Bioactive peptides are peptides released from plant or animal proteins that display biological activity — opioid, immunostimulatory or antihypertensive effects — and they interest the functional-foods sector. Milk proteins yield bioactive peptides especially abundantly — casein phosphopeptides that improve mineral absorption, and beta-casomorphins, for example, while peptides inhibiting peptidyl-dipeptidase A (ACE) occur in various foods and could serve as antihypertensive functional ingredients. They are released during digestion or fermentation, which is why aged cheeses and fermented milks are studied as natural delivery vehicles. Rigorous clinical evidence remains the gatekeeper before health claims reach consumers.