Nutritional Psychiatry Researcher Felice Jacka Addresses the Impact of Ultra-Processed Foods on Brain Health

Felice Jacka, a prominent researcher in the field of nutritional psychiatry, is shedding light on the link between our dietary choices, particularly the consumption of ultra-processed foods, and its profound impact on our mental and brain health. Jacka, who serves as the co-director of Deakin University's Food & Mood Centre in Australia and as the president of the International Society for Nutritional Psychiatry Research, recently discussed her findings and insights in an interview with The Observer.

Felice Jacka: ‘It is very difficult for individuals to make healthy choices.’ 

Photograph: Paul Hermes/Food & Mood Centre, Deakin University

Traditionally, we've considered food's influence on our health from a physical standpoint, focusing on its effects from the mouth down. However, an emerging understanding of the gut microbiome's role has shifted this perspective significantly. Our gut microbiome, comprised of trillions of microorganisms, influences various aspects of our health. It impacts metabolism, blood glucose levels, body weight, gene expression, serotonin production in the brain, stress response systems, and immune function. Given these profound connections to our overall health, including our mental and brain health, dietary choices become of paramount importance.

Ultra-processed foods, in particular, are coming under scrutiny due to their unique role in our health. Although science is still unraveling the full extent of their impact, initial studies have raised concerns. For instance, research has revealed that when individuals who typically maintain a healthy diet temporarily shift to a western junk food diet, cognitive functions within the hippocampus—the area of the brain responsible for memory and learning—deteriorate. Moreover, individuals with less healthy diets tend to exhibit smaller hippocampi, while those with healthier diets boast larger ones.

The flexibility of the hippocampus, able to both grow and shrink, underscores its crucial importance in mental health. A smaller hippocampus is frequently associated with severe depressive illness, and conversely, when depression lifts, the hippocampus regrows. Thus, the hippocampus plays a central role in mental well-being, learning, and memory. Therefore, preserving its health is imperative for maintaining cognitive function as we age.

Jacka's research delves into the reasons behind how ultra-processed foods can affect our brains. A recent study she conducted compared the impact of an ultra-processed food diet with a wholefood, low-calorie diet on the gut microbiome. Her hypothesis is that the human body and gut microbes do not process ultra-processed foods in the same way they process whole foods, even if the former is fortified with vitamins, minerals, and protein. However, further scientific evidence is required to substantiate this claim conclusively.

One of the prevailing misconceptions regarding ultra-processed foods is their potential health benefits, often associated with their fiber and vitamin content. The reality, according to Jacka, is that the broader context is what matters most. The global industrialized food system, responsible for producing ultra-processed foods, is a leading cause of illness and premature death worldwide. The impact on human health alone amounts to approximately $11 trillion annually, affecting people's well-being with issues such as heart disease, high blood pressure, and cancer. Moreover, the environment sustains approximately $7 trillion worth of damage due to this industrialized food system, which results in biodiversity loss and significantly contributes to the ongoing climate crisis.

The heart of the issue lies in the accessibility and affordability of ultra-processed foods, often the cheapest option for many individuals. This challenge is primarily a consequence of government policies that fail to prioritize public health and sustainable food choices.

Jacka's research has extended beyond the realm of personal health into the arena of neurodevelopmental disorders. Observations have indicated a correlation between the dietary choices of mothers and their children's ADHD symptoms and diagnoses. Although this evidence is observational, it aligns with animal studies and emerging research that underscores the influence of the gut microbiome on brain development during the prenatal and early infancy stages. The unhealthy Western diet, coupled with antibiotic exposure and loss of biodiversity from dietary choices, might be contributing to the rising incidence of neurodevelopmental disorders and mental health problems.

In the ongoing discourse surrounding ultra-processed foods, some researchers have raised concerns about the term itself, citing its lack of a precise definition and broad classification. While the complexity of food and its impact on culture, emotional health, and various other aspects of life naturally results in some ambiguity, industries have a vested interest in sowing confusion. Just as the tobacco industry once obscured the link between smoking and lung cancer by emphasizing that correlation does not imply causation, the food industry is now engaging in similar tactics. The discussions around food classification systems, such as the Nova classification, should not be solely driven by industry agendas, but rather, guided by sound scientific evidence and public health concerns.