Gut flora and mental health are connected

There is growing evidence that a healthy gut promotes mental health, according to scientists at a conference on food and the brain in London on October 11-12.

Researchers were not yet at the stage where they could recommend particular probiotic strains to deliver mental health benefits. But the close inter-relationship between the gastrointestinal and the nervous system was the subject of an increasing number of studies, said clinical nutritionist Michael Ash.

He added: “Increasingly, psychiatric disease is being linked to the immune system [the gut serving as the first line of defence]. Trauma, gut infection and loss of immune tolerance can lead to psychological problems. Immune responses alter neural and endocrine function and, in turn, neural and endocrine activity modifies immunologic function.”

Some studies, notably a paper in the European Journal of Clinical Nutrition last year by David Benton at the University of Wales, showed consuming foods containing probiotics improved some subjects’ mood, said Ash. Probiotics could also boost an important protein associated with mental health called ‘brain-derived neurotrophic factor’ or BDNF, he said. “The beneficial effects of probiotics on systemic inflammatory cytokines [small chemical messengers between cells] and oxidative stress may ultimately lead to increased BDNF.”

Innate immune cytokines had also been “shown to influence virtually every pathophysical domain relevant to depression”, suggesting probiotics might in future be used with standard therapies for major depressive disorders.

He added: “We must keep our enteric bacteria happy. At the moment it seems like we’re not doing a very good job given that allergic and autoimmune diseases, including those that affect the gastrointestinal tract, are on the increase.”