Chapter 158
Promoting Mental Health — 6
That exemplifies how other people took initiative to help remedy loneliness and isolation that she was unable to do on her own, leveraging her past contacts, her hobby, and her willingness to relocate to a supportive community. A delightfully vibrant and energized near-centenarian, you wouldn’t think she previously suffered from marked loneliness and isolation.
An aspect of our lives we tend not to talk about much is human touch. A systematic review of being touched by other people in both adults and newborns highlighted its critical importance for mental and physical health. From 137 studies in approximately thirteen thousand individuals, skin-to-skin touch significantly improved sleep, blood pressure, and mobility, while reducing fatigue, anxiety, pain, and depression. Whether it’s a one-off brief hug or handshake or a sixty-minute massage session, human touch appears to be consistently therapeutic, perhaps to an even greater extent among women.
FOOD, MOOD, AND STRESS
When a fecal transplant from a person who is depressed is given to rodents, the animals exhibit behavioral features characteristic of depression. Fecal transplants from young to old mice improve their cognitive performance and memory. We know from imaging the brains of the older mice after these transplants that age-associated inflammation (inflammaging) is reduced and the hippocampus region appears rejuvenated. In healthy human adults, a small randomized, controlled trial of high fiber and reduced processed food for one month lowered perception of stress. The more adherence to that diet, the greater reduction of stress perception score.
The Brunner glands in the small intestine promote the proliferation of Lactobacilli bacteria, which are protective, enhancing immunity. Through vagal nerves, there is a direct connection between these glands and the brain’s amygdala. With chronic stress, the neural circuit between Brunner glands and the brain is inhibited, suppressing the immune response.
Many other observational diet studies have reinforced the relationship between food and mood. The Mediterranean diet and other healthy diets with a low inflammatory index have been associated with less depression and improved mental health compared with unhealthy Western diets. The Mediterranean diet in six large studies showed more than a 30 percent reduction of depression, which was similar to the magnitude of reduction for other healthy diets. In contrast, in two cohort studies, among more than eighty-five thousand participants, a diet with high glycemic index of refined carbohydrates and sugars has been linked to a higher risk of depression. Further, repeated episodes of hypoglycemia have been linked to mood disorders. A systematic review of thirteen studies of vegetarian and vegan diets suggested a mixed effect: they were associated with an increased risk of depression and lower anxiety scores.
There are, of course, many potential confounding factors for evaluating these cohort and cross-sectional studies since the relationship between food and mood is bidirectional. But generally, the theme of avoiding poor diets that induce systemic inflammation, like those high in ultra-processed foods, and favoring diets with a low inflammatory index correlated with better mental health. Once again, the gut microbiome is central in modulating our immune response, so there is an interdependence between stress, immunity, and the gut microbiome. It’s been referred to as the “holy triad” underlying depression.