The peels of lemons and limes are among a small number of foods that contain measurable amounts of oxalates, naturallyoccurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating lemon or lime peels. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peerreviewed research study weve seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalatecontaining foods to contribute calcium to the meal plan.