What Exactly Does Sugar Do to Your Body?

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December 10, 2024

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You are probably overdoing it on the sugar.

The average American consumes 22 teaspoons of sugar daily, more than double the American Heart Association's recommendation.

Added sugar is in everything from granola bars and ketchup to fruit juice and cereal. Too much of it can lead to heart disease, obesity and high blood pressure.

"A way to think about added sugar is that it's a very bad messenger," says Danielle Basta, APRN, MPH, MSN, CDCES, an Endocrinology nurse practitioner and Certified Diabetes Care and Education Specialist at Dartmouth Health's Dartmouth Hitchcock Medical Center (DHMC).

"It's like an accomplice to a crime," she adds.

What exactly does sugar do to your body? More than you might think.

A hit of dopamine

After that first bite of candy or sip of soda, sugar floods your brain with dopamine and makes you feel good. That's why you're more likely to crave a chocolate chip cookie than an apple when powering through a mid-afternoon work meeting.

"Sugar is a mood-altering chemical. We feel happy after eating it, which adds to its addictive quality," says Jean Copeland, RDN, LD, our registered dietitian and nutritionist at DHMC's Heart and Vascular Center.

Not all sugar is bad. It's a matter of understanding the difference between natural sugars in complex carbohydrates and processed added sugars in simple carbohydrates.

Complex carbohydrates include fruits, vegetables, whole grains and dairy. These foods, which won't cause your brain to release as much dopamine, contain nutrients like high fiber, essential minerals and vitamins, antioxidants and protein, alongside natural sugars.

Since your body digests complex carbohydrates slowly, they offer a steady energy supply to your cells and help reduce the risk of chronic disease.

"Carbohydrates fuel every cell in our body, including our brain," says Ashley Medhurst, RD, our registered dietitian at Dartmouth Health's Cheshire Medical Center. "They're our body's primary and preferred fuel source."

But foods with added sugar—simple carbohydrates—like energy drinks, candy bars, baked goods, soda and flavored yogurt are harmful and lack essential nutrients to benefit your body.

The kitchen sink test

Here's a test you can use to determine how foods with added sugar react in your body. Let's say you eat a bowl of cereal for breakfast. You don't finish, so you place your bowl with a few cereal pieces in the sink.

"You come back to the sink in five minutes, and the piece of cereal is bloated up, and it's fallen apart," Medhurst explains. "When we think of that from a digestive standpoint, those simple carbohydrates are almost immediately released into your bloodstream, where they start acting on the body."

But a complex carbohydrate, like a half-eaten piece of butternut squash, can be placed in the sink and stay intact.

"Butternut squash is going to take much longer to break down, which is what you want," she says.

More than a sugar crash

When you eat complex carbohydrates, your blood sugar levels rise. Your pancreas is activated and secretes insulin, which moves glucose (sugar) molecules into your cells and converts them to energy.

But sugar from simple carbohydrates causes blood sugar to spike and crash, bringing on fatigue, irritability and digestive issues.

Sugar affects your body in different ways.

  • High amounts of sugar overload the liver. Your liver metabolizes sugar like alcohol, converting carbohydrates to fat. The accumulation of fat may cause fatty liver disease, which can lead to diabetes and raise your risk for heart disease.
  • Consuming too much added sugar can also increase blood pressure and chronic inflammation, upping your risk for stroke, heart disease and osteoporosis.
  • Cancer cells also have a strong preference for sugar compared to healthy cells.
  • Studies show that diets high in added sugar promote the development of obesity. A high sugar intake doesn't cause diabetes, but obesity puts you at risk for the disease.
  • Sugar is especially harmful to people vulnerable to health conditions like obesity, heart disease, diabetes and other illnesses.

The rise of high-fructose corn syrup

High-fructose corn syrup (HFCS), often overlooked by consumers as it's not listed as "sugar" on nutrition labels, is found in candy, soda and packaged sweets. Diets rich in HFCS are linked to health problems like fatty liver, high triglycerides, insulin resistance, high blood sugar and an increased risk of type 2 diabetes.

Copeland explains that HFCS is also detrimental to gut health.

"When you consume HFCS, a less efficient method of absorption takes place, leaving unabsorbed sugar in your small intestines," Copeland says.

Fluid is then drawn into the gut from the bloodstream, causing distention or bloating and gurgling in the abdomen. Eventually, the sugar moves to the colon, where bacteria ferment it, causing gas or diarrhea.

How you can protect yourself

Medhurst suggests eating foods in their most whole form when trying to lower your sugar intake.

Take oatmeal, for instance. The whole form of oatmeal is steel-cut oats. Because these oats are the least processed, they contain the highest amount of fiber and the least sugar.

By contrast, one-minute oats or instant oatmeal—more processed than regular oatmeal—contain a lot of sugar and less fiber.

"Always think of your body as the processor," Medhurst says. "You want your body—not the place making the food—to be the one processing your food as much as possible."

 

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