ADM’s Naghibi says psychobiotics grew fast, but “mechanisms” still aren’t pinned down

The microbiome used to get sniggered at in seminar rooms. Now ADM executives say the field has accelerated fast, even as they admit the “mechanisms of action” are still not fully understood.

That tension sits at the heart of this story. New Scientist reports that Professor Phil Burnet of the University of Oxford described a time when researchers working on “microbial neuroscience” faced ridicule about 15 years ago, but the pace has changed. Today, microbiome-based interventions are moving through human studies, including approaches that use live beneficial microbes (probiotics), microbe food (prebiotics), and heat-treated or otherwise inactivated microbes (postbiotics). And ADM’s Richard Day, V.P. Medical Affairs and Clinical Development within R&D, explicitly frames where the industry is stuck: “We’re still on that journey to unpick the mechanisms of action,” he says, while also noting the “gut-brain circuit” provides a pathway that researchers can test.

So what is the gut-brain circuit, and why should executives care beyond the science-sci-fi vibe? The source connects three things that matter for mental health research and product strategy: the enteric nervous system, the vagus nerve, and multiple biological pathways that can connect the gut to the brain. The enteric nervous system, which operates digestion, contains an estimated 500 million neurons in humans, more than double the number in the spinal cord. It runs autonomously, but it also sends and receives signals with the brain via the vagus nerve.

That is one route. The source also lays out others: microbes can affect mental health via metabolites that pass into the blood and cross the blood-brain barrier, via gut hormones, and via the immune system. Day also warns against a simplistic single-cause narrative: he says the microbiome is “endlessly complicated,” and that there is likely more than one mechanism behind clinical effects. For a boardroom, that matters because it shapes how you think about clinical endpoints, how durable effects might be, and what kind of regulatory story you can tell if you ever move from “supports wellbeing” toward therapeutic claims.

The field has also moved beyond just correlational studies. The source notes that associations between gut microbiome composition and mood disorders have shown up in research, but now scientists are running experimental interventions to test causality. It cites a mechanistic study led by the University of Oxford where participants receiving a probiotic showed measurable effects on cognitive and emotional processing. It also points to clinical work in diagnosed populations, including a 2023 study by researchers at King’s College London and ADM in JAMA Psychiatry exploring the effects of a probiotic in people with major depression.

Meanwhile, the “two-way street” point is not just academically cute. It describes how mental health can affect digestive health and vice versa. Irritable bowel syndrome (IBS) has an established relationship with anxiety, and research is actively exploring that connection. The source provides a concrete example: ADM’s researchers gave adults with IBS either a live or a heat-treated strain of gut bacteria, and both produced similar results in patients. That finding is a clue for two reasons. First, it suggests the effects may not require the microbes to live. Second, it nudges attention toward what inactive microbes or their components can do, which is where postbiotics come in.

This brings us to the “new kid on the block” described in the source. Postbiotics are preparations of microbes inactivated by heat or other methods. Unlike probiotics (live microbes) or prebiotics (microbe nutrients), postbiotics can include cell fragments and metabolites created by microbes. ADM scientists, the source says, have shown that heat-treated bacteria can produce similar effects to live ones in people with IBS. The source also says some postbiotics effects can be rapid, with a recent study of postbiotics and the gut-brain axis noting physiological changes within an hour of administration. And it adds a practical commercial clue: findings from other trials suggest effects wear off when participants stop taking them.

That “wears off” detail has strategic implications for product development and clinical design. If postbiotics effects are temporary rather than permanent, then companies may need recurring dosing, which affects pricing, patient adherence, and how outcomes are measured over time. The source also says much more research is needed on mechanisms, reinforcing Day’s caution that the field is still figuring out what exactly drives clinical outcomes.

Where does this land for investors, founders, and executives deciding what to back? The source frames the current wave as a proliferation of mostly small but rigorous clinical trials testing microbiome impacts on depression and anxiety, bipolar disorder, obsessive-compulsive disorder (OCD), attention-deficit hyperactivity disorder (ADHD), and stress. It also mentions early research looking at a potential role in Alzheimer’s disease. The catch is scale and duration. What’s needed now, per the source, are larger studies over longer periods to show how robust impacts really are.

Naghibi, Head of Clinical Development at ADM, describes this moment as an “explosion of research” and also the excitement of being early in the process. But the regulatory and clinical translation challenge is visible in the same line. If the mechanism is not pinned down, it becomes harder to define what a regulator would consider a strong, consistent causal pathway. That is why this story is less about one breakthrough miracle and more about an entire category moving from plausibility to proof.

For decision-makers, the strategic stake is simple: timing. If your company is building in psychobiotics or adjacent spaces, the opportunity is widening, but the evidence requirements are tightening. Boards will want to track not just whether studies show effects, but whether they hold up in larger, longer trials, whether live and heat-treated versions behave similarly, and whether rapid physiological changes translate into durable clinical outcomes. In a field where the seminar-room sniggering has faded, the next proving ground is credibility. And credibility, in healthcare, is earned one mechanism at a time.