What Are Nightshades and Why Are People Allergic to Them?
Tom Brady doesn't eat nightshade vegetables, but does that mean they're unhealthy? Brady's personal chef, Allen Campbell, told Boston.com the Patriots' quarterback has cut tomatoes and other nightshades from his diet because they can be inflammatory. However, some research suggests the exact opposite — that nightshades are, in fact, anti-inflammatory. For most people, nightshade vegetables offer plenty of vitamins and minerals that are important for a healthy diet.
What are nightshades?
Nightshade plants make up a large portion of the American diet, particularly if you are a vegetarian. Anything from a fresh salad to fast food can contain ingredients made from nightshade plants. Because of the widespread use of nightshades, those with allergies and sensitivities should learn more about the nightshade family of plants.
Nightshade, also known by its scientific name, Solanaceae, is a family of flowering plants that includes a variety of vines, shrubs, herbs, trees and other plants. People disagree on how this family of plants got the name "nightshade," but it may come from an old belief that the plants grow at night.
What common foods are in the nightshade family?
The nightshade family includes a surprisingly diverse collection of plants. Some of the most popular members of the nightshade family that you might find in your neighborhood grocery store include:
What are the health benefits of nightshades?
While a small minority of people are allergic or sensitive to nightshades, most people benefit from these foods.
“Tomatoes, peppers, and eggplant are very rich in polyphenols (unlike potatoes) which make them anti-inflammatory agents. Furthermore, they are fruits, not starches (like potatoes) because they contain seeds. Not surprisingly, they are also major components of the Mediterranean diet,” said Dr. Barry Sears, Ph.D., creator of the Zone diet and president of the Inflammation Research Foundation.
Tomatoes also contain a long list of nutrients that benefit most people. One large tomato measuring about three inches across contains:
- 23 mg (39 percent DV) of vitamin C
- 1516 IU (30 percent DV) of vitamin A
- 14.4 mcg (18 percent DV) of vitamin K
- 431 mg (12 percent DV) of potassium
Tomatoes also provide a significant source of lycopene, an antioxidant that may help prevent cancer. Despite offering so much nutrition, a large tomato only contains about 33 calories. If you want to enjoy a nutritious but low-calorie snack, you won't find many options healthier than tomatoes.
Potatoes also have plenty of nutritional benefits. One average sized potato contains about 1,554 mg of potassium (44 percent of your recommended daily value, or DV). By comparison, bananas, which many people eat because they want to add potassium to their diets, only has 806 mg (23 percent of your DV).
Potatoes also contain significant amounts of:
- Vitamin C
- Vitamin B6
Why can’t everyone tolerate nightshades?
Most people can eat the fruits of domesticated nightshade plants without any troubles. In fact, according to The Atlantic magazine, people eat more potatoes than any other fruit or vegetable. Unfortunately, some people develop allergies or intolerance to nightshades.
If you have an intolerance to nightshade, then you might notice problems like bloating, gas and diarrhea after eating tomatoes, potatoes, and other common nightshade products. In most cases, you can continue eating small amounts of nightshade produce. The more you eat, though, the more digestive problems you will have.
Dr. Sears explained that all nightshades contain an alkaloid called solanine, which is “a defense mechanism against insect predators. Only a small amount of people (less than 1%) may have a sensitivity to solanine that can potentially cause inflammation.”
Do nightshades aggravate inflammatory conditions like arthritis and IBS?
According to Arthritis.org, many people claim nightshades can cause arthritis pain, but no research studies have been conclusive on this topic. In fact, studies have shown that nightshades can be anti-inflammatory for those who aren’t intolerant.
As for IBS (Irritable Bowel Syndrome), everyone with this condition has different food triggers. If you have an intolerance or sensitivity to any of the chemical compounds in nightshade foods, this could be a major contributing factor to your IBS. Your doctor will likely recommend that you try different elimination diets to find out what causes your condition to flare up.
“It is possible that solanine might cause an inflammatory response in people with existing inflammatory conditions such as arthritis and IBS,” said Dr. Sears. “But the data is far more convincing that increased fish oil will decrease inflammation in both conditions. So if you really want to be on the safe side, remove nightshades from your diet and simultaneously dramatically increase your intake refined fish oil.”
What are the nightshade allergy symptoms?
Nightshade allergies pose more significant issues than nightshade intolerances. All nightshade plants produce chemical compounds called glycoalkaloids, one of which is solanine. The compounds essentially act as a pesticide that prevents insects and bacteria from attacking the plant. It can also cause an immune response or allergic reaction in humans.
“If you have the potential allergy to solanine [found in all nightshades] you might develop hives or have excess mucus formation after eating these foods,’ said Dr. Sears.
Other possible symptoms of allergies to the compounds found in nightshades include:
- Nasal congestion
- Difficulty breathing
People with severe allergies to glycoalkaloids can experience a life-threatening reaction called anaphylaxis. Signs of anaphylaxis include:
- Abdominal pain
- Low pulse
- Swelling in the throat or mouth
- Facial swelling
What to do if someone has a nightshade allergy?
If you or someone else shows signs of anaphylaxis after eating a nightshade food, you should call 911 immediately for help. The person needs to go to the emergency room for a shot of epinephrine that will minimize the allergic reaction to glycoalkaloids. Medical professionals may also use antihistamines or cortisone to control the symptoms.
Even if you have an EpiPen that contains a full dose of epinephrine, you should still call for an ambulance. Anaphylaxis can kill you, so you don't want to take any chances. If someone is having an allergic reaction to nightshade, they should lay on their back, elevate their feet by 12 inches and cover themselves with blankets while they wait for an ambulance to arrive.
Only a tiny percentage of the population has an allergy to domesticated nightshade plants. However, members of this plant family found in the wild often contain higher levels of glycoalkaloids and can be highly toxic, such as the aptly named “deadly nightshade.” Deadly nightshade, also known as Belladonna, produces appealing-looking berries that might look edible but don’t be fooled. The cherry-like berries, which grow on low bushes in parts of the Northwest and Northeast US, can be attractive to children. Always be mindful of what your young kids are putting in their mouths outside. If your child consumes unknown wild berries or plants, be sure to call 911 or the National Poison Control Center right away, at 1-800-222-1222.
What should you cook if you want to avoid nightshades?
While most benefit from eating nightshade plants, no one with a glycoalkaloid allergy should risk using the produce in their meals. Likewise, if you have symptoms of a nightshade sensitivity or intolerance, you might consider trying to eliminate them from your diet to see if it will make you feel better. However, the popularity of potatoes, tomatoes, peppers and other nightshade produce can make this difficult. Knowing how to replace nightshade plants with safe alternatives will make it easier for you to enjoy meals without putting your health in jeopardy.
Some easy replacements include:
- Using radishes, celery or Swiss chard instead of bell peppers.
- Swapping sweet potatoes for recipes that call for potatoes. (Although sweet potatoes may seem similar to potatoes, sweet potatoes are not a part of the nightshade family. You can eat them safely.)
- Spicing up recipes with cumin or black pepper instead of cayenne or red pepper flakes.
- Choosing olive oil, pesto or alfredo sauces instead of marinara when eating pasta.
Most people don't need to worry about nightshade allergies. If you have experienced negative reactions to members of the nightshade family, though, you should get an allergy test to determine which foods upset your system.
Any experienced allergist can conduct an allergy test that will reveal whether you have a sensitivity to nightshades or other foods. After you receive your test results, you’ll be able to choose healthy meals that won't put you at risk.
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- The Atlantic: The Most-Eaten Vegetable in the U.S. Is the Potato
- Arthritis Foundation: Arthritis Food Myths
- AAAAI: Anaphylaxis
- Nutrition Data: Bananas, raw
- Nutrition Data: Potato, flesh and skin, raw
- Nutrition Data: Tomatoes, red, ripe, raw, year round average
- ACAAI: Allergy Testing
- Slate: Big, Bad Botany: Deadly Nightshade (Atropa Belladonna), the Poisonous A-Lister