Based on established dietary reference intakes (DRIs) (e.g. estimated average requirements, recommended dietary allowances (RDAs), and reference nutrient intakes), magnesium (Mg) deficiency in the range 50–99% of the requirement commonly occurs throughout the world. Yet, Mg is not often considered a major nutrient of concern for health and wellbeing, although deficient intakes and serum concentrations have been associated with numerous pathological conditions including atherosclerosis, diabetes, osteoporosis and some cancers. Probable reasons for this dichotomy are that evidence of Mg deficiency is not consistently found in pathological conditions with which it has been associated, and not all individuals considered Mg-deficient consistently exhibit these pathological conditions. These inconsistencies could be the outcome of chronic inflammatory stress exacerbated or induced by Mg deficiency being alleviated or prevented by other factors that have anti-inflammatory action (e.g. long-chain n-3 fatty acids). Questionable DRIs resulting in the incorrect conclusion that individuals are Mg-deficient when they are not also may be responsible for the inconsistencies. Since 1997, improved balance data have been reported for the determination of DRIs, which suggest that the RDA for a 70-kg healthy adult would be ∼250 mg day^–1. Based on the finding that neutral Mg balance was determined to be 2.36 mg day^–1 kg^–1 bodyweight, the RDA would vary by bodyweight. Even with changed DRIs, a significant number of adults who do not eat recommended amounts of foods of plant origin would not achieve the suggested adequate intake of Mg. Foods of plant origin, including green vegetables, nuts, pulses and whole grains, are good sources of Mg. However, Mg in these foods can be influenced by the availability of Mg to plants from the soil, and plant genotype. Thus, crop breeding and cultural practices, through modifying the amount of Mg in plant-origin foods, can have a significant impact on achieving an adequate dietary intake of Mg for health.