Diets promoting inflammation may slowly lead to depression, anxiety

Foods that promote inflammation appear to contribute to the development over time of depression and anxiety in people with multiple sclerosis (MS), a study that followed patients for 10 years reports.

A pro-inflammatory diet, however, was not linked to fatigue, a common MS symptom.

“If the relationship with depression and anxiety is causal, then the longer-term consumption of anti-inflammatory diets could be recommended to decrease depression and anxiety symptoms in people with MS,” the researchers wrote.

The study, “A pro-inflammatory diet is associated with long-term depression and anxiety levels but not fatigue in people with multiple sclerosis,” was published in Multiple Sclerosis and Related Disorders.

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MS occurs when the immune system attacks and destroys the myelin sheath, a protective coating around nerve cell fibers that helps them transmit signals efficiently. The resulting demyelination leads to nerve fiber degeneration and inflammation, with symptoms affecting both the physical and mental health of MS patients.

Although evidence does not support any specific MS diet, dietary approaches for the disease have been developed that generally aim to provide for the body’s nutritional needs and support a healthy gut microbiome, the collection of intestinal microbes thought to influence the immune system.

“In the general population, mental health disorders have been associated with systemic inflammation, and dietary components are a determining factor of post-prandial [post mealtime] inflammation, both acutely and chronically,” the researchers wrote.

However, “no studies have examined the association between dietary-associated inflammation … [and] depression, anxiety, and fatigue in people with MS, a group known to be at elevated risk of these conditions,” they added.

Scientists, led by those in Australia, looked into the possibility of an association between dietary inflammation and levels of depression, anxiety, and fatigue in people with MS.

They analyzed the dietary intake of 190 adults with a first clinical diagnosis of demyelination, who were diagnosed with MS over the following 10 years. They were recruited from the Ausimmune Study, which is investigating the role of environmental factors in first demyelinating events.

Participants, mainly women (80.5%), had a mean age of 44.5 years at a five-year follow-up. Dietary information was collected by a food frequency questionnaire assessing patients’ customary food choices over the year before a first evaluation (baseline), and across the year before a five- and 10-year follow-up.

Higher depression, anxiety levels at 5 years tied to higher dietary indices

Questionnaires evaluated the frequency with which patients’ consumed particular foods, mixed dishes, and beverages, including alcohol. These data were used to determine an overall dietary inflammatory potential, by calculating the dietary inflammatory index (DII) and the energy-adjusted DII (E-DII).

Higher dietary indices at baseline and at the five-year follow-up were significantly associated with higher levels of depression and anxiety five years later, assessed using the Hospital Depression and Anxiety Scale. Moreover, higher dietary indices related with a worsening of depression and anxiety scores between the five- and 10-year follow-up.

Cumulative E-DII scores also associated with depression and anxiety at the 10-year follow-up. However, DII scores based on diet over the previous 12 months were not associated with outcomes at baseline, “suggesting that a pro-inflammatory diet has a long-term rather than an immediate effect on depression and anxiety,” the researchers wrote.

Mean depression scores among patients with extremely inflammation-promoting diets were 2.23 points higher than those with diets least likely to promote inflammation, the team noted.

The study did not specify what food types or consumption levels associated with higher DII or E-DII scores.

Researchers, however, found no link between dietary inflammation scores and fatigue, assessed using the Fatigue Severity Scale.

“Our findings contribute to the body of evidence that suggests that fatigue in MS is not mediated by food-induced changes in immune function or inflammatory burden,” the researchers added.

The use of disease-modifying treatments (DMTs) was not seen to modify the association between dietary inflammatory indices at the five-year follow-up, or to cause a change in depression and anxiety over the next five years.

“Our findings suggest that it is the long-term accumulation of chronic inflammation mediated by foods that is important, rather than the immediate effect,” the researchers concluded. “Immune system modulation may occur via post-prandial inflammation, altering the composition of gut microbiota, and via systemic inflammation, [and] this may be important in increasing the subsequent risk of anxiety and depression.”