Sugar hit

The Heart Foundation has called for a 20 percent soft drink tax, citing a new study out of Mexico as evidence that such taxes really work.

Defenders of soft drink taxes are quite the globetrotters, always hopping from country to country in search of a success story. First it was Denmark, then New York City, and now Mexico.

But if they think Mexico is the flagship case that’s finally going to prove them right, they’re mistaken.

To begin with, the new study purporting to show a reduction in soft drink consumption relies on consumer self-reporting.

Of course, people’s own account of what they eat and drink is highly unreliable. Sales data would be far more conclusive.

Secondly, whether people are consuming less soft drink is beside the point if they are simply substituting fruit juice or something equally sugary. We know that this kind of substitution frequently occurs when a specific product is singled out for a special new tax.

It’s very difficult, not to mention insulting, to micromanage the diet choices of grown adults by imposing new taxes on them. A tax on soft drink would not be any more successful in Australia than it was in Denmark-and nothing in this new study of the Mexico experiment convinces me otherwise.