Cabbage family vegetables (such as kale, collards and spinach) contain Goitrogens, compounds (isothiocyanates) that block the utilization of iodine by the thyroid. This interferes with thyroid hormone production if consumed in large amounts (more than 4 servings per week) or if they are consumed raw. Cooking helps to inactivate these compounds. If you have an existing iodine deficiency, extra iodine can be sourced from kelp and seaweeds and iodized salt. But if you have hypothyroidism symptoms it is best to strictly limit or avoid these vegetables
Oxalates – many vegetables, especially leafy greens and also nuts contain oxalate or oxalic acid. Foods high in oxalates do not interfere with Calcium absorption in the GI tract. However, after absorption, oxalates bind to Calcium in the body to form crystals the body cannot absorb. Instead these crystals are excreted in the urine. However, if those crystals are not excreted, they collected in the kidneys to form kidney stones. The overall effect of oxalates is to promote the loss and excretion of the vital mineral Calcium from the body.
With root vegetables, especially potatoes and parsnips, green discoloration indicates presence of solanine, a toxic alkaloid that can cause circulatory and respiratory depression.
Nightshade family vegetables ( such as bell peppers and egg plant) have been linked to a worsening of arthritic symptoms
Murray, M. (1998). The complete book of juicing. Roseville, CA: Prima publishing
Haas, E. (2006). Staying Healthy with Nutrition. Berkeley, Ca. Celestial Healing Arts.
Murray, M. (2005). Encyclopedia of Healing Food. New York, N.Y.: Atria Books
Savage, G. P., Vanhanen, L., Mason, S. M., & Ross, A. B. (2000). Effect of Cooking on the Soluble and Insoluble Oxalate Content of Some New Zealand Foods. JOURNAL OF FOOD COMPOSITION AND ANALYSIS, 13(201), 206