How Does Sugar Affect Mood?

To understand the impact of sugar on the brain, consider that the organ constitutes 2 percent of the body’s weight but burns 20 percent of its glucose.

“The brain takes up a huge percentage of blood sugar,” says Emmons. He adds that it relies so heavily on glucose because it can’t make energy from other sources, unlike other parts of the body.

Excess sugar consumption can lead to systemic inflammation anywhere in the body, which also affects how we feel. Inside the brain, systemic inflammation disrupts the ability of neurotransmitters to balance mood, he explains. (Our bodies need inflammation to fight off infection, but too much of it for too long can spur a wide range of illnesses. Learning to manage it effectively is key. See “How Chronic Inflammation Affects Your Health” for more.)

Especially important is the balance between glutamate, an activating neurotransmitter, and gamma-aminobutyric acid (GABA), a calming neurotransmitter. One reason people with sugar-fueled mood disorders often have too much brain activity — a cardinal sign of anxiety — may be because glutamate is driving the bus.

People also crave simple sugars when they are anxious, says nutritional psychiatrist Drew Ramsey, MD. “It’s easy to get into a maladaptive pattern with sugar because it’s so very pleasurable, and in nature, when something tastes sweet, it’s ripe and it’s usually safe,” he says. “And more than anything, our brain wants to feel safe.”

Growing evidence points to depression as an inflammatory disease, says Emmons. “That may be one of the reasons why antidepressants offer relief to so many people — they are in part anti-inflammatory.”

Numerous studies show a connection between high-sugar diets and depression risk. One of the most significant correlations was seen in a 2017 scientific trial. Researchers found that men who ate more than 67 grams of sugar a day were 23 percent more likely to be diagnosed with depression and other mental health challenges after five years than those who ate less than 40 grams a day. The authors suspected inflammation.

Growing evidence points to depression as an inflammatory disease, says Emmons. “That may be one of the reasons why antidepressants offer relief to so many people — they are in part anti-inflammatory.”