Boosting Your Metabolism For Dummies
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If your metabolism is the engine of your body, your thyroid is a key that turns the ignition. The thyroid gland, located in your neck just below the Adam’s apple, is responsible for producing hormones that regulate metabolism and growth. If the thyroid isn’t working the way it should, that usually means the hormones it produces are out of whack.

Hone in on thyroid hormones

More than 20 million Americans produce too much (hyperthyroid) or too little (hypothyroid) hormones. Unfortunately, it’s estimated that half of those people suffering don’t even know it! If you’ve been doing everything you can to lose weight and suspect there’s something else going on, visit a physician before assuming there’s something wrong with your thyroid.

The hormones in question are triidothyronine (T3) and thyroxine (T4). To produce them, your thyroid requires the element iodine, which you need to get through your diet. These hormones are triggered to be released when your pituitary gland releases Thyroid Stimulating Hormone (TSH). At that point, T3 and T4 help oxygen get into cells, where they do the following:

  • Increase basal metabolic rate and body heat production

  • Influence the rate of muscle growth and development

  • Impact protein, fat, and carbohydrate metabolism

  • Regulate synthesis of protein from amino acids

  • Increase fat oxidation

  • Assist absorption of glucose into cells as well as create free glucose

  • Promote increased blood flow and mental acuity

If you have hyperthyroid or produce too much thyroid hormones, side effects include weight loss, anxiety, fast heartbeat, insomnia, muscle weakness, and increased bowel movements. But most people diagnosed with a thyroid condition — about 80 percent — have hypothyroid. In this condition, your thyroid isn’t producing enough hormones, and therefore your cells aren’t able to convert calories into the energy they need to function the best they can.

If you have hypothyroidism, it’s possible you’re also dealing with one of these risk factors or symptoms:

  • You’ve had unexplained weight gain.

  • You’re a female (Females are 5–8 times more likely to develop thyroid conditions, especially during big hormonal changes like during pregnancy and menopause)

  • You have a family history of thyroid disease or goiters (enlargement of the thyroid gland caused by iodine deficiency)

  • You have high blood cholesterol levels

  • You’re always cold

  • You’re often sluggish and feel fatigued and depressed

  • You’ve had changes in your menstrual cycle

  • You’re dealing with constipation or digestive issues

  • You’ve noticed you have dry skin, brittle hair, and nails, or a puffy face

  • Your muscles are achy or you have pain or stiffness in joints

It’s clear that your thyroid and the hormones it produces are inextricably connected to your metabolic rate as well as how you look and feel. Once you’ve been diagnosed, your doctor will prescribe medication to treat your thyroid condition, but naturally diet plays a role as well.

Make your diet thyroid-friendly

Ditch the 1,000-calorie crash diets. Restricting calories too much slows down your metabolism, and often your weight won’t budge. Your body is in a type of survival mode where it starts storing fat instead of burning it, and you lose more of your lean muscle mass to compensate. It’s possible that with a thyroid condition, this effect is exacerbated.

Although medication helps regulate your hormones, there are still aspects of your diet to be aware of. Goitrogens refers to any food that impacts how your thyroid works by blocking iodine uptake. Your thyroid needs iodine to create hormones, so, without it, hormone production diminishes too.

  • Go slow with soy. Soybeans contain an antioxidant called isoflavone. Isoflavones may compete with the thyroid in getting iodine to create your hormones. A review of studies published in Thyroid concluded that soy supplementation and excess consumption of soy can slow your thyroid function and also can reduce the effect of your medication.

  • Be in the know about goitrogen veggies. Since childhood, you’ve always been told to eat your veggies — but too much of them may actually impact your thyroid function. The vegetables that have caused decreased production of thyroid hormone in rats are from the Brassica family, and they contain compounds called isothiocyanates which may act the same way as soy isoflavones. These veggies include:

    • Cabbage

    • Broccoli

    • Cauliflower

    • Brussels sprouts

    • Kale

When to keep an eye on iodine

Getting enough iodine through your diet is important for your thyroid to churn out those hormones and to prevent too much of any food, such as soy or Brassica vegetables, from having a real impact on your thyroid function. Iodine is found in the following foods and food products:

  • Seafood and seaweed products

  • Fruits and vegetables grown in iodine-rich soil

  • Dairy products

  • Iodized salt

You may be surprised to know that iodine deficiency isn’t that rare, even though table salt began to be iodized in the 20th century for this reason. Many places around the world have soil that’s deficient in iodine. For example, the area around the Great Lakes in the U.S. was called the goiter belt before salt was iodized.

But even today, depending on where you live and the foods you eat, it’s possible that you’re not getting enough.

Too much iodine is toxic and can result in side effects such as burning in the gastrointestinal tract, vomiting, coma, and even hyperthyroidism and thyroid cancer. Most adults should stay below 900–1,100 micrograms of iodine per day.

Seek out selenium

A deficiency in the trace mineral selenium can impair your thyroid’s ability to convert hormones into their active form. Because of this, too little selenium can actually exacerbate an iodine deficiency by making hormone production even more difficult. Selenium is used to make antioxidants and therefore is important for your immune function. It can potentially help prevent cancer and boost male fertility.

Incorporate more of these selenium-rich foods into your diet:

  • Brazil nuts

  • Shellfish

  • Sunflower seeds

  • Grains

  • Eggs

As with iodine, it’s possible to have too much selenium, so don’t start taking supplements without checking with your doctor and limit intake to less than 400 micrograms per day, and don’t eat more than two Brazil nuts per day.

Making sure you have the right amount of selenium and iodine is important to a healthy thyroid.

About This Article

This article is from the book:

About the book author:

Rachel Berman, RD is the Director of Nutrition for, a free Web site and mobile app which provides tools to help people lead healthier lives. A nationally recognized nutrition expert, she has appeared on The Today Show, several local television and radio health segments, and is frequently quoted in print and online publications.

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