It's summer! The days are longer, the weather is warmer, and kids are off from school. We all want to play more in the summer, taking advantage of longer days and nicer weather. With our coastline and mountains, San Diego is a Mecca for outdoor activity. Surfing, swimming, in-line skating, running, bicycling, mountain biking, rock climbing, and a wide variety of team sports are the tip of the iceberg for our summer activities.
We're all taught to make sure we drink enough water during exercise. Many health care providers recommend drinking at least eight glasses of water per day, and more during the summer or while exercising. What doesn't get mentioned is that drinking much more than this can dilute essential minerals and electrolytes which can cause a whole host of problems. I learned this firsthand while on a bicycle tour in the midwest during one of the most severe heat waves Missouri has seen in June! I found myself drinking nearly 3 gallons of water daily to keep from being thirsty, which filled my belly so much it was hard to eat enough calories to sustain 70-mile days on a bicycle. Even eating salty snacks, salting my food more than usual, and taking a double dose of my usual potassium, multi-mineral, and calcium supplements had me barely keeping up with electrolytes. Several people on the ride spent an afternoon in the emergency room for an IV of Ringer's solution after suffering severe heat exhaustion and electrolyte depletion. This type of emergency can easily be avoided if you pay attention to electrolytes in addition to fluid intake alone.
What are electrolytes, and why do we need them?
In chemistry, every atom has a certain number of protons (positively charged) and electrons (negatively charged). A stable atom has an equal number of protons and electrons, and has no electrical charge. An ion is an atom that has an uneven number of protons and electrons, giving it a positive or negative electrical charge. An electrolyte is any substance containing free ions that behaves as an electrically conductive medium.
In physiology, the primary ions of electrolytes are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and chloride (Cl−). The electric charge symbols of plus (+) and minus (−) indicate that the substance in question is ionic in nature and has an imbalanced distribution of electrons.
Both muscles and nerves are considered electric tissues. Muscles and nerves are activated by electrolyte activity between interstitial fluid (fluid between the cells) and intercellular fluid (fluid within the cells). Electrolytes may enter or leave a cell through the cell membrane and are required for a variety of cellular functions. For example, muscle contraction is dependent upon the presence of calcium (Ca2+), sodium (Na+), and potassium (K+). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.
Electrolyte balance is maintained by intake of electrolyte-containing substances, and is regulated by hormones as well as by the kidneys. back to top
Which electrolytes do we need?
Sodium
While sodium gets a bad rap from the people concerned about blood pressure, it is actually required for a variety of cellular functions and we can't live without it. A human being requires approximately 500mg of sodium per day for basic physiological functions. Sodium is one of the minerals required for nerve impulses to occur (nerve impulses facilitate every message from the brain to our muscles and internal organs). It is also important for maintaining appropriate blood volume.
For most of us, the issue with sodium is overconsumption rather than underconsumption. Most processed foods contain outrageous amounts of sodium, so it is easy to consume far more than 500mg/day. Consumption of large amounts of sodium can become problematic for people with kidney problems or high blood pressure.
When we exercise on hot days, thirst often drives us to drink far more water than we ordinarily would. This is good to a point - once you become thirsty, you are already dehydrated. But, drinking too much water can lead to water intoxication or hyponatremia (low levels of sodium in the blood). Symptoms of sodium imbalance include headache, general malaise, nausea, and vomiting. When levels drop below a certain point, hyponatremia can be life threatening.
Almond et al. (1) found hyponatremia in as many as 13% of runners in a recent Boston Marathon, with life-threatening hyponatremia in 0.6%. The runners at greatest risk of serious water intoxication had moderate weight gain during the race due to excessive water consumption.
Sodium is not the only mineral which becomes diluted when we drink too much water. Potassium, magnesium, calcium, manganese, selenium, and other trace minerals can also become diluted in the bloodstream. back to top
Potassium
Potassium is required for all cellular communication and nerve conduction. It is present in a variety of foods, including almonds, bananas, cucumbers, apricots, avocados, tomatoes, potatoes (especially the skins), wheat germ, and others. Low potassium in the blood stream is called hypokalemia.
Mild hypokalemia is often without symptoms, although it may cause a small elevation of blood pressure and can occasionally lead to an irregular heart beat. Moderate hypokalemia may cause muscular weakness, muscle aching, muscle cramps (due to disturbed function of the skeletal muscles), and constipation (from disturbed function of smooth muscles). back to top
Calcium
Calcium is required for healthy bones, normal muscle contraction, and nerve conduction. Dietary sources of calcium include milk products, broccoli, cauliflower, pinto beans, aduki beans, soybeans, almonds, brazil nuts, hazelnuts, sunflower seeds, sesame seeds, molasses, and others.
Mild calcium deficiency (as could occur during exercise as opposed to long term dietary deficiency) can cause muscle cramps, heart palpitations, numbness or tingling in the hands and feet, irritability, and mental confusion.
A recent study showed that competitive cyclists have a much greater than average chance of osteoporosis because intense physical exercise over long periods of time can deplete calcium in the body. (4,5)
Magnesium, vitamin C, and vitamin D are needed to aid absorption of calcium. back to top
Magnesium
Magnesium is involved in several hundred enzymatic reactions in the human body, many of which contribute to production of energy (conversion of glucose to ATP) and cardiovascular function. It is the "anti-stress" mineral as it functions to relax skeletal muscles as well as the smooth muscles of the blood vessels and digestive tract. It is essential for modulating the electrical potential of cell membranes which allows nutrients to get into and out of cells.
Symptoms of magnesium deficiency can include fatigue, lack of appetite, irritability, insomnia, muscle tremors, and muscle twitching. Severe magnesium deficiency can lead to muscle cramping, mental confusion, and spasm of the coronary artery.
Dietary sources of magnesium include dark green vegetables, almonds, pecans, cashews, brazil nuts, wheat bran, wheat germ, millet, brown rice, avocado, dried apricot, and soy products. back to top
How do we get enough electrolytes while staying hydrated?
For mild to moderate exercise (say 60-90 minutes of moderate-intensity activity), eating some salted almonds, dried apricots, avocado, bananas, or pickles after your workout is probably sufficient. 1/8 tsp of sea salt in one of your water bottles or one bottle of sports drink wouldn't hurt, but you're probably ok without. Plain old iodized salt contains only sodium chloride, and lacks the other trace minerals found in sea salt, so sea salt is what you need for this application!
For more extreme exercise (say riding a mountain bike for 4 hours in 100 degree heat), you will need an electrolyte replacement sports drink for at least 50% of your fluid intake. You may need additional supplements for potassium, calcium, magnesium, and vitamin C. Camelbak's Elixir product contains all these minerals in an easy to carry tablet form which dissolves quickly without powdery residue in your water bottle. (No, I am NOT a representative for Camelbak, nor do I sell their products. I've just been happy with my experience with the Elixir!) Many companies are now making jelly beans, jelly blocks, and other chewy electrolyte replacement products. My favorites (based on my taste preference AND a high percentage of organic ingredients with minimal artificial stuff) include Sharkies electrolyte chews and Cliff Blocks.
If you are routinely doing extreme exercise (more than one day per week), you should also take a basic multi- mineral supplement which provides the macro minerals discussed in this article along with a whole host of trace minerals. I would be happy to make recommendations, and I do carry a multi-mineral supplement in my office. back to top
First aid for electrolyte depletion during exercise
Should you find yourself feeling undue fatigue, malaise, lightheadedness, disorientation, nausea, vomiting, palpitations, muscle aching, or muscle cramping during a warm weather workout, STOP what you are doing!
Get inside and cool off, have a glass of cool apple juice with ¼ tsp of salt in it and a banana or pickle if your stomach allows.
If you do not feel better within 30 minutes, seek medical attention - you may be in a state of electrolyte depletion which requires IV replacement to prevent a medical emergency.
Be safe, and have fun with your summer activities!
1. Almond CS, Shin AY, Fortescue EB, et al. (April 2005). "Hyponatremia among runners in the Boston Marathon". N. Engl. J. Med. 352 (15): 1550-6.
2. "Statement of the Second International Exercise-Associated Hyponatremia Consensus Development Conference 2007"
3. Siegel AJ, Verbalis JG, Clement S, et al. (May 2007). "Hyponatremia in marathon runners due to inappropriate arginine vasopressin secretion". Am. J. Med. 120 (5): 461.e11-7.
4. Smathers AM, Bemben MG, Bemben DA. Bone density comparisons in male competitive road cyclists and untrained controls. Med Sci Sports Exerc. 2009 Feb;41(2):290-6.
5. Barry DW, Kohrt WM. BMD decreases over the course of a year in competitive male cyclists. J Bone Miner Res. 2008 Apr;23(4):484-91.
