News

Iron, iodine and vitamin A deficiency are most common worldwide

July 25, 2014

A new review from the UK says that due to a lack of dietary diversity, deficient intakes of iron, iodine and vitamin A are also widespread in industrialized nations.

The review identified recent reports on the worldwide incidence of micronutrient deficiencies (1). New studies have suggested that iodine status may not be as satisfactory in the UK – affluent southern counties of England – as previously thought (2). So the recently reported evidence of cognitive impairment in children of 8–9 years associated with poor maternal iodine status at the time of the children’s birth needs to be considered carefully (3). Foods may not actually be deficient in certain nutrients but may contain antagonists such as phytate or polyphenols in whole cereals, tea, coffee etc. and block absorption of minerals such as non-heme iron and zinc (4). Thus, bioavailability affects dietary iron, but it is also a factor influencing vitamin A status. The main dietary source of vitamin A for most people in the world is the provitamin A beta-carotene in green vegetables and fruits. Beta-Carotene is found within the cells of plant tissue, and to become available for absorption, the cellulose cytoskeleton needs to be broken up mechanically or by chewing and the beta-carotene released by heat and oil. However, too much heat can destroy the carotenoid and other micronutrients so overcooking can be counterproductive (5). Iron and vitamin A deficiencies continue to exist as many factors need to be corrected to ensure satisfactory absorption. In contrast to a deficiency of iron – the leading cause of anemia worldwide – and vitamin A – causing blindness – the successful supply and use of iodized salt helps to prevent the harmful effects of deficiency. However, in some European countries where salt iodization and iodine supplementation are not actively promoted, surveys are revealing evidence of mild to moderate iodine deficiency in pregnant women (6–8), which has been associated with cognitive impairment in their children (3).

The researchers commented that poor diets and micronutrient deficiencies can cause diseases and have potentially grave economic consequences for the individual, the family, the community and, if the condition is widespread, for the entire country. The type of food available will often determine which nutrient deficiency is of greatest importance. The main risk factors for micronutrient malnutrition are monotonous diets, poor bioavailability, little opportunity for diversification, low intakes of animal-source foods, low prevalence of breastfeeding and low micronutrient density in complementary foods. No staple food contains all the essential micronutrients.

References

  1. Thurnham D. I. Deficiencies of Critical Micronutrients – A Focus on Iodine, Iron and Vitamin A. Sight & Life. 2014; 28(1):34-45.
  2. Bath S. C. et al. Iodine deficiency in pregnant women living in the South East of the UK: the influence of diet and nutritional supplements on iodine status. Brit J Nutr. 2014; 7:1–10.
  3. Bath S. C. et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). Lancet. 2013;
    382:331–337.
  4. Balarajan Y. et al. Anemia in low-income and middle-income countries. Lancet. 2011; 378:2123–2135.
  5. Guidelines on food fortification with micronutrients. Geneva: World Health Organization & Food and Agricultural Organization, 2006.
  6. Roman G. C. et al. Association of gestational maternal hypothyroxinemia and increased autism risk.
    Ann Neurol. 2013; 74:733–742.
  7. Moreno-Reyes R. et al. High prevalence of thyroid disorders in pregnant women in a mildly iodine-deficient country: a population-based study. J Clin Endocrinol Metab. 2013; 98:3694–3701.
  8. Andersen S. L. et al. Iodine deficiency in Danish pregnant women. Dan Med J. 2013; 60:A4657.