Is the ketogenic diet safe for thyroid health? The potential risks of a keto diet

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Dr. Khoshaba

January 9, 2023

We’ve seen a lot of buzz around the ketogenic diet- but can it have long term side effects? Its quite possible.

What is the ketogenic diet?:

The ketogenic diet is a low carbohydrate, adequate protein and high fat diet. This means that a majority of your carbohydrates are coming from fats, a good amount from protein and very little from carbohydrates.

The premise of the ketogenic (or keto) diet is that by starving your body from its main glucose sources (carbohydrates), the body starts to rely on ketone bodies. Ketone bodies are fuel that your liver produces from store fat. Essentially, your body is focused on burning your fat for fuel, instead of dietary glucose from carbohydrates.

The ketogenic diet has gained popularity within the past few years and has helped many people successfully lose weight, reduce insulin resistance and even help manage some chronic conditions like epilepsy.

But is this diet safe long-term and safe for everyone? 

The short answer is no and you should consult with your Physician before initiating such a restrictive diet.

The ketogenic diet has you avoid carbohydrates. While avoiding or restricting refined carbohydrates is generally good for most people, avoiding all carbohydrates can put you at risk for becoming deficiencies in essential micronutrients.

healthy meal

Fruits and vegetables, while “good” carbohydrates, are still considered carbohydrates on the ketogenic diet and restricting them from your diet puts you at risk for missing out on some important vitamins and minerals. Short term, this may not have a big impact on your health, however, your thyroid needs an array of nutrients to function optimally.

Some of these nutrients include selenium, iodine, iron and zinc. You might be thinking- a lot of these nutrients you can get from animal proteins or nuts. Yes- you certainly can. But don’t forget about the other vitamins that are also important in the proper function of your thyroid.

Your other vitamins and minerals like magnesium, Vitamin C and your B Vitamins play an integral role in your thyroid function. But don’t forget- your thyroid doesn’t work alone! Your other glands, like your adrenal glands, for example, rely on adequate nutrition. If your adrenal glands aren’t functioning properly, your thyroid starts to suffer.

Look at your glands like a three-legged chair. For women, think of your adrenal glands, your thyroid gland and your ovaries. Men- think of your adrenal glands, your thyroid gland and testes. When one of these glands isn’t functioning optimally, the 3-legged chair is no longer stable and inadvertently the other glands start to compensate. 

What is your thyroid?

An image showing a thyroid gland
Your Thyroid Gland Illustrated

Your thyroid is a butterfly-shaped endocrine gland located at the base of your neck responsible for many aspects of how your body functions. Your thyroid is located at the front of your neck, along the front of your trachea, above your collarbone, and below your larynx. In males, the thyroid can be found directly below the Adam’s apple.

Your thyroid is responsible for many of your body’s functions. Your thyroid gland helps release and control your thyroid hormones which help regulate metabolism. Your thyroid hormones include thyroxine, also known as T4, and triiodothyronine or T3. Your thyroid hormones play a significant role in your body's metabolism, helping regulate your:

  • body temperature
  • weight
  • energy
  • bowel movements
  • hair
  • skin

So how exactly can a ketogenic thyroid negatively affect your thyroid?

We’ve mentioned your two main thyroid hormones, T3 and T4. Well, you see your thyroid relies on glucose to not produce these hormones but also to convert them to their active form.

When you don’t eat enough carbohydrates in your diet, the production and conversion of your thyroid hormones is slowed down, putting more strain on your thyroid. By suddenly eliminating carbohydrates from your diet completely, your thyroid may make a hormone called reverse T3, which prevents you from producing the most active form of thyroid hormone T3.

Cinnamon rolIs for  the ketogenic diet safe for thyroid health?: The potential risks of a keto diet

This isn’t to say that you should be eating a ton of carbohydrates to optimize your thyroid function, but what we’re saying is to focus on high quality carbohydrates like fruits, vegetables, nuts, seeds and whole grains. By giving your body an appropriate amount of healthy carbohydrates that are rich in nutrients, antioxidants and fiber, you are setting your thyroid health up for success. 

And as if we didn’t emphasize the adrenal glands enough. Your adrenal glands produce a hormone called Cortisol. This is your stress hormone. Your body is unable to differentiate between “good” stress and bad stress. When your body is stressed, it is in a sympathetic state and always thinks you’re running away from a bear. For some people, a restrictive diet can put their body into this type of stress response.

Whether it be the drastic dietary change, a sudden lower intake of calories, or the absence of glucose, your adrenal glands start will start to produce your stress hormone, cortisol. When in excess, your other hormones like your sex hormones may begin to plummet. 

This is not to say that a ketogenic diet will cause hypothyroidism as that is too dramatic of a statement to make, however, there may be a connection with a long-term ketogenic diet and hindered thyroid function. What does this mean?

If you are following a ketogenic diet for other reasons, perhaps increase carbohydrates slightly and focus on net carbs instead of just carbs. Net carbs is the total amount of carbohydrates in a food minus the fiber content. This way you will ensure that you are obtaining an adequate amount of nutrients, fiber, minerals and antioxidants.

Also, make sure to check in and see how you’re feeling. Consult with your Doctor if you sense something is “off” and regularly get your thyroid levels checked. Be sure to ask your Doctor to check a full thyroid panel including thyroid stimulating hormone (TSH), Free T3, Free T4, Reverse T3, Anti-Thyroperoxidase and Thyroglobulin Antibody. Remember- the ketogenic diet is not intended to be done long-term so perhaps cycling in a ketogenic diet for a few weeks at a time may be more beneficial long-term.

Is Keto Really Safe for Your Thyroid?

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Dr. Linda Khoshaba is the Leading Integrative Health and Hormone Doctor in Scottsdale, Arizona. She has extensive experience working in the field as a Hormone Specialist and Natural Endocrinologist.

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