The 26-year-old star, who has suffered bone injuries to both arms in less than a year, is desperate to avoid any more time out of the game.
And in an interview with the Daily Mail, international Vunipola is eager for a long run of rugby, laying out his targets for the coming weeks.
“I won’t say ‘stay fit’ because that is just accepting staying fit and mediocre. I don’t just want to be fit, I want to be fit and good. I don’t want to be the same player, I want to be better,” he said before revealing that blood tests led to him adding more milk to his diet.
“My skin colour and not having much sun has affected it.
“I have started drinking a lot more milk. Mostly because I don’t want it to go off! Cheese as well but I can’t eat too much cheese; camembert is my favourite!”
His return to action in Saracens’ loss at Sale saw Vunipola surprisingly play a full game and he admits it was a scary situation last week.
“I think God wanted me to be afraid,” he continued.
“Before I was a bit too confident to the point that ‘I’m invincible’. That’s why I got injured again.
“I was becoming too big for my shoes. You don’t know it’s happening until you realise how much you rate yourself.
“It’s hard when people keep talking about you. This time I want to keep my head down and work hard.
“At Sale I was a bit tentative and anxious – I readily admit that now.
“Before I was a bit naive that I could fall straight into it, whereas now I’m a bit more prepared. And scared. Not of being injured, but the process of coming back is the hardest thing.
“It’s a good thing to have that fear. I don’t think I had it before. I guess that came down to me being complacent.
“I’m hoping it’ll only be a few games then I can get into it and start flying in.
“I want to play, I want to experience Twickenham and the Six Nations again.”