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More and more, people with thyroid problems and their providers are turning toward nutritional solutions to help keep their thyroid hormones in check. While nutrition is not the only answer for treating conditions like Hashimoto’s disease (autoimmune thyroiditis), it is still important in optimizing your overall thyroid health. Ahead, a look at a lectin, a specific compound found in many foods that may or may not be problematic when ingested in people with autoimmune thyroid disease.

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Lectins are proteins that bind carbohydrates. Most often found in plant-based foods, especially wheat and legumes, lectins protect the plant’s structure in nature. The problem with these proteins is that when they enter the human digestive system, they resist normal breakdown processes in the gut. That is, they do not break down in the acidic environment of the stomach. 

Lectin concentrations can differ between plants and also change with cooking processes. For example, when legumes like kidney beans are cooked in high heat by either boiling or stewing, lectins can become inactivated. Lectins are water-soluble and usually reside on the outer surface of a food source so that water will remove them with the proper cooking practices.

Lectins are in plant-derived foods, including:

• Beans
• Legumes
• Peanuts
• Cashews
• Tomatoes
• Potatoes
• Eggplants
• Peppers
• Grains (including wheat)
• Corn
• Soybeans

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Many popular fad diets have been born out of the theory that lectins are the “anti-nutrient” and are the culprit behind the growing obesity pandemic. Unfortunately, they are also dinged for being problematic in causing autoimmune diseases and chronic inflammation. 

While limited research supports lectins being drivers of disease, some published studies suggest negative attributes to these proteins. 

Firstly, when lectins get consumed in their active state (raw and uncooked), it may cause symptoms like nausea, vomiting, bloating, gas, and diarrhea. In addition, one study finds that people who eat raw or undercooked kidney beans may ingest too much phytohaemagglutinin, which is a type of lectin that can cause red blood cells to bind together and cause clotting. 

Secondly, animal studies show that eating active lectins may block the absorption of essential minerals. Not getting enough calcium, phosphorous, iron, and zinc may be problematic long-term. Many of the foods that contain these minerals also contain lectins.

Thirdly, these same animal studies also suggest that lectins may bind to the digestive tract, preventing the breakdown and absorption of other nutrients from other foods and potentially disrupting the microbiota in your gut. 

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Lectins may cause or exacerbate leaky gut, one of the leading theories behind autoimmune diseases like autoimmune thyroid disorders (Hashimoto’s thyroiditis, Graves’ disease) or rheumatoid arthritis. 

The leaky gut theory suggests that the epithelial lining of the intestinal mucosa becomes more permeable. This permeability allows food antigens, toxins, and pathogens to escape the digestive tract and enter the bloodstream. Under normal conditions, these things should not enter the bloodstream. However, long-term exposure to toxins in the body can cause chronic inflammation and over-responsiveness of the immune system. 

Hashimoto’s thyroiditis is the most common cause of hypothyroidism in the United States. In this condition, the immune system detects cells in the thyroid to be foreign, and it sends TPO antibodies to attack them. Over time, this leads to chronic inflammation of the thyroid and eventual failure. 

People with Hashimoto’s may benefit from avoiding certain foods with lectins or at least ensuring they cook them properly to decrease the number of dietary lectins, to ward off further irritation and disruption of the intestinal lining, which could potentially cause a Hashimoto’s flare-up.

Labeling lectins as “bad” is also problematic, as there are some benefits to these foods. For example, lectins can act as antioxidants, protecting your body from free radicals, which are also known to cause disease. They may also slow down your digestion of carbohydrates, which can keep blood sugar and insulin levels more stable. 

We also have several studies that show foods with lectins offer cardioprotection. Indeed, eating legumes, whole grains, and nuts is encouraged for people at risk for heart disease and type 2 diabetes. 

Not to mention, these foods are also excellent sources of B vitamins, proteins, healthy fats, and fiber.

So, do the negatives outweigh the potential harm of lectin foods? 

Probably. Eating these items offers many nutritional benefits. Furthermore, many of these foods are staples in developing countries, where most of the diet includes legumes, different types of wheat, and nuts. 

Perhaps the key takeaway on lectins is to ensure they are adequately cooked. This way, your gut has the best chance of digesting them without the potential complications of uncooked lectin-containing foods. And, as always, if you identify a lectin-contain food as problematic for your Hashimoto’s symptoms or you have an unpleasant reaction to it (like gas, bloating, and diarrhea), you may want to avoid or reevaluate eating that food.

A note from Paloma Health

Sifting through the different diets and the nutritional do’s and don’ts can be challenging and stressful, especially when you have an autoimmune thyroid disease like Hashimoto’s thyroiditis. Yet, we know that nutrition is a meaningful way to curb symptoms of an autoimmune disorder. If you have a thyroid condition, consider meeting with a Paloma Health thyroid nutritionist as part of your healthcare team to help you optimize your thyroid health.