Spinach plants were grown in different levels of nitrate in the soil to see how much nitrate they absorbed. Three types of spinach leaves were tested: savoyed, semisavoyed, and smooth. Each type absorbed nitrate differently. The critical nitrate levels in the leaves were found to be 0.17%, 0.15%, and 0.045% of their dry weight for the different types of spinach. Even if someone eats a lot of spinach, it is unlikely to harm their health.