The nightshades – tomatoes, white potatoes, eggplant, peppers and tobacco…were used in New World for centuries with little difficulty. The deadly nightshades get their name for a definite reason: they concentrate poisonous alkaloids in various parts of their anatomy, particularly their leaves. Nightshades leaves were used, ground up with poisonous mushroom, as deterrent to flies in the old world. But their fruits were highly mistrusted. Are they all dangerous? We are not sure. The solanines in them certainly are. It is often recommended to avoid nightshade family if you are seeking to eliminate a condition of rheumatoid arthritis.
                 White potatoes are cool, light and dry, therefore they imbalance Vata and assist Kapha, and essentially have neutral effect on Pitta. They are one of few nightshades fruits that can accumulate enough toxins in their edible portion to be overtly toxic. Fortunately, it is relatively easy to tell if they have done so. If potatoes have green shade to its peel, it is suspect. The toxic alkaloid solanin and chaconine accumulate close to the surface of the peel in these areas, especially if potatoes are allowed to sit in light or are stored in very cold or fairly warm places. A cool dark storage spot serves potatoes best. Cooking will not remove these toxins. Cutting out the green portion, usually the surface 1/8inch or less, will. Besides greening, a sharp burning sensation on the tongue upon eating the potato is another sign of excessive alkaloid levels. Cutting the potato is usually sufficient.
                 The preparation of potato has a great deal to do with whether it is calming or irritating to a given dosha. While potato is beneficial to Kapha, French fries, potato chips and baked potato with sour cream are not.  Each of these contains lot of oil, inherently light potato become heavy by preparation. Similarly many Vatas can handle backed potato on occasion, if it has generous amount of ghee, yoghurt or sour cream on it. Pittas and Kaphas get best with their potatoes boiled or stewed in dishes, not fried. Backed potatoes are fine for Pitta if they do not over do it on the fatty condiments. Vatas need their potatoes well spiced and moistened. Potatoes are being rich in Vitamin C, have been used in centuries. They are also recommended as an easy digest starch for those with nervous indigestion related to liver weakness.