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Opinion

Diet and the thyroid

Monica Therese Cating-Cabral, MD

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There are many misconceptions about the thyroid, particularly when it comes to the diet. In celebration of Goiter Awareness Week, which is observed in the Philippines every fourth week of January, let’s set straight some misconceptions about how food can affect the function of your thyroid and your metabolism.

The thyroid is a small butterfly-shaped gland just above your collarbone in the front of the neck. It makes thyroid hormone, a substance that controls your metabolism — the sum total of all chemical processes in the body that allow us to function every day. Any enlargement of the thyroid is known as a goiter, which may also be associated with abnormal hormone levels.

If you lack thyroid hormone due to an underactive thyroid or if the thyroid gland has been surgically removed, this is called hypothyroidism, and your metabolism can be slow where you may gain weight, feel sluggish, cold all the time and constipated.

An excess of thyroid hormone is called hyperthyroidism, and your metabolism can be faster, with weight loss, sweats, tremors, palpitations and frequent bowel movements.

Myth No. 1: You should take iodine supplements if you have a goiter.

Your thyroid needs iodine to make thyroid hormone. But while iodine deficiency is one cause of hypothyroidism, not all goiters are due to a lack of iodine or thyroid hormone.

Unless you know you are iodine-deficient, there is no need to take iodine supplements. Iodine is added to table salt and can be found in other foods such as seaweed, tuna, shrimp and dairy products.

There is no clear scientific evidence that drinking soy milk or eating tofu causes thyroid problems.

Too much iodine can actually make abnormal thyroid function worse, so if you want to take iodine supplements or increase your intake of iodine-rich foods, do this only under the guidance of your doctor.

Myth No. 2: Eating certain kinds of vegetables will give you a thyroid disorder.

Some believe that eating cruciferous vegetables such as broccoli, cabbage, cauliflower and Brussels sprouts is a cause of goiter or hypothyroidism. This is because these vegetables contain compounds called thiocyanates that can interfere with the body’s ability to absorb iodine.

But you would have to consume enormous quantities of these vegetables for them to interfere with thyroid function. These vegetables are part of a healthy, balanced diet and you can — and should — continue to eat them.

Myth No. 3: A gluten-free diet can cure hypothyroidism.

One common cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune disorder of the thyroid.

An autoimmune condition is one where your immune system mistakenly attacks your body. Other autoimmune diseases include lupus, rheumatoid arthritis, and celiac disease, where patients cannot digest foods that contain gluten.

The idea that a gluten-free diet can cure thyroid disease probably comes from the association that both Hashimoto’s and celiac disease are autoimmune diseases. Patients with one autoimmune disease can have another autoimmune disease at the same time, and Hashimoto’s and celiac disease can coexist. A gluten-free diet cannot reverse Hashimoto’s thyroiditis but it is helpful in managing celiac disease.

Myth No. 4: Drinking soy milk or eating soy products will cause hypothyroidism.

There is no clear scientific evidence that drinking soy milk or eating tofu causes thyroid problems. But if you take thyroid hormone replacement for hypothyroidism, soy milk and other foods and medications can interfere with how you absorb your medication.

Take your thyroid hormone medication as directed by your doctor — at the same time everyday, usually first thing in the morning on an empty stomach, taken only with water, and at least 30 minutes before any other food or medication.

With certain foods or medications you should wait longer, about two to four hours before or after you take your thyroid medication, and these include:
* Dairy products — milk, yogurt, cheese;

* Iron supplements or multivitamins containing iron;

* Calcium supplements; and
* Antacids that contain aluminum, magnesium or calcium.

The blood tests for thyroid function may also be affected by supplements that contain biotin, which are often used for hair and nail health. Biotin does not affect thyroid hormone levels, but can interfere with the measurement of these levels. These supplements should be stopped for at least a week before measuring your thyroid function to get accurate results.

Myth No. 5: I am gaining weight because of my hypothyroidism.

There can be some weight gain if you have an underactive thyroid, but it is typically only five to 10 pounds. Once on thyroid hormone replacement, weight gain should be minimal.

Substantial weight gain is related more to increased food intake and has nothing to do with thyroid function. Patients should monitor not just the quality or kind of food they eat, but portions as well. Even low-calorie foods if taken in excess become high calorie foods and this leads to weight gain.

The bottom line
Food in general does not cause or cure thyroid disease. Just like everyone else, patients with thyroid problems need to eat a healthy, well-balanced diet. Take everything in moderation and avoid extremes.

Also, resist turning to the internet if you have concerns or questions. Talk to your doctor first before making any drastic changes to your diet and before taking any unprescribed vitamins or supplements.

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