For most people doing ordinary daily activity, plain water is sufficient for hydration. But the claim that "everyone needs electrolytes" isn't quite right — and neither is "water alone is always enough." Here's when the evidence actually supports supplementing electrolytes, and when it doesn't.
The Basic Science
Hydration isn't just about water volume — it's about osmotic balance. Water follows sodium across cell membranes. If you drink large amounts of plain water without sodium, you can dilute plasma sodium (hyponatraemia), which paradoxically worsens cellular hydration and can be dangerous at extreme levels. Electrolytes — primarily sodium, potassium, and magnesium — maintain the osmotic gradient that allows water to be absorbed and retained in cells rather than excreted.
Under normal conditions, a balanced diet provides adequate electrolytes. The case for supplementation gets stronger under specific conditions: prolonged exercise, excessive sweating, low-carbohydrate or ketogenic diets (which increase urinary sodium excretion), and heat exposure.
When Plain Water Is Enough
Sedentary or lightly active daily life, workouts under 60 minutes, normal temperature environments, and regular whole-food eating. Your kidneys regulate sodium and fluid balance efficiently under these conditions. The electrolyte supplement industry has created a demand for a problem most people don't have. If your urine is pale yellow, you're adequately hydrated and not sodium-depleted.
When Electrolytes Actually Help
Exercise over 60–90 minutes: Sweat sodium losses become significant. Sports science research consistently shows electrolyte replacement (particularly sodium) during prolonged exercise improves performance, reduces cramping, and prevents hyponatraemia in endurance athletes.
Low-carb or ketogenic diets: Carbohydrate restriction reduces insulin levels, which reduces renal sodium reabsorption — the kidneys excrete more sodium and water. The "keto flu" is largely a sodium, potassium, and magnesium deficiency. Supplementing 2,000–3,000mg sodium, 1,000mg potassium, and 300–400mg magnesium daily genuinely resolves most low-carb adaptation symptoms.
Heat exposure and heavy sweating: Sauna sessions, hot climates, physical outdoor work. Sweat is hypotonic (lower electrolyte concentration than blood) but sodium losses still accumulate meaningfully over hours of heat exposure.
Fasting: Extended fasts reduce insulin, increase sodium excretion, and can cause electrolyte depletion over 24–48 hours. Sodium + magnesium supplementation during fasts maintains energy, reduces headaches, and prevents the light-headedness associated with fasting hypotension.
What to Look For in an Electrolyte
Sodium is the most important electrolyte for hydration — it's what allows water to be retained rather than excreted. Many commercial sports drinks (Gatorade, Powerade) contain too much sugar and not enough sodium. Look for at least 500–1000mg sodium per serving, meaningful potassium (200mg+), and ideally magnesium. Avoid products with artificial colours, excessive sugar, or very low sodium content marketed primarily on flavour.
LMNT, Precision Hydration, and Nuun Sport are the most evidence-aligned options. LMNT has the highest sodium content (1000mg) — the right choice for heavy sweaters and keto dieters. Precision Hydration lets you choose sodium concentration (500/1000/1500mg) based on individual sweat rate testing.
Key Takeaways
- Plain water is sufficient for most people under normal daily conditions. The electrolyte supplement industry has marketed a problem that doesn't exist for sedentary or lightly active people.
- Electrolytes genuinely matter during exercise over 60 minutes, low-carb diets (significantly increased urinary sodium loss), prolonged heat exposure, and extended fasting.
- Sodium is the primary electrolyte — it determines how well water is absorbed and retained. Look for 500–1000mg+ per serving in any electrolyte product.
- Most commercial sports drinks have too much sugar and not enough sodium. LMNT, Precision Hydration, and Nuun Sport are better formulated options.
- Keto dieters need electrolytes: 2,000–3,000mg sodium, 1,000mg potassium, 300–400mg magnesium daily to prevent "keto flu" symptoms.
- Urine colour is the best free hydration gauge: pale yellow = adequate, dark yellow = drink more water, clear = already over-hydrated.