In reply: Sherriff is correct in pointing out that the studies showing protection from bronchial asthma (and bronchial hyperresponsiveness) are based on consumption of fish meals rather than a direct measure of omega-3 fatty acid intake. This protection has been observed consistently in cross-sectional studies of New South Wales primary school children. Thus, the level of evidence is at best Level III, albeit using a proxy for omega-3 fatty acid intake.

Results of a randomised-controlled trial of omega-3 fatty acid supplementation currently under way in western Sydney are now in the public arena at 18-month follow-up.1,2 At this early stage, it is uncertain who has genuine asthma rather than other wheezing syndromes. Nevertheless, the group who received omega-3 fatty acid supplementation have differences in rates of wheeze compared with those not supplemented.1,2 For example, the rate of "ever" having had wheeze was 52.6% in the controls versus 42.8% in the supplemented group (absolute risk reduction, 9.8%; number need to treat, about 10).

In the table of recommendations in my article,3 I carefully pointed out that supplementing infants with omega-3 fatty acid is something to "consider" rather than strongly recommending it. It should also be noted the level of evidence is low (Level III). Stronger recommendations will depend on the long-term results of randomised trials, such as the western Sydney trial.1,2 In summary, at this stage the only strong dietary recommendations which can be made are:

• not to use strict elimination diets during pregnancy (Level I evidence); and

• to consider using lactobacillus probiotic supplements.

The evidence for lactobacillus is Level II (from a single randomised controlled trial), although the protection shown is for atopy rather than asthma. Clearly, the children in the lactobacillus study will need further follow-up, and the trial will need to be repeated in other populations.

All of this highlights the need for better-quality studies in the area of primary prevention of asthma, based on dietary factors during pregnancy or early infancy.