Contribution of Cow's Milk to Iodine and Selenium Status in Women of Child-bearing Age
Condition: Selenium and Iodine Status
Study type: Interventional

Summary: 
      Iodine is an essential trace element necessary for the synthesis of thyroid hormones which
      are critical for human growth and development throughout the lifecycle. Iodine is
      particularly important during pregnancy and infancy for brain and neurological development.
      Severe iodine deficiency during pregnancy can cause severe mental impairment and stillbirth
      while mild-to-moderate deficiency has been associated with impaired infant development. As
      such, pregnant women and women of child-bearing age are particularly vulnerable to the
      effects of iodine deficiency.

      Globally, 241 million (30%) school aged children are iodine deficient. Historically, the UK
      and Ireland were believed to be iodine sufficient but concern has been expressed in the last
      decade regarding the iodine status of the UK and Irish populations. A study of Irish women in
      2004 reported 55% of pregnant women in their sample population to be moderately iodine
      deficient and 53% of non-pregnant women to be moderately iodine deficient. A study of UK
      schoolgirls found that 51% were mildly iodine deficient and 16% were moderately deficient.
      Importantly, the prevalence of iodine deficiency was highest in Northern Ireland where 85% of
      those sampled were iodine deficient.

      Iodine is known to interact with selenium in the conversion of the thyroid hormone thyroxine
      (T4) to the metabolically active triiodothyonine (T3) hormone. Selenium is also important for
      immune, cardiovascular and cognitive function. Selenium status has been reported to be
      moderately low using pooled English data on blood selenium concentrations from 1984 to 1992.
      In addition, the latest National Diet and Nutrition Survey reports that selenium intakes are
      below recommendations for several population groups including women of childbearing age where
      mean selenium intakes are 76% of the recommended 60µg/day. This national survey also reported
      that 49% of women aged 19-64 years failed to meet the lower reference nutrient intake of
      40µg/day.

      Milk and dairy products are the major source of iodine for the UK population and are also a
      source of selenium. The contribution of milk and dairy products to iodine and selenium
      intakes is greatest in adult females (35% and 6% respectively). Observational evidence has
      repeatedly reported milk consumption to be positively correlated with iodine status and
      iodine intakes. Research in Iceland and New Zealand has reported that milk consumption is not
      associated with selenium status; however it is unknown if this is true for the UK population.

      To date, no randomised controlled trial has examined the effect of milk consumption on either
      iodine or selenium status. The possibility of increasing iodine and selenium intake by
      increasing milk consumption, a widely available and consumed foodstuff, in a population group
      vulnerable to micronutrient deficiency should be investigated. This would add valuable data
      to the knowledge base for iodine, where there is ongoing debate over the most appropriate
      means of increasing iodine intake amongst women of childbearing age in the UK where salt
      iodisation, the key strategy in preventing deficiency, is not implemented.

      The aim of this study is to investigate the impact of cow's milk consumption on the
      biological status of iodine and selenium among women of child-bearing age.

      The study will be a 12 week randomised-controlled human intervention study. Participants will
      be randomised to consume additional semi-skimmed milk in the Following amounts, control group
      (0mls/day), intervention group (430mls/day or 3l per week).
    


Intervention name(s): Semi-skimmed cow's milk
Intervention type(s): Other
Intervention description(s): 430ml of semi-skimmed cow's milk / day for 12 weeks
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Cow's milk; Iodine; Selenium; Women; Child-bearing age