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Free Radicals, Antioxidants, and Your Hypothyroidism

Learn about free radicals and how they affect your thyroid.
Free Radicals, Antioxidants, and Your Hypothyroidism
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What are free radicals, and what do they have to do with your thyroid? Your days of learning about molecules and atoms may seem like a lifetime ago. But, to understand the concept of free radicals, let’s first do a brief chemistry refresher!

Atoms are the building blocks of all physical substances. Atoms join together to form molecules. For instance, three atoms make up a molecule of water (H2O): two hydrogen atoms and one oxygen.

Each atom has a set number of electrons -- usually pairs of electrons -- that circle its nucleus (the center of the atom). When an atom has all its electrons, it is considered stable. But sometimes, an atom loses an electron, making it unstable. The atom then has to find and “steal” an electron from another atom, allowing the atom to become stable again.

Keep this idea of stable versus unstable in mind as we examine how free radicals affect your thyroid gland.

What are free radicals?

A free radical is an unstable molecule that is missing an electron. In the search for another electron, free radicals can “steal” an electron from other cells in your body. When this occurs, those other cells now have one less electron, affecting how that cell functions.

What causes free radicals?

Free radicals get a bad rap, rightfully so, but some free radicals formation is part of the normal metabolic process in your body. Your body actually needs small numbers of free radicals to function. For instance, the immune system uses free radicals to help destroy germs. Free radicals have adverse effects only when they build up to high levels.

As you age, your body may naturally increase free radical formation. In addition, your body makes more free radicals during times of:

Outside sources may also promote free radical formation. These include:

  • Cigarette smoking or second-hand smoke exposure
  • Alcohol consumption
  • Air and water pollution
  • Heavy metals
  • Radiation exposure

Free radicals can cause oxidative DNA damage and harm to cell membranes and other parts of cells.

How do antioxidants protect against free radicals?

Antioxidants are molecules that neutralize free radicals and prevent or delay some types of cell damage. As “free radical scavengers,” antioxidants travel throughout your body, looking for free radicals. Antioxidants give free radicals an electron, thus making them stable and preventing them from damaging your cells. Antioxidants enzymes can set in motion the breakdown of reactive oxygen species (ROS) -- oxygen-containing free radicals that can be especially damaging. Other antioxidant properties include the ability to “chelate” heavy metals, making them non-reactive and, in some cases, removing them from the body entirely.  

Antioxidants are found in many foods, especially in fruits, vegetables, and other plant-based, whole foods. Vitamins C and E and selenium are just a few antioxidants, but there are many others. Your body also generates some of its own antioxidants, like the cellular antioxidant glutathione.

What is the link between free radicals and oxidative stress?

Oxidative stress is when your body has more free radicals than antioxidants, and you can’t counteract or detoxify the harmful effects of the free radicals. It is caused by an excess production of reactive oxygen species (ROS) relative to antioxidant levels. 

When your antioxidant capacity can’t keep up with the cell damage, you can develop oxidative damage, affecting cell function negatively. 

Oxidative stress plays a role in the development of many medical conditions, including:

  • Autoimmune disorders, including Hashimoto’s and rheumatoid arthritis
  • Cardiovascular disease
  • Kidney problems
  • Asthma
  • Cataracts
  • Neurological conditions such as memory loss, Alzheimer’s, or Parkinson’s disease

As you can see, free radicals can negatively impact many parts of your body. Let’s look specifically at how free radicals affect thyroid function.

How do free radicals affect your thyroid function?

Interestingly, your thyroid needs some free radicals for the production of thyroid hormone and thyroid hormone synthesis. Thyroid hormone production not only uses -- but also produces -- a fair amount of free radicals. Because of this, your thyroid gland is at high risk of exposure to oxidative stress.

Since the thyroid both needs and generates free radicals, your body has antioxidant properties to protect your thyroid and help balance free radical formation. But as we know, this balance can be thrown off. People with hypothyroidism tend to have a high level of free radical production with lower antioxidant levels. Mitochondrial dysfunction, elevated cholesterol levels (hyperlipidemia), metabolic syndrome, and other metabolic disorders are also more common in hypothyroidism, and these conditions can increase oxidative stress.

A recent 2021 study confirms that thyroid disorders increase the release of free radicals. Furthermore, increased free radicals in your thyroid may prevent thyroid peroxidase (TPO), an enzyme needed for making thyroid hormones, from functioning correctly. Because of this, your thyroid hormone production changes, possibly leading to hypothyroidism.

Hashimoto’s thyroiditis and free radicals

Hashimoto’s thyroiditis, one of the most prevalent autoimmune diseases, is the most common cause of hypothyroidism. It occurs when your immune system mistakenly identifies your thyroid cells as foreign invaders and attacks them. The destruction of your thyroid cells by your immune system causes two things to happen:

  • Thyroid cells become damaged and die, affecting the production of thyroid hormone.
  • Production of autoantibodies against your thyroid cells continues your immune system’s attack on them.

This process increases free radicals in your thyroid, leading to increased levels of oxidative stress. And oxidative damage, particularly in those with Hashimoto’s, causes:

What should hypothyroid patients do?

If you’re a patient with hypothyroidism, you should try to incorporate foods high in antioxidants into your diet to improve your antioxidant status. Eating a diet rich in antioxidants can increase your antioxidant levels, help prevent cell damage associated with free radicals, and prevent oxidative damage. Antioxidants are also thought to boost your overall health.

The best source of antioxidants is a diet rich in plant-based foods such as fruits, vegetables, whole grains, nuts, seeds, herbs, and spices. Some antioxidant-rich foods include:

  • Fruits such as blueberries, cranberries, strawberries, blackberries, raspberries, cherries, goji berries, apricots, cantaloupe, mangos, oranges, and grapefruits
  • Vegetables such as asparagus, beets, broccoli, carrots, bell peppers, kale, turnips, and green leafy vegetables, such as spinach, kale, and collard greens
  • Spices such as black pepper, cayenne, cloves, cinnamon, garlic, ginger, and turmeric

(Pssst! Dark chocolate is also an excellent antioxidant!) 

Another way to increase antioxidants is through dietary supplements, especially supplemental vitamin C and vitamin E. It is important to note that getting your antioxidants from a nutritious diet is considered safe, but taking supplements in high amounts can be counterproductive and cause other health issues. Before starting any supplements, be sure to talk with your healthcare provider. You may already get enough antioxidants through your diet or other supplements, especially if you take a multivitamin.  

A note from Paloma Health

For patients with hypothyroidism, increasing antioxidant intake and improving oxidative status may help manage the underactive thyroid condition alongside medical treatment. Working with a Paloma Health nutritionist can help you incorporate foods and safely add supplements high in antioxidant activity to get your antioxidant status back on track. 

Optimal treatment of your hypothyroidism is also a foundation of your overall health. Paloma Health’s thyroid specialists take a personalized, holistic approach to managing your hypothyroidism. Set up an appointment with one of them today for comprehensive care.


Pham-Huy LA, He H, Pham-Huy C. Free radicals, antioxidants in disease and health. Int J Biomed Sci. 2008;4(2):89-96.

Kochman J, Jakubczyk K, Bargiel P, Janda-Milczarek K. The Influence of Oxidative Stress on Thyroid Diseases. Antioxidants (Basel). 2021;10(9):1442. doi:10.3390/antiox10091442

Chakrabarti SK, Ghosh S, Banerjee S, Mukherjee S, Chowdhury S. Oxidative stress in hypothyroid patients and the role of antioxidant supplementation. Indian J Endocrinol Metab. 2016;20(5):674-678. doi: 10.4103/2230-8210.190555

Mikulska AA, Karaźniewicz-Łada M, Filipowicz D, Ruchała M, Główka FK. Metabolic Characteristics of Hashimoto’s Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management—An Overview. Int J Mol Sci. 2022; 23(12):6580. doi:10.3390/ijms23126580

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Emilie White, PharmD

Clinical Pharmacist and Medical Blogger

Emilie White, PharmD is a clinical pharmacist with over a decade of providing direct patient care to those hospitalized. She received her Doctor of Pharmacy degree from Massachusetts College of Pharmacy and Health Sciences. After graduation, Emilie completed a postgraduate pharmacy residency at Bon Secours Memorial Regional Medical Center in Virginia. Her background includes caring for critical care, internal medicine, and surgical patients.

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