Bifidobacterium longum

Tier 2 — promising · Gut · Immunity · Mood-gut axis

Helps reduce stress through the gut-brain connection. A 2024 review of 16 trials found the 1714 strain significantly reduces perceived stress and the morning cortisol spike. Also improves gut barrier health. A great example of how gut bacteria influence your brain and mood. Very safe with no serious side effects. Strain-specific evidence is strongest.

Dose: 1–10 billion CFU/day; strain-specific evidence (1714 for stress, BB536 for immunity)