I've found this, which looks reasonably well done as far as I can see (though I can't get the actual text, so it's hard to tell), but it seems to be very much dependent on epidemiology. It's entirely about allergies, too- I really can't find a shred of direct evidence that IBD or IBS are affected by weaning, and nothing more than vague hand-waving about coeliac. As Soapbox says, it will be very inreresting to see if rates of these diseases fall over the next few years.
Food allergy and the introduction of solid foods to infants: a consensus
document. Adverse Reactions to Foods Committee, American College of Allergy,
Asthma and Immunology.
Fiocchi A, Assa'ad A, Bahna S; Adverse Reactions to Foods Committee; American
College of Allergy, Asthma and Immunology.
American College of Allergy, Asthma and Immunology, Melloni Paediatria,
University of Milan Medical School, Melloni Hospital, Milan, Italy.
[email protected]
OBJECTIVE: To make recommendations based on a critical review of the evidence
for the timing of the introduction of solid foods and its possible role in the
development of food allergy. DATA SOURCES: MEDLINE searches using the following
search algorithm: [weaning AND infant AND allergy]/[food allergy AND
sensitization]/[dietary prevention AND food allergy OR allergens]/[Jan 1980-Feb
2006]. STUDY SELECTION: Using the authors' clinical experience and research
expertise, 52 studies were retrieved that satisfied the following conditions:
English language, journal impact factor above 1 or scientific society, expert,
or institutional publication, and appraisable using the World Health
Organization categories of evidence. RESULTS: Available information suggests
that early introduction can increase the risk of food allergy, that avoidance of
solids can prevent the development of specific food allergies, that some foods
are more allergenic than others, and that some food allergies are more
persistent than others. CONCLUSIONS: Pediatricians and allergists should
cautiously individualize the introduction of solids into the infants' diet. With
assessed risk of allergy, the optimal age for the introduction of selected
supplemental foods should be 6 months, dairy products 12 months, hen's egg 24
months, and peanut, tree nuts, fish, and seafood at least 36 months. For all
infants, complementary feeding can be introduced from the sixth month, and egg,
peanut, tree nuts, fish, and seafood introduction require caution. Foods should
be introduced one at a time in small amounts. Mixed foods containing various
food allergens should not be given unless tolerance to every ingredient has been
assessed.