Analysis of Iodine Content in Salts and Korean Sauces for Low-Iodine Diet Education in Korean Patients with Thyroid Cancer Preparing for Radioiodine Therapy / 대한핵의학회잡지

PURPOSE: A low-iodine diet is necessary in patients about to undergo radioiodine therapy for thyroid cancer to decrease the competitive absorption of ingested nonradioactive iodine. This study aimed to assess the iodine concentrations in salts and basic Korean sauces, and to provide fundamental data for guidelines on a low-iodine diet before radioiodine therapy.METHODS: The iodine contents of refined salts, solar sea salts, fish sauces, and commonly used Korean sauces with added refined salt were determined by ICP-MS.RESULTS: The iodine content of refined salts was found to be very low (0.033 ± 0.05 µg/100 g) compared with that of solar sea salts (434 ± 73.6 µg/100 g). The iodine contents of Korean soy sauce, Korean soybean paste, Gochujang seasoned with refined salt were also very low (0.010, 0.044, 0.002 µg/100 g, respectively). However, the mean iodine contents of the shrimp and fish Jeots analyzed in this study were found to be 41.3 ± 4.2 and 24.8 ± 4.5 µg/100 g, respectively.CONCLUSION: This study is the first to investigate the iodine contents of the salts and basic sauces used in Korea. The results show that refined salts and Korean traditional sauces seasoned with them can be safely used in low-iodine diets before radioiodine therapy.

Dietary evaluation of a low-iodine diet in Korean thyroid cancer patients preparing for radioactive iodine therapy in an iodine-rich region

BACKGROUND/OBJECTIVES: Despite the importance of a low-iodine diet (LID) for thyroid cancer patients preparing for radioactive iodine (RAI) therapy, few studies have evaluated dietary intake during LID. This study evaluated the amount of dietary iodine intake and its major food sources during a typical diet and during LID periods for thyroid cancer patients preparing for RAI therapy, and examined how the type of nutrition education of LID affects iodine intake. SUBJECTS/METHODS: A total of 92 differentiated thyroid cancer patients with total thyroidectomy were enrolled from Seoul National University Hospital. All subjects completed three days of dietary records during usual and low-iodine diets before 131I administration. RESULTS: The median iodine intake was 290 µg/day on the usual diet and 63.2 µg/day on the LID. The major food groups during the usual diet were seaweed, salted vegetables, fish, milk, and dairy products and the consumption of these foods decreased significantly during LID. The mean energy intake on the LID was 1,325 kcal, which was 446 kcal lower than on the usual diet (1,771 kcal). By avoiding iodine, the intake of most other nutrients, including sodium, was significantly reduced during LID (P < 0.005). Regarding nutritional education, intensive education was more effective than a simple education at reducing iodine intake. CONCLUSION: Iodine intake for thyroid cancer patients was significantly reduced during LID and was within the recommended amount. However, the intake of most other nutrients and calories was also reduced. Future studies are needed to develop a practical dietary protocol for a LID in Korean patients.

Low Iodine Diet for Preparation for Radioactive Iodine Therapy in Differentiated Thyroid Carcinoma in Korea

Preparation for radioactive iodine (RAI) therapy includes an increased serum thyroid stimulating hormone level and a low iodine diet (LID). Because of extremely high iodine intake, some physicians have advocated a more stringent LID for greater than 2 weeks in Korean patients with thyroid cancer prior to RAI therapy; however, it is very difficult to maintain a stringent LID for a longer period of time. According to recent reports in Korea, a nonstringent, simple LID for only 1 week might be enough prior to RAI therapy, if the patients can be educated intensively by specially trained staff. The measurement of simple urinary iodine concentration (UIC; microg/L) may underestimate daily iodine excretion in patients with a urinary volume of more than 1 L/day and can also be affected by dilution status. Simple UIC had a weaker correlation than the iodine/creatinine (I/Cr) ratio. Therefore, the urinary I/Cr ratio can replace 24-hour urine iodine excretion instead of simple UIC, although it may overestimate iodine intake in patients with malnutrition or poor muscle mass. The measurement of serum iodine level might be useful as an adjunct parameter for assessing LID preparation, but its sensitivity and specificity were relatively low compared to the urinary I/Cr ratio.

Knowledge, Self-Efficacy, and Perceived Barriers on the Low-Iodine Diet among Thyroid Cancer Patients Preparing for Radioactive Iodine Therapy

The purposes of the study were to assess knowledge, self-efficacy, and perceived barriers on a low-iodine diet among thyroid cancer patients and to identify strategies for nutrition education. A self-administered questionnaire was developed based on a review of literature and pilot-tested. A total of 121 female thyroid cancer patients participated in a survey and 117 responses were used for data analysis. An average knowledge score of the thyroid cancer patients was 4.5 point (available score: 0-10 point). Majority of the respondents knew that seaweeds such as lavers, brown seaweeds, and sea tangles contain large amount of iodine. However they mistook the low iodine diet as a low salt diet and were not aware of foods and seasonings that are allowed on the low iodine diet. While self-efficacy related to consuming various fruits and vegetables, to choosing potatoes and sweet potatoes for snacks, and restricting consumption of eggs, milk and milk products, and processed foods was rated highly, self-efficacy for preparing foods without using sea salts was rated low. The self-efficacy score increased as their interest on the dietary life and perceived cooking skills were greater. Most perceived barriers toward practicing the low iodine diet were related to preparation of the low iodine menus. As their interest in the dietary life and cooking and perceived cooking skills were greater, the patients perceived barriers on practicing the low iodine diet less. While the patients showed higher self-efficacy and lower barrier perception on selecting foods low in iodine and restricting food high in iodine, they showed lower self-efficacy and higher barrier perceptions on preparing low iodine meals. Clinical dietitians should recognize the gap between what the patients should know and what they really know and identify strategies on how to improve self-efficacy and reduce perceived barriers on the low iodine diet. Recent literature and the findings of the study reveal that incorporating cooking classes into nutrition education for thyroid patients is effective to enhance self-efficacy and to reduce perceived barriers on the low iodine diet.

Determination of Urinary Iodine Concentration by Inductively Coupled Plasma-mass Spectrometry in Thyroid Cancer Patients on Low-iodine Diet / 대한진단검사의학회지

BACKGROUND: Thyroid cancer patients should be on low-iodine diet (LID) before radioactive iodine therapy (RAIT) to maximize the effect of RAIT. Urinary iodine excretion is the most accurate marker of very recent dietary iodine intake. We developed and evaluated the analytical performance of inductively coupled plasma-mass spectrometry (ICP-MS) to determine urinary iodine concentration. METHODS: We evaluated the linearity, precision, accuracy, and lower limit of quantification (LLOQ) of an ICP-MS method (Agilent 7500ce) to determine urinary iodine concentration in accordance with the Food and Drug Administration (FDA) guidelines for bioanalytical method validation. This method was used to determine and compare the iodine concentration in random urine samples of 120 thyroid cancer patients on LID for 1 week and 80 healthy adults on normal diet. RESULTS: Our ICP-MS method showed good linearity (1.0-1,913 microgram/L; R2>0.999). Both intra-day and inter-day precision CV were within 20% for the LLOQ (1 microgram/L) and within 15% for the other concentrations. Accuracy was 110-120% for the LLOQ and 95-115% for the other concentrations. The median concentration of iodine in random urine samples from thyroid cancer patients on LID (38.7 microgram/L) was significantly lower than that of healthy subjects (238.8 microgram/L) (P<0.0001). CONCLUSIONS: Urinary iodine analysis by ICP-MS showed good linearity, precision, accuracy, wide measuring range of detection, and lower LLOQ. This method will be very useful to evaluate the status of dietary iodine intake and the appropriateness of LID in thyroid cancer patients, thereby maximizing the effect of RAIT.

Analysis of Urine Iodine Excretion Decrease by Two-Week Stringent Low Iodine Diet for Remnant Thyroid Ablation with Radioactive Iodine in Korean Patients with Thyroid Cancer; Prospective Study / 핵의학분자영상

A low iodine diet (LID) is the recommended preparation for radioactive iodine treatment. However, the recommended duration and stringency of LID are different among each recommendation. More stringent LID is expected in Korea because Korea is a iodine-rich region. We investigated the decrement of urine iodine excretion by two-week stringent LID for remnant thyroid ablation with radioactive iodine in Korean patients with thyroid cancer, prospectively. MATERIAL AND METHOD: From November 2006, patients who referred to our hospital for remnant ablation after total thyroidectomy were included in this study. To decrease total body iodine, our protocol included three strategies. First, we checked medication which could inhibit the radioactive iodine uptake. Second, the date of I-131 treatment was scheduled at least 3 months later if contrast agent had been used. The last strategy was two-week stringent LID education by specialized nutritionist. Before and after two-week stringent LID, 24hr-urine iodine was analyzed respectively. 24hr-urine creatinine was also analyzed for determining more valid 24hr urine sampling subgroup. RESULTS: Total 51 patients were finally enrolled. Average of 24hr-urine iodine excretion was significantly lowered (787+/-2242 -> 85+/-85 microgram/d, p=0.03) after LID and 74.4% of patients reached below the recommended urine iodine excretion level ( 99+/-116 microgram/d, p=0.05) and 78.6% of patients met the criteria. CONCLUSION: Most patients could reach below the recommended urine iodine level after two-week stringent LID. Therefore, in our opinion, at least two-week stringent LID should be recommended in Korea.

Comparison of Urine Iodine/Creatinine ratio between Patients following Stringent and Less Stringent Low Iodine Diet for Radioiodine Remnant Ablation of Thyroid Cancer / 핵의학분자영상

A low iodine diet (LID) for 1~2 weeks is recommended for patients who undergoing radioiodine remnant ablation. However, the LID educations for patients are different among centers because there is no concrete recommendation for protocol of LID. In this investigation, we compared two representative types of LID protocols performed in several centers in Korea using urine iodine to creatinine ratio (urine I/Cr). METHODS: From 2006, April to June, patients referred to our center for radioiodine remnant ablation of thyroid cancer from several local hospitals which had different LID protocols were included. We divided into two groups, stringent LID for 1week and less stringent LID for 2 weeks, then measured their urine I/Cr ratio with spot urine when patients were admitted to the hospital. RESULTS: Total 27 patients were included in this investigation (M:F=1:26; 13 in one-week stringent LID; 14 in two-week less stringent LID). Average of urine I/Cr ratio was 127.87+/-78.52 microgram/g in stringent LID for 1 week, and 289.75+/-188.24 microgram/g in less stringent LID for 2 weeks. It was significantly lower in stringent LID for 1 week group (p=0.008). The number of patients whose urine I/Cr ratios were below 100 microgram/g was 6 of 13 in stringent LID for 1 week group, and 3 of 14 in less stringent LID for 2 weeks group. CONCLUSION: Stringent LID for 1 week resulted in better urinary I/Cr ratio in our investigation compared with the other protocol. However it still resulted in plenty of inadequate range of I/Cr ratio, so more stringent protocol such as stringent LID for 2 weeks is expected more desirable.