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How much iodine is safe for dogs?

iodine for dogs

Everything we assume we know about iodine in dogs is based on studies of conical flask iodine (iodide) and kibble-fed dogs. Like every other mineral (calcium, phosphorus, zinc, iron, magnesium, manganese, copper) the artificial, conical flask version is handled very differently by the body. For the aforementioned minerals, it’s because they are not chelated to a carbon molecule. This the body hates. Eg dogs absorb about 10% of the zinc or iron oxide fed to them, so they have to include LOTS in their mixes (and the AAFCO guidelines thus say to give LOTs, incorrectly – when you are using real food their “minimum” figures are excessive).

Iodine is different. Both conical flask iodine and food-sourced iodine is actually iodide (bound to something like potassium) as iodine on its own would actually kill you. But it turns out it’s the conical flask iodide that has the dramatic effect on the body because it’s not bound up with fibre which slows its delivery to the bloodstream.

Hence studies of dogs fed either kibble OR real food, when supplemented with conical flask iodide, develop thyroid issues.

hand picked seaweed for dogs

The most recent test of our beloved tooth-cleaning, brown seaweed-based product Canident during summer (when it is expected to have its highest iodine content) reveals it contains 664mg/kg or 0.66g of iodine per kilo of dry seaweed.

To give you the maths on that, the AAFCO requirements state a 10kg dog should be getting 1mg of iodide per day PER KILO OF KIBBLE. This equates to around 0.5mg of iodide per kilo of raw. Or, if a 10kg dog eating 2.5% of his body weight (250g) per day in raw, 0.125mg of iodide per day.

As we recommend dogs get 1-2g max per 10kg of body weight of Canident, it means a 10kg dog eating raw (and assuming no other seaweed is used) would be getting around 1mg of iodine per day. This means, at its height, Canident is providing around 8 times the dog’s RDA for iodide, according to AAFCO.

However, please note, the iodine content of Candient was worked out in a laboratory. It is ALL the iodine present in the sample. But unlike the AAFCO’s figures (that are virtually pulled from thin air), this iodine is not an isolated, conical-flask, ready-to-absorb-and-smash-your-thyroid that you find in kibble. This is real iodine, bound up in the food matrix (tied up with protein and fibre, polysaccharides and pigments). This means not all is available to the animal. In fact, in vitro (done in a laboratory) digestion studies have reported the bioavailability of iodine in seaweed as follows: Laminaria spp (17%–28%), Sargassum fusiforme (12%), Palmaria palmata (10%), Undaria pinnatifida (2%–12%), Himanthalia elongata (4%), Porphyra spp (5%) and Ulva rigida (2%). In other words, only a small fraction of the iodine present is available to consumers, at most a quarter.

We perhaps shouldn’t be too surprised at this. We know Japanese folk happily ingest up to 8-20 times their RDA of iodide from seaweed and fish each day, with no problems at that level (and those RDAs are not based on conical flask data, we wouldn’t be so foolish in human nutrition…but then, Ronald Mc Donald doesn’t write our nutritional manuals, for the large part). If anything, the Japanese derive great benefit from the practice, being among the healthiest and longest-living people on the planet.

This means we can expect dogs to absorb 25% of the iodine quoted in this product. So, eight times their RDA of iodine, becomes twice their RDA, far more palatable, even for dry food believers.

This is perhaps why, in a “real life” studies where dogs were fed 15g of Ascophyllum per 1kg of dry food for a month (equating to around 7.5g of Asco per lab eating 500g of dry food, which is around our maximum dose for the same dog) the authors found the “dogs showed good health conditions throughout the study“, affecting neither fecal microbial parameters, intestinal immunity or nutrient digestibility.

Again, in summary, AAFCO feed trials use iodide for their measurement, that is iodine not bound up normally in food. You absolutely need to be careful here. However, natural iodine does not work the same way.

But still, if you’re concerned, go with our lower recommended dose of 1g per 10kg of dog (bang on their RDA of iodine each day). Canident will still work, it will just take longer.

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On knowing more, we badly want to look into this – the thyroid impact on dogs fed a daily feed dose of seaweed. I’m chatting about this with a group. There is an issue here. You need to take bloods and that you are not allowed to do (outside of illness in the vets) as it falls under “experimentation”. The paperwork there is enormous, rightly (mind you, they can test dry food on 6 caged dogs for 6mths, is there anything crueler?!!).

So that’s where we are with the nutrient. It’s a tricky one and folk are very confused but I’m not going to shy away from the discussion. I see some manufacturers stating their iodine contents as incredibly low, I suspect to avoid having this discussion with their clients online. In many instances, including when looking at the figures stated by an industry leader, I’m not aware of any brown seaweeds that clean teeth have so little iodine, even in winter (unless it’s near a leaking nuclear power plant…I’m joking, of course…sort of).

I’m very open to discussion about this. If you have any ideas, I’m all ears. I want this answered as much as everyone else. Howeer, like most other conversations about correct or optimal nutrient inclusions for dogs, we are at sea (pardon the pun), lost in a melee of non-sensical dry food, George-Jetson-style nonsense.

For now, I’m going to see what info I can find on farm animals (pigs, chickens, cows, all get seaweed in great abundance…). I will keep you all posted what I find.

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