NUTRITIONAL STRATEGIES TO PREVENT ADVERSE GASTROINTESTINAL SYMPTOMS DURING EXERCISE
Updated: Feb 2
By Annie Bothma, December 2022
Let's face it we have all had a race or exercise session ruined by unplanned bathrooms breaks or gastrointestinal (GI) symptoms like bloating, diarrhea, cramping or nausea. This post will outline some nutritional strategies that can help you minimize the risk of developing adverse GI-symptoms during exercise or competition so you can perform at your best when it matters most!
MAINTAIN AN ADEQUATE FLUID BALANCE
Avoiding dehydration is very important as evidence shows that dehydration may exacerbate gastrointestinal (GI) disturbances. Maintaining proper fluid balance during endurance or ultra-endurance events like the marathons and iron-man competitions may also be an important factor in attenuating exercise-induced endotoxemia and cytokinaemia.
However, remember, over-hydrating is not the solution either. Drinking too much during exercise increases your risk during of developing exercise-associated hyponatremia, which has also been linked to gastrointestinal symptoms, particularly nausea and regurgitation. Consuming electrolyte containing beverages with added sodium with help better retain fluid than plain water and help reduce the development of exercise-associated hyponatremia. Electrolyte beverages will also stimulate thirst and help minimize palate fatigue.
Therefore, it appears that starting exercise with a positive fluid balance and minimizing fluid and electrolyte loss as much as possible throughout the duration of the session may help reduce GI disturbance. Working out your individual sweat rate can help you stay hydrated without overdoing it and developing hypoglycaemia.
CONSUME CARBOHYDRATES DURING TRAINING
Frequent and consistent consumption of carbohydrate during exercise is a protective strategy against GI disturbance, since the presence in chyme, increased intestinal carbohydrate transport activity and carbohydrate post-absorption stimulate nitric-oxide induced vasodilation, the most potent stimulator for increasing postprandial microvascular blood flow in intestinal villi. Carbohydrate intake during exercise maintains splanchnic perfusion (attenuates exercise-induced hypoperfusion) and ameliorates intestinal permeability in response to exercise stress and NSAID administration. It would be beneficial to identify individual carbohydrate intake tolerance levels in terms of the quantity and quality during exercise that requires an exogenous fuel supply, and consume carbohydrates evenly and more frequently throughout exercise.
RECOMMEND CARBOHYDRATE (CHO) INTAKE PER HOUR TO OPTIMIZE PERFORMANCE
Exercise lasting less than 1-hour: Mouth rinse or nothing.
Exercise lasting 1-2 hours: 30 - 60g of CHO/h
Exercise lasting greater than 2-2.5 hours: 60 - 90g of CHO/h
TRAIN YOUR GUT LIKE YOU TRAIN YOUR MUSCLE
Training the gut to tolerate more fuel over time will help increase the amount that can be tolerated. Athletes should be experimenting in training with pre-race and race-day nutrition plans many times before race day arrives to figure out what works best and reduce the likelihood of GI issues ruining the race. Train with carbohydrate intake during exercise, and ensure the carbohydrate intake is high in the weeks leading up to an important race. This is a strategic approach that may help increase the gut’s capacity to absorb carbohydrates during exercise. This may reduce the residual volume in the intestine and reduce the risk of GI discomfort or problems during exercise.
You need to be practicing your race nutrition weeks in advance to make sure you have it nailed down by the time race day rolls around. Allow me to make you a customized race fuelling plan. Learn more about the nutritional services I provide here.
Fill out the RACE FUELLING FORM on my websites to get started.
DIETARY ADAPTIONS OF THE GASTROINTESTINAL-TRACK PRE-EXERCISE
1. CONSIDER REDUCING OR AVOIDING LACTOSE
Avoid products that contain lactose, because even mild lactose intolerance can cause problems during exercise. Alternatively lactose free milk or dairy-alternatives such as almond milk or soy milk can be consumed, instead of regular milk. Even if athletes are not lactose intolerant or have any other known food allergies certain athletes may still experience GI upset if dairy is consumed prior to exercise. If you have a history of GI discomfort and struggles, it may be worth experimenting eliminating dairy before sessions in training and see if it helps alleviate some of the potential negative symptoms you are experiencing.
2. REDUCE INTAKE OF HIGH-FRUCTOSE FOODS
Food high in fructose, especially drinks that exclusively contain fructose as the carbohydrate component can acerbate GI disturbances. Fructose is found in fruit and in most processed sweets, such as candy, fruit juices, or in the form of high-fructose Fructose is absorbed by the intestines more slowly, and much less tolerated than glucose. This may lead to cramping, loose stool, and diarrhea. Fructose is also considered as FODMAP. FODMAPs are fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are short-chain carbohydrates (sugars) that the small intestine absorbs poorly. Some people experience digestive distress after eating them, thus, it may be helpful to avoid or limit foods high in FODMAPs the last few days prior to a race.
3. MINIMISE FIBRE INTAKE
Avoid high-fiber foods the day of or even in the days before competition. While training, an athlete needs sufficient fiber in their diet to maintain health. However, leading into a competition it is advised to reduce fiber intake, since fiber may increase bowel movements during exercise are not desirable, will accelerate fluid loss, and may result in unnecessary gas production that might cause GI discomfort, such as cramping. Especially, if an athlete is prone to GI symptoms it is best to stick to refined carbohydrates, such as white breads and pastas, opposed to high-fiber breads and cereals. Starchy vegetables are a better option than most green leafy vegetables. Checking the label beforehand is the safest way to ensure a product does not contain too high an amount of fiber per serving. Read more about the delicate fibre balance for athletes.
AVOID TAKING NSAIDs
Avoid taking aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. Athletes commonly use aspirin and NSAIDs, but they have been shown to increase intestinal permeability and may increase the incidence of GI complaints. The use of NSAIDs in the 24 hours before competition is discouraged. The athlete should make sure he is hydrated, and avoid NSAIDs during training and competition, as it is most likely dehydration causing the headaches and NSAIDs could be causing more GI disturbance.
DIETARY SUPPLEMENTATION THAT MAY HELP
Some supplements have shown the potential to help combat GI disturbances, but the research is still limited and inconclusive. However, potential supplements that athletes can consider taking to help minimize GI upset during exercise, include:
The athlete could explore some of these products, and experiment with them in training, but it is strongly advised not to try anything new close to the competition or the day of the race. It is very important that athletes make sure that all supplements are third party tested and safe-sport approved.
Try implementing some of these nutritional strategies in training and determine which ones makes the most meaningful difference for you. Don't let unwanted GI-symptoms stand in your way of getting that personal best on race day or crushing your next training session!
Sport Nutrition, Third Edition. (2019) by Asker Jeukendrup, Micheal Gleeson
Multiple transportable carbohydrates and their benefits (Jeukendrup, 2018)