In some cases, a Traditional Chinese herbal medicine (TCHM) may contain a nightshade or a component derived from a nightshade. Exactly how nightshades negatively impact certain individuals is not entirely clear, but to best serve sensitive patients, information is essential. Product manufacturers must properly label herb-formulas to equip practitioners with necessary information.

Being "In the Know"

Practitioner knowledge is equally essential for the formula design phase to avoid potential antagonists (including additives/carriers) leading to negative side effects for some. Many Chinese herb-prescriptions contain fewer trace elements of nightshade chemical factors than found in blueberry pie. How do practitioners guide patients best to honor concerns and to make beneficial Chinese herb and food nutrient decisions whenever possible?

Complaints of side effects from dietary nightshades often arise in populations with persistent inflammatory or autoimmune conditions. These complaints have been mostly anecdotal patient and clinician reports that have led to experimentations of eliminating nightshade vegetables. There have been human and animal studies testing the effects of common nightshades such as white potatoes, eggplant, tomatoes, peppers, paprika, goji berries, and tomatillos.

However, there is no conclusive data to bring clinical alarm positioning common dietary nightshades as a potentially damaging food item. In many cases, studies have found nightshades to offer benefits to health. It is primarily this reason it is practical for practitioners to engage in dialogue to ensure that only patients with reactions restrict nightshades rather than the general population.

The Dangers of Nightshades

The fear of nightshades began long ago when death ensued after individuals consumed overwhelmingly toxic doses of belladonna which aptly became known as "deadly nightshade." There were other nightshades as well (such as jimson weed), known to be poisonous. These forms of nightshades were not typical food sources and contained extremely high concentrations of a natural toxin called solanine. Herbalists love to hear the 'lore of the dose.' Solanine from nightshades is a perfect dose-dependent drama. In minimal amounts, women used belladonna to dilate their pupils to appear sensual. However, during the medieval and Renaissance periods, people knew that a higher dose could invoke death; belladonna was the poison used in both "Macbeth" and "Romeo and Juliet."

There is little research connecting potential dangers of commonly eaten nightshades with inflammatory responses. A growing number of recommendations to exclude common dietary nightshades exist throughout the internet, written media, and within health symposia. Some patients report that when they eliminate nightshades, they experience a cessation from some or all inflammatory conditions including gastrointestinal dietary complaints. A patient can learn a lot from copious diet and symptom journals that draw potential connections between a food and a side effect. In some cases, patients discover that "nightshades" are not the culprit, but rather, something else.

Natural Pesticides

Much of the food we consume contains naturally occurring pesticides.  These are toxic chemicals that plants create to prevent themselves from being eaten. They include alkaloids and glycoalkaloids such as solanine, nicotine, and capsaicin found in nightshades at various concentrations. Most of the anecdotal complaints targeting nightshades view solanine as the principal antagonist. Humans do not absorb solanine well, and it takes large concentrated doses to cause direct harm. Potatoes and eggplant (not the Chinese eggplant) are the most common foods associated with slightly higher solanine content. Potato breeding has lowered solanine content drastically over time. Sunlight encourages solanine, and a sprouting green potato has a higher solanine content than a fresh one. Still, it would take 4-6 pounds of raw sprouting potatoes to consume a dangerous amount of solanine.

Interestingly, tomatoes are categorized as nightshades and do not contain solanine. They contain tomatine, another non-toxic alkaloid. Other foods such as blueberry, apple, cherries, beets, okra, artichokes, and huckleberry contain solanine as well. Someone that does well with these foods but not nightshades might consider other chemical aspects of nightshades as problematic.

Nightshade Foods

A practitioner can encourage a patient to investigate what specific chemical is particularly antagonizing in "nightshade" foods. Nicotine is another alkaloid produced in drastically minimal amounts as an insecticide to prevent the eggplant from being eaten.  Similar to solanine, concentrated doses of nicotine (NOT through familiar food sources) can result in serious side effects and even death.

Eating eggplant does not pose a nicotine-related problem, but could it be that a person has a specific sensitivity to this chemical? What about capsaicin? Capsaicin creates heat in spicy nightshade foods like chili pepper, paprika, cayenne, and red pepper flakes. It has been positively regarded to help boost metabolism, fight low-grade infections, heal a leaky gut and help with immunity. Capsaicin is not considered to be a harmful food chemical in general populations, but there is little research about frequent consumption.

Perhaps for some individuals, the smallest exposure to one (or all) of these phytotoxins can create a cascade of autoimmune responses. It may be possible that a diet with a preponderance of different nightshades accumulates throughout 24 hours to stimulate a reaction in a small population of individuals with specific sensitivities. Again, we revisit the lore of the dose! It is here that patients and practitioners need to look beyond single encounters with potato or eggplant for example. Perhaps a diet journal may illustrate how a chili and tomato at breakfast, with an eggplant at lunch, then a baked potato for can "layer" foods with similar chemical nuances to create an accumulation of glycoalkaloids. It is essential to ensure that not all potentially beneficial nutrient-rich foods are eliminated. Targeting individual culprits and monitoring extreme behaviors that end in reactionary tipping points is critical.

Consuming Toxins

Phytotoxins (plant toxins) come from plants that also have phytonutrients. Chemicals found in plant foods have beneficial effects. Phytotoxins are slightly toxic, yet minimal amounts consumed from eating may support the body's detoxification pathways and provide substantial nutritional components. Those with unique symptomatic experiences that do not benefit from small amounts of phytotoxins could have compromised immunity or digestive illnesses that result in a sensitivity to alkaloids and lectins (another protein within nightshades).

Chinese herbs are made from whole ground parts of insects, leaves, roots, stems, flowers, and seeds of plants, some of which carry phytotoxins. The most provocative Chinese herb labeled 'nightshade' is Gou Qi Zi (Lycium fruit, wolfberry or "goji berry"). Some prepared traditional Chinese herbal medicines use potato as a base to create excipients, inactive substances used as a carrier for the herbal formula.

Non-GMO potato starch used in concentrated Chinese herb granules is an alternative to granules made from genetically modified corn or potato starch. Potato starch is highly-fermentable insoluble fiber or, resistant starch. Resistant starch means that the molecular composition resists digestion in the small intestine to the degree that it is still a viable food source for certain bacteria in the colon, for some this is considered a dietary benefit. There is a strong connection between gut barrier health and the ability to sufficiently metabolize glycoalkaloids. It is possible that the very gut bacteria that could benefit from resistant starch is unable to metabolize glycoalkaloids helping to continue this reactive cycle in certain individuals.

The Labeling Requirement

Product manufacturers are not required to label the amount of excipient used in making a formula so a practitioner may need to contact their suppliers directly if necessary. Non-GMO potato starch based Chinese herbal formulas are exposed to high temperatures then dried which extends their shelf life significantly more than a decoction. A large amount of solanine in potato is removed with the skin and outer layer during processing. The inner flesh that still contains glycoalkaloids is further processed leaving behind potato starch. Various studies show potato starch as having roughly < 4 µg/g glycoalkaloids (an extremely small amount).¹ The Food and Drug Administration reports that an average potato contains about 8mg of solanine per 100 g. These small levels of glycoalkaloids may be a problem for only those who do not metabolize it well.

The mechanism of action within nightshades that may negatively impact selected individuals is not sufficiently clear but should not be overlooked.  Non-GMO potato starch excipients used in Chinese herbal medicines may carry traces of glycoalkaloids that some patients wish to avoid, but also may provide resistant starch beneficial for gut bacteria. Practitioners can help patients with formulas that avoid nightshade elements and demystify potential threats that nightshades may pose. It is also possible that when a patient clears dietary nightshades, they can tolerate potato starch in the doses required for taking a Chinese herbal formula. Clinical relationships provide the best path to success. The patient and the practitioner learn together how to navigate these tricky and complicated conversations through time and experimentation. Take careful notes, ask detailed questions and require patients to do the same for themselves. As partners in health, practitioners can offer informed dialogue even when the territory is ambiguous and mysterious!

Reference

1. Saito K, et al. High-performance liquid chromatographic determination of glycoalkaloids in potato products. Journal of Chromatography A, 1990; 508:141-147.

Resources

• Alt V, et al. Optimization of Glycoalkaloid Analysis for Use in Industrial Potato Fruit Juice Downstreaming. Eng Life Sci, Dec 2005;5:562-567.
• Driedger D, Sporns P. Glycoalkaloid Concentration In By Products of Potato Starch Extraction As Measured By Matrix-Assisted Laser Desorptioniionization Mass Spectometry. Journal of Food Processing and Preservation, 2007;23: 377-390.
• FDA Poisonous Plant Database. U.S. Food & Drug Administration, 2019.
• Friedman M, et al. Anticarcinogenic effects of glycoalkaloids from potatoes against human cervical, liver, lymphoma, and stomach cancer cells. J Agric Food Chem, Jul 2005;27;53(15):6162-9.
• Friedman M. Potato Glycoalkaloids and Metabolites:  Roles in the Plant and in the Diet. J Agric Food Chem, Oct 2006; 20;54 (23), 8655-8681.
• Friedman M, et al. Tomatine-containing green tomato extracts inhibit growth of human breast, colon, liver, and stomach cancer cells. J Agric Food Chem, 8 Jul 2009;57(13):5727-33.
• Galatz LM, et al. Nicotine delays tendon-to-bone healing in a rat shoulder model. J Bone Joint Surg Am, Sep 2006;88(9):2027-34.
• Cheng-Yu J, et al. Glycoalkaloids and phenolic compounds in three commercial potato cultivars grown in Hebei, China. Food Science and Human Wellness, 2018;7:156–162.
• Patil BC, et al. Evaluation of solanine toxicity. Food and Cosmetics Toxicology, Jul 1972;10:395-398.

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