Runners should avoid fiber before a race!

Runners and other endurance athletes should avoid fiber intake at least 3 hours before a race to prevent stomach pain, cramps, discomfort, bloating, or gas!

Why is fiber bad for runners?

The gastrointestinal system plays a key role in sport performance. Proper gastrointestinal system function is necessary for endurance performance, strenuous exercise and faster recovery after a race.[1]

In contrast, a bad gastrointestinal system may impair performance and delay recovery after exercise. Most noteworthy, it may increase the risk of problems, such as gas, fullness, bloating, feeling uncomfortably, stomach pain or cramps, intestinal discomfort, urge to defecate, nausea, vomiting, abdominal angina, and diarrhea.[2]

Such symptoms are experienced by 25–70% of endurance athletes! Younger endurance athletes, and especially females, are more vulnerable to these symptoms! Running distance and intensity also increase symptoms of a compromised gastrointestinal system.

These are common symptoms among runners who follow a high fiber diet. Moreover, fiber takes up water. So, endurance athletes tend to feel bloated or heavy. A high-fiber diet significantly affects the digestive system.

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 recommended daily intake of fiber is 14g per 1,000 calories. So, we should consume 28g of fiber for a 2,000 calorie diet.[3]

Is fiber good or bad for endurance athletes? Timing is everything! Endurance athletes should consume enough 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 physical exercise. They should avoid foods with a high protein, or fat content as well. Fiber needs at least 3 hours to leave the stomach.[4]

So, athletes should avoid having breakfast with whole-wheat bread or whole-grain cereal before a morning race. They’re particularly high in fiber. White bread with a sweetener is a better option. Skip butter as well. Fat can also impair sport performance.

Pre exercise fiber intake has been significantly linked to increased risk of intestinal cramps.[5]

Dietary fiber ingestion causes increased splanchnic vasodilation and splanchnic flow. On the contrary, endurance exercise demands prolonged splanchnic hypoperfusion![2] 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 to the gastrointestinal system, eating foods rich in fiber!

Timing of eating fiber is everything

Although pre exercise fiber intake is bad for runners and other endurance athletes, athletes shouldn’t avoid fiber altogether. They just have to schedule their meals accordingly.

Avoid eating foods high in fiber before exercise. Especially, 3 hours before a race. You can consume foods with fiber the rest of the day.

Foods rich in fiber are beans, whole cereal, most vegetables and fruits, seeds, and nuts. Also, endurance athletes should avoid eating foods rich in protein and fat before exercise. Protein intake is necessary after exercise.

A great way to boost vitamins and other nutrients from fruits and greens before a long race is to drink their juice. Fruit juices and green juices are packed with vitamins and sugars which are vital for sport performance. As a bonus, they contain negligible to zero fiber!

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 fresh-squeezed orange juice has only 0.5g of fiber. Drinking orange juice is great before exercise. It has about 21g of sugars, vitamin C, carotenoids, and a high dose of electrolytes![6]

In comparison, consuming the same amounts of calories from whole oranges will give you about 5g of fiber!

So, you better drink fruit juices before a race, but you should eat whole fruits after exercise.

Endurance athletes need fiber as well

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 the athlete’s gut microbiota.[7]

Endurance athletes should still consume the recommended daily fiber intake, which is 14g of fiber per 1,000 calories!

If you used to avoid fiber, you should gradually increase fiber intake. Don’t instantly switch from a low-fiber diet to a high-fiber diet. 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 3-5g of fiber in your daily diet every week. Too much fiber may upset your stomach. You’ll probably need a couple of months to adjust to a high-fiber diet.

Increasing daily fiber intake gradually should be easy. For instance, start eating more whole fruits. A couple of weeks later, you could switch from refined carbs to whole grain. When you feel comfortable enough, you can start eating beans and legumes…

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 fully be digested.[8] Therefore, cutting down fiber a couple of days before a big race is beneficial for athletes. There is no need to cut down fiber completely. Decreasing daily fiber intake about 20-30% is enough.

For instance, you should avoid consuming whole grains, beans, or cruciferous vegetables, such as broccoli. Also, you could avoid consuming fruits high in fiber, such as avocado. Prefer fruits and vegetable high in water instead. Watermelon, pineapple, tomato, or cucumber are excellent examples. They also hydrate and replenish electrolytes.

Don’t load on carbs the night before the 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.[9]

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 in the hours before and during 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 greatly helps on the faster replenishment of glycogen stores after a long race.[1]