The rapper, who turns 44 today, and his pop star wife have set themselves a 22-day challenge after being inspired by a close friend to give up meat and dairy products.
Jay Z wrote on his Life and Times blog: ''Psychologists have said it takes 21 days to make or break a habit. On the 22nd day, you've found the way.
''On December 3, 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. It was surprisingly easier on me than I thought.''
The 'Holy Grail' hitmaker said there was something ''spiritual'' about his 44th birthday coupled with the fact that the challenge ends on Christmas Day.
Jay Z added: ''It just feels right! So you can call it a spiritual and physical cleanse. I will post my progress. Any professional vegans out there that have any great food spots please help out! Please! I don't know what happens after Christmas. A semi-vegan, a full plant-based diet? Or just a spiritual and physical challenge? We'll see.''
As vegans the couple should also avoid animal-derived garments, including fur, wool and leather, although Beyonce, 32, was spotted wearing wool and leather while visiting a vegan eatery Real Food Daily in West Hollywood this week.
Take a look back at October's inaugural event.
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