Nightshades are a family group of plants that includes tomatoes, eggplant, sweet and hot peppers, potatoes of both the white and sweet varieties, and paprika, as well as Tobacco. This plant group thus has a wide range of usage in our nutrition, but a number of the group’s members are highly toxic and several contain phytochemicals that are psychoactive (specifically, Atropine, Apoatropine, Hyoscamine and Scopolamine). Toxicity varies from the mildly irritating to substances that are fatal in even small quantities.
The family is formally known as the Solanaceae (or potato) family and includes Datura, mandragora (mandrake root), Atropa belladonna (deadly nightshade), Physalis philadelphica (tomatillo) , Physalis peruviana (Cape gooseberry flower), Capsicum (chili and bell peppers), Solanum (potato, tomato, and eggplant), Nicotiana (tobacco), and Petunia. With the exception of tobacco (Nicotianoideae) and petunia (Petunioideae), most of the economically important genera are contained in the subfamily Solanoideae.
Other Nightshades include Goji berries (Lycium barbarum, whose juice is currently very popular as an antioxidant drink amongst the devotees of ‘health food’) and Ayurveda’s own widely-used herb, Ashwagandha (Withania somnifera) a much beloved “King among Medicines.”
From a biochemical perspective, members of the Solanaceae family have a high concentration of a class of compounds called alkaloids. One of the most important groups of these compounds is called the tropane alkaloids. The term "tropane" comes from a genus in which they are found, Atropa (the belladonna genus). Atropa is named after Atropos, one of the three Fate sisters from Greek mythology, who cut the thread of life. This nomenclature reflects its toxicity and lethality. Despite the extreme toxicity of the tropanes, they are useful drugs when administered in extremely small dosages. Another infamous alkaloid derived from Solanaceae is nicotine.
From a nutritional perspective, the ingestion of members of the Nightshade family has two significant biological effects. The first is that Nightshades interfere with a neurotransmitter that is ubiquitous in the nervous system and required for optimal neural functioning; the second feature is that they bring about an inflammatory affect the joints.
All of the Nightshades contain Nicotine, or one of its close chemical relatives: solanine in potatoes, tomatine in tomatoes, aubergine in Eggplants and alpha-solanine in Bell and Chili peppers. All of these contain an acetylcholinestrase inhibitor that impedes the transmission of nerve impulses from one synapse to the next by retarding the production of acetylcholinesterase. All additionally are believed to possess inflammatory properties. Thus, for this reason they are aggravating to both Vata and Pitta doshas.
Nightshades’ biochemical constituents are known to dehydrate the fluids lubricating the joints (and thereby worsen arthritis and kindred bone disorders), to interfere with calcium metabolism, and to worsen gastric and digestive hyperacidity, sciatica, and kidney and gallstones disorder.
From the perspective of Ayurveda, edible Nightshades all are heating in nature, except for the white potato, explaining their inflammatory activity. This is coupled with the fact that all of them have a pungent and/or sour post digestive effect (vipaka). Thus, during digestion the colon experiences the physiological consequences of the sour and pungent tastes, with the pungent vipaka, being both heating and dehydrating and provoking both vata and pitta doshas, and the sour vipaka, being both heating and moisture-promoting, provoking the kapha and pitta doshas.
Nightshades are therefore said by many authorities to be aggravating for all three doshas.
Insofar as individual foods are concerned, the immeasurably popular white potatoes are reckoned in terms of gunas as cool, light and dry, and therefore most aggravating to Vata and to a lesser extent Pitta, and (depending on means of preparation and when ingested in moderation) potentially beneficial to Kapha (but note, this is in terms of their gunic properties alone as the presence of deleterious alkaloids needs also to be considered – hence the emphasis on moderate consumption). And, to give the potato its just due, it is a relatively easily digested carbohydrate for those with nervous indigestion related to liver weaknesses, and is also a good source of Vitamin C.
The means of cooking potatoes has a great deal to do with whether the food is pacifying or aggravating to a given dosha. If potatoes must be served, their injuriousness can be diminished and benefits maximized for kapha types by dry-cooking methods (baking or roasting) and serving with a digestion-enhancing spice or herb (e.g., black pepper) and their negative impact on vata types by wet-cooking (boiling) them and serving them with a reasonable amount of healthy shortening such as ghee, olive oil, etc. Interestingly, potatoes are alone among the edible nightshades in that they can, when overripe, accumulate enough toxins to be overtly poisonous, a condition clearly heralded by their developing a green shade shade just below their skins.
Red tomatoes are less injurious than the yellow or green ones, and their seeds have an especially concentrated amount of the Nightshade energy. Tomatoes – if served at all - should therefore be cooked and de-seeded (and preferably de-skinned as well).
Potatoes, tomatoes and the other Nightshades should always be cooked, and the addition of cumin, turmeric, black pepper and mustard seeds (as appropriate per the consumer’s constitution) can lessen their toxic effect appreciably.
By way of summary, compared to many other vegetables, Nightshades are over-represented in the average North American diet, and most people will benefit from substituting other vegetables instead of relying on tomatoes and potatoes as daily staples. Many nightshades contain immune-activating molecules called lectins that can provoke an allergic response, and where food allergies are present, they are best curtailed or eliminated, as is also the case with autotoxic states and chronic inflammatory disorders (e.g. GERD, arthritis, fibromyalgia, eczema, psoriasis, etc.), and autoimmune disorders such as LE and SLE.
Article provided by William Courson, BVSA, D. Ayur., an Ayurvedic Practitioner, faculty member and the College Dean of Institutional Development at Sai Ayurvedic College & Ayurvedic Wellness Center.