This week two facts about Vitamin D came to my knowledge. The first one is related to a soy milk product in Brazil, from a company called Yoki. They have a line of soy milk, with different flavours, and I read on line that the Vitamin D they use to fortify their soy milks has an animal origin (D3 and not D2, which is vegetable). This was a shocking news for a lot of vegan friends that used to consume their products to avoid consuming Ades (a popular brand that's owned by Unilever).
The second news was about Kellogs corn flakes. I read that Kellogs used to have Vitamin D2 on their cereal and recently it was replaced by D3. I don't consume them but I know vegan people who do - and one of their reasons if because these cereals are fortified with vitamins while organic ones are not.
The biggest issue for me in cases like that is that the consumer is not informed and if you don't keep reading boxes and asking for information all the time you will end up consuming something that's not suitable for vegans. I know this is a risk that everybody is dealing with when consuming "regular" products that are "accidentally" vegan, mainly because these companies don't care about veganism, they just want to reach more parcels of the consuming market. But I still believe that consumers have the right to know everything about what they are consuming.
About the Vitamin D, I'm not an expert but make sure the products you're consuming have D2 and not D3 (fortified products are the main source of Vitamin D for vegans -and also sunlight). And don't forget to check your blood from time to time to see if you need any supplements (you'll find vegan options for sure).