Is Sugar Really Toxic? Sifting Through the Evidence
16th July 2013
Scientific American looks at the conventional wisdom.
Considering that our cells depend on sugar for energy, it makes sense that we evolved an innate love for sweetness. How much sugar we consume, however—as well as how it enters the body and where we get it from in the first place—has changed dramatically over time. Before agriculture, our ancestors presumably did not have much control over the sugars in their diet, which must have come from whatever plants and animals were available in a given place and season. Around 6,000 BC, people in New Guinea began to grow sugarcane, chewing and sucking on the stalks to drink the sweet juice within. Sugarcane cultivation spread to India, where by 500 BC people had learned to turn bowls of the tropical grass’s juice into crude crystals. From there sugar traveled with migrants and monks to China, Persia, northern Africa and eventually to Europe in the 11th century.
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Because fructose metabolism seems to kick off a chain reaction of potentially harmful chemical changes inside the body, Lustig, Taubes and others have singled out fructose as the rotten apple of the sugar family. When they talk about sugar as a toxin, they mean fructose specifically. In the last few years, however, prominent biochemists and nutrition experts have challenged the idea that fructose is a threat to our health and have argued that replacing fructose with glucose or other sugars would solve nothing. First, as fructose expert John White points out, fructose consumption has been declining for more than a decade, but rates of obesity continued to rise during the same period. Of course, coinciding trends alone do not definitively demonstrate anything. A more compelling criticism is that concern about fructose is based primarily on studies in which rodents and people consumed huge amounts of the molecule—up to 300 grams of fructose each day, which is nearly equivalent to the total sugar in eight cans of Coke—or a diet in which the vast majority of sugars were pure fructose. The reality is that most people consume far less fructose than used in such studies and rarely eat fructose without glucose.