The Complete Cyclist's Guide to Supplements Backed by Science

Cyclists competing across sprint, criterium, and multi-day stage formats face enormously varied physiological demands. This 2026 narrative review from Flinders University, Spain's University of Castilla-La Mancha, and the Royal Adelaide Hospital provides a detailed mechanistic and evidence-based framework for the use of both ergogenic and medical supplements in cycling. The search covered PubMed, Scopus, and Web of Science from January 2000 to May 2025, with foundational bioenergetics literature extending back to 1960. Evidence was graded using the NHMRC Body of Evidence framework combined with GRADE principles, prioritizing systematic reviews and RCTs while downgrading for bias, imprecision, and inconsistency.

The review organizes supplement rationale around four ATP-resynthesis pathways. The phosphagen system dominates the first 5–15 seconds of maximal effort, relying on phosphocreatine (PCr) stores; creatine supplementation expands these stores, supporting peak power. Glycolysis sustains efforts up to two minutes, generating 2–3 ATP per glucose or glycogen monomer, but is throttled by falling intracellular pH — at pH 7.2, phosphofructokinase-1 (PFK-1) activity drops to ~50%, directly slowing energy flux. This underpins the rationale for beta-alanine (carnosine buffering) and sodium bicarbonate (extracellular buffering). Oxidative phosphorylation yields approximately 30–32 ATP per glucose molecule and is the engine of endurance performance; dietary nitrates enhance mitochondrial efficiency via nitric oxide-mediated vasodilation, while exogenous ketones offer an alternative substrate. Beta-oxidation of fats provides sustained energy at moderate intensities, supported by L-carnitine, which facilitates long-chain fatty acid transport into mitochondria.

For ergogenic supplements, the strongest evidence (AIS Group A) was found for caffeine, carbohydrates, creatine monohydrate, dietary nitrates, sodium bicarbonate, beta-alanine, and electrolytes. Caffeine acts via adenosine receptor antagonism, reducing perceived exertion and improving endurance. Dietary nitrates — particularly from beetroot juice — reduce oxygen cost of exercise by 2–3% and improve time-trial performance, especially at altitudes or in untrained to moderately trained cyclists. Beta-alanine loading raises muscle carnosine by 40–80% over 4–10 weeks, delaying fatigue during 1–4 minute maximal efforts. Sodium bicarbonate (0.3 g/kg body weight) acutely raises blood pH and extends high-intensity tolerance, though GI side effects are a limiting factor. Exogenous ketones and N-acetylcysteine (an antioxidant supporting redox balance) have emerging but more limited evidence.

Medical supplements address indirect but equally important performance factors. Iron deficiency — especially prevalent in female endurance athletes — impairs oxygen transport and should be corrected via supplementation when confirmed by blood biomarkers. Vitamin D supports muscle function, immune health, and bone integrity; deficiency is common in indoor-training cyclists. Omega-3 fatty acids reduce exercise-induced inflammation and support cardiovascular adaptation. Collagen plus vitamin C consumed pre-exercise may enhance connective tissue synthesis and reduce tendon injury risk. Cherry juice and curcumin demonstrate anti-inflammatory and antioxidant effects that may accelerate recovery between training sessions. Probiotics support gut barrier function and may reduce upper respiratory illness incidence, though evidence in athletes remains moderate. Pickle juice appears to rapidly resolve exercise-induced muscle cramps, likely through a neural reflex mechanism rather than electrolyte replacement.

The authors emphasize that individualized supplementation — informed by VO2max testing, lactate threshold profiling, metabolic substrate utilization rates, and blood biomarker panels — is superior to generic protocols. They note that sex, age, hormonal status, gut microbiome composition, and genetic variation all modulate supplement efficacy. Anti-doping compliance is highlighted, with WADA strict liability placing full responsibility on athletes for supplement contents; ISO/IEC 17025-accredited third-party testing is recommended. Future research priorities include multi-supplement interaction studies, personalized nutrition frameworks leveraging omics data, and mechanistic studies on molecular adaptation to endurance training combined with nutritional interventions.