Bifidobacterium (mixed strains) has a growing body of scientific research investigating its effects on mood and mood swings, primarily through its role in the gut-brain axis. Human and animal studies suggest that certain strains of Bifidobacterium can influence neurotransmitter production, inflammation, and stress response, all of which are relevant to mood regulation. For example, randomized controlled trials have shown that supplementation with Bifidobacterium longum NCC3001 improved depression scores and reduced anxiety in patients with irritable bowel syndrome. Other studies have indicated that some Bifidobacterium-containing probiotics can reduce psychological distress and improve subjective well-being in healthy individuals.

However, the evidence is still limited, with relatively few large-scale, high-quality studies specifically addressing mood swings (as opposed to general mood or depression/anxiety). The strains used, dosages, and populations studied vary widely, making it difficult to provide clear recommendations. While the mechanistic rationale is strong—given the role of gut microbiota in modulating inflammation, stress hormones, and even neurotransmitter synthesis—clinical validation for the use of mixed Bifidobacterium specifically for mood swings is moderate at best.

In summary, there is some scientific evidence supporting the use of Bifidobacterium (mixed) for mood-related symptoms, but it is not robust or specific enough to warrant a higher evidence score at this time.