Impact of the Food Matrix on Iodine Bioavailability
Condition: Iodine Bioavailability
Study type: Interventional

Summary: 
      This study is a randomized crossover trial, lasting 12 days in total, which will assess the
      difference in iodine bioavailability (as a percentage of iodine consumed that is excreted in
      urine) from three iodine-rich foods; semi-skimmed milk, white fish, and dried seaweed sheets.
      Each of the three foods will provide approximately 140µg of iodine, and iodine excretion will
      be monitored for 36 hours following food ingestion via collection and analysis of urine.
    

Detailed description: 
      Iodine insufficiency is one of the three key micronutrient deficiencies highlighted as major
      public health issues by the World Health Organisation, and recent evidence indicates that the
      UK is now iodine deficient. Iodine deficiency represents a particular threat for women of
      child-bearing age, unborn infants and young children, as iodine is essential to synthesise
      the thyroid hormones, which are involved in key metabolic function including fetal brain
      development. Maternal iodine deficiency and the resulting changes in thyroid function has
      been associated with adverse pregnancy outcomes including spontaneous miscarriage, fetal
      distress and death, preterm delivery, low birth weight and impaired neuropsychological
      development, with significant impact on later life development and quality of life.

      There is no iodine fortification programme in the United Kingdom, and despite worldwide
      efforts to tackle iodine deficiency and associated disorders via iodine supplementation and
      food-fortification (of salt mainly), consumption of supplements in the UK is virtually
      non-existent, with iodised salt used by less than 5%.

      In the UK, the main dietary sources of iodine are dairy and sea-foods. Our previous studies
      have shown that seaweed intake can increase the iodine status of women with diets habitually
      low in iodine. Reduced bioavailability of iodine from the seaweed matrix, which could have
      implications for dietary recommendations.

      This study address the influence of the food matrix on iodine bioavailability, in the context
      of food guidelines and assessment of the iodine status.

      This project is in collaboration with the British Broadcast Corporation (BBC).

      The study design is a crossover randomised trial - to last 9 days, plus three days pre-trial
      washout [total 12 days] - with 3 arms:

        1. fish arm: portion equivalent to 140 µg iodine, approx. 130g.

        2. milk arm: portion equivalent to 140 µg iodine, approx. 450mL.

        3. seaweed arm: portion equivalent to 140 µg iodine, approx. 6g.

      Each arm will be separated by two washout days, and participants will follow a low iodine
      diet (avoiding dairy, and all seafood) throughout the study, as well as three days prior to
      the first arm. Iodine levels will be monitored in urine collected during the 12 hours
      preceding and 36 hours following the meal. Urine will be collected in time fractions

      A parallel design study showed that 56% (SD 20%) of a dose of potassium iodide is excreted
      after 24hours, compared to 36% (SD 13%) when the same dose comes from seaweed. In order to
      detect a similar difference, a sample of at least 13 participants is required (n=19 to allow
      for 30% attrition).
    

Intervention name(s): Milk; Fish; Seaweed
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): One portion of semi-skimmed cow's milk (approx. 450mL), providing ~140µg of iodine.; One portion of cod (approx. 130g), providing ~140µg of iodine.; One portion of dried seaweed sheets (approx. 6g), providing ~140µg of iodine.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: iodine; bioavailability; seaweed; milk; fish