Killing me sweetly

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Jamaica would quite like an apology for the enslavement of the tens of thousands of Africans brought to the island to work on British-owned sugar plantations. But whether that apology is forthcoming or not, there is at least a sort of karma in the effect that sugar is having on the nations that profited from African enslavement.

From recent headlines, you might think that scientists have just discovered the toxic nature of sugar. In fact, we have known about it since the early 19th century, when an experiment showed that dogs fed olive oil and sugar would waste away and die. The experiment was inspired by the 1793 shipwreck of a sugar-laden vessel sailing from the West Indies. The five surviving marooned sailors were found in an appalling state after nine days - having consumed nothing but sugar and rum.

In the 1920s, the era when sweet and soft-drink manufacturers were establishing their business, public health researchers noted that up to 15 times more New Yorkers were dying from diabetes.

We have all been told that fat is the killer to avoid, but that's just because the anti-sugar scientists haven't been terribly skilled at public relations. In the 1970s, researchers were evenly split between the two camps, but the anti-fat camp managed to undermine the credibility of those who wanted to blame sugar for heart disease. That is why, although fat has been vilified for so long, sugar is only just coming into the regulators' sights.

The trouble is that no evidence is ever quite conclusive enough to force the regulators to act. A 2008 study at the University of California, Davis showed that giving people 25 per cent of their daily energy requirement from fructose, the most dangerous form of sugar, put them at great risk of being unable to control their blood sugar. The UC Davis researchers, despite being sponsored by PepsiCo, put out a warning over sugar consumption. But PepsiCo issued a statement saying that the research didn't reflect any real-world situation and that people shouldn't read too much into it. And, addicted to sugar as we are, we didn't.

Sugar's addictive qualities are the new discovery that might just tip the balance. It interferes with the hormones ghrelin and leptin, which would normally curb your appetite. It also disrupts dopamine signalling, and so it takes a lot of the stuff to gain any pleasure from its consumption.

Combine that with the changes sugar imposes on our organs and blood fat, and you have a perfect storm. Your body is a highly specialised chemical processing plant, and sugar is not meant to be one of the main raw materials. As you eat, your pancreas secretes insulin to stop your blood sugar rising too high. However, excessive consumption seems to send this process haywire, causing a chemical reaction in the liver that creates a fatty acid ester called palmitate. This creates a layer of fat that wraps around internal organs.

In the blood
Sugar also stimulates the liver to release triglyceride fats into the bloodstream in a form that makes them stick to artery walls. What's more, it renders our muscles unable to soak up blood sugar, requiring the pancreas to go into overdrive with its insulin production, exacerbating the problem in the liver and sending the body into "metabolic syndrome", now believed to be a leading cause of heart disease, stroke and diabetes.

But scientists have not yet pinned down the details of every one of these processes. And so the food industry will, like the climate-change deniers, argue that it's too soon to act - more research is always needed. Meanwhile, we'll just keep on sweetening ourselves to death.

Michael Brooks's "Free Radicals: the Secret Anarchy of Science" is published by Profile Books (£12.99)