Essential guide to iodine deficiency – why and how to fix

Dr Sarah Brewer and nutritionist Rob Hobson continue their A to Z of vitamins, minerals and herbs. This week I is for iodine.
periodic table - iodine deficiency

What is iodine deficiency and why is it important. Iodine is a trace element and mineral that the body needs to function properly. This mineral is naturally found in the Earth’s soil and ocean waters and marine foods such as seaweed are a rich source. Like all minerals, we cannot make it ourselves and must obtain it from our diet.

Why do we need it? 

Iodine is essential for the production of two thyroid hormones, thyroxine and tri-iodothyronine. These hormones control the metabolic rate, the conversion of food and fat stores into energy and the production of body heat. Iodine helps to prevent lack of energy, tiredness, and excessive weight gain. Iodine is essential for thyroid health as it is used to make thyroid hormones. 

Iodine is especially important for skeletal and central nervous system development in foetuses and infants. For this reason, low iodine intakes in teenage girls is a concern given the high rate of pregnancies and the fact that more than a quarter do not get enough in their diet. However, newborn babies are screened for iodine deficiency as part of the heel prick test carried out soon after delivery.

Research has highlighted that iodine may have other physiological roles in the body such as immune responses, cognition and fibrocystic breast disease. 

A special type of iodine called radioactive iodine is used to treat an overactive thyroid if medication doesn’t help to regulate the thyroid which destroys extra thyroid cells to reduce excessive amounts of thyroid hormone.  

How does it work?

Thyroid stimulating hormone (TSH), which is secreted by the pituitary gland, stimulates the thyroid gland in the neck to absorb iodine where it is used to make two thyroid hormones, T3 and T4. 

If there is not enough iodine the body then levels of TSH remain elevated which leads to goitre – the enlargement of the thyroid gland in an attempt to glean more iodine from the circulation.

Who’s deficient?

The National Diet and Nutrition Survey shows that most adults get enough iodine in their diet with an average daily intake that is 111% of the recommendation. Amongst adults aged 19-64 years old 9% of men and 15% of women have insufficient intakes. Adults over 65 years have better intakes with only 3% of men and 7% of women shown to be insufficient which is likely to do with a higher consumption of fish amongst this group. 

thyroid examination - thyroid deficiency
Endocrinologist examination for thyroid gland ultrasound.

What are the common signs of iodine deficiency?

Iodine deficiency is diagnosed with a urine test which seems to be the most effective.   Blood tests can also be taken to measure thyroid hormones and a protein, thyroglobulin, will also help to confirm the condition.  As iodine plays such as key role in the functioning of the thyroid this is how symptoms may become suspected. Signs of deficiency include:

  • Tiredness and lack of energy
  • Muscle weakness
  • Visible goitre (swelling in the neck)
  • Painful thyroid gland 
  • Breast pain and tenderness
  • Breathing issues (especially when lying down)
  • Difficulty swallowing 
  • Sensitivity to the cold 
  • Hair loss 
  • Brain fog 
  • Low mood
  • Weight gain (due to an underactive thyroid gland).

Where can I get it from? 

Seafoods are the richest sources of iodine and eggs are also a good source laying claim to the healthy advice to start the day with the egg. Dairy foods are also a good source but the actual content depends on whether the cows received iodine feed supplements and whether the cows and the equipment used to milk them was sanitized with iodophor sanitizing agents. All salt used to be iodized to help improve intakes but this is no longer done in the UK. 

Foods richest in iodine include:

  • Milk
  • Yoghurt 
  • Cheese
  • Fish (white fish is higher in iodine that oily fish)
  • Shellfish
  • Sea vegetables (seaweed)
  • Eggs 
  • Meat and poultry 
  • Nuts 
  • Bread 
  • Soy 
  • Cruciferous vegetable (broccoli, cabbage, cauliflower, Brussels sprouts)
smoked salmon scrambled eggs
Scrambled eggs and smoked salmon on toast.

How can I include it in my diet?

The best place to start is by eating more fish on a weekly basis. Seaweed is available as ‘thins’ which make tasty snack. Eggs are a quick and easy to create a healthy iodine rich meal such as an omelette or scrambled with smoked salmon.  Try to also eat plenty of green vegetables which can be used to make stir-fry’s, soups and stews or thrown into salads raw or blanched. 


The EU RDA for folic acid is set at 150mcg.

The upper tolerable level for iodine has been set by the European Food Safety Authority (EFSA) as 600mcg in adults.

Food is the best way to get iodine in the diet but if you know you are deficient then a supplement may be recommended (try Healthspan Kelp Extract – £12.95 for 360 tablets). Do not exceed the recommended daily intake of 150mcg in a supplement. 

What to avoid? 

Excess iodine may lead to a metallic taste in the mouth, oral sores, headache, diarrhoea, vomiting, rash and – as with a deficiency – excess can also lead to thyroid swelling (goitre). Do not exceed manufacturer’s doses except under medical advice. 

Did you know? Up to 3% of people are allergic to iodine. 

To find out further information about supplements or if you have any queries about taking supplements you can visit or speak to a qualified nutritionist. 

If you found I is for iodine – essential guide to iodine deficiency helpful, you find more from our series A to Z of vitamins on our Nutrition channel.

Tags: , , , Last modified: June 13, 2023

Written by 11:13 am A to Z of Vitamins