Best Supplements for Runners and Endurance Athletes

Endurance athletes have unique nutritional demands. Hours of training deplete nutrients, increase oxidative stress, and challenge recovery. The right supplements can support performance, recovery, and long-term health.

Here's what endurance athletes should consider.

Iron

Critical for oxygen transport—and commonly deficient in endurance athletes.

Why it matters:

• Hemoglobin carries oxygen to working muscles
• Endurance training increases iron needs
• Iron loss through sweat, GI tract, and foot strike hemolysis
• Deficiency directly impairs performance

Who needs it:

• Female athletes (menstruation + training losses)
• High-mileage runners
• Those with symptoms (fatigue, declining performance)
• Vegetarian/vegan athletes

Important: Don't supplement without testing. Get ferritin checked. Aim for ferritin >50 ng/mL for optimal athletic performance (some experts suggest even higher).

If deficient: Work with a sports medicine doctor on appropriate supplementation.

Vitamin D

Performance suffers when vitamin D is low.

Why it matters:

• Supports muscle function
• Affects VO2 max and performance
• Important for immune function (endurance training suppresses immunity)
• Most athletes are deficient, especially indoor trainers

Dosing: 2000-5000 IU daily based on blood levels.

Target: 40-60 ng/mL for optimal athletic performance.

Omega-3 fatty acids

Anti-inflammatory support for the high-inflammation demands of endurance training.

Why they matter:

• Reduce exercise-induced inflammation
• Support heart health
• May improve oxygen delivery to muscles
• Support recovery between sessions

Dosing: 2-3g EPA/DHA combined daily.

Beetroot (nitrates)

One of the most evidence-based performance enhancers for endurance.

Why it works:

• Nitrates convert to nitric oxide
• Improves oxygen efficiency
• Enhances blood flow to muscles
• Can improve time-to-exhaustion and time trial performance

Research: Multiple studies show 1-3% performance improvements—significant at competitive levels.

Dosing: 300-600mg nitrates, typically 2-3 hours before exercise.

Forms: Beetroot juice, concentrated shots, or beetroot powder.

Note: Effects may be more pronounced in recreational athletes than elite.

Caffeine

The most proven legal performance enhancer.

Why it works:

• Reduces perceived exertion
• Enhances fat oxidation
• Improves endurance performance
• Well-researched

Dosing: 3-6mg per kg body weight, 30-60 minutes before exercise.

Example: 70kg athlete = 210-420mg caffeine.

Considerations:

• Habitual users may see less benefit
• Can cause GI issues during racing
• Practice in training first

Magnesium

Depleted through sweat; essential for muscle function.

Why it matters:

• Required for energy production
• Supports muscle contraction and relaxation
• Lost in sweat during training
• Deficiency impairs performance

Dosing: 300-400mg daily, possibly more during high-volume training.

Electrolytes

Critical during long efforts, especially in heat.

What you need:

• Sodium: Primary electrolyte lost in sweat
• Potassium: Supports muscle function
• Magnesium: Often depleted

When to supplement:

• Efforts over 60-90 minutes
• Hot/humid conditions
• Heavy sweaters
• Salty sweaters (white residue on clothes)

Strategy: Use electrolyte drinks/tablets during long training and racing. Many athletes underestimate sodium needs.

Beta-alanine

Buffers acid in muscles during high-intensity efforts.

Why it works:

• Increases carnosine (acid buffer) in muscles
• May improve performance in efforts lasting 1-4 minutes
• Could help with finishing kicks
• Requires loading over weeks

Dosing: 3-6g daily for 4+ weeks.

Side effect: Tingling (harmless but annoying). Split doses to minimize.

Best for: Events with high-intensity surges or finishing kicks.

Creatine

Not just for sprinters—endurance athletes can benefit too.

Why it works:

• Supports recovery between sessions
• May help with high-intensity intervals
• Supports muscle maintenance
• Brain energy during fatigued states

Dosing: 3-5g daily.

Concern about weight: Minimal water retention with maintenance dosing. Performance benefits often outweigh small weight gain.

Tart cherry extract

Natural anti-inflammatory for recovery.

Why it works:

• Reduces muscle soreness
• Anti-inflammatory
• Contains natural melatonin (supports sleep)
• May speed recovery

Dosing: 500mg extract twice daily or 8-12oz juice around hard training.

Use: Before/after hard workouts or races.

Protein (adequate intake)

Not just for bodybuilders—endurance athletes need protein for recovery.

Why it matters:

• Repairs exercise-induced muscle damage
• Supports adaptation to training
• Often undereaten by endurance athletes
• Important for maintaining muscle mass during high volume

Dosing: 1.4-2.0g per kg body weight daily.

Timing: 20-40g within a few hours of training.

Adaptogens for training stress

Support recovery from the chronic stress of endurance training.

Rhodiola rosea:

• Reduces fatigue
• Supports performance under stress
• May improve oxygen utilization
• 200-400mg daily

Ashwagandha:

• Reduces cortisol
• Supports recovery
• May improve VO2 max in some studies
• 300-600mg daily

Building an endurance athlete stack

Foundation:

1. Vitamin D (based on levels)
2. Omega-3s (2-3g EPA/DHA)
3. Magnesium (300-400mg)
4. Iron (only if deficient—test first)

Performance support: 5. Beetroot/nitrates (before key sessions) 6. Caffeine (strategic use before races/hard sessions) 7. Electrolytes (during long/hot training)

Recovery: 8. Protein (adequate daily intake) 9. Tart cherry (around hard training) 10. Creatine (optional, 3-5g daily)

Timing around training

2-3 hours before key sessions:

• Beetroot/nitrates
• Pre-workout meal

30-60 minutes before:

• Caffeine (if using)

During (long sessions):

• Electrolytes
• Carbohydrates (not discussed here but critical)

After:

• Protein
• Tart cherry (optional)
• Rehydration with electrolytes

Daily:

• Vitamin D, omega-3s, magnesium, iron (if needed)

What doesn't work (or isn't proven)

Skip these:

• Antioxidant megadoses (may blunt training adaptations)
• Most pre-workouts (just caffeine works)
• Expensive proprietary blends
• Branched-chain amino acids (just eat enough protein)

The bottom line

Endurance athletes benefit most from addressing potential deficiencies (iron, vitamin D) and using targeted performance supplements (beetroot, caffeine) strategically.

Get tested for iron and vitamin D. Use beetroot before key sessions. Support recovery with adequate protein, omega-3s, and sleep.

What we're building

Optimize tracks your supplements alongside training load and performance metrics, helping you identify what's actually improving your endurance.

Sign up free to optimize your endurance performance.