What Too Much Sugar Does to Your Brain

Americans get more than half of their daily calories from ultraprocessed foods, such as packaged snacks, sweet drinks and desserts. These products are tasty and easy, but they’re also packed with added sugars. Added sugars are mixed in when food is prepared, unlike sugars found naturally in foods like fruit.

According to the U.S. Centers for Disease Control and Prevention, the average adult eats 15 to 19 teaspoons of added sugar each day. The recommended limit is about 12 teaspoons. Many health experts think those numbers should be even lower: The American Heart Association suggests a limit of 9 teaspoons of added sugar per day for men and 6 teaspoons for women. For context, one can of soda has about 10 teaspoons of added sugar.

The bittersweet reality of a diet packed with sugar: It's bad for your brain. Too much added sugar can raise your risk of cognitive impairment, according to a research review of 77 studies published in Nutrients in 2024. 

Adults who consumed the most sugar had a higher risk of developing dementia than those who consumed the least in a study of more than 210,000 people published in BMC Medicine in 2024. A high intake of sugar can trigger inflammation and oxidative stress in the brain, both of which can harm cognitive health, the researchers noted.

A high sugar intake can also affect your mood and mental health, possibly by disrupting the typical balance of neurotransmitters, chemicals that nerve cells use to communicate with each other. For a study published in BMC Psychiatry in 2024, researchers analyzed data from 18,439 adults, more than half of whom were age 45 or older. The results: Those who consumed the most sugar were more likely to suffer from depression than those who consumed the least.

Overindulging in sweets may even speed up the aging process. In a study of 342 middle-aged women published in JAMA Network Open in 2024, researchers analyzed diets and saliva samples to calculate the women’s epigenetic ages, a measure of how quickly their cells were aging. Those with the highest sugar consumption showed signs of being biologically older than their actual ages.​

Women who followed a Mediterranean diet, meanwhile, had epigenetic ages that were younger than their actual ages.

In its report “Brain Food,” AARP’s Global Council on Brain Health suggests you do more cooking at home, because this gives you more control over the sugar, fat and salt content in your diet than you have when you frequently buy and eat prepared meals or order from restaurants. Staying Sharp’s 7-Day Mediterranean Diet Meal Plan for Beginners is a great place to start. 

When you do reach for packaged food, check the nutrition facts label, which tells you how many grams of added sugars are in a serving as well as the “% Daily Value.” A food with a daily value of 20% or more is considered high in added sugars, according to the Office of Disease Prevention and Health Promotion.