Molecular Iodine Colloidal

With iodine, the right amount matters more than the brand, so these are the questions our naturopaths ask in store before recommending one.

A good fit if

• You're pregnant, breastfeeding or planning a baby, and your pregnancy multivitamin doesn't already contain iodine
• You're vegan, or you rarely eat bread, dairy or seafood
• You buy organic bread, which isn't made with iodised salt
• Your GP has tested your iodine and it's come back low

Check with us first if

• You have a thyroid condition, now or in the past. FSANZ, NSW Health and the NHMRC all say to get medical advice before taking an iodine supplement.
• You've had low iodine for a long time, because the NHMRC notes you may react badly even below the Upper Level.
• You already take a pregnancy multivitamin, a thyroid formula or a seaweed product, as each may contain iodine.
• You take any prescription medicine. We don't have verified data on iodine and medicine interactions, so this is a conversation rather than a checklist.
• You've read about Lugol's solution or a high-dose iodine protocol. Those doses are far beyond what an Australian listed medicine can provide, and they need a practitioner.

• Potassium iodide (item 4104). Best known for: The measured standard, and the form most pregnancy trials used. Absorption: In a crossover study of 11 adults, it was absorbed no differently from iodine in milk at 263 µg a serve. Typical use: Pregnancy, breastfeeding and general tablets at 150 µg a day.
• Potassium iodate (item 4103). Best known for: More stable in heat and humidity, which is why salt makers use it. Absorption: 150 µg a day lifted median urinary iodine from 65 to 168 µg/L over 24 weeks. Typical use: The same uses as potassium iodide; no trial has compared the two head to head.
• Kelp and seaweed powders (items 2861, 2862 and related species). Best known for: A wholefood source, but not a dependable dose. Absorption: We have no human absorption trial, and iodine content varied more than tenfold within one seaweed species. Typical use: If you want a wholefood form and aren't pregnant.
• Elemental iodine and Lugol's solution (item 2708, plus 4104). Best known for: Hospital use in diagnosed thyroid disease, not everyday supplementing. Absorption: We have no nutritional dosing data. Typical use: Only under practitioner supervision; Lugol's-strength solutions exceed Australia's listed-medicine limits.

Reference values. The NHMRC Recommended Dietary Intake is 150 µg a day for adults and teenagers from 14. It rises to 220 µg in pregnancy and 270 µg while breastfeeding. Children 1 to 8 need 90 µg and 9 to 13 need 120 µg. Babies have an Adequate Intake of 90 µg up to 6 months and 110 µg from 7 to 12 months, and the NHMRC says that should come from breast milk, formula and food only.

Typical supplemental range. 150 µg a day is the standard Australian supplement strength, and it's the amount FSANZ, NSW Health and the NHMRC recommend for women who are pregnant, breastfeeding or planning a pregnancy. Trials have used 150 to 225 µg a day. An Australian listed medicine must provide less than 300 µg of iodine per maximum daily dose, so the high-dose protocols you'll read about online aren't something a listed supplement can offer.

Upper level. The NHMRC Upper Level is 1,100 µg a day for adults, from food and supplements combined, and 900 µg for 14 to 18 year olds. It's much lower for children: 200 µg from 1 to 3, 300 µg from 4 to 8 and 600 µg from 9 to 13. No Upper Level could be set for babies under 12 months. The NHMRC adds that people with thyroid conditions or a long history of low iodine may still react badly below these levels.

Worth knowing. Iodine turns up in pregnancy multivitamins and some thyroid and seaweed blends, so add up every label before you add another product. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Bread (non-organic): made with iodised salt by law since 2009; no per-slice figure held
• Cow milk: 263 µg per 250 mL in one high-iodine test milk, absorbed as well as potassium iodide
• Lean seafood such as cod: four weeks of a seafood-rich diet roughly doubled median urinary iodine, from 70 to 135 µg/L
• Nori: about 16 µg per gram
• Kelp: anywhere from about 500 to over 8,000 µg per gram, depending on species and processing

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Thyroid conditions. FSANZ says: "Women with pre-existing thyroid conditions should seek advice from their doctor before taking a supplement." NSW Health and the NHMRC say the same.
• Thyroid disorders or a long history of low iodine. The NHMRC notes these people "may still respond adversely at levels of intake below the UL" (the safe upper limit).
• Autoimmune thyroiditis, previously treated Graves' disease, or a chronic illness. A review describes large iodide doses causing clinical or subclinical hypothyroidism (an underactive thyroid) in these groups.
• Too much in pregnancy. A meta-analysis of 10,736 pregnant women found 52% had too much iodine, linked to hypothyroxinaemia, hypothyroidism and hyperthyroidism in the mother and to thyroid problems in the newborn.
• Kelp in pregnancy. FSANZ says: "Kelp and seaweed supplements are not recommended as they contain varying amounts of iodine."
• Babies under 12 months. No safe upper limit could be set, and the NHMRC says their iodine should come from milk, formula and food only.
• Children. The safe upper limit is 200 µg from 1 to 3 years, 300 µg from 4 to 8 and 600 µg from 9 to 13.
• High-dose products. Lugol's-strength solutions and high-dose protocols go over Australia's listed-medicine limits and should only be used under practitioner supervision.
• Medicine interactions. We don't have verified data on iodine with thyroid medicines, lithium, amiodarone or potassium-sparing medicines, so none are stated here. Ask your pharmacist.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.