Know2eat

Kelp

Laminaria spp.

What kelp has been studied for

1 association assessed — none with dependable human evidence behind them yet. Strongest first.

  • 1 Insufficient
3 things to know first — allergies, interactions and intake limits

About kelp

Large brown seaweeds of the order Laminariales, used dried as kombu to make dashi and eaten fresh or rehydrated as a vegetable. It is the single richest dietary source of iodine.

Also known as Kombu, Sugar kelp, Oarweed, Haidai

Weight Management

The evidence in depth

Best supported: Insufficient

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how impressive the food is. How we rate evidence.

Body composition

Weight Management
Insufficient evidence

Kelp is marketed for weight loss on the strength of its fucoxanthin content and rodent studies of fat metabolism. Human trials of kelp or fucoxanthin are few, small and inconsistent, and the iodine load is a reason for caution rather than a mechanism for benefit.

Insufficient evidence. Not enough human research to say anything useful yet.

4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

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Answers are written only from the entries on this page — the same nutrients, compounds, claims and citations you can read above. Nothing is added from outside the database, and every answer lists what it was built from.

AI explanations are not switched on for this site, so there is nothing to ask here. Everything above is read straight from the database and does not need them.

Key nutrients

Nutrient content per 100 grams
NutrientAmount% DV
Macronutrients
Calories43 kcal2%
Protein1.68 g3%
Total fat0.56 g1%
Carbohydrate9.57 g3%
Fibre1.3 g5%
Total sugars0.6 g—
Water81.6 g—
Fats
Saturated fat0.247 g1%
Monounsaturated fat0.098 g—
Polyunsaturated fat0.047 g—
Cholesterol0 mg0%
EPA (omega-3)0.0040 g—
DHA (omega-3)0 g—
DPA (omega-3)0 g—
Linoleic acid (omega-6)0.02 g—
Vitamins
Vitamin A6 µg1%
Vitamin C3 mg3%
Vitamin D0 µg0%
Vitamin E0.87 mg6%
Vitamin K66 µg55%
Thiamin (B1)0.05 mg4%
Riboflavin (B2)0.15 mg12%
Niacin (B3)0.47 mg3%
Pantothenic acid (B5)0.642 mg13%
Vitamin B60.0020 mg0%
Folate180 µg45%
Vitamin B120 µg0%
Choline12.8 mg2%
Minerals
Calcium168 mg13%
Iron2.85 mg16%
Magnesium121 mg29%
Phosphorus42 mg3%
Potassium89 mg2%
Sodium233 mg10%
Zinc1.23 mg11%
Copper0.13 mg14%
Manganese0.2 mg9%
Selenium0.7 µg1%
Other measured compounds
Beta-carotene70 µg—
Alpha-carotene0 µg—
Lycopene0 µg—
Lutein + zeaxanthin0 µg—
Caffeine0 mg—
Ash6.61 g—

Nutrient values are per 100 g of the USDA reference entry named on this page and vary with variety, growing conditions, storage and preparation.

Source record: Seaweed, kelp, raw (USDA FoodData Central, FDC ID 168457).

% DV uses the FDA Daily Values for adults and children aged 4 and over. A dash means no Daily Value has been established for that nutrient.

Bioactive compounds

Compounds present in meaningful amounts. Presence is banded rather than quantified, because whole-food levels vary enormously with variety, growing conditions, storage and preparation.

How preparation changes things

Only effects with real support are listed. If a preparation method is missing, it is because nothing dependable is documented — not because it makes no difference.

  • boiledReduces iodine

    Boiling kelp and discarding the water removes a large share of its iodine, which is one reason a kombu broth carries far less than eating the reconstituted seaweed would.

Things to know

Allergies, interactions and intake concerns. Every food gets this section — a reference where everything is uniformly good is not a reference.

  • Avoid

    Iodine excess and thyroid dysfunction

    Kelp contains extraordinary amounts of iodine — a single gram of dried kombu can exceed the tolerable upper intake for an adult several times over, and kelp supplements have caused both hyperthyroidism and hypothyroidism. Occasional use as a stock ingredient that is then removed is very different from eating kelp as a vegetable or taking it daily. Anyone with thyroid disease, or pregnant, should raise regular kelp intake with a clinician rather than adopt it as a health habit.

  • Worth knowing

    Heavy metals and arsenic

    Seaweeds concentrate whatever is in the water they grow in, including cadmium, lead and arsenic. Levels depend heavily on species and origin, and some kelp supplements have been found with arsenic well above acceptable limits.

  • Interaction

    Thyroid medication

    Large iodine loads can interfere with the management of thyroid disease and change the response to levothyroxine or antithyroid drugs. This is a genuine interaction rather than a theoretical one.