Iodine is one of the most underrated minerals for your health, yet many people in the UK aren't getting enough of it. This tiny mineral is essential for your thyroid gland to produce the hormones that regulate everything from your heartbeat to your metabolism. Without adequate iodine, your body simply cannot make thyroxine (T4) and triiodothyronine (T3), the two hormones your thyroid relies on to keep you functioning properly .

Why Is Iodine Deficiency Becoming a Problem in the UK?

For decades, iodine deficiency was considered a solved problem in developed countries. But recent research suggests that's no longer true. The UK is one of the few European countries without an iodine fortification program, meaning iodine isn't routinely added to foods like salt and bread the way it is in countries such as New Zealand and the United States . Meanwhile, changes in how food is produced and the diets people choose are making deficiency more likely.

The concern isn't about severe deficiency anymore, which is now rare in the UK. Instead, experts are worried about mild-to-moderate deficiencies that often go unnoticed because they don't always produce obvious symptoms. Research published in The Lancet Diabetes and Endocrinology has identified iodine deficiency as a significant and re-emerging issue in the UK . Teenage girls and young women are particularly at risk, along with pregnant women and people who avoid dairy products or follow a vegan diet.

What Happens When You Don't Get Enough Iodine?

The symptoms of iodine deficiency vary widely from person to person, and that's part of the problem. Some people experience obvious signs, while others have subtle changes they might not connect to a mineral deficiency at all. Here's what you might notice:

• Cognitive problems: Difficulty concentrating, low work productivity, and slower thinking
• Physical symptoms: Tiredness, muscle weakness, and difficulty regulating body temperature
• Mood changes: Depression and other shifts in emotional well-being
• Metabolic effects: Unexplained weight loss or weight gain
• Reproductive issues: Changes to the menstrual cycle and loss of libido
• Visible signs: A swelling in the neck called a goiter, which occurs when your thyroid works harder to compensate for low iodine

In the long term, chronic iodine deficiency can lead to thyroid conditions like hypothyroidism, an underactive thyroid that produces too little hormone, or hyperthyroidism, an overactive thyroid that produces too much .

The impact on brain development is particularly concerning. A mild iodine deficiency during pregnancy or childhood may affect brain development even when there are no obvious symptoms at the time. Some studies have found that mild-to-moderate iodine deficiency in pregnancy is associated with lower verbal IQ and poorer reading ability in children later in life . Additionally, a large study found that among pregnant women, a mild-to-moderate iodine deficiency was associated with a higher prevalence of preeclampsia or preterm labor .

How to Ensure You're Getting Enough Iodine

• Seafood sources: Shellfish and fish are among the richest natural sources of iodine and should be included regularly if you eat animal products
• Dairy products: Milk and cheese are major contributors to iodine intake in the UK diet, making them important for people who can tolerate dairy
• Eggs: A simple, versatile source that provides iodine along with other essential nutrients
• Fortified alternatives: Iodine-fortified plant milk and iodine-fortified salt can help if you avoid dairy or animal products
• Seaweed products: While seaweed contains iodine, be cautious with supplements, as iodine content can be inconsistent and potentially excessive

Adults generally need 140 milligrams of iodine each day to support normal thyroid hormone production . However, requirements are higher during pregnancy and breastfeeding, rising to around 220 to 290 milligrams daily. It's important to stay within safe limits, as intake should generally remain below the safe upper limit of around 600 to 1,100 milligrams per day .

If you avoid dairy products because of an allergy, intolerance, or dietary choice, you could be at higher risk of iodine deficiency. New research suggests that people who follow a vegan diet are at particularly higher risk, so vegans should actively look for fortified food products to meet their iodine needs .

Should You Take an Iodine Supplement?

The answer isn't straightforward. While iodine is essential in the right amounts, it can be harmful both in deficiency and in excess. Many supplements that seem harmless and natural, such as iodine-containing seaweed supplements, may be inconsistent in their iodine content, making it difficult to know exactly how much you're consuming . Taking too much iodine can affect your thyroid, liver, and gastrointestinal tract.

"Before you consider taking iodine supplements, it's best to discuss this with your doctor, as taking too much iodine can be harmful," noted Dr. Sophie Lester, a registered nutritionist.

Dr. Sophie Lester, Registered Nutritionist (RNutr), BSc

A safer and more cost-effective approach is to increase your intake of iodine-containing foods rather than relying on supplements. However, if you're concerned about your iodine levels, a thyroid blood test can help identify whether iodine may be impacting your thyroid health. Because iodine is essential for thyroid hormone production, testing your thyroid function is often the most practical way to assess whether you're getting enough .

Who Needs to Pay Special Attention to Iodine?

Certain groups face higher risks and should be especially mindful of their iodine intake. Pregnant women are at increased risk of iodine deficiency because their needs are greater; they create more thyroid hormones and provide iodine to the developing baby. Iodine is essential for fetal and infant neurodevelopment, making adequate intake during pregnancy particularly critical . Women should ensure they're getting enough iodine in their diet for many months before getting pregnant, so it's worth checking with your GP before starting any new supplements.

The bottom line is this: iodine deficiency may be quiet and easy to overlook, but its effects on your thyroid, brain, mood, and overall health are significant. If you fall into a higher-risk group, pay attention to your iodine intake through food sources, and talk to your doctor if you're concerned about whether you're getting enough.