Iodine intakes and the main food sources of iodine in adolescent females aged 15-18 years in New Zealand
Background: Iodine plays an essential role in normal growth and development. Formerly iodine deficiency has been common in New Zealand because of the low levels of iodine in the soil. However, in recent times, the Children’s and Adult National Nutrition surveys reported mild iodine deficiency, leading to implementation of mandatory use of iodised salt in bread in 2009. Since then, iodine intake and food sources contributing to dietary iodine intake have not been assessed in New Zealand adolescents. Iodine is particularly important for young women who could become pregnant, because sufficient iodine is needed for normal growth and development of the fetus. This is the first study in New Zealand to assess dietary iodine intakes in adolescent females aged 15-18 years. Objective: The objectives were to assess 1) the dietary intake of iodine in adolescent females; 2) the main food sources and food groups that contribute to iodine intake in adolescent females; and 3) the proportion of adolescent females using iodised salt. Design: This was a cross-sectional survey carried out in high schools in seven different towns across New Zealand involving 145 female adolescents aged 15-18 years. Between March and April 2019, 113 participants completed two 24-hour diet recalls, FFQs and anthropometric measurements, provided spot urine and blood samples, and wore accelerometers to measure physical activity. Diet recalls were entered into FoodWorks to determine macro- and micronutrient intakes. Iodine intakes were determined: 1) from diet alone, 2) with the addition of 48 μg of iodine if iodised salt was used, and 3) with the addition of 48 μg of iodine if iodised salt was used and the iodine content from dietary supplements used on a daily basis. Results: Of the eight schools that consented to participate in the study, the majority (59%) were from deciles 5 to 7. Of 145 participants who undertook enrolment, 113 completed two 24-hour diet recalls. The mean age of participants was 17 years, 72% were of New Zealand European and Other ethnicity, and 56% were weight BMI z-score ≥ -2 to +1 SD. The mean energy intake was 7833 kJ. The mean iodine intake was 81 μg/day (the Estimated Average Requirement for iodine in this age group is 95 μg/day), of which ~10% came from each of the following four food groups: grains and pasta; milk; eggs and egg dishes; and non-alcoholic beverages. Around 7% of total iodine came from bread (including rolls and speciality breads), and ~4% came from each of the following: savoury sauces, condiments, bread based dishes, dairy products, cakes and muffins, and vegetables. Around 41% of participants reported using iodised salt, and only 2 participants reported taking a daily supplement containing iodine. Conclusion: Dietary iodine intake was low suggesting that this group may be at risk of mild iodine deficiency. This group of adolescent females do not seem to be consuming enough of the typical food source of iodine in the New Zealand diet, namely, fortified bread. More than half of the participants were not using iodised salt. Other strategies to increase iodine intakes, in addition to bread and iodised salt use, need to be considered.
Advisor: Skeaff, Sheila
Degree Name: Master of Dietetics
Degree Discipline: Human Nutrition
Publisher: University of Otago
Keywords: New Zealand; Function; Metabolism; Deficiency; Status; History; Iodine; Assessment; Diet; Sources; Adolescents; Teenagers; Females; Girls
Research Type: Thesis