Dried Kelp in dog and cat food

Is it OK for dogs and cats?

Dogs

Kelp adds iodine, which dogs need. Its iodine content varies widely, so what matters is the total iodine in the finished food. FEDIAF lists the EU legal maximum for complete foods as 1.1 mg per 100 g of dry matter and considers it safe for all dogs.

Cats

Healthy cats also need iodine, and the same point about total iodine applies. Cats with hyperthyroidism on a prescription iodine-restricted diet are different. They must not eat any other food or treats, because even tiny amounts of iodine can stop the diet working. Any other food, including one with kelp, does not fit that plan, so ask the vet.

How settled this is: Depends on the amount

What dried kelp is

Kelp is a kind of seaweed. The kelps measured in the research cited here are Laminaria and Ecklonia species. Dried kelp is the seaweed dried and ground. The EU Catalogue of feed materials lists dried and crushed macro-algae, in particular red, brown or green algae, as 'seaweed meal'. Seaweed meal may have been washed to reduce its iodine content. Under the catalogue, the name is to be supplemented by the algae species as appropriate, and any other species above 5% must also be named.

Why it is in pet food

Kelp is very rich in iodine, so it adds iodine to a recipe. In a study of commercial seaweeds, iodine ranged from 16 micrograms per gram in nori to over 8,165 micrograms per gram in processed kelp granules made from Laminaria digitata. In two Namibian kelps it ranged from 514 to 6,571 micrograms per gram, depending on the state of the blades at harvest. The EU requires seaweed meal to declare its iodine content when it is above 100 ppm.

What it does in the food

Dogs and cats both need iodine. FEDIAF's nutritional guidelines set minimum iodine levels for each species and life stage. FEDIAF lists the EU legal maximum for total iodine in complete dog and cat foods as 1.1 mg per 100 g of dry matter (about 11 mg/kg). That limit applies when iodine is added to the recipe as an additive, and it then counts iodine from all ingredients. If the iodine comes only from ingredients such as seaweed, the legal maximum does not apply. FEDIAF says a nutritional maximum should then be taken into account where one is listed, but its tables list no nutritional maximum for iodine. The EU also requires seaweed meal to declare its crude protein, crude fat and crude ash.

Safety and limits

Iodine: kelp's iodine content is high and varies. Iodine also dissolves in cooking water and may be lost in humid storage, so the iodine content of prepared foods is hard to estimate. Dogs: two 2001 studies by Castillo and colleagues reported thyroid changes, including hypothyroidism, in puppies fed a high-iodine commercial diet. A low nutritional maximum for dogs was recommended on the basis of these studies. FEDIAF notes that those puppies were overfed by about 75% above their energy needs and that the food lacked key nutrients. It concludes that the results do not apply to normal balanced foods and that the existing EU legal maximum is safe for all dogs. Cats: the Merck Veterinary Manual says cats treated for hyperthyroidism with an iodine-restricted diet must not eat any other cat food, table food, treats or prey. Even tiny amounts of iodine can make the diet ineffective. A 2013 survey of US cat foods found dramatic variation in iodine among canned foods. The authors suggested that diets that are first low and later high in iodine might lead to hyperthyroidism in cats. That is a hypothesis, not a settled finding. Arsenic: the EU sets specific arsenic limits for seaweed. Total arsenic may be at most 40 mg/kg in seaweed meal and seaweed-derived feed materials. In complete or complementary pet foods that contain seaweed, the limit is 10 mg/kg (both at 12% moisture). If authorities ask, the operator must show that inorganic arsenic is below 2 ppm, particularly for the seaweed Hizikia fusiforme.

What depends on the amount and the recipe

The total iodine in the finished food. This depends on how much kelp is used, the species and harvest, and whether the kelp was washed to reduce iodine. Whether the food also contains an iodine additive, which decides whether the EU legal maximum applies. The pet's thyroid health, especially for cats on iodine-restricted diets. The arsenic content of the seaweed used.

Not the same as

• Seaweed meal — The broader EU name for dried, crushed macro-algae, in particular red, brown or green algae. It may or may not be kelp; the name is to be supplemented by the species as appropriate.
• Algal oil — Oil extracted from algae, listed as a separate feed material in the EU. It is a fat ingredient, not dried seaweed.

Sources

1. Regulation (EU) No 68/2013 on the Catalogue of feed materials, consolidated text of 24 July 2022 (entries 7.1.1–7.1.7, algae and seaweed meal) — Publications Office of the European Union, 2022. Seaweed meal defined as dried, crushed macro-algae, in particular red, brown or green algae, which may be washed to reduce iodine; compulsory declarations of crude protein, crude fat, crude ash and iodine if >100 ppm; name to be supplemented by the species as appropriate, other species above 5% named; algal oil as a separate entry.
2. Directive 2002/32/EC on undesirable substances in animal feed, consolidated text of 28 November 2019 (Annex I, arsenic) — Publications Office of the European Union, 2019. Total arsenic maxima at 12% moisture: 40 mg/kg for seaweed meal and seaweed-derived feed materials; 10 mg/kg for complete and complementary pet food containing seaweed; on request, inorganic arsenic must be shown below 2 ppm, especially for Hizikia fusiforme.
3. FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs (September 2025) — FEDIAF (European Pet Food Industry Federation), 2025. Iodine minimums for dogs and cats; EU legal maximum listed as 1.10 mg/100 g DM with no nutritional maximum for iodine; legal maximum applies to total iodine only when the nutrient is added as an additive, otherwise a listed nutritional maximum should be considered; Castillo puppy studies (overfeeding ~75%, deficient diet) judged irrelevant to balanced foods and the legal maximum safe for all dogs; Castillo reference titles.
4. Teas J, Pino S, Critchley A, Braverman LE (2004). Variability of iodine content in common commercially available edible seaweeds. Thyroid 14(10):836-41 (PubMed abstract) — Thyroid (abstract via NCBI PubMed), 2004. Iodine from 16 µg/g (nori) to over 8,165 µg/g (Laminaria digitata kelp granules); 514–6,571 µg/g in Namibian kelps (Laminaria pallida, Ecklonia maxima) depending on blade condition; iodine lost in cooking and humid storage, making prepared-food content hard to estimate.
5. Hyperthyroidism in Animals — Merck Veterinary Manual, 2024. Iodine-restricted prescription diet as a treatment for feline hyperthyroidism; cats on it must not eat any other cat food, table food, treats or prey because tiny amounts of iodine can make it ineffective.
6. Edinboro CH, Pearce EN, Pino S, Braverman LE (2013). Iodine concentration in commercial cat foods from three regions of the USA, 2008–2009. J Feline Med Surg 15(8):717-724 — Journal of Feline Medicine and Surgery (via PubMed Central), 2013. Dramatic variation in iodine among canned US cat foods; authors suggest diets first deficient and later excessive in iodine may lead to nodular hyperplasia and hyperthyroidism; fluctuating iodine described as a suggested risk factor.

Checked against these sources on 2026-10-15. Definitions are in our own words. This is a reading aid, not veterinary advice: a vet who knows your animal comes first.