Iodine diet for thyroid cancer patients treated with radioactive iodine

Practicing an iodine diet for 2 weeks before thyroid tumors treatment by 131 radioactive iodine has been shown to support and increase the effectiveness of this treatment. However, how to control the amount of iodine within the standard threshold while maintaining nutritional balance? This article will clarify the general principles and update the latest guidelines on this diet.

Correlation between radioactive iodine treatment and iodine dietary practices

Iodine is an important mineral that plays many roles in the body, especially in the thyroid gland. According to the Nutricare Medical Nutrition Institute – USA, Iodine is an essential ingredient used by thyroid cells to create thyroid hormones, contributing to many important processes including regulating metabolism, supports tissue growth and repair^[1]. At the same time, the thyroid gland absorbs almost all of the iodine in the body, so radioactive iodine (or I-131 (Iodine 131)) can be used to treat thyroid cancer. I-131 is absorbed mainly by thyroid cells, where the radiation can destroy the thyroid and any other thyroid cells (including cancer cells) with little effect on the rest of your body.

Radioactive iodine (Iodine 131) can be used to treat thyroid cancer. (Photo: Nonstop Neuron)

Radioactive iodine therapy helps people live longer if they have papillary or follicular thyroid cancer (differentiated thyroid cancer) that has spread to the neck or other body parts, and is currently the standard practice in such cases. However, to increase the effectiveness of radioactive iodine therapy, patients will be prescribed an iodine diet, or a low iodine diet.

According to the American Thyroid Association, a low-iodine diet is a diet that limits daily iodine intake to less than 50 µg, maintained for 1–2 weeks. This amount of iodine is much lower than the average iodine intake from foods of approximately 240 to 300 μg/day for men and 190 to 210 μg/day for women in the United States. This diet has been recommended by the American Thyroid Association for patients prescribed radioactive iodine treatment within 1 – 2 weeks before taking I-131 in order to deplete iodine levels stored in the body, helping to improve treatment effectiveness when radioactive iodine enters the body.

Patients prescribed to use the radioactive iodine method are required to limit their iodine intake for 1-2 weeks before taking I-131. (Photo: The Olive Press)

In addition, there are still studies on the “Restricted Iodine Diet”, which allows patients to consume iodine from 50 – 100 µg and is applied for 4 weeks before treatment. I-131 treatment instead of 2 weeks like low iodine diet. This diet resulted in urinary iodine levels and radioactive iodine consumption that were not statistically different from the low-iodine diet. This diet is often applied in countries with iodine-rich food sources and the habit of consuming salty foods high in iodine such as Korea and Japan.

Difficulties in practicing a low-iodine diet

It can be seen that the amount of iodine in an iodine diet is up to 4 times lower than the amount of iodine in a normal person’s diet. Therefore, to have a meal that is both nutritious and delicious, while also ensuring that the amount of iodine is limited as recommended in treatment, is truly a relatively difficult task for patients and caregivers.

Iodine is widely used in livestock products or in food additives, especially in spices and stabilizers. Therefore, it can be found in many foods and drinks. Food sources high in iodine that patients should

avoid consuming include

• Iodized salt, sea salt and salty foods
• Processed meats such as ham, bacon, sausage
• All common dairy products (milk, cheese, ice cream, sour cream, yogurt, butter, ice cream)
• Egg yolks, regular bakery products, chocolate, dried fruits, canned vegetables, beans
• Seafood and marine products (fish, crustaceans, shrimp, squid, blackfish, octopus, seaweed)
• Foods in the Red Dye No.3 category (candy, liqueur, cocktails)
• Vitamins and supplements containing iodine (check labels and ingredients and stop completely if they contain iodine)
• Medicines: Betadine, Rocaltrol 0.5μg (take Rocaltrol 0.25 μg instead)

Along with limiting foods high in iodine, a low-iodine diet must is required to ensure adequate other nutrients such as protein, sugar, fat, vitamins and minerals other than iodine. Maintaining sufficient nutrients help patients be in the best condition to receive treatment, limit side effects and support recovery after treatment.

Iodine dietary advice for people being treated for thyroid cancer

The principle of the iodine diet is to eliminate or limit foods containing high levels of iodine from the diet and replace them with foods of the same type that do not contain iodine or have low levels of iodine. In other words, controlling iodine amount must be done in parallel with ensuring an adequate supply of essential nutrients including protein, carbohydrates, fats, vitamins and minerals except iodine.

Below are 8 tips from the American Thyroid Association for an iodine diet³:

• Do not use iodized salt
• Do not use regular butter and milk products
• Do not eat seafood
• Limit grain products (like noodles, pasta, pastries), equivalent to 1 slice of bread or ½ cup of pasta per day
• Limit consumption of beef, chicken and turkey
• Avoid having meal at restaurants and eateries during this time as it is difficult to control the iodine content in pre-cooked meals at restaurants.
• Consult your doctor before stopping the use of any drugs with red color or any medicine containing iodine (e.g. Amiodarone, cough expectorants, topical antiseptics).
• Avoid taking all herbal supplements (especially when iodine content is not clearly stated on the product label).
• Instead of consuming the above foods, caregivers can consider a number of other options that can be used in this Iodine diet, including:
• Non-iodized salt or non-iodized sea salt
• Egg whites
• Homemade bread with salt and non-iodized oil (no soybean oil) instead of butter or milk or commercial toast, no iodine-containing additives, milk or eggs
• Fresh fruits and vegetables
• Frozen vegetables
• Cereals, grain products and pasta are not high in iodine
• Canned fruit
• Unsalted, natural nuts and nut butters (peanuts, almonds, etc.)
• Soft drinks, beer, wine, lemonade, fruit juice
• Coffee or tea without cream, milk made from cow’s milk or soy
• Popcorn using vegetable oil or air, with non-iodized salt
• Black pepper, fresh or dried herbs and spices, all vegetable oils
• Sugar, jam, jelly, honey maple syrup
• Matzo cookies

The recommended diet contributes to improved thyroid health. (Photo: Freepik)

Along with recommendations on foods to consume and not to consume, the American Thyroid Association also offers a sample menu for a day as follows::

Table 1: American Thyroid Association’s recommended menu for an iodine diet

In addition to advice on low- and high-iodine foods, patients after thyroid surgery (the main target of an iodine diet) are also recommended to supplement calcium for prevention. Hypocalcemia due to the thyroid gland being removed, causing parathyroid hormone deficiency, directly affecting the process of regulating the amount of calcium in the blood. Hypocalcemia can cause many complications such as muscle contraction disorders, fatigue, dry skin, brittle nails and many other neurological and motor complications if not treated promptly. Unfortunately, the food sources richest in Calcium are seafood, crustaceans and milk, which are often on the list of foods to avoid and limit in practicing an Iodine diet. Therefore, patients and caregivers can consider other foods such as green vegetables, nuts, or even Calcium and Vitamin D3 supplements to help support Calcium absorption from the intestines into the blood.

You can also refer to some other menus mentioned in a research report of the Department of Nuclear Medicine – K Hospital, Tan Trieu Campus with the topic: “Effectiveness of an iodine-restricted diet on patients.” Thyroid cancer underwent surgery with I-131 treatment at K Hospital”. For Vietnamese people, perhaps this menu is easier to apply and closer to Vietnamese eating habits.

Table 2: Nutritional diet for people abstaining from iodine before I-131 treatment with an energy level of 1500 – 1700 Kcal/day

Table 3: Nutritional diet for people abstaining from iodine before I-131 treatment with an energy level of 1800 – 2000 Kcal/day

Conclusion

Abstaining from iodine for the period from 2 weeks before radioactive iodine treatment until the end of treatment is one of the mandatory conditions for optimal treatment effectiveness. To avoid nutritional deficiencies, patients need to clearly understand the general principles of the iodine diet mentioned above and consult a doctor or nutritionist to have a diet that ensures both adequate nutrition and nutrition. Control the amount of iodine taken into the body during this period.