Supplements for endurance athletes

The endurance stack — what to use, when, and why

In-event fuelling — the biggest performance lever you control

For events over 60 minutes: 30–60 g carbohydrate per hour; for events over 2.5 hours: up to 90 g/h using a glucose + fructose combination (typically 2:1 ratio) to bypass the single-transporter intestinal cap. This is the highest-leverage "supplement" in endurance — properly fuelled athletes outperform under-fuelled athletes by margins that no pill can match. Hydration: ~400–800 mL/h depending on rate of sweat loss; sodium 500–1,000 mg/h in hot conditions or for salt-prone athletes.

Caffeine — the biggest acute performance effect

3–6 mg/kg taken 30–60 minutes before exercise improves endurance performance by ~2–4% in meta-analyses. Habituated coffee drinkers retain most of the ergogenic effect. Lower doses (1–3 mg/kg, in-race caffeinated gels) work for sustained effort. Watch the gut: caffeine + race-day stress is a common cause of GI distress.

Nitrate / beetroot — best in sub-elite athletes

6–13 mmol nitrate (≈300–600 mL beetroot juice or ~1 standardised concentrated shot) 2–3 hours pre-exercise. Effect is larger in sub-elite athletes than in elites (limited room to improve in trained athletes) and in events 5–30 minutes in duration; modest effects at longer distances. Continue daily for 3–6 days for chronic-loading benefits; avoid antibacterial mouthwash, which kills the oral bacteria that convert nitrate to nitrite.

Iron — the single most-missed deficiency in endurance athletes

Endurance athletes — particularly female athletes, runners, and athletes at altitude — have higher iron turnover and elevated hepcidin from exercise that reduces iron absorption. Check ferritin annually; target ferritin ≥30 ng/mL minimum, with many endurance medicine groups recommending ≥50 ng/mL in symptomatic athletes. If low: ferrous bisglycinate 30 mg elemental every other day (better absorption than daily; lower GI side effects) with vitamin C, away from coffee/tea/calcium. Recheck in 8–12 weeks.

Creatine for endurance athletes — yes, but for recovery, not directly performance

5 g/day continuously. While most cited for power/strength, creatine improves recovery between sessions, lean mass preservation under high training load, and has cognitive benefits that matter in late-race execution. Endurance athletes often skip creatine fearing weight gain; actual weight gain at 5 g/day is small (~1 kg, mostly intracellular water).

Bone-protective and immune-supportive base

Vitamin D3 to a 25-OH-D target of 30–50 ng/mL (test annually; particularly important in winter, indoor training, dark skin, latitudes >40°). Calcium 1,000 mg/day from food + supplements. Endurance athletes have higher rates of low energy availability and stress fractures — these are the bone-protective basics.

Recovery layer — small effects, layered carefully

Tart cherry concentrate (8–16 oz juice or equivalent in concentrate) around heavy eccentric loading sessions (downhill running, races); modest reduction in soreness and oxidative markers. Magnesium glycinate at bedtime for sleep quality. Omega-3 EPA+DHA 1–2 g/day for inflammation modulation.

Pre-event and race day

Don't try anything new on race day. Test every supplement in training first — particularly caffeine doses, nitrate timing, and any GI-active item. Beta-alanine is taken chronically (3–6 g/day for 4–8 weeks before benefit) for events with significant high-intensity efforts (5–10K, sprint triathlon, cycling crits); pre-race acute beta-alanine doesn't work.