Ahem! Avoid Margarine

In Ireland there used to be a children's insult-rhyme with lyrics implying that people who eat margarine are no good and sickly (butter and lard were apparently the preferred fats):

Me Mother Is Gone to Church

Ahem! Ahem!
Me mother is gone to church.
She told me not to play with you
Because you're in the dirt.
It t'isn't because you're dirty,
It t'isn't because you're clean,
It's because you have the whoopin' cough
And eat margarine! [or "from eatin' margarine"]

The Clancy brothers tell a bit of the story and recite the rhyme here starting at 3:27 -
http://www.youtube.com/watch?v=6fDh7Ck1aF4

This poem was an oral folk news warning to not eat the new-fangled margarine because people had noticed that those who did were more likely to get the sometimes-deadly whooping cough that reached epidemic proportions in the early twentieth century. 

The Irish were right to link manufactured margarine to ill health:

Margarine Lung

Margarine Linked to Increased Risk of Heart Disease

You'd butter believe it: Margarine consumption is linked to lower IQs in children

People have forgotten this poem and its lesson and vaccination rates have been declining, so the whooping cough is slowly on the rise again:

Number of whooping cough cases doubles this year (Ireland)
http://www.thejournal.ie/whooping-cough-cases-double-ireland-714392-Dec2012

Whooping cough epidemic declared in Vermont (USA)
http://www.usatoday.com/story/news/2012/12/13/whooping-cough-epidemic-declared-in-vermont/1768527