Unlike yield, the plant calcium (Ca) : magnesium (Mg) ratio increases at higher soil Ca : Mg and decreases at lower soil Ca : Mg. Edible plant tissue Ca : Mg at various soil ratios has not been robustly studied. Such studies are appropriate because high Ca : Mg dietary ratios may be associated with increased risk of chronic diseases such as cardiovascular disease and diabetes, and human dietary Ca : Mg ratio is rising as populations integrate more processed foods into traditional diets. This review explores whether increasing the soil Ca : Mg ratio is likely to increase edible plant tissue Ca : Mg ratio, a result that could, if substantial, affect human health.
A literature search gathered published articles reporting Ca and Mg values for plants grown in soils or nutrient solutions with various Ca : Mg ratios. For each study, soil or solution ratio was plotted against plant ratio, and Pearson’s r and 2-tailed P values were calculated. Findings reveal that reporting Ca and Mg content of edible plant tissues is rare in studies assessing the impact of soil Ca : Mg on crop yields, nutrient uptake or crop quality; Ca : Mg of whole plants and most shoots increases as soil Ca : Mg rises; leaf Ca : Mg of some but not all crops increases as soil Ca : Mg rises; Ca : Mg ratios of edible grain, fruit and root tissues are smaller than those of leaves or shoots of the same crop; and Ca : Mg of grain, bean and fruit tissue may not respond to changes in soil Ca : Mg as much as Ca : Mg of plants, shoots and leaves. However, the data are too sparse for conclusions or even speculation. Further measurements of Ca and Mg in edible tissues destined for human consumption are necessary to asses any impact of soil Ca : Mg on the rising dietary Ca : Mg of humans and its health consequences.