Candy Capers

When you're a kid, Halloween means one thing: bags and bags of candy. As a kid, it's easy to down a pound of the sweet stuff, but most adults would be left with a painful stomach ache the next day. As it turns out, there's a gene to blame for the onset of adult "candy intolerance." 

Researchers from the Buck Institute of Age Research in California have found the reason why too much sugar can spook an adult's digestive system. Researchers studied a population of fruit flies and found that the Foxo gene, an insulin transcription responder, turns on and off in younger fruit flies, allowing them to seamlessly adapt to changes in diet.

Older flies, however, aren't so lucky, and the Foxo gene remains turned on, which disrupts their metabolism. Foxo is found in both flies and humans. 

"It was unexpected that a process used to respond to nutritional changes in the young animal becomes deleterious in older animals by being constitutively activated," says lead researcher Henri Jasper, Ph.D., a professor at the Buck Institute.

Changes in Foxo expression likely occur because of an evolutionary need. Younger organisms require a more adaptable digestive process.

Try It! Health Halloween Treats »

Follow That Candy Bar!

It seems like a cruel gene that would allow kids to eat the sweet stuff but not adults. But in fact, it's all about the aging digestive system.

After unwrapping a candy bar and taking that first bite (and probably a second, and a third) the sugars in candy go through a dramatic transformation. The candy is mixed with saliva as you chew, and salivary enzymes begin to break down the sugars into smaller units that are easier for your body to digest, according to the American Journal of Clinical Nutrition.

From there, the candy travels down to the stomach through the esophagus and gastric acid takes over, breaking sugars down even further and hydrating them with water to increase bulk and mobility.

At this point, your candy bar has been transformed into chyme. This slurry of different substances is pushed along through the stomach and out of the pyloric sphincter into the small intestine. Here, most sugars are broken down and absorbed into various parts of the body through a series of transporter systems. Insulin, which is a glucose transporter, is greatly affected by the activity of the Foxo gene.

Watch It: How the Digestive System Works »

Insulin Resistance and Diabetes

"Insulin resistance, which results in constitutive Foxo activation, occurs in many tissues of old humans," Jasper says. "This results in the age-associated increase in the incidence of type 2 diabetes, and it is likely that chronic Foxo activation in intestinal cells also results in metabolic dysfunction in humans." 

Glucose (a simple sugar, or monosaccharide) is the culprit in insulin disorders like diabetes. It is largely absorbed in the small intestine. Glucose is the body's main fuel source, and when its absorption and regulation is off-kilter, weight gain, inflammation, and a whole host of health horrors can arise. 

"[It's] important to explore why Foxo is continuously activated in old guts. We suspect that environmental stressors—oxidative stress, infection, cell damage—play a role," Jasper says. 

So this Halloween, go out and enjoy the night with the goblins and ghouls, but keep the candy in the bowl for those with younger guts.

Jasper recommends an alternative for those of us with less adaptable guts: "Have fun, but eat lots of fruits and nuts instead of candy." 

Learn How to Eat Healthy on Halloween »