Probiotics are live microorganisms that, when consumed, can provide health benefits, generally by improving or restoring the gut flora. As probiotics have become increasingly popular in recent years, it is important for consumers and clinicians to understand the details of the potential health effects of these supplements. Chapter 1 focuses on the relationship between different types of milk, the growth of probiotics, and relevant characteristics regarding viability, the quality of the dairy product, and the production of undesirable components. Chapter 2 summarizes studies on the probiotic impact of functional foods on the immune system and analyzes the future of the probiotic functional food market. Chapter 3 describes pathways and mechanisms through which probiotics may improve hypothyroidism and its complications. Chapter 4 presents a literature review of intestinal microbiota and bone health and discusses the effectiveness of probiotics in the treatment and prevention of osteoporosis. Chapter 5 presents an FTIR analysis of protein/peptide-based biopolymers used for probiotic encapsulation. Lastly, Chapter 6 collates experimental studies on probiotics with ameliorative effects on arsenic toxicity.