Are Goitrogens in Foods Harmful? Effects on Thyroid

The thyroid is a butterfly-shaped gland present in the front of the neck. The gland secretes the thyroid hormones thyroxine (T4) and triiodothyronine (T3). 

Thyroid hormones are essential for regulating various vital functions in the body including metabolism, body temperature, heart rate, and blood pressure. These hormones are also vital for fetal growth and development. Moreover, they play a huge role in the development of the brain and sexual functions.

The thyroid gland produces thyroid hormones through a process that uses iodine, the amino acid tyrosine, and several enzymes including thyroid peroxidase (TPO). The release of thyroid hormones from the thyroid gland is regulated by another hormone called thyroid-stimulating hormone (TSH) produced by the pituitary gland, which is located in your skull underneath the brain.

Excessive intake of goitrogens can impair thyroid function in people who already have an underactive thyroid gland. This may be done through three main mechanisms:

1. Interference with iodine uptake by the thyroid gland
2. Inhibition of the TPO enzyme
3. Interference of TSH release from the pituitary

This disruption of thyroid function may make cause several health issues:

• General symptoms:
  • Fatigue
  • Low tolerance to cold
  • Unexplained weight gain
  • Body ache
  • Joint pain
  • Low mood or depression
  • Slow speech
  • Hoarseness 
  • Trouble swallowing
  • Goiter (swelling in front of the neck)
• Skin and hair:
  • Dry, thick skin
  • Thinning or loss of eyebrows
  • Coarse hair
  • Hair loss
  • Reduced sweating
  • Brittle nails
• Eyes:
  • Puffiness around the eyes
  • Droopy eyelids
  • Protruding eyeballs giving a “staring look”
  • Trouble moving the eyes
• Gut:
  • Constipation
  • Bloating
  • Indigestion
• Heart:
  • Reduced heart rate
  • Shortness of breath with physical activity
  • Increased blood pressure
  • Increased blood cholesterol levels
• Respiratory:
  • Poor exercise tolerance
  • Shortness of breath
  • Sleep apnea (temporary cessation of breathing while sleeping)
• Reproductive:
  • Menstrual problems such as heavy bleeding during periods or irregular periods
  • Reduced sex drive
  • Increased risk of abortions
  • Infertility or reduced fertility

Impaired thyroid function can also increase the risk of dementia and bone fractures. In pregnant women, goitrogens can cause harm to the developing fetus, particularly in brain development.

There are three types of goitrogens: goitrins, thiocyanates, and flavonoids.

Goitrins and thiocyanates are produced when plants are chewed or sliced. Although flavonoids are antioxidants, they can sometimes be converted into goitrogens in the gut.

Foods that contain goitrogens include the following:

Cruciferous vegetables

• Broccoli
• Cauliflower
• Cabbage
• Kale
• Brussels sprouts
• Mustard greens 
• Rapeseed
• Horseradish
• Collard greens
• Turnips 
• Spinach
• Kohlrabi
• Watercress

Starchy vegetables and fruits

• Sweet potato
• Cassava
• Corn
• Bamboo shoots
• Peanuts
• Pine nuts
• Peaches
• Strawberries

If you have impaired thyroid function, you can minimize the harmful effects of goitrogens without compromising your health. 

Here are tips to protect yourself from the harmful effects of goitrogens:

• Cook vegetables well: Blanching, roasting, stir-frying, and steaming foods reduce the number of goitrogens by breaking down certain enzymes. 
• Increase iodine and selenium intake: Iodine and selenium are essential for proper thyroid function. You can get plenty of iodine through iodized salt, seafood, kelp, and other seaweeds. Selenium-rich foods include whole grains, Brazil nuts, sunflower seeds, meat, fish, and cheese.
• Eat a varied diet: By eating a variety of fruits, vegetables, whole grains, and animal proteins, you can obtain a wide range of nutrients and limit your overall goitrogen consumption.
• Maintain a healthy lifestyle: Besides eating nutritious foods, avoid smoking, get enough sleep, exercise regularly, and manage stress to help maintain a healthy thyroid.

If your thyroid function is normal, you do not need to worry about goitrogenic foods.

In addition, cooking these foods and consuming them in moderation makes them safe even for people with thyroid issues.

Since most foods with goitrogens are rich in nutrients, the health benefits far outweigh the minor potential risks.