Research confirms that there is a ” U-shaped” curve between iodine and thyroid disease, and that excessive or insufficient iodine intake can impair thyroid function. The World Health Organization (WHO) recommends 150-200 micrograms of iodine per day for healthy adults (not pregnant women) and at least 250 micrograms per day for women during pregnancy and lactation.
If you have had a thyroidectomy and also need radioactive iodine (RAI), your doctor will tell you to go on an “iodine-free diet” for a while before the RAI. This is done so that the cancerous tissue can absorb the radioactive iodine next.
There are more or less trace amounts of iodine in food, and a true “iodine-free diet” is difficult to achieve. But you can do a “low iodine diet”: the low iodine diet recommended by our professional society (Chinese Society of Nuclear Medicine) is under 50 micrograms of iodine per day for at least 1 to 2 weeks.
To be “low iodine,” we need to know how much iodine is in our daily food.
Iodine content of various foods
The amount of iodine in different foods varies. Some seafood is high in iodine, such as kelp, nori, scallops, and dried shellfish, with kelp and nori having the highest iodine content, followed by fish, shrimp, and crab shellfish. In other foods, eggs have a high iodine content, the iodine content of different milk varies greatly, meat does not have a high iodine content, and plant foods have the lowest iodine content, especially fruits and vegetables .
Here are three tables that show you exactly how much iodine is in our everyday foods.
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Table 1. Foods with high iodine content (>100 µg/100 g edible fraction) |
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| Name of food | Iodine content (µg/100g edible fraction) | |
| Dried seaweed | 36240 | |
| Seagrass | 15982 | |
| Dried Nori | 4323 | |
| Spirulina | 3830 | |
| Deep sea kelp, cold sea kelp | 2950 | |
| Seaweed | 2427 | |
| Fish, shrimp, crab and shellfish | ||
| Shrimp | Dried shrimp, dried baby prawns | 983 |
| Dried sea rice | 394 | |
| Shrimp | 373 | |
| Shellfish | Red shell | 162 |
| Fresh Abalone | 102 | |
| Egg | Quail eggs | 233 |
| Table 2. Foods with moderate iodine content (20-100 µg/100 g edible fraction) | ||
| Name of food | Iodine content (µg/100 g edible fraction) | |
| Shrimp | Serrano prawns (Peeps, shrimp crawlers) | 36.1 |
| Crab | Flower crab (female) | 45.4 |
| Pike crab | 33.2 | |
| River crab (male) | 27.8 | |
| Shellfish | Mussels (mussels) | 91.4 |
| Oysters | 66.0 | |
| Razor clams | 65.4 | |
| Scallops | 48.5 | |
| River Clams | 43.1 | |
| Clams | 39.3 | |
| Flower snails | 37.9 | |
| Sea fish | Scallops | 40.8 |
| Codfish |
36.9 |
|
| Doblefish | 33.4 | |
| Sardines | 28.5 | |
| Sea cucumbers | 28.1 | |
| Goose eggs | 59.7 | |
| Duck eggs | 34.2 | |
| Egg | 22.5 | |
| Mengniu Pure Yen Flavored Sour Milk | 35.4 | |
| Yili Shuffle Milk | 32.4 | |
|
Table 3. Foods with low iodine content (less than 20 µg/100g edible fraction) |
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| Name of food | Iodine content (µg/100g edible fraction) | |
| Shrimp | Kiwi shrimp | 16.1 |
| Sea fish | Small yellowtail | 15.6 |
| Rawfish (farmed) | 14.9 | |
| Squid | 12.3 | |
| Sea lamprey | 11.3 | |
|
Silver Pomfret |
10.9 | |
| Tilapia (back) |
9.1 |
|
| Seabass | 7.9 | |
| Pomfret (flatfish) | 7.7 | |
| Huang Huo (small) | 5.8 | |
| Mackerel | 3.5 | |
| Freshwater fish | Carp | 10.1 |
| Grass carp (white carp) | 6.4 | |
| White Chub | 6.7 | |
| Fatheads | 6.6 | |
| Carp | 4.7 | |
| Cereals | Organic brown rice | 14.5 |
| Sorghum rice | 7.0 | |
| Soba | 6.8 | |
| Barley | 4.0 | |
| Oatmeal Rice | 3.9 | |
| Noni | 2.0 | |
| Xiaomi | 1.6 | |
| Wheat flour | 1.5 | |
| Rice | 1.4 | |
| Oat | 1.4 | |
| Corn | 1.1 | |
| Purple potatoes | 2.5 | |
| Potatoes | 1.2 | |
| Sweet potatoes | 0.5 | |
| Dry beans and products | Soybeans | 5.2 |
| Mung beans | 5.0 | |
| Rutabaga beans | 4.7 | |
| Red beans | 4.0 | |
| Fava beans | 1.3 | |
| Fennel | 12.4 | |
| Green amaranth | 7.0 | |
| Dry red peppers | 6.0 | |
| Cabbage | 5.0 | |
| Oilseed rape | 4.7 | |
| Spinach | 4.6 | |
| Cilantro | 4.6 | |
| Hollowed out cabbage | 4.5 | |
| Ginger | 4.3 | |
| Chrysanthemum coronarium | 3.8 | |
| Yam | 3.6 | |
| Green Onion | 3.5 | |
| Lettuce | 3.4 | |
| Olea europaea | 3.1 | |
| Leek | 3.0 | |
| Big White | 2.4 | |
| Carrots | 2.2 | |
| Maundy (peeled) | 1.8 | |
| Winter squash | 1.7 | |
| Bitter melon | 1.7 | |
| White radish | 1.4 | |
| Loofah | 1.4 | |
| Onions | 1.3 | |
| Kale | 1.3 | |
| Celery | 1.3 | |
| Carrots | 1.2 | |
| Beans | 1.2 | |
| Onions | 1.2 | |
| Green peppers | 1.1 | |
| Cucumber | 1.0 | |
| Eggplant | 0.8 | |
| Pepper | 0.8 | |
| Zucchini | 0.8 | |
| Tomatoes | 0.7 | |
| Pumpkin | 0.7 | |
| Garlic scapes | 0.6 | |
|
Green kale (round cabbage) |
0.4 | |
| Hulu | Tr | |
|
Cauliflower (cauliflower) |
Tr | |
| Lettuce | Tr | |
| Walnuts | 10.4 | |
| Almonds | 8.4 | |
| Peanuts | 2.7 | |
| Black Sesame | 1.2 | |
| Black fungus | 10.1 | |
| Silver Fungus | 3.0 | |
| Shrooms | 2.1 | |
| Shimeji Mushroom | 2.0 | |
| Flat mushrooms | 1.9 | |
| Mushroom | 1.6 | |
| Mushrooms | 1.3 | |
| Apricot mushroom | 1.2 | |
| Crabapple mushroom (Proteus mirabilis) | 0.6 | |
| Golden Needle Mushroom | 0.4 | |
| Beef (lean) | 4.1 | |
| Lamb (lean) | 2.9 | |
| Pork (lean) | 1.9 | |
| Poultry meat and products | Chicken leg meat | 4.5 |
| Chicken breast | 3.2 | |
| Duck Meat (Green Head Duck Leg Meat) | 3.0 | |
| Milk and dairy products | Milk (pasteurized) | 1.9 |
| Yogurt | 0.9 | |
As you can see, during the “iodine-free diet” phase, in addition to not eating iodized salt, seafood and seafood should also be avoided. The iodine content of vegetables and fruits is very low, especially cauliflower (cauliflower) and lettuce, which have almost no detectable iodine content and can be consumed appropriately.
Co-written by Dr. Shuwen Yang, Cancer Hospital of Fudan University