10% off €35 OR 15% off €45


10% off €35 OR 15% off €45



🏷️ 3 for 2 Mix & MatchOffersOffers Hub3 for 2 Mix & MatchOutletOnline Only OfferSave up to 1/2 priceBuy One Get One 1/2 Price1/2 PriceBetter than 1/2 priceShort DatedBuy 1 Get 1 FreeVitamins & SupplementsVitamins & Supplements HubVitamins & Supplements Shop AllCBDCollagen & SilicaHair, Skin & NailsShop all Hair, Skin & NailsHair GrowthFunctional MushroomsVitaminsShop all VitaminsMultivitaminsVitamin AVitamin BVitamin CVitamin DVitamin EVitamin KVitamin DrinksMineralsShop all MineralsMagnesiumIronZincCalciumSeleniumChromiumSupplementsShop all SupplementsFibre SupplementsAcidophilus & Friendly BacteriaPeppermint OilGrapeseed ExtractLecithinCollagen & SilicaOmega & Fish OilsPlant Sourced SupplementsSuperfood SupplementsArnicaApple CiderRaspberry KetonesAloe VeraChondroitin & MSMCo Enzyme Q10Evening Primrose OilGarlicGlucosamineGlucomannanSeaweed, Kelps and AquaceuticalsDigestive EnzymesSaw palmettoCharcoalWomen's HealthShop all Women's HealthMenopauseMenstrual SupportUrinary Tract HealthPregnancy & ConceptionMen's HealthShop all Men's HealthProstate HealthChildren's HealthConditionShop all ConditionCholesterolAllergy & Hay Fever CareAnxiety SupportBone & Muscle HealthMuscle Support & Joint PainBrain & Memory SupportWomen's HealthMen's HealthChildren's HealthCold & Immune SupportFatigueDigestive HealthHair, Skin & NailsHeart & CirculationLiver CareMood SupportSexual HealthSleep & RelaxationStress ReliefVisionHerbal & Licensed RemediesShop all Herbal & Licensed RemediesValerianRescue RemedyAshwagandhaEchinaceaMilk ThistleGinseng & GuaranaHomeopathic & Flower RemediesShop all Homeopathic & Flower RemediesRescue RemedyTissue SaltsFlower RemediesVegan Vitamins & Supplements3 for 2 Mix & MatchOnline Only OfferOutletHolland & BarrettVitabioticsSolgarNew NordicBetterYouNatures AidBioglanGrass & Co.PE NutritionNature's WayDairy FreeGluten FreeSesame Seed FreeCelery FreeCereal FreeCrustaceans FreeEgg FreeFish FreeKiwi FreeLupin FreeNew inFood & DrinkFood & Drink HubFood & Drink Shop AllVegan FoodHoney, Jams & SpreadsShop all Honey, Jams & SpreadsManuka HoneyHoneyJams & ChutneysNut ButtersSpreadsPateTeas & Hot BeveragesShop all Teas & Hot BeveragesTeaCoffee & Coffee SubstituteMushroom DrinksDried Fruit, Nuts & SeedsShop all Dried Fruit, Nuts & SeedsNutsDried FruitSeedsMixesSuperfoodsShop all SuperfoodsSpirulinaSuperfood PowdersGoji BerriesBaobabMoringa PowderChia SeedsSnacksShop all SnacksProtein BarsLow Calorie SnacksChocolate, Cakes & BiscuitsSavoury SnacksSweet SnacksSnack BarsCrisps & ChipsFlapjacksPopcornFood CupboardShop all Food CupboardCondiments & SaucesApple Cider VinegarSuperfoodsBreakfast CerealsHoney, Jams & SpreadsTinned FoodsRice, Pasta, Pulses & GrainsBreakfast CerealsShop all Breakfast CerealsCereals, Bran & FlakesGranolaMuesliOats & PorridgeBreakfast BarsDrinksShop all DrinksKombuchaNatural Energy DrinksJuicesSoft DrinksWaterAlcohol Free DrinksCookingShop all CookingCooking IngredientsApple Cider VinegarCondiments & SaucesSoya & Meat AlternativeSoup & Ready MealsRice, Pasta, Pulses & GrainsHerbs, Spices & SeasoningGravy & StockHome BakingShop all Home BakingBaking MixesBreadFlourSweeteners & Sugar AlternativesEgg SubstitutesDairy AlternativesShop all Dairy AlternativesOat, Rice & Hemp DrinksSoya DrinksNut DrinksCoconut DrinksNutritionally Complete Food3 for 2 Mix & MatchBuy One Get One 1/2 PriceOutletHolland & BarrettNaturyaPukkaHeath & HeatherGrenadeMeridianTwiningsOptimum NutritionNakdLinwoodsGluten FreeDairy FreeEgg FreeWheat FreeMilk FreeSulphites FreeCelery FreeKiwi FreeMustard FreeFish FreeNew inSports NutritionSports Nutrition HubSports Nutrition Shop AllProteinShop all ProteinClear ProteinProtein VeganMeal ReplacementsWhey ProteinMass GainersDiet ProteinCaseinBars, Drinks & SnacksShop all Bars, Drinks & SnacksEnergy BarsProtein BarsProtein ShakesProtein SnacksNutritionally Complete FoodMeal Replacement ShakesPre Workout & EnergyShop all Pre Workout & EnergyPre WorkoutAmino Energy DrinksAmino Energy PowdersIntra WorkoutKetoPost WorkoutAmino AcidsShop all Amino AcidsBCAAL-LysineGlutamineArginineCreatineShop all CreatineCreatine PowderSports SupplementsShop all Sports SupplementsTestosteroneSports CollagenRehydrationShop all RehydrationElectrolytesEnergy GelsVegan Sports NutritionShop all Vegan Sports NutritionVegan ProteinVegan Protein BarsVegan Pre Workout & EnergyVegan Amino AcidsVegan CreatineSports AccessoriesShop all Sports AccessoriesBottles & ShakersFitness GoalShop all Fitness GoalRecoveryMuscle & StrengthLean MuscleEnergy & EnduranceDiet & Weight LossKetoSave up to 1/2 price3 for 2 Mix & MatchOutletPE NutritionOptimum NutritionUSNGrenadeApplied NutritionPhDFoodspringSiSHuelYfoodDairy FreeGluten FreeSugar FreeSoya FreeCelery FreeCereal FreeCrustaceans FreeEgg FreeFish FreeKiwi FreeNew inBeautyBeauty HubNatural Beauty Shop AllAromatherapy & HomeShop all Aromatherapy & HomePure Essential OilsBlended Essential OilsBase & Carrier OilsHolisticSkincareShop all SkincarePremium SkincareFace CareBody CareSun CareTanning & BronzingEye CareLip CareFoot CareHand & Nail CareCBD BeautyHair Skin & NailsShop all Hair Skin & NailsNail ConditionsSkin ConditionsCollagenWashing & BathingShop all Washing & BathingShampoo & ConditionerBathing AccessoriesShower Gel & Body WashDeodorantDentalHand WashSoapBath Soak & OilBody ScrubBath Bombs & SaltsFeminine CareIncontinence SupportHair CareShop all Hair CareShampoo & ConditionerHair ColouringHair MasksHair Oil & SerumHair Spray, Gel & MousseHair AccessoriesMother & BabyShop all Mother & BabyBaby Skincare & ToiletriesMakeupElectrical WellnessSexual Wellness3 for 2 Mix & MatchOnline Only OfferOutletDr OrganicFaith in NatureWeledaNaturtintTisserandMiaromaQ+AEthiqueTrilogyChilds FarmAlcohol FreeParaben FreeSLS FreeParfum FreePalm Oil FreeGluten FreeCelery FreeCereal FreeCrustaceans FreeEgg FreeNew inWeight ManagementWeight Management HubWeight Management Shop AllSlimming TabletsFat Burners, Binders & Appetite SuppressantsShop all Fat Burners, Binders & Appetite SuppressantsFat BurnersFat BindersAppetite SuppressantsShakes & Weight Management ShotsShop all Shakes & Weight Management ShotsMeal Replacement ShakesWeight Management ShotsDiet Food & DrinkShop all Diet Food & DrinkDiet FoodLow Calorie SnacksSlimming TeaExercise SupportSave up to 1/2 price3 for 2 Mix & MatchOnline Only OfferOptimum NutritionGrenadeHolland & BarrettPulsinPhDEat WaterUSNNatures AidSlimExpertNew NordicDairy FreeGluten FreeSugar FreeWheat FreeNew inHealth & WellnessShop all Health & WellnessJoints Bones & MusclesGut HealthShop all Gut HealthGut Health FoodGut Health SkincareHair Skin & NailsShop all Hair Skin & NailsNail ConditionsSkin ConditionsCollagenStress AnxietyShop all Stress AnxietyEnergy SupportSleep & RelaxationShop all Sleep & RelaxationRelaxationFood & DietShop all Food & DietKeto FoodMenopause3 for 2 Mix & MatchOnline Only OfferOutletHolland & BarrettDr OrganicVitabioticsNaturtintWeledaSolgarNew NordicHeath & HeatherOptimum NutritionEthiqueDairy FreeGluten FreeParaben FreeSLS FreeAlcohol FreeParfum FreeWheat FreeSugar FreeCelery FreeCereal FreeNew inShop for your WellnessImmunityGut HealthMenopauseWomen's HealthFood & DietMuscle & Joint PainSleep & RelaxationStress ReliefHealthy HeartEnergyLow Mood & DepressionConcentration & AlertnessEye HealthSexual HealthChildren's HealthLearn about WellnessWomen's HealthPeriod & Cycle HealthMenopauseImmunityGut HealthFood & DietJoints, Bones & MusclesSports & FitnessSleep & RelaxationHair Skin & NailsAll articlesHealthFood & nutritionGut healthImmunityJoints, bones & musclesWomen's healthWellnessHair & skinMental wellbeingSeasonalSleep & relaxationSports nutritionRecipesAll recipesGluten freeLow sugarVeganDairy freePodcast
sources of iodine

Iodine: function, foods, deficiency and supplements

23 Nov 2022 • 2 min read

Find out all about iodine, including what it does, how much you need, where to find it and who might need to supplement their diet

Written by Jack Feeney on January 2, 2019 Reviewed by Dr Sarah Schenker on January 23, 2019


What is iodine and what does it do?

Iodine is an essential mineral needed to make thyroid hormones. These hormones are important for:
  • cell growth
  • brain development in early life
  • regulation of metabolism
The European Commission reports that iodine can also contribute to normal cognitive function, maintain healthy skin, and support the functioning of the nervous system.1 Iodine is mainly found in fish and dairy products. It’s also highly concentrated in certain marine algae, like kelp. However, if you eat seaweed frequently, you could risk getting too much iodine because it is toxic in large doses.2 Most people get enough iodine in their diets if they eat fish or dairy foods. However, schoolgirls, pregnant women, vegetarians and vegans are at risk of deficiency in the UK.3 Iodine is available in certain multivitamins and also in algae tablets, in which the iodine levels are restricted.

Function of iodine

What does iodine do in the body?

Iodine is critical for the healthy functioning of your body’s thyroid gland – in fact, 70-80% of your body’s iodine is stored in the thyroid. The thyroid is responsible for the release of the two thyroid hormones, both of which require iodine to work:4
  • thyroxine (T4)
  • triiodothyronine (T3)
These hormones control the rate of cell metabolism – the speed at which your cells function – keeping us alive. Thyroid hormones have essential roles to play throughout the body, including:5,6 An iodine deficiency means the body can’t make enough thyroid hormones, and this can lead to hypothyroidism.7

How much iodine do I need?

Adults need 140mcg of iodine a day.8 However, if you are pregnant or breast-feeding, your body needs more: a total of 200mcg of iodine a day.9

Do children need iodine?

Iodine is important for your child’s growth and development. They need:10
  • 1-3 years – 70mcg a day
  • 4-6 years – 100mcg a day
  • 7-10 years – 110mcg a day
  • 11-14 years – 130mcg a day
  • 15-18 years – 140mcg a day

Iodine foods

Which foods are the best sources of iodine?

The best sources of iodine are:11
  • all seawater fish, especially white fish such as haddock and cod
  • shellfish, for example prawns and crab
  • dairy foods, including cow’s milk, yoghurt and cheese
  • eggs
  • meat and poultry
The best plant sources of iodine are:12
  • seaweed
  • nuts
  • wholegrains
  • fruit and vegetables
For dairy and plant foods, the levels of iodine will vary depending on how much iodine is in the soil in that region.13

Iodine deficiency

Who is at risk of an iodine deficiency?

People who don’t eat fish or dairy foods – and in particular vegans – could be at risk of an iodine deficiency.14 Pregnant women and schoolgirls are reported to have such low intakes of iodine, that the World Health Organisation now classifies the UK as mildly iodine-deficient.15

What are the symptoms of an iodine deficiency?

A lack of iodine can trigger a condition called underactive thyroid, known as hypothyroidism. Symptoms include:16
  • tiredness
  • weight gain
  • feeling cold
  • depression
  • difficulty concentrating
Severe iodine deficiency can lead to an enlarged thyroid, known as a goitre, which appears as a visible swelling on the neck; the thyroid enlarges in order to trap more iodine. However, a severe iodine deficiency is very rare in the UK.17 In pregnancy, iodine deficiency can interfere with the normal brain development and growth of the unborn baby. In fact, a serious iodine deficiency is considered the most common cause of preventable brain damage in children worldwide.18

What happens if I consume too much iodine?

Too much iodine, as well as too little, can interfere with your thyroid function. For some, it causes goitre or hypothyroidism, with the same symptoms as above, but for others it can lead to hyperthyroidism, in which the body produces too many thyroid hormones.19 Symptoms of hyperthyroidism include:20
  • anxiety
  • sweating
  • rapid heart rate
  • increased appetite but also weight loss
  • restlessness

Iodine supplements

When should I take iodine supplements?

You may need to take iodine supplements if you are:
  • vegan or vegetarian
  • pregnant or breast-feeding
  • don’t eat fish or dairy foods
Supplements containing up to 500mcg of iodine a day is considered safe for adults, according to the NHS.21

Should women take an iodine supplement during pregnancy?

It’s really important that you get enough iodine during pregnancy to support your baby’s developing brain – and ideally from a few months before you get pregnant. If you don’t eat fish or dairy foods, consider an iodine supplement or a pregnancy multivitamin that contains iodine.22 Do not consume more than 500mcg a day, as the NHS warns this could cause thyroid problems for your baby.23,24

What are the potential benefits of taking an iodine supplement?

Iodine is mainly given to help prevent and treat iodine deficiency disorders, and to encourage normal brain development in children. But a 2017 study in Frontiers in Immunology found that healthy iodine levels can also help regulate the body’s immune system.25 Shop Supplements Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies. Sources 1. European Commission. EU register of nutrition and health claims made on foods 2. British Dietetic Association. Iodine 3. As above 4. British Thyroid Foundation. Your Thyroid Gland 5. ScienceDirect. Iodine Deficiency 6. Society for Endocrinology. Thyroid gland 7. Chung HR. Iodine and thyroid gland 8. Public Health England. Government Dietary Recommendations 9. As Source 2 10. As Source 8 11. As Source 2 12. As Source 2 13. NHS. Iodine 14. As Source 2 15. Bath SC, Rayman MP. A review of the iodine status of UK pregnant women and its implications for the offspring 16. As Source 4 17. As Source 2 18. As Source 5 19. National Institutes of Health. Iodine: Fact Sheet for Health Professionals 20. MedicineNet. Hyperthyroidism Symptoms, Causes, Treatments, And Diet 21. As Source 13 22. As Source 2 23. As Source 13 24. Health Supplements Information Service. Iodine 25. Bial MY, et al. A Role for Iodide and Thyroglobulin in Modulating the Function of Human Immune Cells
  • Visa
  • MasterCard
  • AmericanExpress
  • PayPal
  • Facebook
  • Twitter
Copyright © Holland & Barrett Limited, 2023. All rights reserved. hollandandbarrett.ie is a trading name of Holland & Barrett Limited. Registered office: 45 Henry Street, Dublin, Dublin 1, D01 E9X8. Registered in Ireland: Company no. 79819. Registered VAT no. 4682002U.