New U.S. research suggests that if you suffer from depression, which can be particularly common during the darker winter months, then avoiding sugary foods could help to ease symptoms.
Carried out by a team of psychologists at the University of Kansas, the new study looked at previous research on the physiological and psychological effects of consuming added sugar and included data taken from the Women's Health Initiative Observational Study, which has recruited 161,808 women since its launch in 1993, and the NIH-AARP Diet and Health Study, which has a total of 567,169 participants.
The findings, published online in the journal Medical Hypotheses, suggested that eating sugary foods, which are particularly common at this time of year as we gear up for the holiday season, may cause some of the metabolic, inflammatory and neurobiological processes that are linked to depression.
This combination of high sugar consumption, darker days and the change in sleep habits associated with winter could together have a negative effect on mental health, say the researchers.
"For many people, reduced sunlight exposure during the winter will throw off circadian rhythms, disrupting healthy sleep and pushing five to 10 percent of the population into a full-blown episode of clinical depression," said co-author Stephen Ilardi.
Ilardi added that experiencing these symptoms of "winter-onset depression" can cause sufferers to crave sugar, which gives a temporary boost in mood, but in fact, can then make symptoms worse.
"One common characteristic of winter-onset depression is craving sugar," he said. "So, we've got up to 30 percent of the population suffering from at least some symptoms of winter-onset depression, causing them to crave carbs -- and now they're constantly confronted with holiday sweets."
"When we consume sweets, they act like a drug," said Ilardi. "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."
According to the team, sugar could not only increase inflammation, which is linked to depression, but also affect the gut microbiome. Some of the parasitic microbes that live in our gut thrive on sugar, explained Ilardi.
"They can produce chemicals that push the brain into a state of anxiety and stress and depression. They're also highly inflammatory."
Ilardi also warned against drinking too much alcohol, which is also packed with sugar.
"We have pretty good evidence that one alcoholic drink a day is safe, and it might have a beneficial effect for some people," he said. "Alcohol is basically pure calories, pure energy, non-nutritive and super toxic at high doses. Sugars are very similar. We're learning when it comes to depression, people who optimize their diet should provide all the nutrients the brain needs and mostly avoid these potential toxins."
Ilardi recommends a diet low in processed food and high in plant-based ones, as well as rich in omega-3 fatty acids.
As for sugar, he says to keep it to a minimum all year-round as well as during the holidays.