>>The genesis of the adage “an apple a day keeps the doctor away”, as near as we can mark it, was that publication.

The notion that apples are good for you has been around for a long time, but AFAIK, "an apple a day keeps the doctor away." comes via the American Prohibition.

Prohibitionists were destroying bottles of liquor, barrels of beer and hard cider - and chopping down apple orchards - so as to remove the source of hard cider.

In response, orchard owners promoted the health benefits of eating apples, using the phrase "an apple a day..."

Through colonization and expansion through the American continent, settlers brought apple seeds - so they could make hard cider. Apples don't "breed true", so raising trees from seed led to an enormous variety of apple trees - which in turn lead to a number of the popular 'modern' apple types (which are propagated through grafting as seeds would be useless for this).

Nice to know that seeds are good for us in this other way. :-)