The couple is attempting to get healthy for the final month of 2013 by banishing meat and diary products from their home.
The challenge comes as Jay Z turned 44 on Wednesday (04Dec13).
The rapper took to his website to write, "On December 3rd, one day before my 44th birthday I will embark on a 22 Days challenge to go completely vegan, or as I prefer to call it, plant-based!!
"This all began a few months back when a good friend and vegan challenged me to embrace a 'plant-based breakfast' everyday.
"There's something spiritual to me about it being my 44th birthday and the serendipity behind the number of days in this challenge; 22 (2+2=4) coupled with the fact that the challenge ends on Christmas day... It just feels right!"
The same day he posted news of his new diet, the couple was spotted eating at vegan restaurant Real Food Daily in West Hollywood, California.