This window of opportunity rubbish is ridiculously difficult to get rid of. Some three years ago, all HVs and communith healthcare professionals were sent copies of the Infant Feeding Recommendations, in place since May 2003 (it took a whole year before they got this material into their hands, though it had been on the web and published in journals, of course).
This four page document is on the web, at the DoH site, and I am quoting from page 3, paragraph 9, where the question is asked 'is waiting to introduce solids until six months likely to produce a 'fussy eater'?
The answer is (paragraph 9.1): 'No. There is no evidence to support the idea that starting solids at 6 months is more likely to be associated with the baby being a fussy eater. Indeed a randomised trial comparing breastfed babies started on solids at either four months or six months in Honduras found no difference in appetite or food acceptance as reported by the mothers.'
The ref is given at J.Nutr Nov 125(11):2787-92 (1995).
You can find the IFR at this part of the DoH website .
Interesting it was a randomised trial - these are better in terms of good evidence that retrospective trials which ask mothers what they did. The study must have assigned babies to one or other group and then followed up.
There are other similar papers if you look for them.
No HV has any excuse for peddling the myth any more....might be an idea, if someone does find their HV says this, to take a print out of the IFR and show it to them, and ask why they are saying something different.