Abstract and Introduction
Objective: The recommended iodine intake is 150 mg/day in adults, 220 µg/day during pregnancy, and 290 µg/day during lactation. Individuals exclusively consuming restricted diets as part of a weight-loss program may be at risk for mild to moderate iodine deficiency. The purpose of this study was to assess the iodine content in meals and snacks from 3 U.S. commercial weight-loss programs, all of which are intended to be the sole source of dietary intake during the desired weight-loss period.
Methods: The iodine contents in the products representing 1 week of all meals and snacks from 3 U.S. commercial weight-loss programs were measured by spectrophotometry. The measured total iodine content in 1 week's worth of food from each program is reported as an average level per day.
Results: A total of 53 total items were analyzed (29 different items [7 breakfasts, 7 lunches, 7 dinners, 6 snacks, 2 desserts] from Jenny Craig®, 21 different items [7 breakfasts, 7 lunches, 7 dinners] from Nutrisystem®, and 3 different items [1 breakfast, 1 lunch, 1 dinner; each to be intended to be eaten daily for 1 week] from Medifast®). Daily iodine content (mean ± SD) of meals and snacks from the weight-loss programs were 34.2 ± 1.2 (Jenny Craig®), 12.2 ± 0.7 (Nutrisystem®), and 70.1 ± 1.1 (Medifast) µg/day.
Conclusion: These results indicate that the dietary content in the foods from 3 U.S. commercial weight- loss programs is far less than the recommendations for iodine intake of 150 µg/day in nonpregnant, nonlactating adults. Individuals following each weight-loss program should be advised to take a multivitamin containing 150 µg of iodine daily.
Iodine is an essential component of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3), which are required for normal metabolic processes. During pregnancy and the postpartum period, adequate iodine nutrition is particularly crucial, as the developing fetus and newborn infant require thyroid hormone for normal growth and neurodevelopment. Iodine deficiency may be associated with goiter and hypothyroidism. Maternal iodine deficiency during pregnancy is associated with adverse outcomes in the offspring, including cretinism and decreased IQ.[1–2] Despite ongoing public health efforts, iodine deficiency affects over 2.2 billion individuals and remains the leading cause of preventable mental retardation worldwide.
Urinary iodine concentrations are a biomarker for dietary iodine intake over the preceding few days and may be used clinically to confirm compliance with a low-iodine diet. However, levels of urinary iodine cannot be used to determine iodine status in an individual given the day-to-day variation in dietary iodine intake. Instead, median urinary iodine levels are used to reflect dietary iodine sufficiency across populations. According to recent data from the National Health and Nutrition Examination Surveys (NHANES), the median urinary iodine concentration in U.S. adults decreased by more than 50% from the early 1970s to the late 1990s. During this period, there was an almost fourfold increase in the prevalence of urinary iodine values <50 µg/L (indicating moderate to severe iodine deficiency) among women of childbearing age. Although subsequent studies have shown that this decrease has stabilized,[6–8)] the most recent NHANES survey (2005–2008) demonstrated that 35.3% of pregnant women had urinary iodine levels less than 100 µg/L, which suggests mild iodine insufficiency.
The diet is the primary source of adequate iodine nutrition. The Recommended Daily Allowances (RDA) for iodine are 150 µg in adults, 220 to 250 µg during pregnancy, and 250 to 290 µg during lactation.[4–9] The major sources of dietary iodine in the U.S. are dairy products, grains, and iodized salt. In the U.S., iodine is present in dairy foods (due to the iodophor cleansers of milk cans and teats) and occasionally in bread dough (due to the use of iodate as bread conditioners).[10–11] The iodine content of plant foods depends on iodine levels in soil and in groundwater used in irrigation, in crop fertilizers, and in livestock feed. Most foods contain 3 to 75 µg of iodine per serving. Salt iodization is a useful approach toward decreasing iodine deficiency in populations, although the U.S. Food and Drug Administration does not mandate the listing of iodine content on food packaging.
Individuals following a restricted diet have been shown to be at risk for inadequate dietary iodine intake. Among 141 Boston-area individuals, the median urinary iodine concentration of vegans (78.5 µg/L; range, 6.8–964.7 µg/L; n = 78) was significantly lower than of vegetarians (147.0 µg/L; range, 9.3–778.6 μg/L; n = 63) (P<.01); the median urinary iodine concentration of the vegan group was in the range consistent with moderate iodine deficiency. In another study, fast foods from McDonald's and Burger King were low in iodine except in milk shakes, iodinated bread, or fish products. In the U.S., approximately one-third of the population fulfills the criteria for obesity, with a greater proportion (50–70%) attempting some degree of weight-loss. Data from 2001–2006 NHANES reported that the prevalence of commercial weight-loss program users among 2,523 individuals (56% women) trying to lose weight was 9.9%.
The objective of this study was to measure the iodine content in 1 week's worth of all provided food products (snacks and meals), each intended to be individuals' sole source of dietary intake, from 3 U.S. weight-loss programs.
Endocr Pract. 2014;20(3):232-235. © 2014 American Association of Clinical Endocrinologists