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Carbohydrates have received a lot of attention in modern culture as fads to lose weight. Low-carb diets and then eventually even high carb diets were keys to unlocking weight loss. Is there a link between carbohydrates and your under-performing thyroid?

An underactive ​thyroid can be caused by three things regularly: 

With an overall prevalence of nearly 11 percent worldwide, an underactive thyroid is a common disease [2]. Patients will present with symptoms of:

  • fatigue,
  • high blood pressure,
  • problems with weight gain
  • concentration, 
  • and hair loss [3].

A first-line therapy for this condition is based on thyroid hormone supplementation but did you know that there are alternative therapies such as following a hypothyroidism diet, using essential oils for hypothyroidism or even avoiding casein and gluten that could benefit you as well? [4] Your hypothyroidism diet can go a long way into improving your symptoms and may even reverse your underactive thyroid entirely. 

Low Carbs and Your Hypothyroidism 

As you read above, one of the main symptoms of an underperforming thyroid gland is the inability to lose weight even after exercise. It can be quite frustrating and carbohydrates still in your diet can make a difficult task even more impossible.

Studies were conducted to determine how patients with an underactive thyroid respond to a low-carbohydrate diet and the results may surprise you. To make up for the loss of calories, participants' diets were substituted with either high-protein or high-fat foods to meet basic metabolic requirements. Scientists determined that the TSH level (the marker used to determine hypothyroidism) decreased equally in patients using either of the alternative diets. Additionally, researchers observed that participants using a high-fat diet also had lower levels of insulin, less drastic changes in blood glucose levels and even lower triglyceride levels. [5] The high-fat diet had better results in patients than the diet high in protein.

The high-fat diet success does not give you the "green-light" to smother everything in sight with butter if you have an underactive thyroid. The fats that appear to give the most benefit to patients consist of polyunsaturated fats. These fats can be found in:

  • fish like salmon, 
  • walnuts, 
  • sunflower seeds, 
  • and soybean oil to name a few [6]. 

Studies show that substituting these types of fats for the grease you can buy in any fast-food joint can reduce your cholesterol level by 19 percent, reduce your LDL (the bad cholesterol) by 22 percent and increase your HDL (the good one) by 14 percent [7].

It is amazing that a simple dietary modification can go a long way in improving your cholesterol levels, works more effectively than any medication on the market and drastically reduces your risk of heart-related diseases. 

What Can a High-Carb Diet Do? 

Once diagnosed with an underactive thyroid, no one in the right mind could argue that "a high-carbohydrate diet could be beneficial to me" and actively seek out as many carbs as possible to begin therapy. Unfortunately, if you aren't aware of the foods that you are eating now, you may be saturating your body with high carbohydrates accidentally. Sugars, chips, potatoes, and sodas are some of the most-concentrated carbohydrates on our grocery store shelves. 

Strangely enough, high-carbohydrate diets have some benefits. These foods have less energy per gram and compared to individuals on a low-carb or medium carb diet showed that participants on a high-carb diet were more likely to have BMIs (body-mass index scores) below 25. [8] Does this mean that a doctor should write you a prescription for Levothyroxine and a carton of Double-Stuffed Oreo cookies?  Unfortunately, no! 

To prove there is some science behind this reasoning, studies were conducted on animals to determine the effect on high levels of carbohydrates and thyroid function.

It was determined that when coupled with a high-carbohydrate diet, thyroid hormone T3 (the active one) was digested at a rate 3 to 7 times more quickly than compared to a low-carbohydrate diet. This means that the thyroid hormone did not have time to fulfill its function before it was digested and as a result, the body needed to signal more thyroid hormone (in the form of TSH) to make the same necessary process. [9] This is the process of what ultimately leads to hypothyroidism. 

If you are still not convinced because this was just done with animals, a landmark study termed the Vermont study should put all your doubts to rest. In this study, human participants were overfed for 7 months to determine the effects of a high-carbohydrate diet on the metabolism of thyroid hormone. As carbohydrates were consumed, there was an expected increase in T3 levels. This should be clear because as we eat food, our metabolisms become more activated (thus the rise in thyroid hormone). The concentration of active thyroid hormone was reduced, however. This is due to the same reason that thyroid hormones were less effective in our animal studies because the hormone was used up much faster. When these high-carbohydrate diets were switched to high-fat diets instead, the concentration of T3 hormone increased significantly; meaning the thyroid function improved. [10]

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