Report on iron and health

The Standing Advisory Committee on Nutrition has published its report on Iron and Nutrition. The purpose of the report was to “to review the dietary intakes of iron in its various forms and the impact of different dietary patterns on the nutritional and health status of the population and to make proposals.”

Most of the media coverage on the issue has been on its recommendation that high consumers of red and processed meats should limit their intakes to 70g/person/day (nb: cooked weight – raw weight will be greater) but since only a very few people in the UK eat much more than this, the report’s broader conclusions are perhaps more interesting as regards the role and importance of meat in the diet.

Key points from the summary are as follows:

The Dietary Reference Values (DRVs) for iron intake estimate the amount of dietary iron that needs to be consumed to meet the systemic physiological needs for iron. It is probable that the current DRVs for iron are too high, particularly for girls and women of reproductive age, because they are based on cautious assumptions about the bioavailability of dietary iron and metabolic adaptation.

The high proportions of the UK population with intakes below the Lower Reference Nutriient Intakes LRNI and the relatively low prevalence of iron deficiency anaemia suggest that the DRVs for iron may be too high. (NB: for explanations of what DRVs and LRNIs mean see here.

The most important determinant of dietary iron absorption is systemic iron need: more is absorbed in a state of iron deficiency and less is absorbed when iron depots are replete. In circumstances of marked iron need, however, the influence of dietary factors on iron absorption may become limiting. Haem iron is 2-6 times more available for absorption from the diet than non-haem iron. Calcium, phytates in cereals and legumes, and phenolic compounds found in tea, coffee and other beverages bind iron and restricts its availability for absorption, while meat and vitamin C found in fruit and vegetables enhance the potential availability of iron for mucosal uptake. However, these effects have been predominantly determined in studies using single meals; the effects of enhancers and inhibitors of iron absorption are attenuated in longer term studies and with the consumption of whole diets. Current evidence suggests that, in populations representative o those in the UK, dietary inhibitors and enhancers of iron absorption do not substantially affect iron status.

Iron fortification of foods has been the main approach used to improve the iron intakes of the UK population. Addition of iron to white and brown wheat flour and to breast milk substitutes is mandatory in the UK and a number of other foods are fortified on a voluntary basis. Elemental iron powders are widely used to fortify foods because they have a longer shelf-life than other iron fortificants; however, evidence suggests that foods fortified with iron are of little practical use in improving iron status in the UK.

Studies comparing the iron intake and status of vegetarians with non-vegetarians have generally shown no significant differences in dietary iron intake or haemoglobin concentrations. Although serum ferritin concentrations are consistently statistically significantly lower in vegetarians, they are usually within the reference ranges.

The report recommends a public health approach to achieving adequate iron status based on a healthy balanced diet that includes a variety of foods containing iron. This is a change to current dietary advice that iron-rich foods should be consumed at the same time as foods/drinks which enhance iron absorption (e.g., fruit, meat) but should not be consumed with those that inhibit iron absorption (e.g., tea, coffee, milk).

Groups identified as being at risk of iron deficiency anaemia include toddlers, girls and women of reproductive age, and some adult groups aged over 65 years. The report recommends that health professionals need to be aware of increased risk of iron deficiency anaemia in these groups and those with evidence suggestive of iron deficiency anaemia should receive appropriate clinical assessment and advice, including dietary advice and the use of iron supplements if required.

Meat, especially red and processed meat, is almost exclusively the source of haem iron. A substantial body of epidemiological evidence suggests that red and processed meat intake is probably associated with increased colorectal cancer risk. It is not possible to discern a clear dose-response relationship, or a threshold level of intakes of red or processed meat associated with increased colorectal cancer risk because of inconsistencies in categorisation and quantification of red and processed meat intake.

Since the evidence does not allow quantification of the amount of red and processed meat that may be linked with increased colorectal cancer risk, SACN is advising high consumers of red and processed meat to consider reducing their intakes. The modelling exercise suggests that reducing red and processed meat intake to the population average for adult consumers (estimated to be about 70 g/day cooked weight in 2000/01) would have little effect on the proportion of the population with iron intakes below the lower limit of recommended intake for iron.

Results from a modelling exercise to explore possible effects of a recommendation for adults to lower their consumption of red and processed meat suggest that red and processed meat makes a greater contribution to total zinc intake (32% for men; 27% for women) than to total iron intake (12% for men; 9% for women). The average red and processed meat consumption of adult consumers is approximately 70 g/day (88 g/day, men; 52 g/day, women). The modelling exercise indicates that reducing total red meat consumption of consumers in the upper range of the distribution of intakes, down to 70 g/day, would have little effect on the proportion of adults with iron intakes below the LRNI.

The Department of Health's comment on the report may be found here.

The English Beef and Lamb Executive's report can be read here while the Soil Association's report (many of whose members are red meat producers) who state that ‘not all meat is equal' can be read here.