First off, what is iodine & why should I care about it? Iodine is a trace mineral, it is essential & necessary for many functions in the body but most notably the thyroid. Iodine is essential for healthy thyroid function. Low levels can even contribute to behavioral issues like sudden aggression. Here's the thing though, too little iodine in the diet...causes problems. Too much iodine in the diet...again, causes problems. Both scenarios will likely lead to thyroid gland disfunction. If you feed a commercial diet (kibble/canned), then iodine has likely been added in sufficient amounts in the form of : potassium iodide, potassium iodate, sodium iodide, or calcium iodide,. Do not add more.
Here's the deal. MOST homemade diets are low in iodine if specific foods are not fed to include iodine. For example if you feed a strict prey model diet (80/10/5/5) with nothing else added, your probably, no, your going to be low. The exception is if you feed whole prey, meaning you feed whole animals in their entirety. If you are regularly feeding whole prey to your dog/cat then iodine isn't going to be an issue....it's in there! Not surprisingly, the thyroid gland in an animal is rich with, you guessed it, iodine! Now understandably most people aren't doing this.
So, if you don't feed whole animals where can you get iodine in adequate amounts into your diet?
The most iodine rich foods come from the sea. Seaweeds, fish, shrimp & oysters are good sources. Also a large chicken egg contains somewhere around 24mcg, actual amount is of course dependent on the hens diet. Now things like shrimp aren't going to hurt your pet if they eat them but it's not something you want included regularly or in the daily diet. Fish, well the amounts can vary quite a bit and well there are a lot of factors...is the fish whole? Is it an iodine rich species such as cod which contains 90mcg in a 3oz portion. With fish it can turn into a bit of a guessing game. Don't get me wrong you should feed fish, just don't rely on it solely for iodine. So what's left & easy.....seaweed.
Seaweed, specifically Kelp!
Kelp is the food where we can turn to easily & naturally meet iodine needs. Kelp is a large brown seaweed that is most notably rich in iodine. (Side note: Do NOT add kelp if your pet knowingly suffers with thyroid problems, consult a holistic vet.) You can easily add kelp to your homemade diets with the use of a quality, measurable kelp powder.
Now, if your wondering how do you know what your dogs iodine requirement is? Do a quick math calculation once & then write the number down so you don't have to do it again:
You take your dogs weight in kilograms to the power of .75 (the ^ button on your calculator), this number is your dogs metabolic weight. Now you multiply this number by 29.6. The result is your individual dogs iodine needs.
Or if you prefer based on calories:
Recommended allowance per 1000kcal is as follows:
Adult dog & puppies: 220mcg
Adult cat: 350mcg
FYI: The Now brand I have recommended is 450mcg in one scoop.
Now this is important. Don't assume your diet has zero iodine in it, as discussed earlier foods like fish & eggs have measurable amounts and meat has some (very minimal), so take this into consideration when dosing kelp. For example if your dogs requirement is 300mcg iodine you don't need to feed this all in kelp if the meal has oysters or fish & egg in it. Just scale the amount back a bit. Your better off to not over do it!
As important as fulfilling nutritional needs is don't let it become too technical, or stressful. Nothing in nature needs "perfect" measurable amounts of anything in every meal of every day. It just doesn't work like that, despite what some people will lead you to believe. Having the knowledge to know where & what may be coming up short in your dog or cats diet gives you the power to intelligently make some additions or changes in how you feed. Ultimately giving them a better shot at longer, healthier lives with you!
Sources: NRC Nutrient Requirements of Dogs and Cats 2006
USDA database food search , FDA.gov tyroid/safety