I think theres something in it I guess the thing is it dosent work for everyone and at the end of the day I really believe we get what we are ment to have.
However I know people who have swayed several times now to get the desired gender each time and its worked but I also know people who have swayed and got the opposite
I do think it can help and I spose its worth a try I think the key is not to get too hopeful just incase it turns out to not be the gender you hoped for as that can be a horrible experience.
There has been scientific tests done to suggest that diets high in salt and pottasium favour boys. and Diets high in magnesium and calcium favours girls
if you look it up on google you may find some of it worth reading