The Duchess of Cambridge is drinking "green juice" for an "extra boost" in the mornings.

Duchess of Cambridge

Duchess of Cambridge

The 33-year-old mother-of-two is currently looking after her 22-month-old son Prince George and three-weeks-old daughter Princess Charlotte at Anmer Hall, while Prince William is out working. However, her sister Pippa Middleton is looking after her, getting her juices delivered, as a "surprise".

A family source said: "Pippa arranged to have fresh juices delivered to Kate every three days. It was a surprise treat. Kate used to blend her own juices and this is much easier. She just enjoys green juice in the morning. It's Kate's go-to for an extra boost."

The Duke of Cambridge is also a convert to healthy juices thanks to his 31-year-old sister-in-law, who is studying to be a nutritionist with an eye toward writing a book on healthy eating.

The source told Us Weekly: "Pippa was the one who got them into juicing. They all love it!"

As part of her health kick, Kate has been visiting Back to the Garden, an organic farm shop near the tiny Norfolk village of Anmer, on a regular basis, and is never hassled by the public for selfies.

The source added: "(Kate) is buying fresh local produce. All organic. People give her space. No one is rushing over to ask for selfies."