Wellbeing with Nutrition
Nurturing the Mind and Body

I have often read that certain health-promoting foods like  almonds, cashews and broccoli are 'goitrogenic' and therefore bad for the thyroid gland.

Should we be avoiding goitrogenic foods like almonds and brocolli?

What are Goitrogens?

The thyroid gland is a small butterfly-shaped gland found near the vocal chords in the throat. It has many important functions centred around metabolism including: managing body energy, growth and temperature. A goitrogen is any substance which triggers the enlargement of the thyroid gland. This usually occurs when iodine uptake is insufficient and/or goitrogens are interfering with the thyroid's requirement for iodine to make thyroid hormones. In this situation the brain signals the thyroid to increase in size, which is called goiter.

Where Do Goitrogens Come from?

The main source of goitrogens are:

  1. Medications/drugs,
  2. Foods
  3. Environment.

Goitrogenic Medication

Certain drugs are described as having "goitrogenic effects”. Examples of these drugs include lithium (used to treat bipolar disorder) and phenylbutazone (a non-steroidal anti-inflammatory drug).

Since the thyroid needs iodine to produce thyroid hormones, drugs with goitrogenic effects usually interfere with iodine metabolism and prevent the thyroid from making its iodine-containing hormones properly.

Goitrogenic Foods 

Certain foods are described as 'goitrogenic'.  For example cruciferous vegetables such as: broccoli, cauliflower, Brussels sprouts, bok choy, broccoli, Chinese cabbage, kale, kohlrabi, radish, mustard greens, collard greens, choy sum, horseradish and turnips contain many health promoting nutrients but are also described as goitrogens.

Cruciferous vegetables have many documented health benefits and cause no health issues for healthy individuals. They however contain substances called glucosinolates which are converted in the body to isothiocyanates, which have been associated with decreased thyroid function.

Another nutrient which contributes to the risk of thyroid problems involves the excessive intake of isoflavones which are found in large quantities in soya and soya-based products. Isoflavones have also been shown to interfere with iodine metabolism and thyroid functioning.

Cooking has been found to inactivate isothiocyanates and Isoflavones.

It is important to understand that how a particular food and the nutrients it contains behave within the body depends on the individual’s

  • Health and Digestive health,
  • Nutritional status and
  • Daily intake of gotrogens from medications, food and the environment

So for example if there are nutritional deficiencies such as low iodine levels combined with symptoms reflecting poor thyroid functioning then consuming large amounts of raw goitrogenic foods could adversely affect the thyroid gland further!

Why is iodine so important and how do deficiencies occur?

It is not just the thyroid which requires iodine. Every cell of the body utilises iodine in the form of either iodine or iodide.  For instance, iodide is primarily needed by the skin and thyroid gland.  The breasts, however, require iodine.  Without iodine, it is believed breast tissue can become fibrocystic or develop precancerous and cancerous lesions.

Iodine deficiency is becoming an increasing problem. This is partly due to low dietary iodine levels and numerous iodine antagonists which prevent uptake of iodine from the diet. The current mainstream recommendations for iodine are only based on the minimum levels required to prevent goiter of the thyoid gland and do not take into account the other requirements of iodine in the body!

Iodine is a member of the halogen family of elements.  The halogens include: fluorine, chlorine, bromine, iodine and astatine.  All of these elements compete with each other for absorption and utilisation in certain enzyme binding sites.  Unfortunately these iodine antagonists are widely found within the environment.

Goitrogens from the Environment

Bromine and Bromides

In the past, iodine was used for bread-making and in baked products which has been replaced by bromides. This increased exposure of bromides can interfere with iodine uptake and utilisation. 

Chlorine and Chlorinated compounds such as chloramines

These also interfere with iodine utilisation in the body. Chlorine is added to water supplies and it is also added to flour to bleach/whiten it, even though it forms toxic compounds when baked. 

Chlorine is also widely used in industry as a bleaching agent and an anti-bacterial/viral agent to sterilise or sanitise numerous products such as papers, rubber and plastics.Unfortunately chlorinated compounds also interfere with iodine uptake and utilisation.


The main source of fluorides today is from fluoridated water supplies, processed table salt and toothpaste.  Fluoridated water is also used to make many food products such as breads, bakery goods, dips, pickles, beverages and so on.

The fluorides from the water have also found their way into the water table and irrigation systems, which means that crops grown in these soils will have high levels of fluorides.

Other Issues Affecting Thyroid Health

  1. Selenium is another important mineral influencing thyroid functioning.  It is involved in the conversion of iodine to iodide and in the conversion of the relatively inactive thyroid hormoneT4 (thyroxine) to the more active thyroid hormone state T3 (triiodothyronine). A deficiency in selenium is common due to its poor levels in soils.
  2. Oestrogen dominance is becoming an increasing problem. Excess oestrogen inhibits thyroid functioning. The build up of oestrogen may be coming from the diet and environment in the form of oestrogen mimickers which interfere with thyroid functioning.
  3. Poor liver functioning may also be contributing to this situation. An overburdened liver may not be properly deactivating oestrogen leading to oestrogen dominance and poor thyroid functioning.


From a holistic perspective an individual's state of health, diet, stage of life and any environmental/lifestyle stress should always  be taken into account.

  • Cooking helps to inactivate some of the potentially goitrogenic substances such as isothiocyanates (found incruciferous vegetables) and isoflavones (found in soy food). Any individual wishing to lower his or her intake could consume these foods in cooked rather than raw form.
  • Address iodine nutritional deficiencies Include iodine-rich foods in the diet. Brown and red seaweeds (kombu, kelp) contain the most iodine of the sea vegetables. Small sea fish such as sardines also contain iodine and concentrate less mercury in their tissues than larger sea fish.
  • Avoid iodine antagonists (bromine, chlorine, fluorine) as much as possible from the diet and environment
  • Address selenium nutritional deficiencies Include selenium-rich foods like seaweeds and small sea fish such as sardines which concentrate less mercury in their tissues than larger sea fish. The amounts of selenium found in foods depends on the levels found within soils.
  • Consider if there any other nutrient deficiencies which have a knock on effect on iodine metabolism and the thyroid. For example dietary deficiency of vitamin A, vitamin E, zinc and/or iron can compound iodine deficiency.