Everyone loves chowing down on McDonald’s fries… but not everyone is so certain about what’s really in them.

The fast food giant is known for its convenient and delicious menu, which many people will tell you doesn’t get any better than the fries.

But there’s been some recent confusion over what it is that makes those fries so special.

It turns out that some branches of McDonald’s are serving up fries with a little-known ingredient added to the mix: “natural beef flavoring.”

The beefy addition gives the fries an extra kick of flavor, but it means that they aren’t vegan, since the flavoring is actually made from milk.

However, you won’t find this extra ingredient in every branch. McDonald’s uses different recipes in different countries — but the extra flavoring is added in US and Canadian McDonald’s.

In UK branches, the fries are milk free and don’t contain the beef flavoring which has surprised some US customers.

The Sun Online spoke to McDonald’s to make sure and the fast food giant confirmed that the flavoring is absent from UK fries.

In fact, UK fries only contain a handful of ingredients: potatoes, sunflower oil, rapeseed oil and dextrose, a natural sugar.

But while fries in the UK are accredited by the Vegetarian society, herbivores in the US are less than impressed with the beefy flavoring.

And vegans are even less pleased since the beef-inspired ingredient is made with milk as a starting ingredient.