Fueling on the move: pros and cons of going natural

The findings

When all the data was collected and analyzed, the researchers found that the time trial performance of the cyclists was the same regardless of whether they had consumed bananas or carbohydrate drink. Moreover, the cyclists’ blood sugar levels also followed the same trajectories regardless of the type of carbohydrate consumed, indicating that the metabolic response to consuming bananas was very similar to consuming drinks. And when markers of oxidative stress and immunity were compared, it was clear that the bananas fared just as well as the carbohydrate drink in helping to reduce oxidative stress and maintaining immune function. Participants did report feeling significantly fuller when consuming bananas, which may have been due to the high fiber intake (around 15 grams). Although this did not affect exercise performance, the researchers commented that it could become a greater issue during much longer distances requiring more carbohydrate intake.

In another study three years later, the same research group also compared banana ingestion to pear ingestion or plain water ingestion during a 75 km cycling time trial⁽¹⁵⁾. In this study, 20 male cyclists initially ingested 0.4 grams per kilo of bodyweight from either banana or pear (taken with 5mls of water per kilo) or water alone twenty minutes before a time trial. Then, during the time trial, they ingested either another 0.6 grams per kilo per hour of banana (just under 50 grams for an 80kg athlete), 0.6 grams per kilo per hour of pear or just more water.

The performance times for the banana and pear ingestion were significantly faster than water alone, demonstrating that both foods could be a good carbohydrate source during exercise for endurance performance. However, because there was no carbohydrate drink condition in this study, it was not possible to say how these foods compared with the ingestion of the same amount of a commercial carbohydrate drink.

More research on food carbohydrates

It’s not just bananas that have been investigated as natural food alternatives for carbohydrate supplementation to improve endurance performance; other foods have too. Here are some examples:

Honey - Two studies have shown endurance performance gains when ingesting honey during bouts of cycling⁽¹⁶⁾ and running⁽¹⁷⁾. In the cycling study, amateur cyclists ingested 15 grams of carbohydrate every 16km during a 64km cycling time trial. Half of the cyclists ingested carbs in the form of a commercial sports gel while the other half ingested honey. The results showed that both forms of carbohydrate allowed cyclists to generate more power during the last 16km compared to when they ingested plain water, and that the performance gains were similar between gels and honey.

Honey may be a particularly interesting option during exercise where fast absorption is required because it provides carbohydrate both as glucose and fructose. It’s also easy transported and provides a compact source of calories. However, the downside of honey is that it is classed as a ‘high-FODMAP’ food due to its high fructose content⁽¹⁸⁾, which means those with sensitive tummies may struggle with gastric distress (see this article for an in-depth discussion on the impact of high-FODMAP foods in sport). This means that honey must be tested by athletes in training sessions first, and not trialled during competition!

Raisins - Raisins are a compact natural source carbohydrate providing a glucose:fructose ratio of around 1:1⁽¹⁹⁾ and which find favor with some endurance athletes. Studies also show that ingesting raisins during exercise produces performance benefits. For example, one study compared the effects of six servings of 28 grams raisins or 26 grams of ‘sport jellybeans’ (specifically designed to enhance endurance performance) every 20 minutes during a 120-minute hard bike ride immediately followed by a 10km time trial⁽²⁰⁾. The findings were that both forms of carb supplement maintained similar blood glucose levels during exercise and resulted in similar time trial performances.

In another study, researchers compared raisin ingestion to carbohydrate-rich sport chews and plain water drinks⁽²¹⁾. Eleven competitive endurance runners consumed 0.5 grams per kilo of bodyweight of carbohydrate as raisins or chews before exercise, then 0.2g per kilo every 20 minutes throughout a challenge consisting of an 80-minute treadmill run at 75% VO2max followed by a 5km time trial. It turned out that both carb interventions led to a greater performance compared to water alone and that the raisins were equally as effective as the sport chews.

In a similar vein, ingesting 1.5 grams per kilo of bodyweight of Corinthian currants produced the same performance gains as consuming the same amount of a glucose drink in a task consisting of 90 minutes of cycling at 60–70% VO2max followed by a ride to exhaustion at 95% VO2max (hard!)⁽²²⁾. Even better, these studies all found that raisins and currants were well tolerated by the athletes with minimal gastric distress effects.

Potatoes – Although not sweet in any way, potatoes are rich in readily digestible carbohydrate, and anecdotally, cyclists are known to transport baked potatoes on long rides for fuel – precisely because some athletes find that constantly consuming sweet products hour after hour leaves them craving for the taste of something more savory! In a 2019 study, researchers compared the cycling performance effects of carbohydrate obtained from mashed potatoes with an equivalent amount a gel⁽²³⁾.

The cyclists performed 120 minutes of intermittent cycling at 60–85% of VO2peak (moderate intensity) before performing a time trial. In this time trial, the cyclists had to complete a total workload of 6kJ for every kilo of their body mass. Note that the purpose of setting a workload per kilo of body mass is to ensure that the nutritional demand per kilo of bodyweight is the same for all participants. Throughout the intermittent moderate cycling task, the cyclists ingested 15 grams of carbohydrate every 15 minutes throughout the intermittent test from either potato or from gels. On a separate occasion, all the cyclists complete the same intermittent task/time trial but this time only consuming pure water (control condition).

The results showed that that compared to water ingestion, time trial performance was improved with both potato and gel carbohydrate, and to the same extent. The downside of the potato ingestion however was that to obtain 15 grams of carbs, the participants had to ingest 128.5 grams of mashed potato but only 23 grams of gel. Unsurprisingly, the potato ingestion was associated with more gastrointestinal discomfort during the test, almost certainly due to the greater volume ingested!

In summary, these studies show that food-based sources such as banana, honey and raisins can be excellent alternative sources of carbohydrate for in-exercise feeding. In terms of the performance benefits, they can be as effective as commercially available carb drinks and gels in terms of sustaining endurance performance. There are drawbacks however, particularly for those with more sensitive tummies; the higher levels of fiber, bulk and volume needed to reach the recommended carbohydrate intake rate of 60-80 grams per hour can increases the risk of gastric distress, resulting in bloating and cramps. This can be exacerbated by the relatively high fructose levels in many naturally sweet foods, which can slow down gastric emptying.

Practical advice

You might be surprised and encouraged to discover that a number of natural foods can make excellent alternatives to processed, factory-produced and sometimes quite expensive carbohydrate products – especially given that many of these natural foods are also good sources of fiber, vitamins, minerals and antioxidants. But does this mean that athletes should ditch all their carbohydrate drinks and gels, and instead switch exclusively to natural foods?

For many athletes, the answer is almost certainly ‘no’. A well-formulated carbohydrate supplies an almost perfect balance of water, carbohydrate and electrolyte minerals - especially important at this time of year to replace the minerals lost during sweating. The other benefit of course is that these well-formulated drinks and gels are designed to be rapidly absorbed from the gastrointestinal tract with minimal distress to the tummy.

However, what this research shows is that a number of natural foods such as bananas are remarkably effective at supplying easily-absorbed carbohydrate and maintaining or prolonging endurance performance. So if you’re the kind of person who likes to keep the diet as natural as possible, there’s a good argument for consuming at least some natural foods during exercise. Athletes with cast iron tummies might find that natural foods can be tolerated even during race conditions. Others might find that natural foods are fine during longer, more moderately paced training sessions, but that formulated drinks and gels are best in race conditions. Those with the most sensitive tummies may not be able to tolerate the extra bulk and fiber in natural foods full stop.

Because there are pros and cons to each approach (see figure 1), it doesn’t have to be an ‘either-or’ choice. In an excellent 2023 summary paper on this topic, the researchers pointed out that athletes can consume different combinations of natural foods and drinks/gels to meet their carbohydrate needs in a way that works for each athlete (see figure 2)⁽²⁴⁾. Moreover, this combined approach can be used during recovery and replenishment after exercise, or for pre-exercise feeding. Since pre and post-exercise feeding does not take place when the body is under exercise stress, this is the ideal opportunity to maximize your intake of natural foods when seeking to top up muscle glycogen. In their narrative review paper on the topic (well worth a read), the authors provide an excellent graphic on portion sizes of natural foods needed to deliver 30 grams of pure carbohydrate, which is shown in figure 3 below.

Figure 1: Pros and cons of natural carbohydrate during exercise 

Figure 2: Combining sports drinks and natural foods during exercise

Figure 3: Natural food amounts delivering 30g of carbohydrate

References

1.       Sports Med 1992; 14: 27–42

2.       Metabolism 1996; 45: 915–921

3.       Am J Physiol Endocrinol Metab 1999; 276: E672–E683

4.       Med Sci Sports Ex 1993; 25:4251

5.       Int J Sports Med 1994; 15:122-125

6.       Med Sci Sports Ex 1996; 28: i-vii

7.       J Athletic Training 2000; 35:212-214

8.       Int J Sports Nutr 1997; 7:26-38

9.       Nutrition Reviews 1996; 54: S136-S139

10.    Med. Sci. Sports Exerc. 2004; Vol. 36, No. 9, pp. 1551–1558

11.    J Appl Physiol 2006; 100:807-816

12.    Med Sci Sports Exerc. 2008 Feb;40(2):275-81

13.    Crit. Rev. Food Sci. Nutr. 2022;62:1480–1501

14.    PLoS One. 2012;7(5):e37479. Epub 2012 May 17

15.    J. Proteome Res. 2015;14:5367–5377

16.    J. Strength Cond. Res. 2004;18:466–472

17.    Asian J. Sports Med. 2015;6:e24044

18.    Nutr. Clin. Pract. 2013;28:300–306

19.    Nutr. Res. 2010;30:511–519

20.    J. Strength Cond. Res. 2011;25:3150–3156

21.    J. Int. Soc. Sports Nutr. 2012;9:27

22.    J. Sports Sci. 2018;36:2172–2180

23.    J. Appl. Physiol. 2019;127:1651–1659

24.    Nutrients. 2023 Mar; 15(6): 1367