Although chlorophyll is a natural plant pigment that is tasteless and harmless, the green of potato tubers should signal us to be aware of another substance that is forming inside tubers. This substance is known as solanine, and it forms when any part of a potato plant is exposed to light.
Solanine is a toxic substance that is produced naturally in potatoes and other plants to aid in resistance of insects and animals. Solanine is present in all parts of the potato plant, including the sprouts, roots, leaves, flowers and fruits.
Solanine has a bitter taste and can cause stomach symptoms such as vomiting and diarrhea if you eat enough of it. If ingested in large amounts, it can cause illness or even death in extreme cases. Because of the bitter taste, most people do not eat enough to get sick. In addition, consumers always should avoid consuming sprouts.
Small tuber sprouts contain the highest levels of solanine to protect new growth and provide solanine to the growing plant. If tubers have sprouts, remove the sprouts prior to cooking and consumption.