How much fiber before a race for endurance athletes?

Runners and other athletes should avoid fiber intake at least 3 hours before a race or a workout to prevent stomach pain, cramps, discomfort, bloating, or gas! Cutting down fiber by 30%, 2–3 days before a big race, is also beneficial for endurance athletes.

Is fiber bad for runners & other endurance athletes?

Certainly, adequate fiber intake is crucial for good health. For instance, low fiber intake may increase the risk of high blood pressure, high cholesterol, coronary heart disease, stroke, diabetes, obesity, reduced insulin sensitivity and many more. The minimum recommended daily intake of fiber is 28 grams on a 2,000 calorie diet.[1]

Proper gastrointestinal system function is vital for endurance performance as well as recovery after a race. A gastrointestinal system that doesn’t function properly may increase the risk of gas, bloating, stomach pain/cramps, intestinal discomfort, urge to defecate, nausea, vomiting, abdominal angina, and diarrhea.[2,3]

Such symptoms are experienced by 25–70% of endurance athletes! Younger endurance athletes, and especially females, are more vulnerable to these symptoms!

A high-fiber diet significantly affects the digestive system. Fiber absorbs water in the body. So, endurance athletes tend to feel bloated or heavy.

Timing is everything, though! Endurance athletes should consume fiber. But, they should avoid fiber a couple of hours before exercise or a big race.

As a rule of thumb, runners and other endurance athletes should avoid eating foods rich in fiber 3 hours prior to strenuous exercise. Fiber takes at least 3 hours to digest. Pre-exercise fiber intake has been linked to increased risk of intestinal cramps.[4,5]

So, athletes should avoid having breakfast with whole-wheat bread or whole-grain cereal before a morning race. White bread is a better option. Moreover, white bread is great post-workout food.

Dietary fiber ingestion causes increased splanchnic vasodilation and splanchnic flow. On the contrary, endurance exercise demands prolonged splanchnic hypoperfusion. To put it simply, the body has completely opposite needs during exercise compared to digesting.

Mechanical forces during exercise can alter the blood flow, and the mucosal activity of the gastrointestinal system. Also, running may cause neuroendocrine changes, and put a tremendous stress on the gastrointestinal system. Hence, endurance exercise can cause abdominal disturbance.

Therefore, it’s vital for an athlete to avoid putting extra stress on the gastrointestinal system by eating foods rich in fiber before a race!

Foods high in fiber to avoid before a race

Foods rich in fiber are beans, whole cereals, seeds, nuts, and most vegetables and fruits.

Also, endurance athletes should avoid eating foods rich in protein and fat before exercise. Protein is beneficial after exercise, though.

A small amount of fiber won’t upset you

You don’t have to avoid pre exercise fiber intake altogether. Just limit them to the minimum.

For instance, a glass of freshly squeezed orange juice has only 0.5 grams of fiber. Drinking orange juice before exercise is good for athletes. It has about 21 grams of sugars, vitamin C, carotenoids, and electrolytes!

So, athletes could drink fruit juices before exercise. It is better to eat whole fruits after exercise, though.

Endurance athletes need fiber

Many athletes avoid fiber altogether. Although skipping foods high in fiber before a run reduces gastrointestinal distress, avoiding them altogether reduces microbial diversity and compromise the health of gut microbiota.[6]

Endurance athletes should still consume the recommended daily fiber intake.

If you used to avoid fiber, you should gradually increase fiber intake. Don’t suddenly switch from a low-fiber diet to a high-fiber diet. The growth of good bacteria and enzymes needs time. More bacteria and enzymes in your gut means less gas and stomach disturbances.

As a rule of thumb, add only 3–5 grams of fiber to your daily diet every week. High amounts of fiber may upset your stomach. You’ll probably need a couple of months to adjust to a high-fiber diet.

Lower fiber intake a few days before a race!

Furthermore, endurance athletes should lower their fiber intake before a big race. Higher effort, along with the anxiety of the race, will further stress your gastrointestinal system.

Fiber may need even more than 2 days to be fully digested. Therefore, cutting down fiber 2–3 days before a big race is beneficial for athletes. Decreasing the daily fiber intake about 20-30% should be enough. So, endurance athletes could consume about 10 grams of fiber per 1,000 calories a couple of days before a big race. There is no need to completely cut down fiber, though.[7]

As a rule of thumb, athletes should avoid consuming whole grains, beans, cruciferous vegetables, or fruits high in fiber, such as avocado. Prefer fruits and vegetable high in water instead. Watermelon, pineapple, tomato, or cucumber are great before a race. In addition, they hydrate the body and replenish electrolyte stores.

Don’t load on carbs the night before a race!

Finally, despite popular belief, you shouldn’t load on carbs the day before a big race. Carb loading could actually harm sport performance. Especially if you are running for less than 90 minutes.

On the contrary, short-term carb loading may make you feel sluggish and bloated in the day of the race.[8]

So, you should go easy on carbs the day before your big race. Certainly, you should avoid carb sources containing fiber. Don’t eat whole pasta, oats, beans, nuts, and other foods high in fiber.

Runners and other endurance athletes should eat small amounts of easily digestible foods before exercise. Furthermore, during exercise, athletes should get a combination of glucose and fructose for improved endurance capacity and performance. Getting carbs during exercise prevents the depletion of glycogen stores, and also promotes the replenishment of glycogen stores after a long race.

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