Kidney Stones and Colas
<p class="default">Rust remover--phosphoric acid
The ingredient of colas which looks rather odd, and rather menacing, is phosphoric acid. Generally we are more familiar with this acid as the active agent in rust-removers, and with its salts, which are called phosphates, and are used in detergents. In the 1970s and 80s, phosphates became a dirty word, and were blamed for the pollution of rivers and lakes, with detergents being fingered as the most important source. We will look a little closer at this issue in Gallery 6, where there is a portrait of phosphates.
People need phosphate in their diet as an essential nutrient to make DNA, build their bones and form their membranes. It also is needed for the chemical adenosine triphosphate (ATP), which plays a central role in helping get the energy we need from food. Phosphate-containing molecules also act as messengers, and govern calcium transport. In addition to these major roles phosphate has many minor uses in the body. It might seem that such a key element could be in danger of being in short supply in our diet, but this rarely happens because the body recycles it very effectively and in any case we have an enormous store of phosphate in our skeleton. The phosphoric acid in colas can be regarded as making a useful but minor contribution.
Sometimes the phosphoric acid in colas has found other uses. Motorists, motorcyclists and truck drivers in the 1950s and 60s used cola to clean the chrome bumpers (fenders), grilles and headlights which lavishly adorned their vehicles in the fashion of those times. The phosphoric acid reacted chemically with the chrome to form a hard surface layer of chromium phosphate which protected it. It also dissolved any rust that formed and protected any of the underlying steel which had become exposed. Industrially phosphoric acid is still used for this purpose, and all anti-rust paints rely on it.
There is nothing sinister about phosphoric acid or its salts. To say that colas contain an industrial cleaner, as one book has claimed, is strictly true, but this is no reason to not drink them. Any phosphate in our food becomes phosphoric acid in the acidic conditions of the stomach. Every living cell needs phosphoric acid to function and it matters not where it comes from.
The phosphoric acid in colas presents no threat to health; indeed, we could regard it as an essential mineral. Plants begin the process of supplying the food chain with phosphate by extracting it from the soil, and they store phosphate in their seeds as the chemical phytic acid. They use this store when they germinate so they can put down roots without needing to take in any phosphate from the environment. Although seeds are highly nutritious on account of the protein, carbohydrate, fats and minerals they contain, they provide us with little in the way of phosphate because we cannot digest the phytic acid store since we lack the enzymes to release its phosphoric acids. So the phytic acid passes straight through us--not that we need it, because every plant and animal cell that we eat contains more than enough phosphate.
We get most of the phosphate in our diet from natural sources such as fish, meat, eggs and dairy products, and a little from unnatural sources such as colas, processed cheese, cheese spreads, sausages and cooked meats, to which it is added to improve texture and regulate acidity.
[] Portrait 5
 </p>