Training and racing in hotter weather absolutely demands getting hydration right. For years, we’ve been told that key elements of doing so include avoiding caffeinated beverages and drinking small amounts throughout the day. Is that true? Let’s look at some hydration claims and facts.
CLAIM: CAFFEINE CAUSES DEHYDRATION
Caffeine naturally occurs in the leaves, nuts and seeds of plants. It enters the runner’s diet through various foods and beverages consumed every day, such as tea, coffee, colas, chocolate and energy drinks. (Put another way, items that many of us consume on a daily basis with great enjoyment.) Caffeine has long been identified as being a diuretic; it promotes the excretion of urine by increasing blood flow to the kidneys. Therefore, runners have traditionally been told, avoid caffeinated beverages, especially when it’s hot, because increased water losses could impair performance.
In 2005, the American College of Sports Medicine clarified how caffeine affects hydration. The organization’s statement on hydration includes this sentence: “Caffeine ingestion has a modest diuretic effect in some individuals but does not affect water replacement in habitual caffeine users, so caffeinated beverages can be ingested during the day by athletes who are not caffeine naive.” In other words, if you’re used to it, moderate amounts of caffeine don’t increase urine output more than a similar amount of water.
How is this possible, given the well-known urge to find the nearest bathroom not long after having a coffee? Caffeine is rapidly absorbed by the body, and reaches its highest concentration about an hour after it’s consumed; it can maintain that peak for several hours. During that time, yes, it often contributes to greater urine output for several hours, but that phenomenon is followed by a decrease in urine output. Over the course of 24 hours, then, caffeine results in no significant difference in overall urine volume. On a daily basis, habitual caffeine users aren’t dehydrated by their beloved beverages.
A natural concern for even regular caffeine users is avoiding increases in the urge to urinate during the early stages of a race. Fortunately, since there’s an increase in catecholamines and less blood flow to the kidneys, the early diuretic effect of caffeine is often lacking during exercise.
Response to caffeine varies from person to person. Identify if and when caffeine fits appropriately into your running. Caffeine right before a hard workout or race may induce an upset stomach or jittery feeling. On the other hand, regular caffeine users may suffer nausea and headaches if they go without. For most people, caffeinated beverages can count toward daily fluid intake and aren’t long-term dehydrators.
CLAIM: SIP SMALL AMOUNTS OF FLUIDS THROUGHOUT THE DAY, BECAUSE ONLY SO MUCH CAN BE ABSORBED AT A TIME
Runners are used to hearing that the stomach can’t process more than 7 ounces of fluid every 15 minutes and that, therefore, the key to staying hydrated is to consume small amounts. In reality, recent research shows that drinking more fluid less frequently, compared with drinking the same total volume spread out in smaller, more frequent intakes, speeds gastric emptying (the movement of fluid from your stomach to intestines).
This is so because as fluid volume increases, gastric-emptying rate also increases, allowing the small intestine to be more proficient at absorbing and delivering essential fluids, carbohydrates, and electrolytes to the body. Ingesting the appropriate fluid volume may be more valuable than the actual timing (although drinking at regular intervals still supports maintaining this faster rate of gastric emptying).
The overall goal remains to match fluid intake with fluid loss during a run. Maintaining body mass that’s within 2 to 3 percent of your pre-run weight and avoiding weight gain conveys appropriate hydration. This is done most effectively by tracking your pre-run nude body weight compared to post-run nude weight; calculating your sweat rate offers insight as to about how many ounces to drink per hour. If you gained weight on the run, you drank too much during it. Conversely, and more commonly, weight loss greater than 2 to 3 percent indicates you need to take in more fluid; your performance, especially at faster paces, starts to suffer significantly once you get past that amount of dehydration.
Once your overall volume need is determined, experiment with training your gut to tolerate greater fluid volumes at regular intervals while matching sweat loss. For instance, if 18 ounces per hour is your ideal volume, try consuming 6 ounces every 20 minutes as compared to 3 ounces every 10 minutes. By practicing in training, it’s possible to teach the body to tolerate greater fluid volume less frequently and support faster gastric emptying.
CLAIM: RUNNERS SHOULD LIMIT SALT INTAKE TO AVOID HEART DISEASE
Hypertension isn’t common in the young, but it increases in prevalence with age. Because sodium is often associated with hypertension, it’s common to be concerned about sodium intake as we age. For a healthy runner with low sweat losses, 2-3 grams of sodium a day may be sufficient. During hot running conditions, however, sodium loss alone may well exceed the standard intake guidelines. Where should most of us hedge our bets: Less sodium out of concern for heart disease years from now, or more sodium out of concern for poorer performance on tomorrow’s run?
If you don’t have a personal or family history of hypertension, go with the better-running-performance option. Research confirms sodium loading before exercising in the heat supports fluid balance and endurance during exercise. Sodium ingestion is beneficial during a run because it stimulates thirst and helps to replace electrolyte losses from sweat. Failing to take adequate sodium after running hinders the return to a state of normal hydration.
Sodium loss is harder to assess than fluid loss. A grainy texture to the face and skin, a white sweat ring on clothing, and sweat-saturated clothes are signs of high sodium losses after a run. Inadequate sodium may also be the culprit behind nagging muscle cramps. These recognizable signs of greater sodium losses warrant a little extra sodium in the diet. Recent research suggests the body adapts to a greater appetite for salt when sweat loss is high, as compared to distaste for salt when sweat loss is low.
Sodium replacement doesn’t mean pouring salt over all your food or snacking on chips all day. Aim for food choices that are not only rich in sodium, but also rich in other nutrients on days when your sodium losses are likely to be higher. Such options include cheeses and other forms of dairy, bagels, canned tuna, olives, vegetable juice and chili.
Runners with a strong family history or diagnosis of hypertension will find the most reliable way to manage the situation is with regular physical examinations and communication with their physician. General hypertensive guidelines still apply, but it’s possible limiting the amount of exceedingly high-sodium foods like processed meats and fast food would be adequate during hot summer training sessions.