It's one of the toughest races on the calendar and fuelling riders sufficiently that they are able to get through it is no easy task.
Dr James Morton, head of nutrition at Team Sky has therefore got his hands full, of carb-loaded products by all accounts.
"In many ways it's harder than a grand tour stage because you've got the intensity of the stage and the duration of it and the riders can't come back to the car to get extra products ... So carbohydrate is king."
That means 75g to 90g per hour, he says. Gawd only knows how many baked potatoes that equates to.
Watch the video to see how Team Sky deals with these enormous nutritional demands.