As the Cozy Beehive also uncovered, during NASA’s research they found that it increased cycling endurance in astronauts by 20% on ergometer tests. I think the 20% is compared to drinking regular water (but all sports drinks claim to bolster the diet and increase endurance). Of course this electrolyte formula has now been commercialized by a company called Wellness Brands and the product of interest is “The Right Stuff”.
Fellow Tipster named Mark Kelly has done some heavy investigation into this formula. He tracked down the US patent document for this “Right Stuff” formula and worked out how to make it for a few cents per litre using ingredients you can buy at the supermarket. Mark has a background in engineering and biological sciences and has worked as a winemaker and brewer for almost 25 years. I think this qualifies him to speak with authority on this topic.
Thank you Mark for sharing your expertise with us to help us save money and go faster on the bike!
The formulation for the hydration fluid is revealed in US Patent 5447730.
The fluid has a sodium content equivalent to isotonic saline (3.6 g/l as Na), with half of the sodium present as common salt giving an NaCl concentration of 4.5 g/l.
The other half of the sodium content is present as sodium citrate, giving a concentration of 6.7 g/l. An easy way to make sodium citrate is by neutralising citric acid with sodium hydrogen carbonate (bicarb soda). To get 6.7 g/l sodium citrate, add 5 g/l citric acid plus 6.6 g/l bicarb soda.
One problem is that it tastes simply awful at this strength, like salty lemon juice without the sweetness. The easy answer is to sweeten it but you can’t add sugar because it will disturb the osmotic balance (this is the mistake that all the commercial Gatorade type fluids make). To maintain osmotic balance you need to use an artificial sweetener, I tried the aspartyl phenylalanine (Aspartame) based “Equal” and found that 2 tabs per litre was about right, your mileage may vary.
To make NASA’s rehydration fluid:
Easy method: Add 1½ teaspoons salt, 2½ teaspoons citric acid and 2¾ teaspoons bicarb soda to a bowl, slowly add a cup of warm water and stir until the bubbling stops and everything is dissolved. Add sweetener of choice. Make up to 2 litres with tap water. Sorry about the 2¾ but 2½ is not quite enough and 3 is too much. If you add too little bicarb the mixture will taste a bit sharp. If you add too much the residual will react with stomach acid and generate CO2 which may cause gastric discomfort (like taking an antacid).
More precise method: Measure 90 grams salt, 100 grams citric acid and 132 grams bicarb soda into a bowl. Slowly add 3 cups warm water and stir until the bubbling stops and everything is dissolved. Add sweetener of choice and make up to 1 litre with water. Store the concentrate in fridge and make 50 ml up to 1 litre with water as needed. Makes 20 litres total.
The purpose of the extra dilution steps is to reduce the carbonate concentration in the water. The purpose of adding the sweetener after cooling is that some sweeteners are heat labile. With some sweeteners you may get a slight cloudiness, this is due to the carrier compounds used in the sweetener. If this is a concern leave the solution to settle then decant the clear fluid off.
The cost depends on the source of the citric acid – in the wine industry we pay about $4 per kg for food grade citric but Safeway sees fit to charge $2.20 for 75 g (almost $30 per kg). If you can get the citric at a decent price the cost is under 15c per litre, even paying inflated supermarket prices for the ingredients the total cost is less than 30c per litre.
Don’t worry about the salt content of the tap water, it’s tiny in comparison: I measured my tap water at about 200ppm TDS which is less than 0.01% Na. Even Adelaide water at its worst is less than 0.03% according to the SA water authority.
The one question I had for Mark was this:
Q: The statement “One problem is that it tastes simply awful at this strength, like salty lemon juice without the sweetness. The easy answer is to sweeten it but you can’t add sugar because it will disturb the osmotic balance (this is the mistake that all the commercial Gatorade type fluids make).” Does that mean that you should avoid ingesting sugary foods while exercising as well so that you don’t disturb the balance of this fluid? Or does your body treat it separately if you ingest it a reasonable time apart?
A: Yes, taking food at the same time as taking the drink will reduce its effect. To the best of my knowledge a 15 minute period is enough to absorb the majority of the fluid so optimal hydration would require a gap of that length between drinking and food intake.