Get Your Personalized Supplement StackSupplement Stack Quiz

Carbs

Also known as: Carbs, sugars, starches, glycogen, monosaccharides, disaccharides, polysaccharides, glucose, fructose, sucrose, lactose, maltodextrin, Carbohydrates

Overview

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, serving as the body's primary energy source. They are found naturally in grains, fruits, vegetables, and dairy. As supplements, they are commonly available as glucose, maltodextrin, or mixed carbohydrate solutions. Their main application is in sports nutrition, where they are used to enhance endurance performance, delay fatigue, and improve post-exercise recovery by replenishing glycogen stores. Rapidly digestible carbohydrates quickly elevate blood glucose and insulin, facilitating glycogen resynthesis. The efficacy of carbohydrate supplementation is well-established through extensive high-quality research, including numerous randomized controlled trials, systematic reviews, and meta-analyses, particularly in the context of endurance exercise and recovery.

Benefits

Carbohydrate supplementation during prolonged endurance exercise (over 90 minutes) significantly improves performance, with meta-analyses showing meaningful ergogenic benefits and statistically significant improvements in time to exhaustion and time-trial performance. Effect sizes for endurance performance improvements are moderate to large (e.g., SMD > 0.5), indicating clinical relevance. Post-exercise carbohydrate intake accelerates muscle glycogen resynthesis, which is crucial for recovery and subsequent performance. While combining carbohydrates with proteins may further enhance glycogen restoration, the evidence is mixed and requires individualized consideration. These benefits are most pronounced in trained endurance athletes, particularly males, during prolonged exercise bouts. Acute supplementation improves immediate performance, while post-exercise intake supports recovery over hours to days.

How it works

Carbohydrates provide glucose, which is the primary substrate for ATP production through glycolysis and oxidative phosphorylation during physical activity. By supplying exogenous glucose, carbohydrates spare muscle glycogen depletion and help maintain stable blood glucose levels, thereby delaying the onset of fatigue. Carbohydrate intake stimulates the release of insulin, a hormone that promotes the uptake of glucose into muscle and liver cells and facilitates glycogen synthesis. Glucose uptake into cells is mediated by GLUT transporters. Rapidly absorbed monosaccharides and disaccharides quickly increase blood glucose. Utilizing mixed carbohydrate formulations, such as glucose and fructose, can improve absorption rates and oxidation rates during exercise, maximizing energy delivery.

Side effects

Carbohydrates are generally safe when consumed within recommended amounts. The most common side effect, occurring in over 5% of individuals, is gastrointestinal discomfort, particularly when consumed in excessive amounts or at high concentrations. This can manifest as mild bloating or diarrhea in sensitive individuals, affecting 1-5% of users. No significant rare side effects (less than 1%) have been reported in healthy populations. There are no clinically significant drug interactions. However, individuals with glucose metabolism disorders, such as diabetes, must monitor their intake carefully and consult healthcare providers due to potential impacts on blood sugar regulation. Athletes with pre-existing gastrointestinal sensitivities may need to experiment with different carbohydrate types and adjust dosages to minimize discomfort.

Dosage

For prolonged exercise lasting over 90 minutes, a minimum effective dose of approximately 30-60 grams of carbohydrate per hour is recommended to improve performance. Optimal dosage ranges typically involve 6-8% carbohydrate solutions (60-80 g/L) during exercise, which are effective and generally well-tolerated. Highly trained athletes can consume up to 90 g/hour using multiple transportable carbohydrates (e.g., a glucose and fructose blend) without significant gastrointestinal distress. Timing is crucial: carbohydrates should be ingested during exercise for performance benefits and post-exercise, ideally within 30 minutes to 2 hours, to optimize glycogen resynthesis. Liquid carbohydrate solutions are often preferred during exercise for rapid absorption. Combining glucose and fructose enhances absorption and oxidation rates. Adequate hydration is essential, and co-ingestion with protein post-exercise may further enhance recovery.

FAQs

Is carbohydrate supplementation safe for all athletes?

Generally yes, but individuals with metabolic disorders like diabetes should consult healthcare providers to manage blood sugar levels effectively.

When should carbs be taken for the best effect?

For performance, consume during prolonged exercise. For recovery, ingest immediately post-exercise, ideally within 30 minutes to 2 hours.

How quickly can performance improvements be expected?

Acute improvements in endurance performance can be observed during exercise, while recovery benefits, such as glycogen replenishment, occur within hours.

Are all carbs equally effective?

No, mixed carbohydrate formulations (e.g., glucose + fructose) are often more effective than single-source carbs due to enhanced absorption and oxidation rates.

Research Sources

https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1567438/full – This meta-analysis highlights that the timing of carbohydrate supplementation significantly impacts fatigue and muscle recovery. It emphasizes the benefits of early post-exercise carbohydrate intake for optimizing recovery processes. The study suggests that while there is moderate heterogeneity, early intake is generally beneficial.
https://www.semanticscholar.org/paper/Effects-of-Acute-Carbohydrate-Supplementation-on-Vandenbogaerde-Hopkins/4dc4e953742779e70c67c3edf3ea8bb234481c66 – This systematic review and meta-analysis found that carbohydrate supplementation, particularly 6-8% solutions, significantly improves endurance performance in trained athletes. It also noted that using multiple transportable carbohydrates further enhances these benefits. The study is considered high quality due to its rigorous methodology and clear effect sizes, despite some heterogeneity in protocols and a focus on male athletes.
https://pubmed.ncbi.nlm.nih.gov/27408608/ – This systematic review and meta-analysis, including over 30 RCTs, concluded that carbohydrate intake shortens exercise time and improves time-trial performance, demonstrating a significant ergogenic effect. The study's high quality is attributed to its well-controlled RCT inclusion criteria, despite variations in exercise modalities and some heterogeneity across studies.
https://pubmed.ncbi.nlm.nih.gov/32443678/ – This comprehensive systematic review and meta-analysis, involving over 30 RCTs, confirmed that carbohydrate ingestion improves time-to-exhaustion and time-trial performance in athletes during acute and repeated exercise. It also explored the potential for combined carbohydrate-protein intake to enhance recovery, though results were mixed. The study's robust methodology and comprehensive analysis contribute to its high quality, despite limited data on female athletes.