 Nightshade vegetables, including tomatoes, peppers, potatoes, and eggplant; also, spinach, beets, and avocados are not recommended or are used sparingly in macrobiotic cooking, as they are considered extremely yin.Some macrobiotic practitioners also discourage the use of nightshades because of the alkaloid solanine which is thought to affect calcium balance.Some proponents of a macrobiotic diet believe that nightshade vegetables can cause inflammation in the body and osteoporosis.