Scope: This review represents a focus on the structure and properties of the common nutritional disaccharides (lactose, maltose, and sucrose) in health and disease. The aim is to provide a comprehensive reference source related to the role of disaccharides in human nutrition. Methods and results: Key reference sources are searched, including Web of Science, PubMed, Science Direct, and Wiley Online, and key reference works are selected to support the factual basis of the text where interpretations and relevance of the works are discussed in the review. There are key nutritional health benefits of receiving dietary energy in the form of sugars, but equally life-threatening issues exist associated with constant/excess consumption. These issues are discussed together with genetic disorders, which impact upon health associated with consumption of the disaccharides (e.g., specific disaccharide intolerance due to deficiency of relevant digestive enzymes). Conclusions: As the three common dietary disaccharides (lactose, maltose, and sucrose) are consumed on a very regular basis in the human diet, it is critical to understand insofar as possible their role in health and disease. This review provides an insight into the structure and properties of these molecules in health and disease.