Seaweed has been a daily food in Japan, Korea, China and across the Pacific for as long as there are records of what people ate. In most of the West it is something that happens to sushi.
This article used to be a list of seven things seaweed does for your body. We have rewritten it, because most of that list was not supportable and one section of it was frankly reckless. What follows is the version that holds up.
We sell a seaweed drink. Read accordingly.
What is actually in it
This part is not in dispute, and it is genuinely impressive for a vegetable.
- Iodine, in larger amounts than any other food. See the caution below, because this cuts both ways. - Minerals taken up directly from seawater: calcium, magnesium, potassium, iron. Seawater is a more complete mineral solution than most farmland soil, and seaweed does not have to wait for a farmer to add anything to it. - Fibre, including several types found in few other foods. - B vitamins, nori in particular. - Some omega-3, in a plant form. Worth noting that this is where fish get theirs: fish do not make omega-3, they accumulate it from algae. - Protein, in modest but real amounts, and unusually complete for a vegetable.
If you are eating a Western diet, seaweed supplies several things that are otherwise awkward to get, and it does it as food rather than as a tablet. That is the honest case for it and it is a good one.
Why that does not become a list of health benefits
Here is the step most articles on this subject skip, including the one that used to be on this page.
"Seaweed contains magnesium, and magnesium is important for the nervous system" is two true statements. "Seaweed improves brain function" is a third statement that does not follow from them. The same move underpins almost every nutrient-based health claim you will read: identify a nutrient, find something that nutrient is involved in, and describe the food as doing that thing.
It falls down for reasons that are not subtle. The amount in a normal serving is usually far below what any study used. Most people are not deficient in the nutrient in question, and topping up something that is not low does very little. And whole foods are not their ingredient list.
We went through this at more length, on our own supplier's research, in Reading the Research.
The caution this article owed you and never gave
Seaweed is very high in iodine, and more is not better.
Iodine content varies enormously by species. Nori is modest. Kombu can be high enough that eating a lot of it regularly pushes intake well past anything a person needs, and excess iodine causes problems of its own.
If you are under a doctor's care for your thyroid, or you have been told to watch your iodine intake, talk to them before adding seaweed as a daily habit rather than after.
The previous version of this article discussed thyroid medication and then offered seaweed "by contrast". Nothing here is an alternative to a prescription, and we should never have implied otherwise.
How much is sensible
Small amounts, regularly, and variety across species rather than a lot of one. A sheet of nori, a strip of kombu in a stock, a spoon of wakame in a soup.
The traditional diets that inform all of this are not built on large daily quantities of a single seaweed. They use it as a seasoning and a stock base, which is also the easiest way to eat it if you did not grow up with it.
Easy ways in
- Kombu in stock. Drop a strip in while soup or beans simmer, take it out before serving. You get the minerals and the savoury depth and nobody has to look at seaweed. - Crushed dried seaweed as a seasoning. Works on rice, eggs, pasta, roasted vegetables. - Wakame in salad. Rehydrates in about five minutes. - Nori as a snack. The least nutritionally interesting option, since snack sheets are small and lightly salted, but the easiest sell to a household.
If you would rather gather your own, we wrote a practical guide to harvesting on the Oregon coast.
And if you want the broader corrections to what gets said about seaweed, including a few things this site itself used to claim, Seaweed 101 is the one to read.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
More on this subject: Fucoidan & Seaweed