Eating Probiotic Yogurt for Eight Weeks Physically Grows the Hippocampus in Human Brains
"After 8 weeks of these small sachets a day, that the women who got the real stuff, they had an increase in the volume of their hippocampus. It actually grew. This is what we saw after 8 weeks of them consuming this. We didn't see that happen in the placebo group."
About this episode
In this groundbreaking episode, host Jonathan Wolff speaks with Professor Felice Jacka, founder of nutritional psychiatry, and ZOE co-founder Professor Tim Spector about the powerful links between diet, gut microbiome, and mental health. Jacka reveals that her landmark SMILES trial achieved full depression remission in one-third of severely ill patients through dietary intervention alone, outperforming typical antidepressant outcomes. She also presents new research showing that consuming probiotic yogurt for just eight weeks measurably increased hippocampus volume in healthy women. Perhaps most strikingly, the professors discuss research demonstrating that fecal transplants from humans with depression or schizophrenia can induce similar behavioral symptoms in mice, suggesting gut microbes may causally drive mental illness. An umbrella review of over 10 million people revealed that 70% of major health outcomes, including depression, anxiety, heart disease, and death, are linked to ultra-processed food consumption. The experts explain that poor diet triggers inflammation and disrupts gut microbes that produce critical brain chemicals like butyrate, GABA, and glutathione. Mental disorders now represent the leading cause of disability globally, yet psychiatrists receive virtually no nutrition training. Both professors emphasize that whole grains, legumes, and fermented foods are the most evidence-backed dietary interventions, while emulsifiers in processed foods may damage the gut lining. Surprisingly, they also reveal that shingles and flu vaccines have been shown to reduce dementia risk. The overarching message: the food-mood connection is not about willpower or body weight, but about feeding gut microbes that directly signal the brain, offering a revolutionary, accessible treatment pathway for mental and cognitive health.
Key takeaways
- Professor Felice Jacka's SMILES trial achieved full depression remission in 33% of severely ill patients through diet alone, compared to 8% with social support, exceeding typical antidepressant effect sizes.
- Fecal transplants from humans with depression or schizophrenia can induce similar behavioral symptoms in mice, demonstrating gut microbes may causally drive mental illness rather than just correlating with it.
- Consuming 130ml of probiotic yogurt daily for eight weeks measurably increased hippocampus volume in healthy women, the brain region critical for memory and mood that typically shrinks with age and depression.
- An umbrella review of over 10 million people found 70% of major health outcomes, including death, heart disease, diabetes, depression, and anxiety, are linked to higher ultra-processed food consumption.
- People with serious mental disorders consistently show reduced butyrate-producing gut bacteria, increased lactic acid-producing bacteria, and dysregulated GABA and glutamate pathways, all reflected in their blood and brain chemistry.
- Mental disorders represent the leading cause of disability globally, with depression and anxiety accounting for the majority, yet psychiatrists receive virtually no training in nutrition or metabolic health.
- Shingles and annual flu vaccines have been shown to reduce dementia risk, likely by beneficially stimulating the immune system in ways similar to fermented foods.