Overview
Total dietary carbohydrate is a primary energy source for the body, particularly critical during endurance exercise and for maintaining glycemic control. While the human body can synthesize glucose endogenously, dietary carbohydrates are considered conditionally essential, especially in certain metabolic disorders like glycogen storage disease type I [4]. For athletic performance, carbohydrate ingestion during prolonged exercise (typically 30–60 g/hour) improves endurance capacity and time-trial performance, with evidence supporting both high and low glycemic index carbohydrates such as maltodextrin, trehalose, and isomaltulose [1]. A 'food first' approach—using whole foods like bananas or sandwiches—can be as effective as commercial supplements for delivering carbohydrates during endurance activities and may reduce gastrointestinal symptoms in some individuals [10]. In individuals with prediabetes or type 2 diabetes, specific types of carbohydrates such as inulin-type fructans (ITF) have been shown to significantly improve glycemic control in a dose-dependent manner [6]. Total carbohydrate quantity in meals has a greater impact on blood glucose than the source or type, particularly important for people managing diabetes [2]. Combining carbohydrates with other ergogenic aids like caffeine may further enhance physical performance [9].
Dosage Guide
Recommended Daily Allowance
For generally healthy individuals
Therapeutic Doses
For treatment of specific conditions
Upper Intake Limit
Maximum safe daily intake
g— No established UL for total carbohydrates; excessive intake of added sugars (>10% total calories) is discouraged
Special Forms
Alternative forms for specific needs
High GI carbohydrate; commonly used in sports supplements for rapid energy
Low GI disaccharide; shown to improve endurance performance
Low GI carbohydrate; provides sustained glucose release
Prebiotic fiber; improves glycemic control and gut health
Clinical Notes
- Monitor blood glucose when using high-carbohydrate regimens in diabetes; adjust insulin accordingly
- High intake of added sugars (not complex carbs) is associated with increased risk of metabolic syndrome and dental caries
- Individual tolerance to carbohydrate type and amount during exercise varies; practice in training before competition
- Fiber-rich carbohydrate sources (e.g., whole grains, legumes) are preferred for long-term metabolic health
- Combining glucose and fructose in a 2:1 ratio may enhance carbohydrate oxidation rates during endurance exercise
Research
Trehalose (30 g/hr) improved 20-min cycling time-trial performance after 100-min cycling in amateur cyclists.
Total carbohydrate amount in meals is more important than source or type for glycemic control in diabetes.
Food-based carbohydrates (e.g., bananas, sandwiches) are as effective as supplements for endurance performance and may improve GI tolerance.
Dietary carbohydrates are conditionally essential; required in certain genetic disorders like glycogen storage disease type I.
Combining carbohydrate and caffeine ingestion may have synergistic effects on exercise performance.
Inulin-type fructans supplementation significantly improved glycemic control in prediabetes and type 2 diabetes populations in a dose-response manner.
Crocin supplementation reduced fasting blood glucose, but this effect may be indirectly related to carbohydrate metabolism.
Increasing fruit and vegetable intake increases carbohydrate and fiber intake and improves overall diet quality without increasing energy intake.
Carbohydrate and caffeine co-ingestion enhances performance more than placebo and may have additive metabolic effects.
Carbohydrate dosing from 24–80 g/hour in food or supplement form supports endurance performance
