Nasturtians have lots of flavor and contain vitamin D?

This article about the edible qualities of nasturtians says that they contain vitamin D. That's a rare claim when it comes to reading about plants, in my experience. The only other plant I know where someone has made the claim about it is the Cape Gooseberry ground cherry; of course, the amount isn't said to be a lot for the ground cherry (not sure about nasturtians):

https://garden.org/learn/articles/view/4112/

The article says that the flowers have a peppery, zippy taste, and that the leaves are also edible (and it implies that the buds are edible).

I wonder if you can eat the seeds, too.