Biografía de Hellen Keller: Nació el 27 de Junio de 1880 en Alabama, Estados Unidos de Norteamérica Hija de un editor de prensa (ver

This study identified six individual variables predictive o f haemoglobin concentration <11.0g/dl (Model 1) and two variables predictive o f haemoglobin concentration <10.5g/dl (Model 2). These variables are listed in Table 7.7. On initial examination all the variables appear to have face validity. It is conceivable, for example, that a parent with only one child to care for is able to attend to their child’s diet more effectively, both in terms o f time and monetary resources, then when there are other children in the family. This could have an impact on a child’s iron status. A similar finding has been reported in Japanese one year olds who were more likely to be anaemic if they have three or more siblings (Hokama 1999). One might expect the younger children in this study to have a greater risk o f anaemic as it has been observed that nationally, prevalence significantly decreases with increasing age (Gregory et al 1995, Thane et al 2000). Given the inverse relationships reported between iron status and cow ’s milk intake (Appendix to Chapter 3) it is not surprising that habitual milk drinking in the morning and afremoon is predictive o f anaemia. Cow ’s milk has a low iron content and drinking milk between meals may well reduce appetite at the next mealtime. Initially it appears counterintuitive that the regression coefficient for the variable, child drinks over 600ml o f cow ’s milk, is negative. In

fact, the correct interpretation here is that including this variable in the model adjusts for the fact that children who always or usually drink milk in the morning and afternoon are also likely to be the children who have a high intake o f milk. So, independent o f high milk intake, habitual milk drinking in the morning or afternoon is predictive o f anaemia.

The finding that eating fish once a week or less is associated with increased risk o f anaemia is very interesting. Fish, like other animal flesh, has been shown to promote iron absorption. Martinez-Torres & Layrisse (1970) showed that on average, lOOg o f fish increased non-haem iron absorption from a vegetable meal from 1.54% to 2.81% in adult subjects. Cook & Monsen (1976) conducted an experiment where groups o f subjects were given a standard meal differing only in the main protein source which was either beef, pork, lamb, liver, chicken, fish, milk, cheese or egg. The effect o f the protein substitutions was assessed by expressing the percentage absorption results o f each protein meal in a ratio to the beef including meal. The meats proved to be comparable to beef in terms o f promoting iron absorption whereas fish, although better at promoting iron absorption than milk, cheese or egg, was significantly less effective than beef or the other meats (p=0.05). Earlier comments made in Chapter 5 that it can be difficult to extrapolate findings from single meal studies, as these are, to the complete diet, apply here. Although fish does seem to have an inherent property that enhances non-haem iron absorption and this may have some effect on iron status, there are other explanations as to why this factor predicts anaemia in the children in this study. One might suppose, on the basis o f the evidence from the study by Cook and M onsen (1976), that meat would be a more important factor than fish in promoting iron absorption and perhaps so improving iron status. No aspect o f meat consumption in this study proved to predict anaemia. This leads one to suspect that minimal fish consumption is a marker for some other factor, either dietary or lifestyle, that is related to iron status.

It may be a marker for dietary variety. Any individual who consumes a wide variety o f foods is more likely to have balanced diet o f terms o f micronutrient intake. Furthermore, there is some evidence that consuming small amounts o f food, (implying few foods), is associated with anaemia in children. Morton et al (1988) found that children, slightly younger than those in this study, were more likely to be

anaemic if consuming less than 3 teaspoons o f food per day. In addition, personal clinical experience indicates that children with IDA are often eating very few foods. Alternatively one might speculate that minimal fish consumption was a marker for social class. Families o f higher social class may have more knowledge o f diet and nutrition or greater family income, both factors that might cause them to include fish in their child’s diet. However, there is no evidence in this study that anaemia is related to social class. These interpretations o f the nature o f the relationship between fish consumption and iron status are made cautiously.

There is another issue about the minimal fish consumption variable and that is it was derived from the FFQ developed for use in this study. As indicated in Chapter 6, the FFQ proved to not measure food intake in individuals satisfactorily and the intention is to use this variable in a checklist designed for use in individuals. However, asking how many times a week a child eats fish is somewhat different from using the FFQ in its entirety. It is arguable that this is a technical rather then actual limitation.

It is equally intriguing that many factors found to be related to poorer iron status in other studies, such as social class, ethnic group and high daily intake o f cow’s milk (see Appendix 3), proved to have no relationship with anaemia in this study. This may be a genuine finding or again a consequence o f the sample being unrepresentative o f the actual population. Alternatively, differences may exist but the

study had insufficient power to detect the difference. In the case o f milk

consumption, with the final subject numbers in this study, it was possible to detect an 11.3% difference in the proportions o f anaemic children drinking above the median intake o f cow ’s milk compared to those drinking below median intake (at 80% power and 5% significance). Median intake o f milk was 520ml and about a third o f the cases o f anaemia occurred in those drinking the median amount or less and about two thirds o f cases were in those drinking above the median amount.

W hen considering what dietary and socio-economic factors predict anaemia in children it is worth remembering that it is likely that some as yet unknown factor(s) is (are) important. Lawson et al (1998) reported that variables shown by multivariate analysis to be associated with haemoglobin concentration in 2 year old Asian children account for 9-10% o f the variation. The majority o f the variation in haemoglobin

concentration in this study was therefore related to unknown or unmeasured factors. This raises the possibility that screening using dietary and socio-economic variables might fail because even in a population where IDA is highly prevalent, as in Asian children living in Britain, these variables are not the factors that account for the majority o f the differences in iron status. One might speculate that at least part o f the variation is related to differences in the ability to absorb iron from the gut.