Many of us have a sweet tooth. It's hardwired into our
brains. Several thousand years ago, when we went long
periods of time between meals, we needed to get all the
calories we could whenever we had the chance. Sweet and
fatty foods are high in calories, so our brains made them
taste good to get us to eat them. It was a survival
instinct back then that made for fit brains. It doesn't
work so well for us now.
Taste Isn't Everything
We've known this for some time. We know that when you eat
something sweet you light up pleasure centers, driven by
dopamine, in your brain. New research shows it's not just
the sweet flavor that pleasures us. We will light up
pleasure centers even if we can't taste the sweet foods.
The high sugar content of sweet foods cranks up our
insulin. It turns out that the insulin spike is enough to
activate our pleasure centers.
In a recent study, researchers knocked out the ability of
mice to taste sweetness. They proved it by allowing mice to
choose between plain water and water spiked with sucralose
(a non-digestible sugar with no available calories). Normal
mice will prefer the sucrolose water because it's sweet,
but these mice couldn't tell the difference. Next, the
researchers gave the un-sweetened mice a choice between
plain water and sugar water, and they those the sugar
water, even though they couldn't taste the difference.
In the same studies, the researchers looked at the pleasure
centers in the brains of the mice. Sucralose water (sweet
but no calories) had no affect, but sucrose water (regular
sugar) cranked up the dopamine in please circuits, whereas
in regular mice, both sucrolose and sucrose activate
pleasure. This showed that the high calorie content alone
was enough to activate pleasure, even in the absence of
taste.
Sweet Pleasures, or Not
So what does this mean for us sweet-toothed humans? First,
since our pleasure circuitry is similar, it's likely that
the same thing happens in our brains (although this remains
to be tested directly). Second, we've discussed in the past
how high glycemic foods (simple carbohydrate, high sugar)
spike your blood sugar and insulin levels. This is likely
tickling your pleasure centers and reinforcing high
glycemic eating. The problem is that this type of eating is
gaining more and more data on increasing your risk for
metabolic and cognitive diseases, like diabetes and
dementia.
Like anything that stimulates your brain pleasure circuits,
it becomes less intense over time. So the more you eat high
glycemic foods, the less intensely your pleasure centers
are likely to respond. This is also how drug addiction
works, and is why people need more of a drug to get the
same high over time. Not only that, but when you come off
the drug your pleasure centers crash to really low
activation and you feel horrible. Similarly, when you try
to improve your diet to reduce low glycemic foods you are
not getting that pleasure boost so you crave sugar.
Now, to be clear, drugs of abuse and high glycemic foods
operate at completely different levels. In the words of
Nigel from Spinal Tap, drugs turn your volume up to 11,
while high glycemic foods probably crank it up to 3 or 4.
But the principle is the same.
It's Never Too Late to Change
The human brain is an amazingly adaptive thing. Even though
it's wired to enjoy sweet and fatty foods, we can modify
and retrain those brain circuits to adapt to health in
today's environment. After all, our brains weren't designed
to be pleasured by sweet foods on a daily basis as is the
case today.
Fortunately, you can reset your dopamine scale with a focus
on low glycemic eating. It takes a week or two of strictly
removing excess sugar from your diet, but you can reset the
circuits and lose the bulk of your cravings for sweet
foods. Furthermore, if you replace the pleasure activating
foods with active healthy behaviors that you enjoy, like
playing tennis or shooting hoops, you'll have a much
greater chance of success.
Reference: de Araujo, Neuron 57 (2008), 930'941.
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