The more we use these substances, the less dopamine we produce naturally in the brain. The result is that we need more of the drug to get the same pleasurable response, while natural pleasures, such as sex and eating, please us less and less.

There is little doubt that sugar can allay the physical craving for alcohol, the neurologist James Leonard Corning observed over a century ago. The 12-step bible of Alcoholics Anonymous recommends the consumption of sweets and chocolate in lieu of alcohol when the cravings for drink arise. Indeed, the per capita consumption of sweets in the US doubled with the beginning of prohibition in 1919, as Americans apparently turned en masse from alcohol to sweets.

Sugar and sweets inexorably came to saturate our diets as the annual global production of sugar increased exponentially. By the early 20th century, sugar had assimilated itself into all aspects of our eating experience, and was being consumed during breakfast, lunch, dinner and snacks. Nutritional authorities were already suggesting what appeared to be obvious: that this increased consumption was a product of at least a kind of addiction – "the development of the sugar appetite, which, like any other appetite – for instance, the liquor appetite – grows by gratification".

A century later still, sugar has become an ingredient in prepared and packaged foods so ubiquitous it can only be avoided by concerted and determined effort. There is sugar not just in the obvious sweet foods – cookies, ice creams, chocolates, fizzy drinks, sodas, sports and energy drinks, sweetened iced tea, jams, jellies and breakfast cereals – but also in peanut butter, salad dressing, ketchup, barbecue sauces, canned soups, processed meats, bacon, hot dogs, crisps, roasted peanuts, pasta sauces, tinned tomatoes and breads.