In the search for reasons for food-related health problems (like obesity and heart disease), blame has fallen on many suspects. Fat, sugar and sodium are the usuals, but somehow we've tended to see sugar as the lesser of those evils. We know it's bad, but it's just so yummy — and it seems harder to give up than fat or salt. But the tide is starting to turn, with study after study revealing the hidden hazards of sugar consumption. It turns out that sugar (the refined stuff, anyway) might be the main culprit, after all — and maybe the reason we resist giving it up is that we're all addicted.
It might seem strange to put sweet old sugar into the same category as horribly destructive drugs like cocaine and heroin. But think about it: You've probably had countless loss-of-control moments with sugar. The sugar rush-crash-cravings cycle is a classic addiction progression. It might not be as dramatic as a heavy-drug situation, but it's the same basic thing. Cocaine-addicted rats in one study, in fact, regularly chose Oreos over cocaine [source: Lambert].
When we talk about sugar addiction, the main offender is fructose, which is found in all refined sugars (glucose is the sugar in fruit). Table sugar, high-fructose corn syrup, honey and agave nectar all have some percentage of fructose, which is twice as sweet as glucose. Our bodies have no problem processing glucose – it's efficiently converted into energy. Fructose is not so easy.
The liver deals with fructose, and gets overwhelmed when you eat too much of it. Excess fructose in the liver can start chain reactions all over the body that result in obesity, diabetes, heart disease and cancer, to name a few. It can slow down your metabolism. It can also trick your brain.
Sugar consumption activates the nucleus accumbens, the pleasure center in the brain that is also lit up by heroin and cocaine. The brain releases dopamine, which makes you feel great – and want to eat more sugar. After a while, though, you have to consume ever-more quantities of sugar in order to get an equal amount of dopamine. And so a tolerance-withdrawal cycle begins, which is standard addictive behavior.
Too much sugar can also trigger leptin resistance. Leptin is produced by fat cells that tell the brain you're full. If your liver gets overworked with fructose, it'll store the sugar in fat cells, which will then release too much leptin. Eventually, your brain might stop listening to it. So you won't know you're full and keep stuffing your face with sugar.
When you consume glucose, the pancreas produces insulin to regulate your blood sugar. Insulin production triggers leptin, signaling the brain that you're done eating, and decreases levels of ghrelin, the hunger hormone. Fructose, however, interferes with leptin and doesn't decrease ghrelin, so there's a double whammy – the brain doesn't know you're full and also thinks you're still hungry.
The average American consumes 22 teaspoons or 110 grams a day of added sugar, most of that in the form of fructose [source: Barclay]. The American Heart Association recommends a drastic decrease — to 6 teaspoons a day for women and 9 teaspoons for men [source: Barclay]. That's a tough task, given that fructose is slipped into just about every packaged food out there. But knowing the myriad dangers that lurk in fructose, it's probably worth a try.