I thought I would share some research Ive been doing regarding the common thought that spinach and kale should not be fed due to their oxalic acid content. The theory is that since these two greens (and others like them) are high in oxalic acid, they should not be fed, or at least fed very sparingly. Essentially, oxalic acid is present in many foods, and when digestion occurs, it can join with calcium to form calcium oxalate, which is not absorbed and just passes out of the body. Just to clarify, this does not ever draw out calcium from the body or cause a depletion, but rather only binds with free calcium in the gut at the same time.
However, there are two things here to keep in mind when making this decision. First, you are talking about two of the healthiest greens we know about. While they do have oxalic acid, its important to keep in mind that there are a number of other nutrients in these greens that are incredibly beneficial. For instance, spinach also has a high amount of magnesium in it, which actually aids in calcium absorption. Kale is high in Vitamin A and C, something in short supply for insectivores. And these are just a couple examples amongst many. Second, the oxalic acid does not bind calcium fully or even that much in many cases. The amount of calcium that is bound by oxalic acid in kale is usually only around 25-40%. Since there is a high amount of calcium in this green, that still means your dragon will be getting a good amount from the remaining 60-75% available calcium. Spinach seems to have more formation of oxalates, but even with spinach, the bioavailability of calcium is around 30-50%. Also, there is great variability in the oxalic acid content depending on how the plant was grown. Studies have shown that plants grown in high ammonia soils have much less oxalic acid content. Phosphorous levels also influence oxalic acid content. In other words, none of these supposedly high oxalate greens come out in the negative category regarding calcium bioavailability, they just dont come out quite as great as you might think from looking at straight content.
So the moral of the story is keep feeding that kale and even spinach, but just make sure its in rotation with other greens and vegetables. As always, the better the variety you feed, the less likely there are to be nutritional deficiencies for your dragon.
However, there are two things here to keep in mind when making this decision. First, you are talking about two of the healthiest greens we know about. While they do have oxalic acid, its important to keep in mind that there are a number of other nutrients in these greens that are incredibly beneficial. For instance, spinach also has a high amount of magnesium in it, which actually aids in calcium absorption. Kale is high in Vitamin A and C, something in short supply for insectivores. And these are just a couple examples amongst many. Second, the oxalic acid does not bind calcium fully or even that much in many cases. The amount of calcium that is bound by oxalic acid in kale is usually only around 25-40%. Since there is a high amount of calcium in this green, that still means your dragon will be getting a good amount from the remaining 60-75% available calcium. Spinach seems to have more formation of oxalates, but even with spinach, the bioavailability of calcium is around 30-50%. Also, there is great variability in the oxalic acid content depending on how the plant was grown. Studies have shown that plants grown in high ammonia soils have much less oxalic acid content. Phosphorous levels also influence oxalic acid content. In other words, none of these supposedly high oxalate greens come out in the negative category regarding calcium bioavailability, they just dont come out quite as great as you might think from looking at straight content.
So the moral of the story is keep feeding that kale and even spinach, but just make sure its in rotation with other greens and vegetables. As always, the better the variety you feed, the less likely there are to be nutritional deficiencies for your dragon.
