by Zachari Breeding, MS, RDN, LDN, FAND
There is a lot of speculation out in the media, the internet, and in word-of-mouth conversation about nightshade vegetables and how they can contribute or worsen inflammatory conditions such as inflammatory bowel syndrome (IBS), inflammatory bowel disease (IBD), arthritis, and even osteoporosis. But what are nightshade vegetables? They are vegetables that fall under the Solanum group of vegetables believed to contain “dangerous alkaloids.” These vegetables have been cultivated for consumption for centuries and include favorites such as potatoes, tomatoes, eggplant, sweet (bell) and hot peppers, and even cayenne pepper. While searching nightshade vegetables in a search engine, the results supporting these beliefs are staggering. This can be confusing, even with some of the articles having supporting documentation. So, let’s discuss what these types of vegetables are and uncover the truth behind the speculation (1).
Before we get into the nitty-gritty of this topic, there is something important to know about supporting documentation. Whether it be on www.The-Sage.org, an online article, or an opinion piece, it is important to know when to believe supporting documentation (like references) or not. Articles that are not from a scientific journal, are from an organization that benefits from positive results, and/or are more than 10 years old should usually be deemed inaccurate. For instance, if there is a study on how mushrooms can contribute to reduced cancer risk and it is published by the Institute of Mushrooms… one can deduct that this is biased information and move on. This is what has been found in a lot of the “supporting documentation” found on the articles that deem nightshade vegetables to be pro-inflammatory.
The “toxic alkaloid” claimed to be present in nightshade vegetables is called Solanine. Though these compounds are present in nightshade vegetables to some extent, they are used as a defense mechanism against insects. These compounds may develop to be stronger in potatoes that turn green or sprout, which is why discarding green potatoes has always been recommended. However, simply eating potatoes is not proven to contribute to arthritis or any other inflammatory response. As for the other nightshades, they do not even contain this compound and therefore, are non-contributory. In fact, research has indicated some anti-inflammatory properties from certain Solanum plants. With this said, there is no research that provides sufficient evidence to recommend avoid nightshade vegetables as a potential treatment for any inflammatory condition. Remember, though individual results may vary, it does not mean all nightshade vegetables are detrimental to your health. However, it is recommended to avoid any foods that are proven to worsen your health in any way (2,3,4).
As for nightshade vegetables and their association with osteoporosis, no evidence suggests their correlation. A member of the scientific advisory committee for Osteoporosis Canada notes that nightshade vegetables are not high in oxalic acid, which is the supposed contributory factor that related osteoporosis with nightshade vegetables. The alkali contributed by vegetables and fruits is beneficial for bones as it protects them from using bone to neutralize blood acid (2).
If you feel that a food is contributing to your condition or creating a new one altogether, speak to a dietitian and physician. He or she will guide you through a food elimination trial to see what foods you might be sensitive to. This has no indication on whether a food is considered “nightshade” or not, so avoiding these foods in hopes of preventing or improving your health is not recommended. Always remember that the media is always out to create hype about something, and there are only so many new topics to discuss. It is always best to discuss any concerns you might have with a registered dietitian and your primary care physician before embarking on any restrictive eating regimen.
Zach Breeding, MS, RDN, LDN, FAND, is a Philadelphia-based registered dietitian nutritionist, professional chef and clinical dietitian at Drexel Medicine. He is the author of The Slice Plan: An Integrative Approach to a Healthy Lifestyle and a Better You. Connect with Zach on his website, The-Sage: Nutritious Solutions.
References:
- Website: “The World’s Healthiest Foods.” What are nightshades and in which foods are they found? http://www.whfoods.com/genpage.php?tname=george&dbid=62. Visited 8/2014.
- Website: “Cleveland Clinic.” Foods that fight inflammation – and why you need them. http://my.clevelandclinic.org/multimedia/transcripts/1395_foods-that-fight-inflammation-and-why-you-need-them.aspx . Visited 8/2014.
- Website: “Best Health Magazine.” 4 myths about nightshade vegetables. http://www.besthealthmag.ca/eat-well/nutrition/4-myths-about-nightshade-vegetables. Visited 8/2014.
- Pandurangan A, Khosa RL, et al. Anti-inflammatory activity of an alkaloid from Solanum trilobatum on acute and chronic inflammation models. Natural Product Research. 2011: 25;1132-41.
