If you have a sweet tooth, you know how hard it is to resist sugary foods. But have you ever wondered where your sugar cravings come from?
A recent study might reveal some clues, and it has to do with the way your brain is wired.
In the study, published in the American Journal of Clinical Nutrition, a team from Boston Children’s Hospital looked at brain scans of two groups of study participants. One group drank milkshakes containing fast-absorbing, high-glycemic ingredients (which lead to sharp increases and decreases in blood sugar), like corn syrup. The other group drank milkshakes that had an identical caloric and nutritional composition but were made from slow-absorbing, low-glycemic ingredients.
As expected, the first group reported experiencing a more pronounced “sugar crash” – a quick drop in blood sugar levels marked by increased hunger – about four hours after drinking the shake. But brain scans taken of this group also revealed greater activity in the nucleus accumbens area of the brain. This region is linked to feelings of reward and craving, and has been associated with substance addiction and abuse behaviors. The low-glycemic group did not show such high levels of activity in the nucleus accumbens.
This does not imply that having a sweet tooth is on the same page as, say, a drug or alcohol addiction. But it does suggest that our food preferences – and perhaps some of the underlying causes of our current obesity crisis – may have a neurobiological component.
Many other studies done in the past also suggest a connection between our attraction to sugary foods and our brain. Various parts of the brain, including the aforementioned nucleus accumbens as well as the hypothalamus (which regulates feelings of hunger), along with many types of hormones, together create a complex neurobiological system that greatly influences what, when, why and how much we eat.
Earlier this year, a study in the Journal of the American Medical Association attempted to find out how different types of sugar – specifically, fructose and glucose – impact brain activity. They discovered that fructose triggered increased blood flow in the hypothalamus. Those who drank glucose showed less activity in the hypothalamus. The glucose group also had reduced activity in the insula and striatum regions of the brain, which control appetite and hunger.
These patterns suggest that “when the human brain is exposed to fructose, neurobiological pathways involved in appetite regulation are modulated, thereby promoting increased food intake,” according to an editorial by Jonathan Purnell, MD, and Damien Fair, PhD, of Oregon Health & Science University. In other words, glucose appears to blunt hunger signals while fructose may trigger the brain to want more, which could explain why it’s so hard to have just one piece of chocolate or candy. (See the article “Fructose and the Brain” for more.)
It’s important to note that most of the sweets we eat contain a combination of fructose and glucose (including table sugar and the common sweetening ingredient, high-fructose corn syrup), so to choose high-glucose foods over high-fructose foods would be inadvisable and impractical. However, such research does give us insight into how our brain processes and reacts to the taste of sugar. While an occasional sweet treat isn’t harmful for most (unless you have a medical condition), moderation is key. Many people find that their sugar cravings can be met with healthier alternatives, such as fruit (aka “nature’s candy”) or – my personal favorite – dark chocolate.
Mind your health,
Dr. Keith Black
