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Nightshades and Thyroid Health

Published January 12th 2015

There are many different foods which are restricted as part of an autoimmune Paleo diet.  This includes the nightshades, which are members of a family of plants called Solanacea.  Some of the common foods in this family include tomatoes, white potatoes, eggplant, as well as peppers of all types.  Why are these foods commonly recommended to be avoided, and should everyone with an autoimmune thyroid condition such as Graves’ Disease and Hashimoto’s Thyroiditis avoid the nightshades?

First of all, I’ll start out by saying that even though nightshades are part of an autoimmune Paleo diet, this doesn’t mean that everyone with autoimmune conditions will have a negative reaction to nightshades.  However, nightshades consist of certain compounds which can cause inflammation.  And since inflammation is a big factor in autoimmunity, it is a good idea for those people who have Graves’ Disease or Hashimoto’s Thyroiditis to at least consider avoiding these foods for a period of time.  And then some people will be able to reintroduce these foods without a problem.  Others will find that they can’t eat nightshades without experiencing certain health issues, such as muscle and/or joint pain, rashes, acne, acid reflux, etc.  The problem is that many people don’t make this connection until they actually eliminate these foods from their diet.

Why Do The Nightshades Commonly Cause Problems?

As I mentioned earlier, the nightshade foods have compounds which can be problematic.  These include lectins, as well as alkaloids and glycoalkaloids.  I’ve discussed lectins in a few different articles and blog posts, including one entitled “Should People With Thyroid and Autoimmune Thyroid Conditions Avoid Foods With Lectins? [1]”  Lectins can potentially cause damage to the intestinal lining, which in turn can cause an increase in intestinal permeability (a leaky gut).  And since a leaky gut is common in autoimmune conditions, it would make sense to avoid foods which have lectins while trying to restore one’s health back to normal.  This includes nuts, seeds, and legumes, but also includes tomatoes.  So I would at least consider going on a trial where you avoid tomatoes, and yes, this does include tomato sauce.

But what about alkaloids and glycoalkaloids?  Capsaicin is an alkaloid which is found in spicy peppers.  Capsaicin is also the active ingredient in pepper spray, and is highly responsible for the acute inflammation and burning feeling when sprayed, and might even cause bronchoconstriction (1) [2].  In fact, there have been numerous reports of pepper spray-related injuries (2) [3] (3) [4], and this very well might be because some people are highly sensitive to capsaicin.  This doesn’t mean that everyone will have a negative reaction when consuming hot peppers, but it’s something to keep in mind, and like tomatoes, these probably should be avoided while trying to restore one’s health back to normal.  But it’s not just hot peppers that should be avoided, as if you are trying to avoid the nightshades then you will want to avoid other types of peppers as well.

Solanine is a glycoalkaloid found in the nightshade foods, especially eggplant and potatoes, although it’s also found in tomatoes and peppers.  Solanine has fungicidal and pesticidal properties, and the reason for this is because these compounds are used as a form of protection by plants.  The way it affects insects who feed on these plants is by the inhibition of acetylcholinesterase (4) [5], which breaks down acetylcholine.  Acetylcholine inhibitors can lead to problems with the nervous system, and can cause other health issues such as hypotension, bronchoconstriction, and hypermotility of the GI tract.  This doesn’t mean that everyone who eats these foods will have problems breaking down acetylcholine, but many people do react to the solanines and experience a significant relief in some of their symptoms upon avoiding these foods.

Are There Other Foods In The Nightshade Family Which Should Be Avoided?

Okay, so at this point you should realize that if you have an autoimmune thyroid condition it would be a good idea to exclude tomatoes, potatoes, eggplants, and peppers from your diet.  Remember that this includes most types of peppers, including bell peppers, chili peppers, jalapenos, red and green peppers, cayenne pepper, and even paprika.  However, according to some sources black pepper isn’t considered to be a nightshade.  In addition to tomatoes, tomatillos and tomarillos should also be avoided.  Most potatoes should be avoided, but fortunately not sweet potatoes.  Other foods which should be avoided include goji berries and garden huckleberries.

The herb ashwagandha is also considered to be a nightshade.  I really like this herb, and in the past I even wrote an article entitled “Ashwagandha and Thyroid Health [6]“.  I personally haven’t had too many people react to ashwagandha, as over the years I have recommended it to many of my patients with Graves’ Disease and Hashimoto’s Thyroiditis without a problem.  However, if someone is following a strict autoimmune protocol and is taking ashwagandha, they might want to take a break from this for at least one month, and if they don’t notice any positive changes in their symptoms they can try reintroducing this back.

Dr. Lorein Cordain, author of the “Paleo Diet”, wrote an interesting paper entitled “Consumption of Nightshade Plants, Human Health, and Autoimmune Disease“.  He discusses how Americans eat almost 230 pounds of nightshades on an annual basis, and discusses the potential health consequences of these foods.  With regards to potatoes, he discusses how the glykolalkaloid saponins alpha-chaconine and alpha-solanine create pores in the gut lining, which cause an increase in intestinal permeability.  Dr. Cordain also talks about how eating tomatoes can cause a leaky gut due to the glycoalkaloid alpha-tomatine and the tomato lectin.  He actually spends a good amount of time discussing how tomatoes specifically can lead to autoimmune conditions.  In this paper it is also discussed how the capsaicinoids from chili peppers can cause an increase in intestinal permeability.  Although Dr. Cordain briefly mentions eggplants in his paper, he doesn’t specifically talk about how this food can cause problems, but he still advises people to avoid these, along with the other nightshade foods.

Who Specifically Should Avoid Nightshade Foods?

Anyone with an autoimmune condition should at least consider going on a one-month trial where they avoid all of the nightshades.  This obviously would include those people with Graves’ Disease and Hashimoto’s Thyroiditis.  if you don’t have an autoimmune condition but are experiencing symptoms such as muscle and/or joint pain, or skin problems such as rashes or acne, then you might also want to consider avoiding the nightshades for a short trial.  If after one month of avoiding these foods you’re struggling with the diet and if you’re unsure whether or not the avoidance of these foods is making a difference in your symptoms, you can try reintroducing these foods one at a time for three consecutive days and see how you respond.

Although some people are able to eventually reintroduce nightshades back into their diet without a problem, others find that eating these foods worsens their condition, even after avoiding them for a prolonged period of time.  If this is the case then you very well might need to give up certain nightshades on a permanent basis.  But since these foods do have some good health benefits, if someone is able to eat them without causing any negative health issues then that’s wonderful.  While one might still want to limit their consumption of these foods due to the antinutrients, overall these foods have some good health benefits.  Also, keep in mind that while some people react to all of the nightshades, other people are able to tolerate some of these foods but not others.  For example, someone might do fine eating eggplant, but experience joint pain, migraines, or other symptoms when eating tomatoes.

In summary, although nightshade foods have numerous health benefits, they also can cause problems in susceptible individuals.  Because those people with autoimmune conditions seem to have a greater risk of having a negative reaction to these foods, people with Graves’ Disease and Hashimoto’s Thyroiditis should at least consider avoiding these foods for one month.  If someone has noticeable symptoms when reintroducing nightshades they of course will want to eliminate them on a permanent basis.  The evidence Dr. Loren Cordain presents in his paper might seem to suggest that everyone should avoid these foods, but I don’t necessarily agree, although it might be wise not to consume too many of these foods.  For more information on nightshades I would read Dr. Cordain’s paper, and there’s also an excellent article on nightshades [7] by Dr. Garret Smith of the Weston A. Price foundation.  Another terrific resource to check out is the book “The Paleo Approach” by Sarah Ballantyne, as in the first part of her book she discusses the science behind why certain foods such as the nightshades should be avoided by those with autoimmune conditions.  In my opinion, everyone with an autoimmune thyroid condition can benefit from reading this book.