Oxalate is considered an antinutrient that renders calcium unavailable for nutritional absorption by humans. Efforts have been made to generate and identify edible plants with decreased levels of this antinutrient. The extent to which a food can be nutritionally improved through genetic alterations in calcium oxalate content, however, has not been determined. The recent identification of near isogenic lines of the forage legume, Medicago truncatula Gaertn. (cv. Jemalong genotype A17), that differ in calcium oxalate content aids in filling this gap in our knowledge. In this study, we use an in vitro dialysis system to show that the decrease in calcium oxalate results in an enhancement in calcium availability. By comparing virtually identical plants a more direct assignment of the calcium availability to the presence or absence of oxalate was made. In addition, this study shows, for the first time, the feasibility of improving plant foods through the genetic manipulation of its oxalate content.