Supplements for Cyclists: What the Evidence Actually Supports

The sports supplement industry generates billions in revenue by selling cyclists products ranging from well-evidenced to scientifically worthless. Knowing the difference saves money and prevents the common mistake of loading up on ineffective supplements while neglecting the basics that actually work.

This is not an exhaustive survey. It focuses on the supplements where the evidence is strong enough to justify a practical recommendation, and those where the marketing significantly outpaces the research.

Tier 1: Supported by Strong Evidence

Caffeine

Consistently one of the best-studied and most effective legal performance supplements. A 2025 meta-analysis found 4.3% improvements in cycling time trial performance at the effective dose range of 3 to 6mg per kilogram of body weight. Mechanisms are well understood (adenosine receptor blockade, reduced perceived exertion). Effective and cheap. (Covered in detail in the dedicated caffeine post.)

Creatine Monohydrate

Creatine is often dismissed as a "bodybuilder supplement" by endurance cyclists. This is a mistake. Creatine enhances the phosphocreatine energy system, which powers efforts lasting 1 to 30 seconds. For cyclists, this means improved sprint power, better performance in repeated anaerobic efforts (criterium attacks, short climbs), and faster recovery between high-intensity intervals.

A 2024 systematic review found creatine supplementation improved repeated sprint performance by 5 to 8% and may modestly improve VO2 max power when used alongside high-intensity training. It also supports strength training adaptation and may reduce muscle damage markers after intense exercise.

Standard protocol: 3 to 5g per day consistently. Loading phases (20g per day for 5 days) are not necessary and increase GI side effects. Creatine monohydrate is the best-studied and cheapest form; more expensive forms (creatine HCl, creatine ethyl ester) have no meaningful advantage.

Dietary Nitrate (Beetroot Juice)

Dietary nitrate from beetroot juice (and other nitrate-rich vegetables) is converted to nitric oxide in the body, which dilates blood vessels, reduces the oxygen cost of exercise, and may increase muscle contractile efficiency. Research has shown improvements in cycling time trial performance of 1 to 3% in well-trained athletes.

Timing: consume 500ml of beetroot juice (or equivalent nitrate dose, approximately 400mg) 2 to 3 hours before exercise. Some brands produce concentrated shots (70ml) for convenience. High-nitrate leafy vegetables (spinach, rocket, Swiss chard) provide meaningful dietary nitrate but in less predictable doses than standardised products.

Note that using antiseptic mouthwash reduces the conversion of nitrate to nitrite by oral bacteria, negating much of the benefit. Avoid mouthwash on days you use beetroot juice for performance.

Vitamin D

Vitamin D is technically a hormone precursor, not a traditional vitamin. Deficiency is widespread in athletes training in northern latitudes (like the UK), particularly in winter when sunlight exposure is minimal. Deficiency is associated with reduced muscle function, increased injury risk (particularly stress fractures), impaired immune function, and lower testosterone levels.

A 2023 meta-analysis of athletic populations found that vitamin D supplementation improved muscle power and reduced injury incidence in athletes with deficiency. Supplementation does not appear to benefit athletes with already-adequate vitamin D status.

Testing is the correct approach: a simple blood test tells you your 25-OH-D status. If below 50 nmol/L, supplement at 2,000 to 4,000 IU daily. If above 75 nmol/L, supplementation adds no clear benefit. UK cyclists testing in winter frequently show deficiency.

Tier 2: Modest Evidence, Situational Benefit

Beta-Alanine

Beta-alanine increases carnosine concentration in muscle tissue, which acts as an intracellular buffer against hydrogen ion accumulation during high-intensity exercise. In theory, this delays the onset of the burning sensation in muscles during hard efforts.

The evidence is real but modest: studies show 2 to 3% improvements in efforts lasting 1 to 4 minutes at high intensity. For cycling events dominated by shorter anaerobic efforts, this is relevant. For predominantly aerobic events (sportives, time trials over 20 minutes), the benefit is small.

The main practical issue is paraesthesia: a harmless but often uncomfortable tingling sensation in the skin at higher doses. Splitting into smaller doses (800mg to 1g, several times per day) reduces this effect.

Sodium Bicarbonate

Sodium bicarbonate acts as an extracellular buffer, raising blood pH and providing an additional route for hydrogen ion clearance during intense exercise. The performance effect is real: 0.3g/kg consumed 60 to 90 minutes before exercise has been shown to improve performance in events lasting 1 to 7 minutes by 1 to 3%.

The main limitation is gastrointestinal: a significant proportion of athletes experience nausea, cramping, and diarrhoea at the effective dose. Testing well before any important event is essential. Those who tolerate it can use it strategically for criterium racing, short time trials, or race finishes.

Omega-3 Fatty Acids (Fish Oil)

Omega-3 supplementation (EPA and DHA from fish oil) has modest but consistent evidence supporting reduced inflammation, improved exercise recovery, and small improvements in muscle protein synthesis when combined with adequate protein. A dose of 2 to 4g per day of EPA/DHA is the range studied in most sports research.

Benefits are modest rather than dramatic and are best seen in athletes who eat limited fatty fish. Not a primary performance tool, but a reasonable addition to a supplement stack for recovery support.

Tier 3: Poor Evidence, Common Use

BCAAs (Branched-Chain Amino Acids)

BCAAs (leucine, isoleucine, valine) were once popular as muscle-building and recovery supplements. More recent research has clarified that BCAAs, isolated from other essential amino acids, do not stimulate meaningful MPS. A complete protein source (whey, milk, eggs) with naturally high leucine content is far more effective than isolated BCAAs for the same cost or less.

If you are eating adequate total protein from quality sources, BCAAs add nothing.

Glutamine

Heavily marketed for immune support and recovery. Studies in athletes with adequate nutritional status have not shown meaningful benefits. The immune impairment hypothesis (intense exercise depletes glutamine, impairing immunity) has not been supported in adequately powered trials. Unnecessary expense for most cyclists.

HMB (Beta-Hydroxy Beta-Methylbutyrate)

Initially showed promise as a muscle-protection supplement. Subsequent research has found effects to be small and inconsistent in trained athletes. Not worth the cost.

The Foundation Comes First

Supplements work at the margins. No supplement compensates for inadequate sleep, insufficient carbohydrate fuelling, poor training structure, or caloric deficiency. The hierarchy matters: sleep, total calories, protein, carbohydrate, structured training, then supplements.

The effective supplement stack for most cyclists: caffeine, vitamin D if deficient, dietary nitrate occasionally, creatine if sprint power and recovery support are priorities. Everything else requires individual justification.

---