Does carbohydrate plus protein intake improve cycling performance?

In the world of exercise, nutritional intake is an important factor in determining not only the response to training, but also athletic performance. To date there have been a number of nutritional strategies used in cycling to improve performance. However media and commercial interest in these various nutritional strategies has resulted in a lack of clarity to whether they work or not. In most, but not all cases, these strategies lack scientific support. Therefore, as an athlete, making your mind up about what works and does not work can sometimes be difficult and confusing.

Intake of Carbohydrate and Protein may be Important for Endurance Athletes

Of the numerous nutritional strategies, it is well documented that carbohydrate (CHO) intake during cycling exercise can improve performance. This is reflected by the large use of CHO based energy drinks by cyclists. Typical guidelines include the ingestion of 4-8% CHO solution, with doses in the range of 60-90g of CHO per hour.

More recently, it is believed that adding protein (PRO) to CHO will also improve endurance performance, as well as providing additional benefits to recovery post exercise. Based on this current thinking, a number of commercial drinks, bars and gels are available that contain both CHO and PRO (Table 1). This article will discuss some of the scientific evidence that has investigated the performance effects of CHO and PRO intake during exercise.



Table 1: Examples of carbohydrate plus protein products.



Amount   of CHO / serving

Amount   of PRO / serving

High Five 4:1 Energy Source

Powdered Drink



Power Bar IsoMax

Powdered Drink



Accel Gel




PowerBar gel blast





The evidence

A number of studies have shown that when CHO and PRO (37-47g/hr of CHO and 9-12g/hr of PRO) are ingested at regular intervals (15-20min) during cycling exercise, the time taken to reach exhaustion is improved. This improvement is in the range of 13-36%, when compared to CHO alone. However, well controlled time trial based performance studies have shown no performance effect when higher CHO is ingested (60g CHO and 20g PRO). There are a number of potential reasons to explain the lack of consistent evidence.

Lab results may not reveal the complete picture

Firstly the type of laboratory based performance test selected may explain the lack of consistent effect. Cycling performance can be measured in two ways. Time to exhaustion tests involve cyclists exercising at a set intensity, until they are no longer able to exercise. Alternatively a time trial test, is where a cyclist will be given a set distance or workload to complete in as quicker time as possible. The time trial protocol is a more representative measure of cycling performance, as very few cyclists exercise at a fixed intensity until fatigue. In addition the time trial has been shown to be a more reliable performance test when compared to a time to exhaustion. .In view of this, a recent well controlled study by Dr Leigh Breen showed that cyclists did not perform better during a time trial performance test when consuming CHO plus PRO (65g/hr plus 19g/hr) when compared to CHO only (65g/hr). Therefore the studies showing positive effects of CHO and PRO on time to exhaustion tests cannot necessarily be transferred to cycling performance.

Secondly, the exact amount of CHO, PRO and form of ingestion is less understood, which might explain the lack of clear recommendations for its use. The amount of CHO ingested with PRO in the majority of studies have been lower (27-47g/hr) than the well documented doses of CHO shown previously to improve performance (60-90g/hr). It is therefore difficult to assess whether the improvements in performance are a result of the added PRO or due to the additional calories? The reason being is that CHO doses were matched in all studies, without matching the calorie content when adding PRO. When the calorie content has been matched no improvement in  performance has been observed . In addition a study in the Journal of Medicine and Science in Sports and Exercise showed that when adequate amounts of CHO were ingested (60g/hr), the addition of 20g/hr of PRO had no effect  It therefore seems unlikely that CHO and PRO results in better improvements in performance when CHO intake is in the range of 60-90g/hr.

On the other hand higher doses of PRO (>20g/hr) may not necessarily result in performance improvements. The main argument for this is that compared to CHO and FAT, PRO is not a predominant fuel source during endurance exercise, contributing ~5% of total energy demand. As CHO, especially during prolonged exercise, is a limiting factor to performance, it seems sensible to think that PRO content should remain lower than the CHO content of a beverage consumed during exercise. In most cases PRO has consisted of ~20% of total caloric intake, at approximately 1-2% of the total volume consumed. Yet no study has investigated the effect of increasing the dose further.

Timing Important

Tour de France riders Timing Nutrition

During ultra endurance events (Ironman), PRO intake in the later stages of exercise (>4 hours) may prevent protein breakdown from the exercising muscle (protein catabolism) especially when CHO stores become depleted, known as glycogen. Therefore the timing of the PRO intake may be important during prolonged exercise (>2 hrs), especially in the later stages. At the same time it is also unclear what source of PRO is required to result in potential improvements to performance. It has been discussed that branch chain amino acids (BCAA), the predominant amino acids of PRO, maybe required to improve performance. Yet to date, the majority of studies have only used a whey PRO source.  

Other effects of Carbohydrate plus PRO

Besides the performance effects, CHO plus PRO intake may also contribute to improving post exercise recovery. Prolonged, repeated and high intensity exercise will result in large CHO use from muscle and liver glycogen. As glycogen is an important fuel during exercise, contributing 50% of total energy requirements, restoring lost glycogen is crucial if exercise is being performed in the hours or days following the previous bout. Ingesting CHO plus PRO during exercise may aid the recovery of depleted glycogen following exercise. In addition the added PRO to CHO may also prevent muscle damage, and improve the adaptations that alter the muscle structure and power generating capacity as a result of exercise training. These changes in the exercising muscle following CHO plus PRO intake during exercise may play important roles in exercise performance the days after a hard bout of training or competition.

The mechanisms

The physiological effects of the added PRO in the human body are less well understood. CHO and PRO may be involved in maintaining energy production in the muscle cells via tricarboxylic acid (TCA) intermediates. Alternatively the additional PRO may prevent the accumulation of serotonin in the brain. Serotonin is a neurotransmitter found in the brain which has been reported to cause fatigue during endurance exercise when it accumulates in the brain. This is known as the central fatigue mechanism. PRO intake with CHO may delay the onset of fatigue, by reducing serotonin in the brain. While others have shown that CHO plus PRO may increase the uptake of CHO at the stomach level and also the muscle level, via the action of insulin.

Conclusion and Recommendations

For now it seems that in order to improve cycling performance, CHO intake between 60-90g/hr is recommended. There is little scientific evidence for the use of PRO with CHO, as the evidence at present is mixed in findings. However the benefits of PRO added to CHO may occur when CHO intake is lower than 60g/hr. In addition athletes who are also exercising for long durations (>3 hrs) may also benefit from the use of PRO during exercise (Table 2).  

Table 2: Practical recommendations for the use of CHO plus PRO during exercise

Duration   of exercise

Dose   of CHO during exercise

Dose   of PRO during exercise

Example   of cycling event

<60 min



Sprint event

60-120 min



40-100km TT event

60-120 min



40-100km TT event

>120 min



Ironman event


It also seems that based on anecdotal evidence from athletes PRO added to CHO drinks increases satiety (the feeling of being full) and can settle the stomach from GI distress after large amounts of sweet CHO solutions. Therefore PRO added to CHO may not improve performance if CHO intake is sufficient (60-90g/hr), but may be of preference to certain athletes to prevent GI distress and improve post exercise recovery. However it should be noted that the use of a CHO and PRO products by athletes maybe highly individualised, depending on taste, tolerance of high amounts of CHO during exercise, and duration and type of exercise. It would be advised for an athlete to try out a variety of products in training before implementing nutritional strategies in competition.

What nutrition strategies do you use? What is your tolerance to Carbohydrates and Protein during your workouts and races?

Leave a comment below and start a conversation


Adrian Hodgson

Adrian Hodgson is a doctoral researcher in exercise metabolism and nutrition working alongside Professor Asker Jeukendrup in the School of Sport and Exercise Sciences, University of Birmingham (UK). His research focuses on how dietary nutrients and supplements can be used by athletes to aid training and improve performance, as well as improve health. Alongside his research, Adrian has also worked with a number of athletes in order to obtain their specific sporting goals and optimise their training and performance. Adrian is also the creator and writer of his own nutrition and exercise training blog




  1. LeighBreen says

    Nice work, but you missed the most important reference on the topic out! 😉 (

    Adding protein to your post-cycle drink MAY promote an aerobic adaptation but not at the muscle level. Protein appears to be used to help the muscle rebuild after intense training, not make new mitochondria. However, protein ingestion with endurance training clearly improves VO2 (…..but how?!

    It may promote aerobic adaptations in cardiac tissue ( as evidenced by plasma volume expansion in a study by a Japanese group.

    Dr Leigh Breen!/LeighBreen

  2. says

    @adrianhodgson63 Thanks so much for your well thought out post. As you stated that it is highly individualized. I have found I can tolerate very small amounts of Pro during low intensity, But have GI problems at higher intensities

  3. adrianhodgson63 says

    @LeighBreen Leigh, thanks for your comments. After all you are one of the worlds experts in protein metabolism and exercise. : )

    The most important study is included in the discussion. You are right, based on your study it seems that protein is able to induce adaptations after cycling exercise (> 2hours maybe? or hard intensity), but not through mitochondrial adaptations, which is unusual based on the type of exercise? Is protein only used for muscular repair rather than mitochondrial adaptations? However you have showed previously that protein does not alter muscle soreness following a hard bout of cycling exercise. Therefore providing clear recommendations may be a little difficult, which I hope you got from the article.

    Interesting comment about improvements to VO2 max, I do not know? Any ideas? Cant be via improved mitochondrial density?

    However these factors you highlight are all very important for scientific discussion, but may not be appropriate / well understood by a cyclist with little knowledge of exercise physiology? 😉

    Thanks for the comments Dr Breen.

  4. LeighBreen says

    @adrianhodgson63 @LeighBreen

    Oh yeah i see you included it, my bad eyesight is to blame mate!

    To sum up briefly. There were no effects of protein ingestion on 24 h recovery, as we hypothesized. This makes sense because muscle proteins are built at a rate that is too slow to result in improved recovery this early-on. I have a couple of opinions on protein with endurance exercise:

    1) If you ingest post-exercise protein over the course of your race prep (say 8 weeks for example) then, ultimately, you will eventually benefit from improved recovery and your muscles will adapt to produce greater power (although in elite cyclists the improvement is slight but, potentially, important).

    2) The improvements in VO2 shown by others are not the result of any change in muscle mitochondria building. That’s not to say endurance exercise doesn’t produce mitochondria….of course it does, but my point is protein doesn’t enhance this adaptation. Instead i agree with the Japanese group that protein ingestion over the course of a training regimen increase stroke volume (volume of blood being pumped by the heart).

    In short, although protein ingestion during a race doesn’t seem to have a performance benefit, protein supplementation over time will, in all likelihood, help to improve performance (my opinion). However, in an elite (high level) cyclist, the margins become smaller but i believe there is still a benefit.

    I think you sum up the important points nicely in your well-rounded article. Thanks for listening!

    Dr Leigh Breen

  5. says

    @LeighBreen @adrianhodgson63 Are you saying that a non elite cyclists may have a larger benefit than elite athletes? Again thanks for your insightful comments.

  6. LeighBreen says

    @BicycleLab @adrianhodgson63 I’m saying that the benefit may be more noticeable in amateurs who change their supplements to include some protein, but it won’t have an instant impact, it needs to be practiced frequently. Of course over time, as this regimen becomes routine to the cyclist, the improvements will no longer be as great, but i would say a cyclist is better off with protein in their carb drinks after training than without. We are still uncovering the ‘true’ effects of protein supplementation for the endurance athlete but it’s important to remember that whilst we answer that question no-one has ever shown protein-carb co-ingestion to be a bad thing…..except perhaps on GI symptoms when taken during exercise, but i don’t advocate mid-race consumption at all!



  7. adrianhodgson63 says

    @LeighBreen I think you make a good point about the differences between an elite cyclist versus a novice cyclists. It could be argued that the effects of training are different between these two groups (trained versus untrained – work by Wilkinson et al) and therefore responses to feeding may be different? Some evidence to support this…

    Thanks for the discussion.

  8. susanalexander says


    What an excellent post. I truly believe that following sensible nutrition metrics is key not only for performance in cycling and other sports, but for good health in general. I’ve observed so many athletes and non-athletes who really have no idea what their nutrition requirements are. The common strategy seems to be to wing it and hope for the best.

    I’ve seen this specifically in many cyclists, who seem to think that participation in the sport means getting to eat tons of carbs whenever they want, off and on the bike, including rides that aren’t even that taxing. The not-so-surprising result is a lot of overweight cyclists (many of whom, ironically, go to great effort and expense to equip themselves with sleek lightweight bikes).

    What I’d love to see is a post containing specific guidance for cyclists on how to figure out one’s ideal nutritional intake based on varying activity levels. Specifically, I think the question to be answered is: How do you go about figuring out your ideal caloric intake, broken down by macronutrients, for varying activity levels and goals?

    A lot comes from trial and error, I realize that, but it helps to have a basic plan laid out in the first place, and t go from there tweaking it. So how do you figure out a basic plan? That’s what I think the world needs more information on, especially the cycling world :-)

    Many thanks for a great post., Adrian. Hope to see more from you.


  9. adrianhodgson63 says

    @susanalexander Thanks Susan for your comment. Glad you enjoyed some of the material throughout the article.

    Nutrition guidelines are hugely individual, and scientific research has been and still is trying to establish more coherent guidelines for athletes. It all depends on firstly your performance goal, and secondly your current training programme.

    I would love to find a way of defining clear advise for all atheltes, but this may be ambitious as it is highly individualised and dependent on a number of other factors that you touch upon.

    For now, there is some good information out there for recommendations for some sports for individual macronutrients either before, during or after exercise. For example guidelines for carbohydrate intake during exercise is well documented. If you are interested in reading about these specific carbohydrate guidelines i recommend you to the following paper by one of the world experts:


  10. close_nutrition says

    @BicycleLab very interesting and with Leigh Breen joining in the discussion your getting it straight from the horses mouth.

  11. says

    @susanalexander Susan Thanks for the comment. You are correct in you observations that most middle of the road athletes always look towards something to buy to make them faster. Bikes, Wheels, Etc. What the really should be focused on is improving the engine. This article sets the stage for one of the strategies that may help athletes improve their performance.

    We could do a post that could outline on the bike fueling strategies. Even some basic guidelines. We will put that on the list.


  12. rgrissom says

    @BicycleLab @ridempowered I have used both glutamine and BCAAs in my sports bottle. Has helped reduce soreness during and after rides/races

  13. rgrissom says

    @Celliant I am not sports nutritionist but I have used both glutamine and BCAAs in my sports bottle. It has helped reduce soreness.

  14. Celliant says

    @rgrissom Great points about the glutamine. We’ll share it with our community of runners and fitness enthusiasts!

  15. rgrissom says

    @Celliant I have found that glutamine dissolves well in fluid but not so well in a smoothy. Easier on gastro than BCAA powders when training


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