New research continues to make the case for sugar’s role in depression.
University of Kansas clinical psychologists theorize in the journal Medical Hypotheses that added dietary sugars can create a depressogenic effect by sparking the metabolic, inflammatory, and neurobiological processes tied to depression.
“When we consume sweets, they act like a drug,” explains study coauthor Stephen Ilardi, PhD. “They have an immediate mood-elevating effect, but in high doses they can also have a paradoxical, pernicious longer-term consequence of making mood worse, reducing well-being, elevating inflammation, and causing weight gain.”
And because added sugars lack nutritional benefits, Ilardi and his coauthors note, the “depressogenic processes can be affected both by the relative absence of key nutrients and by the excessive presence of harmful foods.”
The team analyzed a wide range of research on the physiological and psychological effects of added sugar consumption, including the 69,954-participant, three-year Women’s Health Initiative Observational Study; the 263,923-person NIH–AARP Diet and Health Study; and other large-scale international trials.
Researchers identified these depressogenic effects of added sugars:
1. Bodywide inflammation, which has been recognized as a “potent physiological trigger of depression.” It also leads to fatigue and sleep disruption, which contribute to poor mental health.
“A large subset of people with depression have high levels of systemic inflammation,” says Ilardi, author of The Depression Cure. “When we think about inflammatory disease, we think about things like diabetes and rheumatoid arthritis — diseases with a high level of systemic inflammation. We don’t normally think about depression being in that category, but it turns out that it really is.
“Inflammatory hormones can directly push the brain into a state of severe depression. So, an inflamed brain is typically a depressed brain.”
2. Microbiome disruption that can lead to gut dysbiosis, an overgrowth of harmful bacteria that’s been linked to depression and other psychological pathologies.
“Our bodies host over 10 trillion microbes, and many of them know how to hack into the brain,” Ilardi explains. “The symbiotic microbial species — the beneficial microbes —basically hack the brain to enhance our well-being. They want us to thrive so they can thrive.
“But there are also some opportunistic species that can be thought of as more purely parasitic — they don’t have our best interests in mind at all. Many of those parasitic microbes thrive on added sugars, and they can produce chemicals that push the brain [into] a state of anxiety and stress and depression.”
3. Insulin resistance that can reduce production of the energizing hormone needed to fuel the brain.
4. Other effects may include dopamine dysregulation, oxidative stress, and the production of advanced glycation end-products, or AGEs, toxic byproducts of sugar metabolism.
(For more on the dangers of added sugars, see “Sugar Shock”.)
By the Numbers
16.2 million: Number of American adults who report at least one major depressive episode in a given year, according to the National Institute of Mental Health.
18: Teaspoons of added sugar Americans eat daily, accounting for 14 percent of total calories ingested.
75%: Percentage of packaged foods that include added sugars. Soda and other sugary beverages are the single leading source.