Salt made by evaporation supplies too little iodine to prevent goiter, so a community needs iodine from seafood, dairy from iodine-sufficient regions, or measured supplements, with pregnant women and young children protected first. Adults need about 150 micrograms a day and should stay under about 1,100, and because dried kelp ranges from about 16 to 2,984 micrograms per gram, seaweed is a food to eat in varied modest amounts, never a dose to measure out by eye.
Part of Salt Production & Sourcing
Iodine and mineral supplementation is the provision of trace nutrients that salt made at home does not carry, for people and for stock, without creating a dosing risk.
The Gap, And The Parent’s Remedies
The parent states that natural salt contains no iodine, and that without dietary iodine a community will develop goiter and other thyroid disorders within 1-2 years. The cause is real: the thyroid needs iodine to make its hormones, and iodine deficiency is a leading preventable cause of intellectual disability, with the worst harm to the fetus and young child (Goiter & Beriberi). Sea salt does contain a little iodine, but not reliably enough to count on. I cannot source the parent’s 1-2 year timeline; how fast deficiency shows depends on how severe it is and who is affected.
The parent’s sources: seaweed (the richest), ocean fish, dairy from animals grazing on iodine-rich soil, and, near the coast, burning dried seaweed and mixing the ash into the salt.
The Numbers That Matter
From the US National Institutes of Health Office of Dietary Supplements (recalled):
- recommended daily intake for adults: 150 micrograms (µg)
- tolerable upper intake for adults: 1,100 µg
- needs are higher in pregnancy and while breastfeeding
- dried kelp products range from about 16 to 2,984 µg per gram
The kelp range is 2,984 ÷ 16 = about 187-fold. At the top of it a single gram is 2,984 ÷ 1,100 = 2.7 times the adult upper limit; at the bottom, 150 ÷ 16 = nearly 10 grams would be needed for the daily intake. Nobody can tell from looking at a seaweed where it sits in that range. Excess iodine disturbs the thyroid as surely as too little does, causing both over- and under-active thyroid disease.
The ash suggestion should not be followed. Burning seaweed drives much of its iodine off as vapour (iodine is volatile), the remainder in the ash is unmeasured, and mixing ash into a salt supply gives an uneven, uncontrolled dose and also adds alkali and potassium. I recommend against it, although the parent suggests it.
What Can Be Done Safely
- Use food sources steadily: ocean fish, shellfish and sea vegetables in varied, modest amounts, and dairy and eggs where soils are not iodine-poor.
- Protect priority groups first: pregnant and breastfeeding women, infants and children.
- Save iodised salt and iodine supplements found in salvage for those groups.
- Trade for iodised salt where a coast or supplier exists (Salt as trade commodity).
- Watch for signs: a swelling at the front of the neck, fatigue, cold intolerance, and in children poor growth and learning (Goiter & Beriberi).
This article gives no recipe for iodising salt at home. Commercial iodised salt carries tens of milligrams of iodine per kilogram of salt (recalled), a few parts in a hundred thousand, which is very hard to mix evenly by hand; uneven mixing gives hot spots that overdose and cold spots that do nothing.
Livestock And Minerals
The parent gives livestock salt needs of 1-2 oz a day for cattle and horses and 0.3-0.5 oz for goats and sheep. Over a year that is 1-2 oz × 365 ÷ 16 = 22.8 to 45.6 lbs for a cow, and 0.3-0.5 oz × 365 ÷ 16 = 6.8 to 11.4 lbs for a sheep or goat. Stock may also need trace minerals that vary by region, but do not feed a mineral mix made for one species to another: sheep are especially sensitive to copper, and a mix made for cattle can poison them.
What You Need
- Records of who eats what, and a list of priority people
- A source of reliable iodine, whether iodised salt, fish, or supplements
- A health watch for goiter signs
- Separate livestock mineral blocks, labelled by species
Method: Cover The Gap
Step 1: Identify the iodine sources your community has and which are consistent.
Step 2: Prioritise pregnant women and children for any measured source.
Step 3: Keep seaweed as a varied food, not a supplement.
Step 4: Watch for the signs, and act early.
Common Mistakes
- Treating seaweed as a measured dose.
- Using seaweed ash in salt.
- Giving cattle mineral mix to sheep.
- Giving high-iodine supplements to everyone.
Safety
Too much iodine harms the thyroid, and so does too little
A single gram of some kelp products exceeds the adult upper limit of 1,100 µg several times over, and excess iodine causes thyroid disease. Do not improvise doses of iodine compounds, do not add iodine or iodide to salt by guess, and do not give kelp supplements to children or pregnant women except under informed advice. Use food sources and measured products with a stated content.
What’s Next
- Learn next: Community salt rations — how much salt each person and animal is allotted
- Combine with: Essential Minerals — the wider picture of essential minerals