Visitor Questions

Kale is among a small number of foods that contain measurable amounts of oxalates, naturally occurring 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 kale. Laboratory studies have shown that oxalates may also interfere with absorption of calcium from the body. Yet, in every peer-reviewed research study we’ve seen, the ability of oxalates to lower calcium absorption is relatively small and definitely does not outweigh the ability of oxalate-containing foods to contribute calcium to the meal plan. If your digestive tract is healthy, and you do a good job of chewing and relaxing while you enjoy your meals, you will get significant benefits — including absorption of calcium—from calcium-rich foods plant foods that also contain oxalic acid. Ordinarily, a healthcare practitioner would not discourage a person focused on ensuring that they are meeting their calcium requirements from eating these nutrient-rich foods because of their oxalate content. For more on this subject, please see “Can you tell me what oxalates are and in which foods they can be found?’ via this URL:

As long as you do not have any kidney concerns then you should be able to eat kale on a regular basis. While kale is super nutritious and a vegetable we recommend you eat on a consistent basis several times a week, we would encourage you to eat a wide variety of cruciferous vegetables to improve your nutrient intake and lower your disease risk. We typically don’t recommend that you concentrate on one specific food on a daily basis, but rather mix up the variety to improve your health. Here is some background information on cruciferous vegetables.

Most of the research on dietary intake of cruciferous vegetables and their physiological benefits has focused on intake of glucosinolates from this food group. For total glucosinolates, we’ve seen reliable estimates that cover a wide range of daily intake values. At the lower end of this range, we’ve seen studies in which individuals average only 6 milligrams of total glucosinolates from cruciferous vegetables each day. At the higher end of the range, we’ve seen studies showing an average of about 50 milligrams. Health benefits have been seen across this wide range of glucosinolate intake levels. Depending on the specific cruciferous vegetables in question and the method of preparation, we’re talking about daily cruciferous vegetable intake levels beginning at approximately one-half cup and ranging upward to approximately 2 cups as being necessary to provide these glucosinolate intake levels. At the lower end of this range, it would be possible for a person to consume a moderate amount of cruciferous vegetables 2-3 times per week and come out with a one-half cup per day average. At the higher end of the range, it would take more like 4-5 servings per week to reach the glucosinolate levels involved. Yet, that’s really not that much if you think about it; it’s just including one serving of cruciferous vegetables almost every day. For persons who enjoy the textures, aromas, and flavors of cruciferous vegetables, foods in this unique group can usually be enjoyed on a daily basis. For individuals who aren’t as fond of foods in this group, working them into the diet 2-3 days per week would still be highly recommended in most cases.