Beverage Hydration Index

The The Beverage Hydration Index (BHI) compares how much of a beverage remains in your body over a set period relative to the same amount of plain water.

Understanding the Beverage Hydration Index

The BHI is determined by giving test subjects a fixed volume of a beverage and the same volume of water on separate occasions, then measuring urine output over several hours. The index is calculated as the ratio of fluid retained from the beverage to fluid retained from water, with water defined as 1. A BHI greater than 1 means the drink helps you retain more fluid than water, whereas a BHI below 1 indicates a stronger diuretic effect. Beverages containing sodium, carbohydrates or protein generally have higher BHIs because they slow gastric emptying and enhance absorption; milk or oral rehydration drinks can have values around 1.2–1.5. Caffeinated or high‑alcohol drinks often yield BHIs below 1. Research indicates that adding electrolytes to water increases BHI, but typical sports drinks containing about 20 mmol of sodium may not provide much greater fluid retention than plain water, whereas drinks with higher sodium concentrations can markedly raise the BHI. The index does not account for taste, calories or personal tolerance but offers a laboratory measure of fluid retention.

Practical examples and usage

If you consume 500 ml of water, roughly half of it may still be retained after two hours (BHI = 1). Drinking the same volume of a milk‑based or oral rehydration drink might result in retaining 60–70 % of the fluid, giving a BHI above 1. In contrast, an equal amount of a caffeinated soft drink may produce a BHI around 0.9, meaning more urine is produced. Athletes engaged in long training sessions or competitions may choose beverages with a higher BHI to maintain hydration, especially when combined with sodium and carbohydrate intake. For shorter activities, water is usually sufficient. Keep in mind that a high BHI alone does not make a drink ideal; the beverage should also suit your taste, digestion and energy needs, and you should avoid excessive sodium intake.

A brief wrap‑up: The Beverage Hydration Index is a useful tool for comparing drinks, but hydration strategies should also consider palatability, nutritional content and your own response.

Related Terms: Hydration, Rehydration, Sweat sodium concentration, Euhydration, Heat acclimation