________________________________________________

Shawn dolan

Shawn Dolan, Ph.D, R.D., C.S.S.D., is an assistant professor in the Department of Kinesiology at California State University, Long Beach. She teaches primarily in the Fitness Option and consults as a sports dietitian for Olympic Training Center in Chula Vista, Calif. Her research focuses on the role nutrition and exercise play in the health and performance of endurance athletes and fitness professionals. She is also the assistant director of Sports Dietetics USA which is a sub-unit of Sports, Cardiovascular, and Wellness Nutrition (SCAN) within the American Dietetic Association.


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