“It’s a survival mechanism.”
“Sugar, The Bitter Truth” has received nearly 7 million views on YouTube. In this video, Dr. Robert Lustig of UCSF spends ninety minutes convincing his audience that Americans’ excessive fructose consumption is the primary contributor to metabolic disruption. By the transitive property, high consumption of added fructose (table sugar and the even worse high fructose corn syrup) is responsible for this nation’s spike in diagnoses of type II diabetes, non-alcoholic fatty liver disease, and obesity.
I visited Dr. McCormick to ask him about his opinion on fructose: is it really the evil that’s causing these health issues?
“It’s really hard to say obesity is due to fructose”, Dr. McCormick said. Singling out one contributor is too simplistic.
“It’s also hard to separate sucrose and fructose; the difference is very subtle”. Fructose is one of the two components that make up table sugar (sucrose), but it can also be found in its free form in natural sources (fiber rich fruits) and refined, processed sources (in junk foods as high fructose corn syrup). “I don’t think it’s disputable that a high sugar diet will contribute to obesity, and the key is to find things people can’t dispute”.
What Dr. Lustig finds so dangerous about fructose is the way it is metabolized in the human body. Fructose metabolism occurs primarily in the liver, where it is converted into stored energy (glycogen). The liver’s available space for energy storage is limited, and when energy reserves are maximized, excess energy is stored as fat. This metabolic process is not the same for glucose (the other half of table sugar, and another common, naturally-occurring sugar); glucose can be metabolized by many other organs. Fat deposition is much more spread out, but not with fructose, as it’s almost exclusively metabolized by the liver.
“The uniqueness of fructose metabolism didn’t happen overnight”; it’s a process that humans have been capable of for a long time.
Dr. McCormick was reminded of a quote: “there’s a unique way in which fructose signals an abundance of energy.” Excess energy is stored as fat — fructose stimulates fat storage. This is not all bad, however. “It’s a survival mechanism.”
Think back to our ancestors; you don’t even have to go too far back. “In the past, fruits were only available for a certain period of time, so it may have made sense to have this mechanism. But now, we have all the access we want, and our bodies aren’t used to this surplus of food. This surplus has only occurred over the last hundred years or so.
When I was a kid, coke used to be only six ounces. It was a treat! Now, you can’t even find six ounces of coke, let alone anything else! You see people with 32 ounce bottles.
The problem is that we have all this energy, and there is no mechanism by which we can get rid of it.”
He provided examples of other nutrients: sodium, calcium – all are excreted through urine, but energy isn’t.
“Energy is the only one without a capacity or mechanism for excretion.” Though food quality is important, Dr. McCormick explains that it’s a very “calories in, calories out” issue. Stepping back, there’s an excess intake of energy, and no regulatory mechanism to get rid of it.
In summary, “it’s really hard to point to one thing”. Fructose does have a unique way of being processed in our bodies, but it’s very difficult, and quite frankly too simplistic, to point fingers at fructose alone.