Supplements & Overnutrition: Iodine and Salt

One thing that rarely gets discussed is overnutrition; part of that is due to there being very few nutritional maximums per the NRC and AAFCO. FEDIAF does have a few additional legal maximums, but those are largely due to environmental concerns.

Iodine

The AAFCO Minimum is .25 Mgs Per 1000 Kcals While the maximum is 2.75mgs per 1000 kcals.

While the maximum level is largely an educated guess, it is 12.5 times the recommended amount per the NRC (22 mg per 1000 kcals) Given that just three doses at 100mg/kg resulted in anorexia and vomiting, while 3 doses at 200mgs/kg and 250mgs/kg resulted in anorexia, extreme physical weakness, coma followed quickly by death. 2.75 mgs per 1000 kcals is a relatively good place for the maximum daily exposure. This equates to around .36 mgs per kg bw^.75.

One thing that is extremely important to understand, is that the minimum level was increased to deal with the Goitrogenic effects of some ingredients commonly used in pet food (Not just Soy).

While the maximum levels could be fine-tuned with more research, there is not really a valid justification for subjecting more dogs to experimentation to find the actual maximum safe exposure level over the course of weeks, months, several years or a lifetime.

Kelp and excess Iodine

Kelp is a broad term for seaweed and algae in the order Laminariales. Kelp is now commonly included as an ingredient in both pet food and supplements.

Kelp, other seaweeds, and algae can also be very high in Iodine. Microalgae such as Chlorella and Spirulina are not high in iodine.

The amount of iodine in different kelp species generally falls between .5mgs to 4.5 mgs per gram, with some outliers. This is influenced by growing conditions, season, and the exact processing method. There are supplements using those on the higher end.

Most pet foods, treats, and supplements that include them don’t disclose the exact species used or the iodine content.

Some supplements only mention the genus i.e., Fucus, or Laminaria, while others call it seaweed.  If you see these or other generic terms listed, you should always request clarification from the manufacturer on the species used and the iodine content.

The potential issue with kelp and seaweed in supplements is that it can greatly increase the amount of iodine your dog receives and can put them over the maximum. Especially when most foods are not formulated to the minimum level of iodine, and if your dog is highly active, they end up getting even more. 

The variability in iodine content is why some pet food manufacturers prefer using standardized sources of nutrients because then each batch would have to be reformulated. For example, a company can use iodized salt and not have to worry as much about the variation in iodine.

The use of kelp in formulating pet food does cut both ways. If a batch of kelp is lower, the food can end up with too little, or if it’s higher in iodine, the food can end up with too much iodine.

Note: Some people who advocate consuming seaweed for both dogs and humans will point towards the fact that a large portion of people in Japan consumes several times the RDA of Iodine with no ill effects.

This completely ignores the fact that this is nothing new; they have been consuming significantly higher levels of Iodine for thousands of years. Meaning it’s possible, if not likely, that some genetic adaptation allows for the consumption of significantly higher levels. Additionally, research indicates that microbes within the gut microbiome of those in Japan, not North America, are capable of digesting seaweed. While it's technically possible that this was a relatively recent occurrence, it's more likely that it occurred hundreds if not thousands of years ago. 

There are also other dietary, environmental, and lifestyle differences that could contribute. To use another example, just because people in certain parts of Bolivia and Argentina have a mutation that allows them to tolerate significantly higher levels of arsenic doesn’t mean it is safe for everyone.

Kelp and Salt

With Kelp and other seaweeds, you can also add significant sodium levels, as kelp is commonly above 3% Sodium.  Unlike iodine, there is no maximum amount. At the same time, those dogs with heart or kidney conditions should avoid adding excessive sodium levels.

Radioactive Iodine Therapy

Radioactive iodine therapy is used to treat hyperthyroidism and thyroid cancer. In human medicine, it is now relatively common to recommend a low-iodine diet before treatment. When it comes to dogs being treated for thyroid carcinoma, some do recommend a low home-cooked diet low in iodine for a brief interval to increase uptake, while for cats, it is much less common as there is already sufficient uptake. The therapy is much more common in cats, being treated for hyperthyroidism, while there are only a few specialty hospitals that conduct the procedure for dogs.

Source of Kelp

While you might imagine the kelp is grown in the pristine waters of Norway, it really depends on where in Norway it is grown, as Norway is home to many Salmon Farms off their coast, and that applies to many other locations that might generally be viewed as pristine such as Iceland.

While there are specific compounds in seaweed that can be beneficial, sourcing is extremely important as you wouldn’t necessarily want kelp that is grown anywhere near most fish farms.

Conclusion

If you are making treats for your dogs at home and the recipe calls for salt, it is best to avoid iodized salt, which, while it’s been great for humans to prevent high levels of iodine deficiency, it’s not necessarily ideal for dogs that are already receiving sufficient levels of iodine from their diet.

If you are giving your dog a supplement with kelp, seaweed, or algae, you should not be adding another supplement with iodine-rich seaweed or algae. It’s always best to ask the manufacturer about the iodine content of the seaweed or microalgae they use.

Example: 15 Kgs Dog

Food Fed is 1mg of Iodine per 1000 kcals. 1000 Kcals is what AAFCO and the NRC consider for a 15kg dog. This leaves you with 1.75 Mgs of iodine.

	Allowance 15kg Dog
Kelp is .5 mgs per gram	3500 mgs of Kelp
Kelp is 1 mgs per gram	1750 mgs of Kelp
Kelp is 1.5 mgs per gram	1166 mgs of Kelp
Kelp is 2 mgs per gram	875 mgs of Kelp
Kelp is 2.5 mgs per gram	700 mgs of Kelp
Kelp is 3 mgs per gram	583 mgs of Kelp
Kelp is 3.5 mgs per gram	500 mgs of Kelp
Kelp is 4 Mgs per gram	437.5 mg of Kelp
Kelp is 4.5 mgs per gram	388.9 mg of Kelp

 

One supplement that did disclose the species and dose recommended 290 Mgs for a 25-50 Lbs (11.3-22.6Kgs) Dog. The species also happened to be one of the highest in iodine. Consistently testing above 4.5mgs per gram. So at least 1.305 mgs. This will put most dogs close to or above the maximum iodine. In addition to the Iodine, you also added at least, but probably more than, 8.7 mgs of Sodium.