What are nightshades and in which foods are they found?

Nightshade foods

What are nightshades and in which foods are they found?

What are nightshades and in which foods are they found?

Nightshades-a description

Nightshades are a diverse group of foods, herbs, shrubs, and trees that have fascinated scientists, doctors, and nutritionists for centuries. “Nightshade” is actually the common name used to describe over 2,800 species of plants, many with very different properties and constituents. All of the plants, however, belong to a scientific order called Polemoniales, and to a scientific family called Solanaceae.

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:

Nightshade vegetables and fruit Nightshade spices Pharmaceutical nightshades
·      potatoes

·      tomatoes

·      many species of sweet and hot peppers (all species of Capsicum)

·      eggplant

·      ground cherries

·      tomatillos

·      garden huckleberry

·      tamarillos

·      pepinos

·      naranjillas

·      Pimentos (Pimento cheese and pimento-stuffed olives)

·      paprika

·      cayenne

·      Hot sauces that contain hot peppers


·      mandrake

·      tobacco

·      belladonna (also called deadly nightshade)


Practical tips

If you are an individual with existing autoimmune or joint problems like osteoarthritis, rheumatoid arthritis, or gout, temporary 4-6 week elimination of nightshade foods from your meal plan may be a worthwhile step to determine if these foods could be contributing to your health woes. This same recommendation would apply to individuals with existing nervous system problems, particularly nerve-muscle related problems.  If after eliminationg nightshardes from your diet you found relief from your symptoms, go through the same food reintroduction protocol you followed after completing the detox (i.e. add one food back at a time every 3-4 days and if you experience a flare-up of your old symptoms pull that food back out of your diet.)

A particular group of substances in these foods, called alkaloids, can impact nerve-muscle function and digestive function in animals and humans, and may also be able to compromise joint function. Because the amount of alkaloids is very low in nightshade foods when compared with other nightshade plants, health problems from nightshade foods may only occur in individuals who are especially sensitive to these alkaloid substances. Since cooking only lowers alkaloid content of nightshade foods by about 40-50%, highly sensitive individuals may want to avoid this category of food altogether, while non-sensitive individuals may be able to eat these foods, especially in cooked form, without problem.

Effect of steroid alkaloids on the nervous system

The steroid alkaloids in potato – primarily solanine and chaonine – have been studied for their health effects in two areas. First is their ability to block activity of an enzyme in nerve cells called cholintesterase. Many of the alkaloids found in nightshades possess this kind of activity, called cholinesterase inhibition. If the activity of cholinesterase is too strongly blocked, the nervous system control of muscle movement becomes disrupted, and muscle twitching, trembling, paralyzed breathing, or convulsions can result. The steroid alkaloids found in potato have clearly been shown to block cholinesterase activity, but this block does not usually appear strong enough to produce nerve-muscle disruptions like twitching or trembling.

Effect of steroid alkaloids on joint health

A second type of problem potentially related to the potato alkaloids involves damage to the joints caused by inflammation and altered mineral status. Whether alkaloids can contribute to joint damage of this kind is not clear from current levels of research. Some researchers have speculated that nightshade alkaloids can contribute to excessive loss of calcium from bone and excessive depositing of calcium in soft tissue. For this reason, these researchers have recommended elimination of nightshade foods from the meal plans of all individuals with osteoarthritis, rheumatoid arthritis, or other joint problems like gout.

Effect of nicotine alkaloid on health

To the surprise of many people, Nicotine is found not only in non-food nightshades like tobacco, but also in the food nightshades including eggplant and tomato. While alkaloids like nicotine are definitely found in nightshade foods, the amount involved is dramatically less. Even in the case of eggplant, which is the food nightshade that appears to have the highest nicotine content after tobacco, the amount of nicotine is far lower than the amount found in tobacco. In the case of green tomatoes, which also contain nicotine, the amount is even less. The levels of nicotine in all nightshade foods are so low that most healthcare practitioners have simply ignored the presence of nicotine in these foods as a potential compromising factor in our health. At Apex Functional Medicine we agree that the amount of nicotine in nightshade foods is very, very small, but it still seems possible to us that some individuals might be particularly sensitive to the alkaloids found in nightshades, and that even very small amounts might compromise function in the bodies of these individuals.

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