Quercetin Side Effects Thyroid

For people struggling with common thyroid disorders, such as hypothyroidism or hyperthyroidism, nutrition plays an important role in maintaining overall health. While getting the right nutrition is crucial, taking too much of some nutrients could impact – and even hinder, in some cases – proper thyroid function. Keep reading to find out about how plant-derived flavonoids like quercetin, specifically, may interfere with thyroid function. Learn about the potential effects of quercetin on thyroid function and which foods to eat for thyroid support.

For people struggling with common thyroid disorders, such as hypothyroidism or hyperthyroidism, nutrition plays an important role in maintaining overall health. While getting the right nutrition is crucial, taking too much of some nutrients could impact – and even hinder, in some cases – proper thyroid function. Keep reading to find out about how plant-derived flavonoids like quercetin, specifically, may interfere with thyroid function. Learn about the potential effects of quercetin on thyroid function and which foods to eat for thyroid support.

What is Quercetin?

The flavonoid quercetin is one of the plant pigments (polyphenols) that gives fruits and vegetables their color. The effects of flavonoids like quercetin also provide health benefits by supporting cell receptors and by offering antioxidant and anti-inflammatory properties. (1) Among the subgroups of flavonoids are flavonols, including quercetin (the most common flavonol, which is found in ginkgo biloba, onions, and other plant compounds) and kaempferol (commonly found in red fruits like cherries). (2)

Flavonoids (and therefore flavonols) have antioxidant properties that help neutralize free radicals, protect cell membranes against damage and maintain a healthy cell line, and prevent some of the damage caused by oxidative stress. They also have anti-inflammatory properties (by acting as inhibitors in the production of inflammation-producing enzymes) and antihistamine effects, which is why some people take a quercetin supplement to temporarily relieve allergy symptoms, support the immune system, and support a healthy internal response, among other potential health benefits. (3)

In addition, quercetin is taken to support healthy blood pressure and cholesterol levels already in a normal range. A quercetin treatment in clinical trials was shown to reduce systolic blood pressure significantly when taken by women with Type 2 diabetes as a 500 mg capsule daily. However, quercetin did not show inhibition to cardiovascular risk factors. Further in vitro studies are warranted. (4) Other studies show that quercetin protects LDL ("good") cholesterol, and people who eat fruits and vegetables high in flavonoids such as quercetin have lower cholesterol, potentially lowering their risk for heart disease. (5)​​

Summary

Quercetin is a plant-derived pigment with antioxidant and anti-inflammatory properties that is found naturally in foods and can be taken as a daily supplement to support overall health and wellness.

How Flavonoids Like Quercetin Affect Thyroid Function

When it comes to quercetin side effects, thyroid-related and otherwise, there is some controversy over the potential toxic effects of excessive intake of flavonoids. Studies have demonstrated that quercetin and similar flavonoids may interfere with thyroid function when taken in high doses. (6)

When it comes to endocrinology, quercetin is believed to be an endocrine disruptor, interfering with the body's hormones and inhibiting thyroid cell growth. Experimental data suggests that quercetin side effects, thyroid-related and otherwise, include interfering with many aspects of the synthesis of thyroid hormones. While flavonoids were shown to inhibit cell growth in thyroid tumor cells, they also decreased thyroid hormone levels. This could lead to an overactive thyroid stimulating hormone (TSH), which could cause goiter, and it could reduce efficacy of radioiodine therapy used in some thyroid disorder treatments. (7)

Summary

Studies have shown that excessive intake of flavonoids such as quercetin may interfere with thyroid function, so people with thyroid disorders should use caution when introducing quercetin and other flavonoids into their diet.

Hypothyroidism vs. Hyperthyroidism: What’s the Difference?

If you have thyroid disorders, you probably already know the difference between hypothyroidism and hyperthyroidism. But if you don’t, we’ll review the basics here.

The thyroid gland has been described as a small, butterfly-shaped gland in the neck that is part of the endocrine system. Its job is to release hormones that regulate the body's metabolism, growth, and development, nervous system, muscles, and blood circulation. Each year, an estimated 13 million Americans are affected by thyroid disorders such as hypothyroidism and hyperthyroidism. (8)

Hypothyroidism

Hashimoto’s thyroiditis, also known as Hashimoto’s disease, is an autoimmune disorder that occurs when the thyroid gland doesn’t produce enough hormones, and the immune system produces white blood cells and antibodies that attack (and sometimes scar) the thyroid. Genetics and environmental factors are believed to be the cause of this disorder. In addition, the body slows down its metabolism, causing weight gain, fatigue, constipation, and hair loss. Hormone therapy is usually given as a treatment.

Menopause and Hypothyroidism Diet: Menopause can also cause symptoms similar to hypothyroidism, including sensitivity to cold, increased body fat, depression, poor memory, and other symptoms. Middle-aged women experiencing menopause produce a reduced amount of estrogen levels, which can affect thyroid function and lead to thyroid disorders. (9)

When it comes to a menopause and hypothyroidism diet, eating healthy, well-balanced meals is important. Women with an estrogen deficiency may be prescribed HRT to help manage menopausal symptoms. Women with hypothyroidism who are being treated for menopause with HRT may need thyroid function tests to be re-checked to see if they need a boost in their thyroxine dose. (Thyroxine is used to treat an underactive thyroid.) (10)

While there is little evidence that soy may adversely affect thyroid function in people with normal thyroid function, soy foods may increase the risk of hypothyroidism. The key to the menopause and hypothyroidism diet for women who regularly consume soy is to ensure they're getting enough iodine. Also, since the thyroid hormone helps maintain healthy, strong bones, a woman experiencing menopause and hypothyroidism at the same time may be at higher risk for bone fractures. If a woman takes a calcium carbonate supplement, keep in mind it may decrease the absorption of thyroxine by nearly a third. (11)

However, research shows that for post-menopausal women, specifically, intake of flavonoids from foods such as soy, did not affect thyroid function. Soybeans contain antioxidant properties and mimic estrogens. So people with thyroid disorders, especially post-menopausal women, need to check with their healthcare provider before consuming soy, which contains flavonoids like quercetin. (12)

Hyperthyroidism

A bit less common, hyperthyroidism occurs with Graves’ disease, when the thyroid gland produces too much of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), speeding up metabolism and causing rapid weight loss, heart palpitations, tremors, and anxiety. Sometimes treatment options include radioactive iodine or surgery to remove the gland, as well as anti-thyroid medication. (13, 14)

In addition to medication, diet, and lifestyle changes, nutritional supplementation – which we’ll review later in this article – can help to reduce thyroid damage and improve quality of life for people with thyroid disorders.

There are a few more basics to cover first. Let’s start with the myths about how certain foods affect the thyroid gland.

Summary

Hypothyroidism, also known as Hashimoto’s disease, is an autoimmune disorder involving an underactive thyroid. The body's white blood cells and antibodies attack the thyroid gland. Menopause can also cause symptoms similar to hypothyroidism; therefore, women should supplement with iodine and check with their healthcare provider or nutritionist when considering their diet. Hyperthyroidism, also called Graves’ disease, involves an overactive thyroid, increased metabolism and weight loss.

Myths About Foods and Thyroid Disorders

Overall, some of the best dietary flavonoid food sources include green tea, red wine (which contains the powerful antioxidant resveratrol), dark chocolate, berries, red cabbage, kale, and parsley – all foods that people with thyroid disorders are told not to consume.

Common fruits like tomatoes, apples, grapes, berries, as well as vegetables like onions and lettuce, for example, are believed to interfere with thyroid function. While studies show that excessive intake of foods containing flavonoids such as quercetin may actually disrupt thyroid function by inhibiting thyroid-cell growth and iodide uptake, complete food avoidance is unnecessary, unless you have a specific food allergy. The safe bet is to discuss your diet with your healthcare provider or nutritionist before making any major decisions. (15)

According to an article from Northwestern Medicine, most foods are not off limits to people with thyroid disorders, because “the bottom line is everything is fine in moderation, and food will not affect thyroid function for the most part.” One myth is that people with thyroid disorders cannot eat cruciferous vegetables, which include broccoli, cauliflower, Brussels sprouts, and kale, because they are thought to interfere with how your thyroid uses iodine. However, this is not the case if these vegetables are part of a healthy, balanced diet. (16)

Oftentimes, thyroid disorders exist in conjunction with another disorder, such as Celiac disease. Whereas a gluten-free diet cannot reverse a thyroid disorder such as Hashimoto’s disease, a gluten free diet for hypothyroidism may help improve and maintain the health of someone with Celiac disease. (17)

Summary

If you have a thyroid disorder, complete food avoidance is unnecessary. You should be able to consume all foods within moderation and not interfere with thyroid function. However, you should still consult with your healthcare provider or nutritionist.

Gluten Free Diet for Hypothyroidism

The high level of antibodies in someone with Hashimoto’s disease is believed to react adversely to the protein structure of gluten, which is similar to the structure of the thyroid. So avoiding gluten if you have hypothyroidism may help reduce symptoms related to antibodies. (18)

A gluten free diet for hypothyroidism could help people who have both the thyroid disease and Celiac disease by reducing inflammation and antibodies. One study of 34 women with Hashimoto’s disease reported that a gluten free diet for hypothyroidism reduced antibody levels. However, further research is needed. (19)

Instead of avoiding foods and supplements containing flavonoids if you have quercetin thyroid concerns, it’s important to look for foods and supplements containing thyroid-supporting vitamins and minerals, as follows.

Summary

A gluten free diet could help people with hypothyroidism and Celiac disease by reducing inflammation and antibodies.

Thyroid-Supporting Vitamins and Minerals

For those people with thyroid disorders who are worried about quercetin side effects, thyroid-related and otherwise, you can turn to thyroid-supporting, antioxidant-rich vitamins and minerals such as vitamin B12 and B complex vitamins, vitamin C, vitamin D, curcumin, iron, magnesium, myo-inositol, selenium, and zinc. (20)

Vitamin B12 / B Complex Vitamins: People with Hashimoto’s disease commonly have a vitamin B12 deficiency, which is why taking a vitamin B12 or B complex supplement may help maintain optimal B12 levels. (21)

Liposomal B-Complex Multivitamin by Core Med Science is a dietary supplement that contains all essential B vitamins in their active, usable form in a highly absorbable liposomal blend of phospholipids from non-GMO sunflower oil and sunflower lecithin. This superior formula also contains vitamins A, C, D3, E, K, iodine, zinc, and methylated vitamin B12 in convenient softgels to support healthy energy levels, heart health, clear thinking, mood, cravings, sleep, and more. (22, 23)

Vitamin B12 can also be found in whole grains, legumes, nuts, milk, yogurt, meat, fish, eggs, seeds, and dark leafy greens. (24)

Vitamin C: Research suggests that vitamin C from citrus fruits may help reduce thyroid antibodies in people with Hashimoto’s disease, which is the most common cause of hypothyroidism in the U.S. In patients with hypothyroidism, vitamin C improves the abnormalities in T3, T4, and TSH. (25, 26)

Lypospheric Vitamin C by LivOn Labs is a drinkable powdered dietary supplement delivering nutrients for antioxidant support, including 1,000 mg of vitamin C, (1,111% of daily allowance) as sodium ascorbate, 1,000 mg of essential phospholipids, and 60 mg choline. Liposomal vitamin C is the most easily absorbable form of the supplement, which the body can use right away to protect the immune system and other critical bodily functions. (27, 28)

Vitamin D: The body relies on vitamin D to maintain homeostasis between calcium and phosphorus, thus protecting bone health. Studies show that people with Hashimoto’s disease and Graves disease tend to have lower vitamin D levels. That's why supplementation is important. (29)

Vitamin D Gummies by Genestra is a dietary supplement of delicious chewable vitamin D gummies in a natural raspberry flavor that delivers 25 mcg of vitamin D3 (as cholecalciferol) for ages 3 and up. It contains NO artificial colors or flavors, and less than 0.5 g total sugars per gummy. So if you’re looking for vitamin D gummies, these are worth a try. (30, 31)

You can also get vitamin D from food sources such as egg yolks, salmon, and some fortified foods like breakfast cereals.

Curcumin: Curcumin from turmeric root has powerful, natural antioxidant properties that may help reduce the size of thyroid nodules. You can also add a curcumin supplement to your diet to experience the potential health benefits, but be sure to take one that has piperine (black pepper) in it for enhanced absorption. (32)

Iron: Low iron levels or iron deficiency anemia has an adverse effect on thyroid function, which is why an iron supplement may be necessary. Iron deficiency is common in women with thyroid disorders. Good sources of heme iron can be found in red meats, fish, and poultry. Non-heme iron from plant sources such as whole grains, nuts, seeds, legumes, and leafy greens. (33, 34, 35)

Magnesium: A magnesium deficiency could increase your risk of developing Hashimoto’s disease. It is also associated with increased thyroid antibody levels. Take a magnesium supplement to reduce symptoms related to thyroid disorders. Or eat foods rich in magnesium, such as almonds, pumpkin seeds, peanuts, cashews, and spinach. (36, 37)

Myo-inositol: A type of sugar, inositol plays a critical role in thyroid function. Research recommends taking 600 mg of myo-inositol and 83 mcg of selenium every day to help improve thyroid function in people with Hashimoto’s disease. Foods containing myo-inositol include cantaloupe, oats, bran, and citrus fruits (other than lemons). (38, 39)

Selenium: Studies show that 200 mcg of selenium per day may help decrease thyroid antibodies and improve mood in patients with Hashimoto’s disease. You can take a selenium supplement, or find it in natural food sources like yellowfin tuna, which contains 92 mcg of selenium per 3 ounces. (40, 41)

Zinc: This essential mineral is required for thyroid hormone production. It’s recommended to take 30 mg of zinc per day alone or with selenium. Good natural food sources of zinc include oysters, red meat, poultry, baked beans, chickpeas, cashews, and almonds. Zinc supplementation is also recommended to help fill any nutritional gaps in your diet. (42, 43)

Zinc Gummies by Genestra are great-tasting zinc gummies made from an organic gluten-free, GMO-free, and vegan fruit blend to support a healthy internal response. Each blueberry-flavored gummy contains 12 mg of zinc citrate per gummy, great for ages 4 and up. This supplement contains NO artificial colors or flavors, and less than 0.5 g total sugars per gummy. (44, 45)

Summary

People with thyroid disorders typically are deficient in certain vitamins and minerals. Therefore, it’s important to supplement with vitamin B12 and B complex vitamins, vitamin C, vitamin D, curcumin, iron, magnesium, myo-inositol, selenium, and zinc.

When shopping for dietary supplements free of potential quercetin side effects, thyroid-related and otherwise, you can trust Natural Healthy Concepts to offer the highest quality, natural vitamins and supplements for your unique needs. (46) Just browse NHC.com for your thyroid health regimen, and see if the potential health effects make a difference for you.

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