A reader writes:
My kid was diagnosed with fructose malabsorption early in 2012. Essentially, any fructose that he eats, in excess of approximately the same amount of glucose, makes him sick. Most fruits are relatively balanced 1:1 with fructose to glucose, so they're okay: pineapples, berries, a lot of citrus fruits. But popular fruits like apples, mangoes and watermelons are screamingly high in fructose relative to glucose. Oh, and wheat. And honey. And agave syrup. Fruit juice is just as bad as Honey Boo Boo's Mountain Dew habit from a metabolic standpoint, but at least it doesn't have the other crap in it.
You'd think such a disorder is rare? It's really common. Estimates are 30-50% of the U.S. population. And they tend to have metabolic syndrome.
Fructose-heavy fruits and grains come from parts of the world where people are better able to tolerate them (warmer parts of Asia, the Middle East – anywhere with a long, warm/hot growing season and/or a lack of seasons). And if you're from an area where those fructose heavy fruits and grains don't grow year round (Northern Europe), you're really screwed, as your body treats fructose differently in the absence of sunlight. The idea is that you'd have gorged on those fruits during the summer months, and depositing that fat around your middle (again, metabolic syndrome) would have been helpful for fertility – hell, survival, in general – during the cold winter months when there's little food.
Metabolic syndrome is really common in my family, as are high triglycerides and pasty white skin. We joke around that my kid's diagnosis of fructose malabsorption and his subsequent avoidance of fructose sources will make him one of the healthiest kids we know, as kids are all on high-fructose corn syrup and fruit juice from an early age. It's no surprise that obesity rates and metabolic syndrome have gone through the roof since the introduction of HFCS in everything.
By the way, in support of Dr. Lustig's argument about the relative perils of fructose, a recent study (subscriber only) in the Journal of the American Medical Association shows how the brain responds differently to different types of sugars:
[Researchers found] an increased sensation of fullness and satiety after glucose, but not fructose, consumption. These findings support the conceptual framework that when the human brain is exposed to fructose, neurobiological pathways involved in the appetite region are modulated, thereby promoting increased food intake.
(Photo by COPCWa)