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Low Carb Diets: Why Your Thyroid Needs Carbohydrates

Learn how low-carb diets impact your thyroid function.
Low Carb Diets: Why Your Thyroid Needs Carbohydrates
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Many people with hypothyroidism suffer from weight gain or find it hard to lose weight, making low-carbohydrate diets an attractive option for weight loss. While cutting your carb intake will help you lose weight, drastically cutting carbohydrates can affect your thyroid function.

If you want to learn how a low-carbohydrate diet can impact your thyroid function, keep reading as we dive deeper into this topic.

What are carbs?

Carbohydrates, commonly shortened to “carbs,” tend to get a bad reputation in the dieting world. The problem? Carbs are sugar (glucose), and we associate sugar with weight gain.

After eating, your body breaks carbs down into individual sugar molecules. Your cells use this sugar as their primary energy source. Without an energy source, your cells have a hard time functioning. It’s like a car: without gas, it won’t work.

Sometimes your body uses carbs right away. But your muscles and liver can also store glucose for later use when needed.

Types of carbs

Not all carbohydrates are created equal. There are two main types of dietary carbs - simple and complex.

A simple carbohydrate is a straight-up sugar. It is the sugar you put in your coffee or in regular soda and processed foods. But simple sugars are also found naturally in fruits, vegetables, and milk.

Complex carbohydrates are .formed from many simple sugar molecules. This group is further broken down based on whether your body can digest them. Here are two examples of complex carbohydrates:

  • Starches are broken down into simple sugars. Common starches include rice, potatoes, peas, and corn.
  • Fiber can’t be broken down by your body. Foods with fiber leave you feeling full longer and can help prevent constipation and lower cholesterol and blood sugar levels. Fiber is found naturally in fruits, vegetables, nuts, seeds, beans, and whole grains.

What is a low-carb diet?

Three macronutrients make up your diet - protein, fat, and carbohydrates. Your body needs a certain amount of each to keep your body functioning. Overconsumption of any of these macronutrients can lead to weight gain if your energy intake exceeds your energy expenditure.

Conventional nutritional guidance recommends that about 50% of your food be carbohydrates. The recommended Daily Value for carbohydrates, as seen on Nutrition Fact labels, is 275 grams daily. But, this amount varies based on age, health conditions, and weight status.

Low-carb diets limit the amount of carbs you can eat, sometimes between 25 grams to 150 grams per day. Examples of low-carb diets include the ketogenic diet, low-carb paleo, and the Atkins diet.

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Effects low-carb diets have on your thyroid

As mentioned, cells need an energy source. Without an energy source, your cell function will decrease. Here are four reasons why carbohydrates are essential for thyroid function:

  1. Thyroid hormones influence your metabolism or how your body uses energy. When your thyroid hormone levels are too high, your metabolism speeds up. Low thyroid hormone levels -- hypothyroidism -- causes your metabolism to slow down. The production of thyroid hormone depends on a constant energy source. Restricting carbohydrate intake can decrease your thyroid’s ability to produce and secrete thyroid hormone. Ultimately, this can leave you feeling more tired or sluggish.
  2. Your thyroid makes two types of thyroid hormone: the inactive T4 (thyroxine) and the active hormone, T3 (triiodothyronine). Most thyroid hormone secreted is T4, which needs to be converted into T3, the active form. This conversion requires a specific enzyme called 5’-deiodinase. Low-carb diets can reduce the activity of this enzyme, resulting in low levels of T3 production.
  3. Carbohydrates trigger the release of insulin, a hormone that regulates blood sugar levels by moving the sugar into your cells. Once inside, your cells use sugar for energy. If your body does not get enough carbs over time, this can impact how your cells respond to insulin, known as insulin sensitivity. A decrease in insulin sensitivity means your cells can’t move sugar into your cells, thus, impacting how they function. In the case of your thyroid, the outcome would be a lack of thyroid hormone production.
  4. Low-carb diets mimic a fasting state, causing your body to rely on other macronutrients for energy. Gluconeogenesis is the process of making sugar from a non-carbohydrate source. Gluconeogenesis increases slightly in those following a low-carb diet. But gluconeogenesis can’t make enough sugar to supply all your cells with a constant energy source. Evidence shows that during a state of fasting, your T3 levels decrease.

In summary, carbohydrates are an essential energy source for all your cells, including your thyroid cells. Not eating enough carbohydrates impacts thyroid hormone production, conversion, and regulation. Thus, low-carb diets may disrupt your thyroid function.

Which diet is best for those with hypothyroidism?

There are many diets to choose from, and there’s no one perfect diet for those with hypothyroidism. Some general tips for creating your thyroid-friendly diet include:

  • Know your sensitivities to certain foods, additives, or chemicals
  • Remove foods that aggravate your body
  • Add healing foods such as ones high in zinc, selenium, and omega-3
  • Stay hydrated

For those with Hashimoto’s thyroiditis, an autoimmune thyroid condition that causes hypothyroidism, following the autoimmune protocol (AIP) diet can be beneficial.

The AIP diet focuses on removing foods that can trigger inflammation in your body, which is particularly helpful for people with autoimmune diseases since inflammation plays a big part in symptoms. A small study showed women with Hashimoto’s saw an improvement in their quality of life, including physical and emotional well-being, while following the AIP diet.

A note from Paloma Health

Finding a thyroid-friendly diet that meets your lifestyle and food preferences can be challenging. Have you considered adding a nutritionist to your thyroid healthcare team? With a nutritionist on your team, you can:

  • Learn about the connection between your thyroid and gut health
  • Address underlying nutritional deficiencies
  • Identify dietary triggers
  • Get a diet specifically tailored to you

Schedule a telemedicine appointment with one of Paloma Health’s nutritionists today!


MedlinePlus. Carbohydrates. Published January 17, 2022. Accessed July 13, 2023.

Mullur R, Liu YY, Brent GA. Thyroid hormone regulation of metabolism. Physiol Rev. 2014 Apr;94(2):355-82. doi:

Russo SC, Salas-Lucia F, Bianco AC. Deiodinases and the Metabolic Code for Thyroid Hormone Action. Endocrinology. 2021 Aug 1;162(8):bqab059. doi:

Harber MP, Schenk S, Barkan AL, Horowitz JF. Alterations in carbohydrate metabolism in response to short-term dietary carbohydrate restriction. Am J Physiol Endocrinol Metab. 2005 Aug;289(2):E306-12. doi:

Danforth E Jr, Horton ES, O’Connell M, Sims EA, Burger AG, Ingbar SH, Braverman L, Vagenakis AG. Dietary-induced alterations in thyroid hormone metabolism during overnutrition. J Clin Invest. 1979 Nov;64(5):1336-47. doi:

Abbott RD, Sadowski A, Alt AG. Efficacy of the Autoimmune Protocol Diet as Part of a Multi-disciplinary, Supported Lifestyle Intervention for Hashimoto’s Thyroiditis. Cureus. 2019 Apr 27;11(4):e4556. doi:

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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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