The Quick and Simple Iodine Test for Starch and How it Helped Relieve my AS Symptoms

Pictured: cooked grains of white rice (left), Pita Tortilla Naan Bread (right)

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Once I cut all starch from my diet my AS-related symptoms subsided miraculously. This was no easy task, as hidden starches snuck into my diet without me even giving it a second thought. I thought I had been starch-free for several months but wasn’t feeling fantastic yet. Finally, I realized that some of my supplements were laden with starch. It wasn’t until I replaced those supplements with starch-free versions that I noticed improvement rather quickly.

When someone asks me, “How do you know if something contains starch?” I always respond with “The Iodine Test!” – an excellent, quick, and accurate way of learning whether a food contains starch.

The How-To

To test for starch, put a few drops of iodine on a small food sample. Wait for up to 15 minutes to see if the iodine changes color from red/orange to dark blue/black. The color change happens when the iodine comes in contact with starch. Therefore, if a food sample turns black upon coming in contact with iodine the food contains starch.

In the picture above you can see a few drops of iodine dropped onto a starch-free Pita Tortilla Naan Bread (right) which did not change color (the iodine stayed its red/orange color). Next to it, on the left, the iodine on grains of rice instantly changed to a dark black color. The color change to black marks the high starch content in the rice.

Below, is a photo below of a piece of cooked spaghetti squash which didn’t really change color, except for a tiny amount of faint blue compared to a cooked piece of butternut squash which went jet black instantly. This means the spaghetti squash is super low in starch (hardly any color change) while the butternut squash is very starchy.

You will also find some raw fruits and veggies test “starch-free” raw, but after the cell walls break down in the cooking process they will fail the iodine test after cooking, as is often the case with carrots and zucchini.

The Tricky Details

Fruits and veggies will vary in starch content because the specific varieties of each fruit or veggie will vary, the region grown varies, and ripening times will vary. Spaghetti squash can sometimes show a bit more starch, but I have never had one turn dark black. Apples are another food that varies greatly by variety and starch content, as there are over 5,000 different varieties of apples around the world. Add to that the different amounts of time the apples were allowed to ripen on the tree and in cold storage before showing up at the market. My advice for finding lower starch and starch-free apples is to actually buy them out of season when they have had more of a chance to ripen by sitting in cold storage for a longer period of time. Apples are the one food I don’t eat in season.

The goal is for you to develop your own individual list of foods that you also tolerate well, and once you do that you don’t need to test each food with iodine every time you eat it, at least I don’t. I have also found that the longer I have been on this diet, and the more my gut has healed, the more I tolerate fruits and veggies that have a little bit of starch, but I still avoid eating anything that turns jet black like the butternut squash or wheat bread.

Click here for an unofficial ‘Low Starch and Starch-Free Foods’ List (downloadable PDFs). The starch content in certain foods like apples or cauliflower can vary greatly depending on the variety, region grown, and ripening time. This list is meant to be a loose guide instead of a set of hard fast rules. Please note that foods like nightshades, nuts, and dairy are low-starch but can often contribute to inflammation.

Please Note:

• Never consume a sample that was in contact with iodine. Discard samples immediately.

• Sodium Iodine U.S.P 2% tincture can be found at most pharmacies and drug stores in North America. Sodium-iodine or potassium-iodine are best for showing starch content, while povidone-iodine doesn’t work nearly as well.