As the other answer says there is not much in the way of definitive information on this subject. You also need to consider that there are a vast number of different D&D settings and what applies in one may not apply in others so there can be no definitive answer that covers everywhere.
My opinion though runs the other way. Why would Orcs turn down perfectly good meat if it was there in front of them? Most likely different Orcs, Tribes and Leaders would have different positions on the subject but I'd be surprised if a substantial percentage of Orcs are not willing or even eager to eat meat no matter where it comes from.
In fact the "brutish beasts planning to cook up the poor helpless victims" is such a common trope that I'd be very surprised if there isn't at least one D&D book somewhere in one of the settings where it happens.
After all consuming the weak to feed he strong is very much within the Orcish mindset.
As requested - more reasoned arguments. I'll use the evidence kindly provided above.
The racial god of the Orcs, the chief of their pantheon and the very embodiment, literally, of what it means to be an 'Orc' in the collective D&D setting is Gruumsh One-Eye, a Greater power notable for being the God of Revenge - and of Survival. Gruumsh embodies the Chaotic Evil principle of self-reliance to the core, and rejects those too weak or pitiful to thrive on their own while rewarding those who advance his cause and his name.
Gruumsh rejects weak and pitiful, favors strength and survival. When an Orcish tribe is running low on food they kill and eat the weaker members of their own tribe so that the strong can survive. The strong are then able to last through the lean times and the whole tribe survives.
For all that they have an Intelligence penalty, Orcs in D&D have been pretty consistently described as well-organized under strong, cunning leadership that experiences a balance of power between the more martial leader(s) and various kinds of spellcasters, often clerics of some variety. These two forces form Orcs into mighty hordes - which are well-supplied, well-rested, and usually pretty well-run. Their battlefield tactics may often lack originality but no story or setting has ever depicted an Orcish horde running out of supplies or, indeed, suffering from common difficulties of hygiene and filth fever (dungeon master's guide) that would plague less experienced forces.
Eating your own forces can be a good tactical move. If you have wounded Orcs and do not wish to leave them to be captured and interrogated but cannot move them then you kill them. Once you have killed them then assuming morals were not applied (after all these are evil creatures) why would you waste that meat?
Perhaps part of the reason that Orcish hordes never run out of food is because each battlefield provides fresh supplies for the next step of their rampage as the fallen on both sides are recycled into the cooking pots.
Between this consistent martial mindset and Gruumsh's inclination towards leaving enemies alive (yet in your power) in order to be turned against their former allies, I find it difficult to believe that Orcs would eat sapients, whose meat tends to be diseased and which gains them absolutely nothing while wasting valuable sources of information. They may feed sapients to allies such as worgs or dragons, and I doubt they care if other ("strong") races choose to eat sapients, but from their perspective the practice doesn't have a lot of appeal.
What canon support is there for the meat being diseased? Yes in the real world we have prion disease but there are no instances that I am aware of of similar things in D&D. The closest thing is the Pathfinder template that can be given to cannibals and causes them to devolve. I don't know off-hand if D&D core has an equivalent and that template has no rules saying it must be applied to cannibals, just that it can be caused by cannibalism.
Once you have questioned the prisoners why would you leave them alive unless you had a use for them? If you had no use for them why would you keep them? If they are dead why would you not eat them?
If the Orcs capture a human village after they finish decorating the place with heads on spikes why would the next step not be a BBQ? They certainly have no use for the prisoners and a bunch of villagers are limited in terms of how usefully they could be turned against an enemy. Their best use is to fill the bellies of real fighters.
