A Driving Instructor's Blog

Sitting in the car all day can be bad for your health. Apart from the more obvious risks like lack of exercise, the matter of dehydration is easily overlooked.Dehydration image

Although I never had anything like it as a child, these days I get early season hay fever symptoms (it’s the tree blossom). Nothing too serious, but itchy eyes and a tickly throat – the latter of which always seems to be worse when the air is dry, and which I can also trigger if I have the aircon on for too long. To try and do something about it I recently started drinking water during the day. Now anyone who does a job like this will know that you normally try to avoid drinking too much of anything so that you don’t end up having to take a leak every five minutes, and that was me to a “T”. I would often start work at 10am and finish at 8pm, sneaking in a couple of McDonalds’ white coffees along the way, and apart from the inevitable need to offload these at some point, I’d wait until I got home before drinking a load of tea.

It seems fairly obvious looking back, but when you’re only drinking things that make you wee even more, and especially in the warmer weather, dehydration is likely to be an issue. So it shouldn’t come as much of a surprise to hear that my tickly throat cleared up completely almost immediately I began drinking water. It should come as even less of a surprise to hear me point out that after the first half litre water is boring.

A quick Google revealed myriad rehydration drinks. What I was after was a make-your-own flavouring I could buy in bulk, and since I was expelling minerals as well as fluids every time I took a whiz, replacing them using isotonic drinks made sense. What didn’t make sense were the prices – the typical cost of 500g of isotonic powder (ten servings) is around £10 – and although I found one particular brand at about a quarter of the price (and with 20% extra for free), it turned out this was a special offer. With every Spandex Boy in the country on to the case, they’d sold out when I tried to get some more.

So, long story short, I decided to make my own. After some research (and trial and error), here’s a recipe for an isotonic rehydration drink (it makes 400g, one 40g serving is dissolved in 500mls of water):

Maltodextrin 80g
Glucose 199g
Fructose 100g
Citric Acid 5g
Malic Acid 1.5g
Sodium Citrate 2g
Sodium Chloride 5.36g
Potassium Chloride 1.15g
Flavouring 6g

Making it is simple: just put all the ingredients in a food processor and make sure it is fully mixed. Then store it in an airtight jar and use as required. I also add a pinch of food colouring powder during mixing, but the amount used is too small to quantify.

Based on the prices I paid for all the ingredients, this mixture costs £4 per kg (25 servings). Compare that to at least £15 per kg (unless you can get it on short-lived special offer) for commercial mixes.

I bought the sugars from Bulk Powders (you need to buy the 5kg pack to get the lowest price).

I obtained Citric Acid, Malic Acid, Sodium Citrate, and Potassium Chloride from various sellers on eBay and Amazon (make sure you get food grade material). I’ve got tons of fine sea salt (sodium chloride) at home, but you can get that from just about anywhere. And the concentrated flavourings (by far the most expensive ingredient in terms of contribution to overall cost) can also be had from various online sellers. Remember that the larger pack size you choose, the lower the cost.

Ordinary kitchen scales (measuring to 1g) are fine for weighing out the sugars, but you may want to get a more accurate balance for the other ingredients. You can get small scales which weigh up to 500g with 0.1g resolution on eBay for about £15 (they look like CD jewel cases), and they’re accurate enough. Don’t even think about the tiny ones which supposedly weigh to 0.01g and cost a few pounds, because they are crap.

I buy 12 x 500ml packs of spring water from Asda for about £2.00 and add my powder to those. At 17p a bottle, each finished drink works out at around 33p. It’s worth noting that if you didn’t flavour the blend, it would only cost about £2.80 per kg, and each completed drink would cost about 28p (this is the base price). With commercial powders, each drink comes in at around £1.20!

You can adjust the recipe if you want longer term energy supply by cutting down the glucose and fructose (keep the ratio at 2:1), and increasing the maltodextrin. It’ll be less sweet, since maltodextrin isn’t sweet, but your body has to break this down into glucose by itself. You could also replace it with sucrose (cane sugar), which is sweet. And you may want to increase or decrease the amount of flavour slightly depending on what strength you buy. Just make sure everything adds up to 400g. Each 40g serving delivers 258mg of sodium and 60mg of Potassium.

It tastes rather good. I had a few fun issues to start with. First of all, it tastes very bland without any acidification, and – as I discovered – the level of Citric Acid doesn’t need to be as high as it is in the fresh fruit (my first try had eight times more acid and it gave me wicked indigestion). The acid has to be buffered using Citrate. And Malic Acid rounds off the flavour dramatically. Once I researched the formulation of soft drinks and built in the ingredients listed on several commercial packs, everything came together perfectly.

On a final note, the acids and the citrate have E numbers associated with them. You will find lots of nonsense on the internet about how that is bad. It isn’t. Citric Acid is made from natural ingredients, and sodium citrate is made from it. Malic Acid occurs naturally, although the manufacture of it commercially is via a synthetic process.