Plant Alkaloids: Dangers to your Health?

Plants in the nightshade family include many of our most common foods. They developed bitter-tasting alkaloids as protection from being eaten. Alkaloids can be poisonous at high concentrations and alter animal metabolism at low concentrations. Alkaloids can harm nerve-muscle, joint, and digestive functions.


Nightshades belong to the scientific order called Polemoniales, the scientific family called Solanaceae and include 

• potatoes (Solanum tuberosum), 
• tomatoes (Lycopersicon esculentum), 
• many species of sweet and hot peppers (all species of Capsicum, including Capsicum annum),  
• eggplant (Solanum melongena), 
• tomatillos (Physallis ixocapra), 
• garden huckleberry (Solanum melanocerasum), 
• tamarillos (Cyphomandra betacea), 
• pepinos (Solanum muricatum), 
• naranjillas (Solanum quitoense), 
• Pimentos (also called pimientos) (Capsicum annum)
• paprika, cayenne, and Tabasco sauce.

Green parts of potato plants such as the stems, leaves, and eye sprouts contain alkaloids. It is a good idea to peel potatoes to remove green a possible green layer below the skin. New potato species cannot be sold as food if they have alkaloid concentrations greater than 20 mg per 100 grams of potato. 


To keep alkaloid levels low, store potatoes in dark areas and do not eat any green parts of the potatoes. If the potatoes taste bitter, they probably contain large alkaloid concentrations. For more information go to
http://www.ansci.cornell.edu/plants/toxicagents/steroid.html,

In a New York Times article, Harold McGee discussed the toxicity of tomatoes. Europeans initially considered tomato plants and fruits toxic when they were first introduced from the Americas, however the ripe fruits are now highly admired. 


The alkaloid in tomatoes that could be harmful is called tomatin, however there is very little confirmed evidence to support the popular belief that it is harmful. Even tomato leaves, which are widely considered harmful, would only harm a person if ingested in large quantities. Green tomatoes contain large quantities of tomatin, but when they are pickled or fried, they may actually help reduce buildup of cholesterol. For more information you can find the article at http://www.nytimes.com/2009/07/29/dining/29curi.html.


Cooking only lowers alkaloid content of nightshade foods by about 40-50%, so highly sensitive individuals may want to avoid them altogether, while non-sensitive individuals may be able to eat these foods, especially in cooked form, without problem. 

"Nightshade" is actually the common name used to describe over 2,800 species of plants, many with very different properties and constituents. To give you an idea of the diversity associated with this group of plants, consider the fact that tobacco, morning glory, potato, and tomato are all classified as nightshades.

Nightshades are also famous as drugs. The best-known of these nightshades include mandrake (Mandragora officinum), tobacco (Nicotiana tabacum) and belladonna, also called deadly nightshade (Atropa belladonna).


More information about the health effects of food alkaloids can be found at

• http://www.whfoods.com/genpage.php?tname=george&dbid=62 and
• http://www.embracinghealthblog.com/k-is-for-kale/.

Practical tips for avoiding excessive intake of potato alkaloids

• Store potatoes no longer than 1-3 weeks in a cool, dry, dark place. Light increases alkaloid formation. 
• Wash all potatoes before cooking so you can see the green areas, if any.
• Thoroughly cut out all green areas, especially green areas on the peel, before cooking. After cooking, discard the potato if it tastes bitter.
• Do not buy potatoes that have been waxed, or apply wax to potatoes yourself. Waxes do not help reduce greening and can increase potato decay by cutting down on gas exchange in and out of the potato.