The Connection Between Thyroid and Digestive Health

Discover the connection between healthy digestion and a healthy thyroid to help balance your hormones and weight.

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Participate in stress-relieving activities, such as exercise or meditation, to reduce cortisol levels.

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It’s easy to see why it seems everyone is suddenly talking about the  thyroid—one in every 12 Americans has a thyroid disorder, according to 2008 statistics from the National Institutes of Health. Symptoms of thyroid disorders can include changes in weight; anxiety or depression; exhaustion; infertility; and possibly even problems with blood sugar.

The thyroid is a butterfly-shaped gland that sits at the base of our throats and affects functions throughout our bodies via hormones that control metabolism. As one digs deeper into the endocrine system—the thyroid gland in particular—it seems there’s no way to truly separate our endocrine health from what’s happening with our digestion. In fact, the two are so tightly linked it becomes a “chicken or egg” situation: Poor gut health can suppress thyroid function, while poor thyroid function can affect the digestive tract and potentially lead to an inflamed gut.

If your digestion is slow, or you suffer from bloating or gas issues, ulcers or acid reflux, you may be experiencing or developing thyroid issues. As with many aspects of health, it’s comforting to know that we can often effect change on such complex disorders by listening to our bodies and making simple changes to our diets and habits.

Note: If you think you have a thyroid problem or have been diagnosed with one, be sure to discuss any efforts to remedy the issue with your doctor. 

Diet and Thyroid Function

These days, thyroid trouble often stems from our diets. Too much or too little iodine is a common culprit—iodine is necessary to produce thyroid hormones. Iodine is commonly found in iodized salt (it’s also in some heart medications and cold and flu medicines), but many people have decreased their iodized salt intake for a number of reasons: concerns over its impact on blood pressure; a preference for sea salt, which doesn’t contain iodine; or to avoid anticaking agents, some of which are aluminum compounds. And although many Americans eat processed foods that are high in salt, according to the National Institutes of Health, “The majority of salt intake in the U.S. comes from processed foods, and food manufacturers almost always use non-iodized salt in processed foods.” Even for those who do consume enough, water that contains chlorine or fluoride may inhibit iodine absorption. However, iodine consumption is a delicate balance. We don’t recommend supplementation without the advice of a professional health-care provider.

Selenium is another important nutrient for the thyroid, but much of it can be lost in the processing, storage and cooking of our food. Portions of our country are covered in soil that’s deficient in this trace mineral. Because of this, meats and vegetables we expect to contain selenium may not.

One of the most common problems with digestion in America is also an emerging field of study: We are increasingly realizing that healthy gut flora is critical. If your digestion is not functioning optimally (one to two bowel movements per day and no bloating, reflux or significant gas), it’s possible that your gut flora is not well-balanced. Unhealthy bacterial overgrowth can occur in this case, and these bacteria also interact with selenium, potentially making less available for us to absorb from our food. Finally, some outbreaks, such as E. coli, may lead to inhibited thyroid hormone production.

Other Contributing Factors

Hormone-Distrupting Chemicals: Because the thyroid is dependent on proper hormone function, hormone-disrupting chemicals can unbalance our endocrine systems. For example, plastic food-storage containers and cups often contain hormone-disrupting chemicals such as bisphenol-A (BPA) or phthalates. Storing food and beverages in plastic may eventually alter hormone production. Other plastic products on the market, such as toothbrushes, cutting boards and kitchen tools, can also contain the antibacterial chemicals triclosan and triclocarban, which are also potent endocrine disruptors. Ingestion of pesticide residues; prescription antidepressants; corticosteroids (over-the-counter medications for allergies, asthma and arthritis, and topical rash creams); and long-term use of salicylates (found in aspirin) and dicoumarol (found in blood thinners) are also common potential sources of problems. Finally, the thyroid may be inhibited by otherwise healthy dietary choices such as raw turnips, cabbage, mustard, peanuts, pine nuts and millet, as well as soy. These plants may act as goitrogens, which can interfere with the absorption of iodine.

Stress: Stress is often ground zero for both digestive and thyroid issues. In our collective distant past, stressful events were often fewer—albeit larger—and farther apart. Our bodies may have had more time to return to normal levels of peace between stressful incidents. When faced with stress, digestion can come to a full stop as the body diverts energy away from more frivolous pastimes such as assimilating what you had for lunch to more important matters such as quickly getting away from something that wants to eat you for lunch. Today, we are less likely to have to run from a predator, but may be more likely to experience daily stresses rather than occasional ones. Our digestive system, however, reacts in the same way to either stressor, and can shut down its important duties of digestion. A digestive system that’s halted too frequently becomes unable to digest properly. This not only contributes to an impoverished nutritional state but also creates an environment rich in inflammation.

Cortisol is a stress hormone that’s released when we sense danger, but increased daily stress has led to long-term increased cortisol levels. The thyroid and adrenal glands are involved in a complex feedback system, resulting in the secretion of various hormones. As the adrenal glands produce more and more cortisol, production of the most active of the thyroid hormones, triiodothyronine (T3), is inhibited. Alterations to T3 levels can lead to various thyroid disorder symptoms, including changes in bowel function, weight loss or weight gain, and an increase in carbohydrate cravings.

Extreme Calorie Restricting/Fasting: Finally, we can create the perfect storm in our bodies when we add calorie-restrictive diets and/or fasting to the continual stress we experience. Fasting and significant dieting lowers production of T3. When the thyroid is over- or underactive, we experience changes in our appetites. With these feelings we mistake for “hunger,” we can become obsessed with food in the extreme of too much or too little.

How to Support Digestive and Thyroid Health

1. Eat a pinch of “living” foods at every meal. Good options include fermented vegetables such as kimchi or sauerkraut, and the living bacteria found within high-quality yogurt, kefir and kombucha.

2. Eat organic food as much as possible to reduce pesticide exposures, which may negatively affect our hormones and our microbiome (gut bacteria).

3. Reduce stress or increase stress-relieving activities. Stress is directly linked to an increase in cortisol levels.

4. Increase the intake of prebiotics such as garlic, onions, bananas, Jerusalem artichoke, burdock root and dandelion root to feed your healthy gut flora.

5. Increase your intake of essential fatty acids, found in fatty fish, pasture-raised beef, many nuts and seeds, enhanced eggs and dairy products, and more.

6. If you have been diagnosed with hyperthyroidism or Graves’ disease, eat seaweed sparingly—about 1⁄8 to 1⁄4 teaspoon of kelp per day—and have your iodine levels monitored by a professional.

7. Change your diet. Many professionals recommend avoiding gluten altogether for at least six months. In my opinion, unless you have a true food allergy (such as Celiac disease), gluten is not the problem. Simply avoid eating a meal filled with large, hard-to-digest foods (such as meat, dairy and grains) directly after eating another meal filled with large, hard-to-digest foods. Intersperse these meals with easy-to-digest foods—steamed vegetables, bone broth, soup—to keep the workload light and manageable.

8. Add these key nutrients to your diet: Selenium (oysters; Brazil nuts; tuna; kelp; whole grains and vegetables grown in selenium-rich soil; mushrooms; chicken, pork and beef raised on selenium-rich soil; sunflower and sesame seeds); zinc; beta-carotene; vitamins B2, B3, B6, C and E; and iodine (garlic, asparagus, lima beans, mushrooms, sesame seeds, spinach, turnip greens, Swiss chard, summer squash).

9. Support your adrenal glands at the same time by aiming to get the Recommended Dietary Allowance of magnesium, calcium and vitamin C through your diet.