As part of a meal, potatoes are primarily seen as a source of energy in the form of starch, although they also contribute fibre, proteins with a good amino acid balance, minerals, particularly potassium, vitamins, particularly B vitamins and vitamin C, and antioxidants. They can replace wheat and rice in meals and hence have a role as a food security crop. When potatoes form most of the diet, they need to provide nutritionally balanced meals, for which increased amounts of micronutrients are desirable, with a current emphasis on iron and zinc biofortification. The chemical composition of potatoes is affected by storage, cooking and processing. Furthermore, the bioavailability of ingested nutrients for utilization by the body needs to be determined in vivo using human subjects, although there are some in vitro proxies. Only then can one assess the contributions of potatoes to a healthy diet. Other nutritional issues are the need to reduce the glycaemic index of potatoes and the production of acrylamide in fried and roasted products. Finally, their relatively low requirement for land is one reason potatoes could contribute more to feeding the world and why they have often been the staple food of the poor.