Iron deficiency in young Australian women: role of iron knowledge, dietary intake and supplementation, and the effects on cognition

Research Doctorate - Doctor of Philosophy (PhD)Iron deficiency was labelled a major public health concern in the late 1980s due to its recognition as the most prevalent nutritional disorder in the world. According to the World Health Organization (2001), iron deficiency remains the most common nutritional deficiency worldwide. Within Australia, one in five young women are affected by iron deficiency. A strong link between iron deficiency anaemia and impaired cognitive function has been established in children. The effect of latent iron deficiency on cognition in young women has not been well investigated. The aims of this research were to: 1) determine the level of nutrition knowledge of dietary iron in a subgroup of young women living in Newcastle, NSW and its relationship to their iron intake and iron status; 2) examine the suitability of a validated battery of tests (IntegNeuro) for assessing cognitive function in iron deficient and iron sufficient women; 3) determine an appropriate sample size for a future RCT on iron deficiency and cognition in young women; 4) determine an effective dose of elemental iron to treat iron deficiency in latent iron-deficient participants, while maintaining blinding to treatment. A study on the effect of nutrition knowledge on dietary iron intake and iron status was conducted in young women. This involved the distribution of a Nutrition Knowledge Questionnaire and Food Frequency Questionnaire to females who were enrolled or interested in enrolling in the pilot RCT (described below). The results of this study showed a significant relationship between knowledge and total iron intake. However, better knowledge did not result in better iron status. Results also showed a positive relationship between the frequency of flesh food intake and iron status. A pilot double-blinded, placebo-controlled intervention trial was conducted in iron-deficient and iron-sufficient young women (18-35 years). Cognitive function and haematological markers of iron status were measured at baseline and follow-up. Iron-deficient participants were randomised to receive placebo, 60mg or 80mg elemental iron daily for 16 weeks. A control group of iron-sufficient participants was allocated placebo capsules. Participants in the iron treatment groups had greater cognitive change scores compared to no-treatment groups. Change scores for Impulsivity and Attention were significantly greater in plasma ferritin improvers than in non-improvers (p=.004, and p=.026, respectively). IntegNeuro was easy to administer and acceptable to young women. Based on differences in Memory and Attention scores between iron-sufficient and iron-deficient participants, further research with a sample size of 26 or 84 iron-deficient participants per group is required for an adequately powered trial. In conclusion, this thesis contributes to various areas of iron deficiency research in young women. Nutrition knowledge regarding iron in young women is a novel area of research. Some positive associations between knowledge and intake were found. Results revealed that a validated questionnaire with a greater focus on dietary enhancers and inhibitors of iron is required to further this area of research. Dietary intake of flesh foods was positively related to serum ferritin. There is a need to establish strategies for increasing iron intake and absorption in young women. Such strategies may include educating non-vegetarians about the benefits of increased flesh food consumption and vegetarians about dietary iron enhancers and inhibitors. Few significant differences in cognition scores between iron-deficient and iron-sufficient young women at baseline, and after the 16 week intervention were expected in an under-powered pilot study. It is important to consider that the detection of differences in cognition was not the primary aim of this pilot study. Future studies in this area should be well powered, multi-centred randomised-controlled trials using a cognitive battery that has been validated for use in this population. The pilot RCT revealed some important information relating to methodological advancements in this area of research. These include: 1) the IntegNeuro battery of cognitive tests is a useful method for use in young women, which is important due to the diverse range of cognitive tests used in previous research; 2) a 60mg dose of elemental iron is as effective in treating iron deficiency and causes fewer side effects than an 80mg dose; and 3) sTfR alone does not enhance the ability to detect iron deficiency in its early stages, although the sTfR-ferritin index is more useful