You secrete insulin in response to the foods you eat — particularly the carbohydrates — to keep blood sugar in control after a meal. When your cells are resistant to insulin, your body (your pancreas, to be precise) responds to rising blood sugar by pumping out more and more insulin. Eventually the pancreas can no longer keep up with the demand or it gives in to what diabetologists call “pancreatic exhaustion.” Now your blood sugar will rise out of control, and you’ve got diabetes.
An excellent point and I am guilty as charged. This is an inherent problem, though, in writing science for the lay public. The science invariably has to be simplified considerably to make the articles flow and to prevent readers from getting bogged down early in technical details -- the difference, in this case, between type 1 and type 2 diabetes. So the detail is delayed for later in the article, by which time, as you point out, readers could have already come to mistaken conclusions about which diabetes we're discussing. This is always a judgment call, but it's a hard problem to avoid and there are no easy solutions. Or if there are, I haven't mastered them.
Lustig’s argument, however, is not about the consumption of empty calories — and biochemists have made the same case previously, though not so publicly. It is that sugar has unique characteristics, specifically in the way the human body metabolizes the fructose in it, that may make it singularly harmful, at least if consumed in sufficient quantities.
The phrase Lustig uses when he describes this concept is “isocaloric but not isometabolic.” This means we can eat 100 calories of glucose (from a potato or bread or other starch) or 100 calories of sugar (half glucose and half fructose), and they will be metabolized differently and have a different effect on the body. The calories are the same, but the metabolic consequences are quite different.
The fructose component of sugar and H.F.C.S. is metabolized primarily by the liver, while the glucose from sugar and starches is metabolized by every cell in the body. Consuming sugar (fructose and glucose) means more work for the liver than if you consumed the same number of calories of starch (glucose). And if you take that sugar in liquid form — soda or fruit juices — the fructose and glucose will hit the liver more quickly than if you consume them, say, in an apple (or several apples, to get what researchers would call the equivalent dose of sugar). The speed with which the liver has to do its work will also affect how it metabolizes the fructose and glucose.
In animals, or at least in laboratory rats and mice, it’s clear that if the fructose hits the liver in sufficient quantity and with sufficient speed, the liver will convert much of it to fat. This apparently induces a condition known as insulin resistance, which is now considered the fundamental problem in obesity, and the underlying defect in heart disease and in the type of diabetes, type 2, that is common to obese and overweight individuals. It might also be the underlying defect in many cancers.
Assuming sugar is toxic, as Dr. Lustig says, then it's always possible to cut back on consumption significantly. As you say, avoiding it entirely pretty much requires that we cook everyone of our meals from scratch. Sucrose and HFCS have a lot of qualities other than sweetness, as the sugar industry and corn refiners are always pointing out, that make them very valuable in food production. But a large proportion of the sugars we consume come in the form of sweets and sweetened-beverages (including fruit juices) and cutting back on those would go a long way to reducing sugar consumption to whatever safe levels might happen to be. It's also conceivable that the fundamental problem is consuming these sugars in liquid form which forces the body (liver and pancreas) to deal with the sugars quickly, and so avoiding juices and sodas would help here, as well.
Toxicity is the degree to which a substance can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ (organotoxicity), such as the liver (hepatotoxicity). [snip] A central concept of toxicology is that effects are dose-dependent;
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