Show Notes
Dr Dan Plews sits down with Dr Alan McCubbin - sports nutrition researcher and one of the most credible voices on sodium and hydration in endurance sport - to separate the science from the marketing. They cover what sodium actually does in the body, why fluid balance matters more than sodium dose alone, and where supplementation genuinely makes a difference.
10 key takeaways for athletes Sodium's primary job is signalling to your brain whether to drink more, retain fluid, or excrete water - not hydrating you directly.
Changing your diet for three days shifts sweat sodium concentration by around 10 to 12 percent. Real but modest.
True sodium deficiency from sweat losses is extremely unlikely in modern diets. Most problems come from fluid imbalance not sodium depletion.
Your kidneys adapt fast. Athletes who lost 5,500mg of sodium over five hours cut their urinary sodium excretion by two thirds in the 24 hours after -- without supplementing.
The 1,000mg morning sodium trend is a hydration retention play. It works when drinking large volumes on an empty stomach. Once food is involved the effect largely disappears.
Pre-exercise hyperhydration is the clearest use case for sodium -- most relevant for hot, high intensity events where fluid access is limited during competition.
Sodium during exercise doesn't directly improve performance. If it helps you drink enough fluid to stay hydrated, performance may improve as a result.
Hyponatremia is a fluid problem not a sodium problem. Overdrinking is the risk. Sodium cannot rescue clear overhydration.
Sweat sodium testing has limited value if your event is under four hours. General guidelines are enough for most athletes.
Sodium matters but context matters more. Event duration, heat, and drinking behaviour should drive your hydration strategy -- not chasing a specific number every session.
00:00 - Why Dan wanted Alan on to talk sodium 03:34 - The old research on diet and sweat sodium 09:10 - What sodium actually does in the body 11:32 - How sodium drives thirst and kidney responses 22:16 - Five hours of heat running and kidney adaptation 26:32 - The rise of the 1,000 milligram morning sodium trend 36:44 - Pre-loading fluid for hot, long events 47:04 - During-exercise sodium and the real mechanism 49:24 - What hyponatremia actually does in the body 60:21 - Why recovery and post-exercise hydration is where sodium helps most 64:25 - Whether sweat sodium testing is worth it for most athletes 69:21 - Where Pillar's 400 milligram hydration product fits
Connect: Dr Alan McCubbin: https://www.instagram.com/fuelingendurance/ Dr. Dan Plews: instagram.com/theplews Shop: pillarperformance.shop Instagram: instagram.com/pillarperformance Strava: strava.com/clubs/1108245
More from The Formula
The Formula by PILLAR Performance - Paul Booth PhD nutritionist Paul Booth - the coach behind both 2025 UTMB winners - sits down with Dr. Dan Plews to challenge some of the most widely accepted conventions in endurance nutrition. Why the push toward 120g of carbohydrate per hour is getting ahead of the evidence. Why your gut, not your fitness, is often the deciding factor on race day. And how elite ultra runners are actually fuelling in competition. Timestamps: 00:00 - Introduction to carbohydrate fuelling debates in endurance sports 00:13 - Paul's balanced approach: science-driven carbohydrate recommendations 00:43 - Variability among athletes: from 70 to 110 grams per hour 02:25 - Paul's background: from film industry to elite sports nutrition 09:28 - Elite athletes like Tom Evans: metabolic characteristics and genetic advantages 13:02 - The process of working with elite athletes: brief, data analysis, lab testing 15:04 - Nutritional strategies: setting carbohydrate and fuelling goals 18:56 - Cycling carbohydrate intake to match terrain and effort 22:38 - Real-world studies on carbohydrate intake: from 70 to 120 grams per hour 28:56 - Lab testing on Tom Evans' carbohydrate metabolism 32:48 - The role of carbohydrate loading: optimal duration and timing 41:28 - The aim of Paul's PhD: understanding ultra runner metabolism 48:14 - The effect of carbohydrate ratios on absorption and performance 52:18 - Study results: GI issues linked to higher carbohydrate doses 60:47 - How dual carbohydrate strategies improve oxidation and reduce gut issues 63:08 - Debunking outdated myths: the inefficacy of 2:1 carbohydrate ratios 75:02 - Risks of over or under fuelling during races 80:30 - Case study: an elite runner's nutritional strategy and race success 83:01 - Final thoughts: science-guided, adaptable fuelling strategies Connect: Paul Booth: instagram.com/ultra.endurance.nutritionist Dr. Dan Plews: instagram.com/theplews Shop: pillarperformance.shop Instagram: instagram.com/pillarperformance Strava: strava.com/clubs/1108245
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