Essentials of Nutrition for Sports

In many events, beginners who spend longer than average on the
course, especially those who overdrink salt-poor fluids, are most at risk. Many sports drinks are relatively low in sodium.

Cyclists may have a relatively easy time ingesting sodium

snacks. Triathletes can ingest salt

snacks while cycling. Runners tend

to have finished their event before trouble with sodium sets in. Walkers, in the heat for many hours, are the most at risk, especially if they rely only on gels and water for their event nutrition.

For example, marathon walkers, who take 8 hours to walk a

marathon, are more at risk than

seasoned marathon runners who may

complete the course in 3 hours.

In some large events, (1) when randomly tested, more than 20%

of athletes have had hyponatremia and (2) more than 3% of athletes have required medical attention for hyponatremia.

In a study of Iditasport human-powered ultra-marathon athletes 7

of 16 (44%) had hyponatremia. Th

ese competitors drank more and

consumed less sodium per hour

than their normonatremic

counterparts.

Another study showed that 89%

of marathon runners had lower

blood sodium levels after their marathon than before. Those most prone to hyponatremia lost less weight and drank more.

It has been speculated that

the use of non-steroidal anti-

inflammatory drugs (NSAIDs) ma

y increase the risk of exercise-

related hyponatremia by impairing water excretion; firm evidence is lacking.

For aerobic-endurance athletes, it is reasonable to plan on an

intake of up to a maximum of one gram (1,000 milligrams) of sodium per liter of fluid loss. This

is about one-half teaspoon of salt.

It is preferable to eat salty foods or drinks rather than ingest salt

tablets. Studies have shown that sa

lty foods and drinks appropriately

stimulate thirst, and so prevent the unintentional ingestion of dangerously high amounts of sodium.

Many athletes who are sodium-depleted are also dehydrated.

However, those with low blood sodium are often relatively less dehydrated than their competitors who have blood levels closer to normal.

The reason is that athletes tend to

rehydrate with fluids that have

a lower sodium concentration than blood. Those who drink the most tend to dilute sodium the most a

nd have lower blood concentrations.

Here is another reason for c

onsuming salt: It helps the body

rehydrate.

Read more about sodium and sw

eat losses during events on page

21

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Bottom Line

Diets relatively low in salt (6 grams salt per day or less, 2,500

milligrams sodium) and high in pot

assium (at least 4.5 grams per

day) are associated with decreased

risk of high blood pressure and

associated risks of cardiovascular and kidney diseases, especially in salt-sensitive individuals.

Fruits and vegetables (at least 5 servings per day) together with a

low-salt diet may interact to further reduce high blood pressure risk.

Aerobic endurance athletes need

to increase their salt intakes

with workouts or events where more than several quarts (liters) of sweat occur.

Nutrition for Sports, Essentials of 167