Robert Lustig is a specialist on pediatric hormone disorders and the leading expert in childhood obesity at the University of California, San Francisco, School of Medicine. According to the enormous feature in The New York Times Magazine about his theories, UCSF has one of the best medical schools in the country. Lustig published his first paper on childhood obesity over a decade ago, and he believes the leading cause of the epidemic is something we all consume every day: sugar.
But not only does Lustig believe that sugar causes obesity and diabetes in children and adults, he goes so far as to describe sugar and high fructose corn syrup as toxic, poisonous and downright evil. Times scribe Gary Taubes is upfront about the fact that after 10 years of research, he’s in complete agreement with Lustig. Early in the lengthy piece, Taubes writes, “when you bake your children a birthday cake or give them lemonade on a hot summer day, you may be doing them more harm than good, despite all the love that goes with it.” Lustig, Taubes and others believe that sugar can even cause cancer.
Taubes says that “the conventional wisdom has long been that the worst that can be said about sugars of any kind is that they cause tooth decay and represent empty calories that we eat in excess because they taste so good.” On the contrary, though, Lustig believes that it’s not sugar’s empty calories that are the enemy, but sugar’s “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.”
Lustig has determined that glucose and fructose are “metabolized differently and have a different effect on the body.” The stuff to watch out for is fructose and by extension high fructose corn syrup, which is metabolized primarily by the liver. Taubes explains:
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.
It turns out – in lab rats, anyway – that if fructose hits the liver quickly (via chugging a can of Coke, let’s say), “the liver will convert much of it to fat.” That metabolic dynamic “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.” And here’s the clincher, as I mentioned earlier: “It might also be the underlying defect in many cancers.” Here’s how that works:
The connection between obesity, diabetes and cancer was first reported in 2004 in large population studies by researchers from the World Health Organization’s International Agency for Research on Cancer. It is not controversial. What it means is that you are more likely to get cancer if you’re obese or diabetic than if you’re not, and you’re more likely to get cancer if you have metabolic syndrome than if you don’t. Cancer researchers now consider that the problem with insulin resistance is that it leads us to secrete more insulin, and insulin (as well as a related hormone known as insulin-like growth factor) actually promotes tumor growth.
Craig Thompson of Memorial Sloan-Kettering believes that “many pre-cancerous cells would never acquire the mutations that turn them into malignant tumors if they weren’t being driven by insulin to take up more and more blood sugar and metabolize it,” and Lewis Cantley, director of the Cancer Center at Beth Israel Deaconess Medical Center at Harvard, says “up to 80 percent of all human cancers are driven by either mutations or environmental factors that work to enhance or mimic the effect of insulin on the incipient tumor cells.”
Researchers have previously concluded that there was no evidence that added sugar (beyond what is naturally contained in fruits and vegetables) demonstrated harm at the levels which it was being consumed. But those same experts “estimated those levels at 40 pounds per person per year,” or 200 calories per day of sugar. That’s less than the amount “in a can and a half of Coca-Cola or two cups of apple juice.”
Unfortunately, though, the average American now consumes 90 pounds of added sugar per year. Yikes.
In one study referenced by Taubes, when human subjects were fed “the equivalent of the fructose in 8 to 10 cans of Coke or Pepsi a day… their livers would start to become insulin-resistant, and their triglycerides would go up in just a few days.” Which is why Lustig believes sugar and high-fructose corn syrup are “chronic toxins,” meaning they are “not toxic after one meal, but after 1,000 meals.” (Don’t forget, we eat 1,000 meals in just one year.)
One reason to eliminate added sugar from your family’s diet? Neither Thompson nor Cantley will eat sugar or high-fructose corn syrup. “I have eliminated refined sugar from my diet and eat as little as I possibly can, because I believe ultimately it’s something I can do to decrease my risk of cancer,” Thompson said. According to Taubes, Cantley put it this way: “Sugar scares me.”
Source: New York Times