Sugar.

In New Zealand, a man called Frankenstein is calling for a tax on sugar.

Really. Sugar. That basic chemical that all your body cells run on. A lack of which will cause your body to burn protein for energy, send you into ketosis and eventually kill you.

It's okay though. Mr. Frankenstein has the answer. He'll sell you some water.

This is way below the level of biological knowledge we were once expected to understand at O level. By the end of the first year at university I had all the pathways and equations in my head. Only for the duration of the biochemistry exam, of course. Now I just need to remember which book they're in and they are conveniently all in one very big book.

Salt and sugar are essential to life. If you don't eat fast food and never add any salt, you are risking salt deprivation. No, there is not enough in natural foods. That's why we started digging it up in the first place.

The sugar doesn't have to be refined and it can be in the form of some carbohydrates, such as starch. Not cellulose, mammals can't digest that. You need it or your body will break protein to make it and it will throw away the bits of the protein it doesn't need. Some of that will appear on your breath as acetone. You can spot Atkins diet afficionados with a quick sniff.

It's not good for you. Metabolically, it's a disaster. Your body can use protein for energy but it's not designed to do that for very long. This is a backup system for use in emergencies, it is not designed to be a way of life.

Ruminants such as sheep, goats and cows get no sugars directly from their diet. None. All their sugars are made in their liver from fatty acids. Bacteria in the rumen break their cellulosic feed and the cow absorbs their waste products. There's a reason they evolved to live on bacteria crap, and indeed on bacteria because they get their protein when the bacteria are digested further down the gut. It means they can live on cellulosic stuff like grass, which is no use to humans. Cows can't digest it but bacteria can. Since the cow's bacteria can make all the amino acids, and the cow's liver can make sugar from fatty acids, cows can live on newspaper and urine. Their bacteria will make everything they need from that.

We can't do that. Our bacteria are mainly in the lower gut, too far down to be digested. They are throughout the gut, sure, but not enough to provide a protein source in the stomach. Our livers can make sugar from fatty acids but they are set up primarily to deal with actual sugar. Glucose, specifically. The alternative pathways are a backup and will be overwhelmed if over-used.

So yes, we could live with no sugar input. But not for very long.

This proposal is a tax on staying alive. A breathing tax cannot be far behind.