Oral rehydration therapy at home

Oral rehydration therapy is one of the most cost-effective lifesavers in the history of medicine. It stops people dying from cholera and other diarrheal diseases. It works because of the sodium-glucose co-transport mechanism in the intestines, discovered by Robert K. Crane around 1960.

The WHO has guidelines for Oral Rehydration Solution, and the recipe pictured at the top of this post is my attempt to approximate these guidelines using ordinary kitchen ingredients and easy measurements (doing a computerised search through the space of valid options). The mix actually tastes OK too. The recipe is:

• 1 litre of water
• 8 metric teaspoons (40 ml) of lemon or lime juice, as a source of citrate (10 millimoles, by my calculation)
• 3 metric teaspoons (15 ml) of honey, as a source of glucose and other sugars (90 millimoles)
• 1 metric teaspoon (5 ml) of cream of tartar (potassium bitartrate), as a source of potassium (19 millimoles)
• ¾ metric teaspoon of salt, as a source of chloride (73 millimoles) and sodium
• ¼ metric teaspoon of baking soda (sodium bicarbonate), as an additional source of sodium (giving 87 millimoles in total), and as a way of neutralising the acidity in the lemon or lime juice

The total osmolarity here is just under 300 millimoles, which is above the optimum of 245, but under the upper limit of 310. The specific WHO criteria for glucose (between the sodium level and 111 millimoles), sodium (60–90), potassium (15–25), citrate (8–12) and chloride (50–80) are also satisfied.

Possible substitutions are 13.5 grams of glucose powder for the honey and 2.1 grams of citric acid monohydrate for the lemon juice. The three other ingredients can also be replaced by ½ teaspoon “lite salt” (which provides sodium and potassium), ¼ teaspoon ordinary salt, and ½ teaspoon baking soda.

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