News

Excessive Sugar Intake May Contribute to Aggressive Behavior and ADHD

little girl holding cotton candy

Sally Anscombe / Getty Images

Key Takeaways

  • In a recent study, researchers suggest excessive fructose may lead to a hyperactive foraging response and behavioral disorders.
  • High intake of sugar has put this survival pathway into overdrive, they suggest, contributing to problems like ADHD and bipolar disorder.
  • Sugar in multiple forms has been linked to other health issues as well, particularly heart health, providing even more incentive for cutting back.

In recent commentary published in Evolution and Human Behavior , researchers suggest fructose—a component of sugar and high fructose corn syrup (HFCS)—activates an evolutionary-based pathway that stimulates foraging behavior, a response that could lead to behavioral issues.

This might be good information to keep in mind as many kids and parents alike dig into leftover Halloween candy and begin dreaming of upcoming holiday sweets.

Foraging Instinct on Overdrive

In previous research, attention deficit hyperactivity disorder (ADHD), bipolar disorder, and aggressiveness have been linked to sugar, but the basis of the association has been unclear, according to lead researcher Richard Johnson, MD, from the University of Colorado Anschutz Medical Campus.

Richard Johnson, MD

Occasional stimulation of the foraging response is likely not a problem, in the same way that moments of stress don't have long-term effects on the body. But when there's overload then the issue becomes chronic.

— Richard Johnson, MD

Looking at how high intake of sugar and HFCS is converted into energy, the researchers propose that the foraging response kicks off a chain reaction of:

  • Cravings
  • Impulsivity
  • Risk-taking
  • Aggression

"When these combine, they increase the risk of behavioral challenges," he says. The issue isn't just sugary foods, he adds. High glycemic carbohydrates and salty foods may also be converted to fructose in the body.

"Occasional stimulation of the foraging response is likely not a problem," says Johnson, "in the same way that moments of stress don't have long-term effects on the body. But when there's overload then the issue becomes chronic".

This could lead to desensitization of pleasant responses and potential depression. That often causes people to need more stimulation just to reach their previous baseline. That means more sugar just to get back to "normal."

Metabolic Link

With added sugar in the form of fructose, and particularly HFCS, there isn't just a connection to behavior, says Johnson. He points out that recent studies have suggested there's a link between fructose and the development of metabolic syndrome, a group of risk factors that can increase the likelihood of developing several serious conditions, including heart disease, stroke, and diabetes.

Metabolic syndrome includes five factors:

  • A large waistline
  • Elevated blood sugar levels
  • High blood pressure
  • High triglyceride levels
  • Low levels of HDL cholesterol

A recent research letter in the Journal of the American Medical Association concluded that the rate of metabolic syndrome is rising in all age groups, and as many as half of adults over 60 have the condition. The rate is increasing in younger people the fastest, and researchers noted there's been a 5 percent increase over the past five years among those age 20 to 39.

By Any Name, Just as Sweet

Although the recent study focused on fructose, sugar comes in numerous forms, including dextrose, HFCS, sucrose, galactose, and "natural" versions like agave, molasses, and honey.

The number of names for added sugar is estimated at around 60, which makes it challenging for consumers who are reading labels and trying to keep sugar intake low, says dietitian Vanessa Rissetto, RD.

Also, sugars may be present in products that are surprising, she adds. People may read the labels for sugar on items like breakfast cereal or pasta sauce, but it might also be included in salad dressing, protein bars, bread, frozen pizza, and more.

Building Awareness

Rissetto explains, "Just starting to build awareness of your current consumption is a good first step," she says. "For many people, writing down what they're eating, and understanding what has added sugars and what doesn't can be eye-opening."

Vanessa Risetto, RD

Just starting to build awareness of your current consumption is a good first step. For many people, writing down what they're eating, and understanding what has added sugars and what doesn't can be eye-opening.

— Vanessa Risetto, RD

After becoming aware of sugar intake, some strategies for cutting back include:

  • Eating more whole fruits, since the fiber can slow down sugar effects
  • Considering a low-sugar diet
  • Adding more protein into meals and snacks

The recommendation from the Dietary Guidelines Advisory Committee is that Americans limit sugar intake to 6% of their daily calories. That translates to 20 grams daily for women and 25 grams for men.

What This Means for You

It's easy to lose track of how much sugar you're consuming, especially as colder weather and difficult circumstances make it tempting to reach for our favorite sweet comfort foods. Just be mindful of your and your children's eating habits, pay attention to labels, and do your best to eat treats in moderation.

Was this page helpful?
Article Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johnson RJ, Wilson WL, Bland ST, Lanaspa MA. Fructose and uric acid as drivers of a hyperactive foraging response: A clue to behavioral disorders associated with impulsivity or mania? Evolution and Human Behavior. Published online October 2020:S1090513820301215. doi:10.1016/j.evolhumbehav.2020.09.006

  2. Hirode G, Wong RJ. Trends in the prevalence of metabolic syndrome in the United States, 2011-2016JAMA. 2020;323(24):2526–2528. doi:10.1001/jama.2020.4501

  3. USDA. Scientific Report of the 2020 Dietary Guidelines Advisory Committee. Advisory Report to the Secretary of Agriculture and Secretary of Health and Human Services. First Print: July 2020