Calcium is an essential nutrient required for numerous biological functions. Studies have demonstrated an association between low calcium intake and chronic diseases, including osteoporosis, colon cancer, hypertension and obesity. However, most of the Brazilian population has calcium intake below recommended. This review focuses on the endogenous factors (age and hormonal status) and exogenous (phytates, oxalates, sodium, bioactive compounds and vitamin D) that influence the absorption of calcium, as well as the major methodologies used to evaluate the absorption and bioavailability. It talks about the possible factors for low calcium intake: 1) Food habits - substitution of milk for drinks with low calcium content as soda, eating away from home and skipping meals like breakfast; 2) High cost of food sources of calcium. Additionally, this article discusses strategies to optimize calcium intake, which include: 1) Increasing knowledge about the importance of calcium intake for health and major food sources; 2) Increase the availability of foods fortified with calcium; 3) Supplement use in specific groups - when and how to administer calcium salts.