To Salt or Not To Salt

Hydration is of crucial importance for optimizing an athlete's training and performance. The types of fluids you consume to rehydrate is equally more important for the prevention of serious electrolyte imbalances. There is an alarming trend towards electrolyte imbalance amongst endurance athletes competing in stressful environmental conditions(1,2,3). Specific sodium guidelines do not exist because of the individuality of sweat rate and sodium content in sweat. However, the well informed athlete can monitor trends in their own sweat rate and sweat composition to prevent the risk of decreased performance. In very hot and humid conditions this becomes crucial and may prevent injury, heat illness, or even death.

The most frequently asked questions revolve around whether salt tablets can aid in optimal fluid to electrolyte balance or whether potassium should be supplemented. The answer lies in replacing electrolytes (sodium and potassium) and fluid to maintain a balance. This means fine tuning your individual intake of these essential nutrients.

The American Dietary recommendation for sodium is to restrict intake to less than 2400 mg per day, which is equivalent to 6g of table salt. This amount should provide sufficient sodium for normal levels of activity. This recommendation is of course based on the average individual, typically sedentary in nature, and not an athlete.

Athletes will lose copious amounts of sodium through sweat in high intensity and/or heated conditions. Athletes training for long endurance events in hot and humid environments may require extra sodium as a part of their hydration strategies. Sodium is the “gate keeper” of fluid in your body. It enables the body to hold onto water for hydration, plays a role in hydration on the cellular level, and the normal function of glucose entry into cells to be used as energy.

Heat exhaustion caused by salt depletion occurs most frequently in individuals who are not acclimatized to heat and attempt training in these conditions. Individuals who do not replace lost salt over a period of several days can also be effected. Symptoms include fatigue, nausea, and cramps. The skin is usually becomes pale and cool and sweat rates may decrease. Heavy training session in the heat can cause a sweat loss of 4 liters of fluid. This amount of sweat may contain up to 7.2g of sodium in the unacclimatized individual, but only around 3 g for the acclimatized athlete.

Sodium is found abundantly in a wide variety of foods, therefore it is not difficult to get an adequate supply. An average meal contains 2 – 3 g of sodium, and thus 3 average meals could provide somewhere around 6 – 9 g, This should adequately cover the normal losses for the average sweat rates and sodium concentrations in sweat. However, it is not unreasonable for heavy sweaters or salty sweaters to require increase sodium intake; especially those acclimatizing to heat and humidity.

Because salt requirements are thus individualized, there is the question of whether to take extra salt for training and events.First, always plan to hydrate well. Training sessions between 90 and 120 minutes requires hydration strategies.

If these sessions are planned in the heat, or for any training greater than 2 hours, hydration in combination with electrolyte replenishment becomes vital. Calculate your individual sweat rate to determine how much fluid intake you require per hour. In general, electrolyte supplements to replace losses are not necessary for training sessions lasting less than 75 to 90 minutes. However, most athletes training for events lasting greater than 2 - 3 hours (endurance events) should add a little extra salt in meals (unless there is sensitivity towards high blood pressure) and consume foods high in potassium, such as bananas and citrus fruits. Protein also has an effect on hydration because heat is produced in the body as protein is metabolized which can contribute to increased sweat and salt loss. Athlete’s require between 20 - 25% of an athletes daily intake and should avoid extra protein. A diet adequate in salt and electrolytes combined with the use of sports drinks such as Gatorade or Accelerade, will replace electrolytes lost through daily activity and training. However, this is a broad statement, as with any other nutritional concern, issues such as these should be studied on an individual basis.

Common salt tablets contain sodium and chloride, and may be appropriate for profuse or salty sweaters or for individuals attempting to acclimatize to increased heat conditions. When heat and humidity increases, endurance athletes may increase sodium intake to around 10 – 25g of salt or 4 – 10 g of sodium daily (4). Start by adding a sprinkle of salt to your regular meals. You may also add a ¼ tsp of salt to 20 fl oz water bottles. Over and above that, salt tablets can be experimented with. Keep in mind that if you are thinking of using them in a race, you should first experiment with different brands and amounts during long endurance training in similar race conditions. Your body metabolizes differently in low and high levels of intensity, therefore race pace should also be simulated. Carrying salt packets is convenient, but make sure you are chasing straight salt down with water and not a sports drink. Be VERY conscious that a high amount of salt in the blood may shift your water to salt balance off kilter and predispose you to hypernatremia (blood contains excess salt with not enough water to dilute it). Symptoms of hypernatremia are similar to dehydration, such as cramping, dizziness, intense headaches, sweaty palms, nausea and vomiting, and if unattended, coma and death. At first, choose salt tablets that have minimal salt and then slowly increase the dosage as needed, in order to determine how your metabolism reacts to differing levels. Start with less than 200 mg tablets. (1 tsp salt = 5g = 2g of sodium).

A common method to determine your individual salt intake parameters would be to check body weight before and after training sessions. Experiment with salt tablets if you as an individual find it common to need to replace 4 quarts of fluid loss, which would equal an 8lb fluid loss from sweat. A general rule is to take 2 salt tablets (1g sodium) with each additional quart over and above 4 quarts. If you plan to take these tablets during your training/events, versus as a rehydration strategy, no more than one gram per hour is recommended, along with the fluid requirements of 24 - 40 ounces per hour.

Potassium supplements are not recommended for a number of reasons. First, potassium deficiencies are rare even in profuse sweater. Furthermore, potassium can disturb the electrical rhythm of the heart and may be lethal if not dosed correctly. Remember a glass of orange juice can replace the potassium lost in 2 liters of sweat, so a very small amount is needed.

An article on sodium to water balance would not be complete without an explanation on hyponatremia (an extremely dangerous fluid to electrolyte imbalance). The word hyponatremia literally means low (hypo) sodium (natremia). Symptoms of hyponatremia include gastrointestinal distress and cramping, nausea and vomiting, extreme headaches, seizures, and possible death. A sound overall nutrition plan and rehydration strategy can help prevent this condition. Note whether you are at risk, factors include heavy sweaters, particularly salty sweaters , training (or competing) in particularly hot and humid conditions for long periods of time (endurance). It can be caused by either taking in too much fluid with not enough electrolytes to allow for proper hydration, or by taking in too much electrolytes, with not enough fluid to dilute it appropriately. These situations are intensified when sweating heavily due to the further sodium loss in sweat. A simple rule of thumb is to first determine your sweat rate, then note the salt concentration and residue on your clothing post work out. If you are having trouble with your salt or fluid intake, note that the only accurate asessment would occur in a human performance laboratory.

Athletes experiencing muscle or gastrointestinal cramping may also ease symptoms by increasing salt intake or by consuming electrolyte containing sports drinks, This may also resolve the development of hyponatremia. However, if you experience symptoms such as disorientation, severe headaches and reduced ability to speak, you require immediate medical attention. It is also important to note that certain medications which induce a diuretic effect can increase the risk of hyponatremia. Athletes on any medications, particularly aspirin and ibuprofin, or any meds with a diuretic side-effect, should check with their health provider before training for or participating in endurance events.

Balancing your fluid and sodium intake requires knowledge of your self, your training, and the conditions you will train in. For most endurance athletes, hyponatremia and other electrolyte or hydration issues can be easily avoided by knowing your individual sweat rate, salty concentration, and your reaction to your training environment.

References

1. Maughan RJ. Water and electroluyte loss and replacement in exercise. Nutrition in sport (ed Maughan RJ). London:Blackwell Science. 2000: p 226.
2. Noakes, TD., Adams B.A., Myburgh K.H., Greeff C., Lotz T., and Nathan M. The danger of inadequate water intake during prolonged exercise. A novel concept revisited. Eur. J.Appl. Physiol, 57 (2), 210 – 219.
3. Millard-Stafford, M.L., Sparling, P.B., Rosskopf L.B., and DiCarlo L. J. Carbohydrate-electrolyte replacement improves distance running performances in the heat. Med. Sci. Sports Exerc. 24 (8): 934-940.
4. Seebohar, Bob. Nutrition Periodization for Endurance Athletes. 2004. Bull Publishing Company, Boulder CO.
5. Dan Benardot. Advanced Sports Nutrition. 2006. Human Kinetics, Champaign IL.