What are electrolytes — do I need to supplement them?

Electrolytes are electrically charged minerals (sodium, potassium, magnesium, calcium, chloride, phosphate) that govern cellular membrane potential, nerve conduction, cardiac rhythm, and fluid distribution, the most clinically relevant for men over 40 in the context of exercise and diet are sodium (the primary determinant of plasma volume), potassium (cardiac rhythm maintenance), and magnesium (over 300 enzymatic reactions, including cardiac conduction) (Bhave & Bhatta, J Clin Endocrinol Metab, 2017).

Most men consuming an adequate diet do not need electrolyte supplementation at rest. The clinical situations requiring attention: (1) sweat loss above 2–3 hours of exercise (sodium and potassium replacement warranted); (2) low-carbohydrate or ketogenic diets (reduce sodium retention, increasing urinary losses); (3) diuretic use (increases urinary electrolyte loss); (4) chronic alcohol use (increases magnesium and potassium urinary loss). Sports drinks are appropriate during exercise lasting over 90 minutes; they are a caloric waste for men doing a 45-minute gym session.

Honesty Scale: Solid (1) for electrolyte needs during prolonged exercise. Solid (1) for increased needs on ketogenic diets and diuretics.

What to do: For exercise under 90 minutes: water is sufficient. For exercise over 90 minutes or in high heat: sodium-containing beverages (sports drink, LMNT, Nuun) are appropriate. For keto or low-carb diet followers: deliberate sodium supplementation (3–5 g NaCl per day) and potassium from whole foods is important to avoid the "keto flu" which is primarily hyponatremia and hypokalemia.

For the full picture, read The Hydration Deep Dive