Fibre in sports nutrition

In a previous post, I highlighted the relationship between fibre and health. In general, dietary fibre is good for you. However, the role of fibre in sports nutrition is a little more complex.

Fibre in sports nutrition

When talking about dietary fibre intake in the context of sports nutrition, we need to think beyond health. It is also important to consider weight and body composition, performance during training and competition, and recovery.

As a reminder, the recommended daily intake of dietary fibre is 25 grams per day for most adult women and 30 grams per day for most adult men.

Regulation of energy intake

Dietary fibre intake increases satiety. Therefore, increasing fibre intake is a good strategy for athletes who need to manage their weight.

On the flip side, athletes who struggle to meet their energy requirements could benefit from dialling down their dietary fibre intake to a maximum of 25-35 grams per day. This includes injured athletes, who normally require a higher than usual energy intake for recovery purposes (1).

Female athletes with disordered eating behaviours tend to restrict energy intake and consume high amounts of fibre. Both factors can lead to functional hypothalamic amenorrhea, i.e. lack of menstruation. Therefore, these athletes should limit consumption of dietary fibre to meet recommendations (1).

Making weight

Athletes who compete in weight-based sports such as boxing and Olympic weightlifting can use a short-term (2-3 days) low-fibre diet to make weight by reduction of bowel contents. This strategy produces a modest reduction in total weight. Moreover, it should not be sustained beyond weigh-in as it can cause detrimental side effects such as constipation and abdominal distention, which can in turn lead to diverticulitis and hiatus hernia or aggravate irritable bowel symptoms. After weighing in, athletes should use high-carb low-fat low-fibre fluids for recovery (1).

A low fibre intake may also be a viable short-term pre-competition strategy for non-weight category sports such as athletics. This is because athletes such as jumpers can benefit from a small reduction in body mass without limiting total energy intake (2).

Training and competition

Athletes who load on carbohydrates before long training sessions or endurance/ultra-endurance competition may choose to lower fibre intake to minimise gastrointestinal issues such as abdominal discomfort, flatulence and diarrhoea (1). This is particularly important in the pre-competition meal, which should should be low-fibre, low-fat, low to moderate protein (1, 3) and low in FODMAPs (3).

It is important to note that gastrointestinal discomfort can affect any athlete, not just those competing in endurance events. For example, a high fibre pre-workout meal can also cause digestive discomfort before intense training sessions or competition (4) regardless of the duration of the event.

Gastrointestinal recovery

Athletes who experience diarrhoea and vomiting (e.g. traveller’s diarrhoea) should consume low-fat and low-fibre food when able to tolerate solids (1).

Health

As seen in the article about fibre and health, there are many health benefits associated with dietary fibre intake.

In addition, fibre from plant foods may help counteract potential detrimental effects of animal protein intake, which is typically high in omnivorous athletes. In addition, fibre consumption is fundamental for gut health. This is important because the gut and the microbiome deliver water, nutrients and hormones to the athlete’s organs and tissues during exercise (4).

Summary and recommendations

The health of the athlete should be the priority as a sick or symptomatic individual will not be able to train and perform at their best. With this in mind, athletes should consume adequate dietary fibre from whole plant foods except for when making weight and before intense/long training sessions and competition.

Excessive fibre intake can be detrimental for athletes who are not meeting their energy requirements or who exhibit disordered eating behaviours.

References

1. Burke, Louise. Clinical Sports Nutrition, 5th Edition. McGraw-Hill Australia, 09/2015. VitalBook file.
2. Sygo J, Kendig Glass A, Killer SC, Stellingwerff T. Fueling for the Field: Nutrition for Jumps, Throws, and Combined Events. Int J Sport Nutr Exerc Metab. 2019 Mar;29(2):95–105.
3. Costa RJS, Knechtle B, Tarnopolsky M, Hoffman MD. Nutrition for Ultramarathon Running: Trail, Track, and Road. Int J Sport Nutr Exerc Metab [Internet]. 29(2):130–40.
4. Clark A, Mach N. Exercise-induced stress behavior, gut-microbiota-brain axis and diet: a systematic review for athletes. J Int Soc Sport Nutr. 2016/12/08. 2016;13:43.

[Photo by Quino Al on Unsplash]

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