Seaweed (Boiled)
Food · Vegetable · Food, Typed Supps
Fifty-four calories, and still twice a day’s iodine in a hundred grams.
Stage by stage
- Rehydrated (The pot): Boiling both softens it and leaches out a large share of the iodine.
- Iodine (Thyroid): 337 mcg per 100 g even after boiling — still double a day’s requirement.
- Protein (Muscle): 8.4 g per 100 g on 54 calories, a high ratio for a vegetable.
- Fibre (Gut): 6.2 g per 100 g, retained through cooking.
Timing
Boil longer and discard the water if iodine is a concern. Fifteen minutes is the figure usually cited for kombu.
Time to effect
- 15 min boil: The standard method for reducing seaweed iodine substantially.
- Weeks: Thyroid response to sustained excess iodine.
Allergens
None of the fourteen major allergens. Derived from what this food is, not from a product label.
Eating patterns
Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Keto, Gluten-free. Depends on the product: Low-FODMAP.
Satiety
289 on the satiety index, where white bread is 100 — very high. Modelled from the Holt et al. (1995) measurements.
Environmental footprint
0.5 kg CO2e and 108 litres of freshwater per kg, matched to "Other vegetables" in Poore & Nemecek (2018), Science 360.
Cost band
Cheap — roughly £2.5 per kg, as a band midpoint rather than a price.
Key nutrients
Nutrition per 100g
- Calories: 54
- Protein: 8.4g
- Carbohydrate: 0.4g
- Fat: 0.8g
- of which saturated: 0.2g
- Fibre: 6.2g
- Sodium: 83mg
Food vs. supplement
Most cooking methods are about flavour and texture. Boiling seaweed and discarding the water is one of the few that meaningfully changes a nutrient load, which makes it a genuine dietary tool rather than a technique.
Kitchen tip
Boil it and throw the water away. Iodine dissolves out, which is the only practical way to eat seaweed regularly on a restricted intake.
Common myth
“Cooking doesn’t change the minerals in food.” In reality: For iodine in seaweed it changes them a great deal. Iodide is water-soluble, so boiling and discarding the water strips a large share of it — which is why boiled seaweed sits at 337 mcg per 100 g where dried nori is 2,200. For anyone on a restricted iodine intake who still wants to eat seaweed, that is the practical answer.
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