I think six minimum. Google thinks eight. Realistically I think I go for ten or even a dozen.
Obviously, other factors like glazed in balsamic, cooked with pine nuts or butter is a factor.
But for the sake of experiment, let's say these are plain, salted with gravy available. In addition to your full Christmas dinner.
How many sprouts is acceptable?
Yanbu-not more than eight!
Yabu- eight is not enough!
(Yes, I realise the answer is none if you are a sprout Grinch!)