Between shopping for gifts and finishing up year-end projects at work (not to mention booking all your holiday-travel arrangements), this time of year can be unbearably stressful. And for those who struggle with depression, the holidays are especially challenging for mental health. Luckily there’s one simple guideline that can help keep your brain healthy: skip the sweets, according to new research published in the journal Medical Hypotheses. Added sugar found in cookies and candy (and lots of other foods) can alter the body’s metabolism and trigger inflammatory responses that contribute to depression, the study suggests.
To study how sugar affects mental health, the University of Kansas researchers conducted a meta-analysis of several existing diet studies. These included the Women’s Health Initiative Observational Study, which followed over 69,000 American women over a three-year period; the NIH-AARP Diet and Health Study; and a study that tracked the dietary habits of over 15,000 Spanish college graduates. In all three of these large studies, the researchers found a link between high added sugar intake and later diagnoses of depression. The correlation also appeared in several cross-sectional population studies in countries across the globe, as well as animal studies involving rats that where fed a high-sugar diet.
Although sugar has the same effect on the body all year, it’s especially potent around the holidays because of other contributing factors. Less daylight disrupts the body’s sleep patterns, which causes winter onset depression in “5 to 10 percent of the population,” study author Stephen Iliardi said in a KU blog post. Winter-onset depression can increase cravings for sweets, which are easy to find this time of year. Some seek out the sweets because they initially produce a mood lift.
“When we consume sweets, they act like a drug,” said Iliardi. “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.”
The researchers found that inflammation, one of the main detriments sugar has on the body, can also play a negative role in mental health. Roughly half of those diagnosed with depression also show high levels of systemic inflammation, Iliardi said. Based on the data they analyzed, the researchers make a strong case that inflammation can trigger depressive symptoms in the brain. And eating more sugar can cause that inflammation, or make it worse.
“Inflammatory hormones can directly push the brain into a state of severe depression,” he said. “Sugars have a pro-inflammatory effect on the body and brain.”
Sugar also wreaks havoc on the body’s microbiome. Iliardi notes that the human body contains 10 trillion microbes, and many of them have a strong effect on the brain. Normally, these beneficial microbes help the body stay healthy. But consuming more sugar can support the growth of harmful bacteria that can have wide-ranging physical and psychological consequences.
“Many of those parasitic microbes thrive on added sugars,” said Iliardi, “and they can produce chemicals that push the brain in a state of anxiety and stress and depression.”
The comprehensive new study is one more piece of evidence pointing to the harm that processed sugar can do. Iliardi even suggested that above a certain level, added sugar should be viewed like alcohol—toxic in high doses, according to the KU blog. Consider that before reaching for an extra gingerbread man.
So how can you keep your brain and body healthy this holiday season? Ilardi recommends sticking with minimally processed foods, and ones that are plant-based and rich in Omega-3 fatty acids. When it comes to sugar, he says that the American Heart Association guideline of 25 grams of added sugars per day is a good rule to follow for most people.
Of course, this doesn’t just apply to holiday sweets. It’s good advice year-round.
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