A study published on the first day of 2016 suggests that sugar encourages the growth and spread of breast cancer tumors in rats, and fructose was singled out as having particularly carcinogenic activity. This is similar to recent evidence that pancreatic cancer cells can distinguish between fructose and glucose, and perform better when fed the former. And thus, the wagons of scrutiny circled a little closer around fructose, which was long thought to have a near-identical effect on the body as glucose.
These days, as the scientific and medical communities become more unified in the stance that sugar is bad, many in these fields are also coming to the conclusion that fructose is even worse. This idea, sometimes called the “fructose hypothesis,” refers to many studies that suggest fructose is processed differently in the body than other sugars, and with more deleterious effects, including inflammation, obesity, fatty liver disease, diabetes, blood lipid levels and Alzheimer’s.
When people hear the word “fructose,” many think of the mass-produced industrial brew known as high fructose corn syrup, and the many junk foods and sugary drinks that deliver HFCS to the world’s belly fat. But there are also a lot of people who, at the mention of fructose, think of fruit, honey, carrots, and wine. Should these sweet babies be thrown out with the high-fructose bathwater?
While present in many plant-based foods, fructose isn’t necessary for any physiological function in the human body. In fact, we can’t even use fructose, so we mst convert it to other forms of energy storage, like glycogen, fat, different sugars, or other things like palmitate-the presence of which in diet is thought to promote heart disease.
Fructose, in isolation, thus represents the emptiest of calories, with only a slight bump of redeeming value owing to the fact that the body must spend energy to convert fructose to one of these other forms, an effort that burns an amount of energy roughly analogous to the amount burned by the work of opening a Pepsi before drinking it.
For those who don’t do much more than opening processed foods, the many apparent deleterious effects of fructose are made worse by inactivity. The more active you are, it seems, the less you have to worry about fructose.
Glucose, meanwhile, is used by every cell in the body, 24/7. But we don’t need to eat glucose in order to have as much as we need. Starch, fat and every other form of energy storage, like fructose, can be converted to glucose.
For all practical purposes, we can’t eat pure glucose without also consuming fructose. Table sugar is a 50/50 mix of the two, while in HFCS the ratio of fructose to glucose varies. Typically it’s 55/45 percent fructose-to-glucose, but can be as high as 90 percent fructose.
While glucose is processed everywhere, fructose is only processed in the liver. Too much fructose can overload the liver’s capacity to deal, and cause a host of issues like insulin resistance, which leads to diabetes, and fat deposits in the liver, which can lead to liver disease and cancer.
By depositing fructose-generated fat in our livers, we are basically turning them into human foie gras. But unlike those poor, delicious ducks, we are force-feeding ourselves by making food so addictive we can’t stop eating it. Fructose has been shown to be less satiatingthan other energy storage forms, which means you can eat more of it without being full. (Note to self: investigate viability of a foie gras business model where ducks are fed KitKats).
So far the biggest challenge to the fructose hypothesis has come from a University of Toronto-based team lead by Dr. John Sievenpiper, who argues many of the animal based studies of the fructose hypothesis don’t apply to people. With funding from Coca-Cola and other junk food companies, Dr. Sievenpiper and company produced a metastudy of strictly human studies that found no evidence that fructose produces high blood pressure, diabetes, and obesity any more than any other calorie would.
These conclusions couldn’t be better tailored to match the current position of the junk food lobby: the idea that all calories are equally bad, including fructose. At least one group cited in Sievenpiper’s metastudy claims its data was misinterpreted and has formally requested a correction.
Nonetheless, it’s true that there is little direct proof that, beyond a shadow of doubt, fructose-specific damage is occurring in humans, despite the growing number of circumstantial, anecdotal and animal-based pieces of evidence suggesting this is so. Part of the problem here is that for ethical reasons it’s problematic to micromanage the lifestyles and eating habits of human study participants to the same degree we do to lab rats.
The new cancer study, while on rats and not humans, nonetheless demonstrates a fructose-specific avenue for the genesis and spread of cancer that operates via biochemical and cellular pathways that we also possess.
“We determined that it was specifically fructose, in table sugar and high-fructose corn syrup, ubiquitous within our food system, which was responsible for facilitating lung metastasis and 12-HETE production in breast tumors,” the study’s co-author, Dr. Lorenzo Cohen, said in a press release.
So, does this mean we should look suspiciously at apples and oranges, because of all the fructose?
On one hand, the fructose in fruit is tempered by the fiber also found in whole fruit, which makes it an overall less fattening food. On the other hand, our bodies evolved in circumstances where fruit was neither as abundant nor as sweet as it is today. Today’s fruits are more like juicy candy bars dangling from trees than what our hunter/gatherer ancestors ate. But if you are as active as they were, maybe you can handle that much sugar.
And if you’re thinking that maybe you should cut back to less than an apple a day, just in case, here is a better idea: eat that apple. And get some exercise.