Nikon recommends class 6 cards, but since the data rate of 1080p recordings with that camera do not even come close to the class 4 write capabilities (6 MB/s), you will be fine with it.
But to really find out, test it out for yourself and see, if your are satisfied with the results and if your SD card is up to it to write 14 Mb/s (1.75 MB/s) constantly.
To edit your thread title to a descriptive one, to get a knowledgable audience and help making the thread easier to find for people looking for the same information, just click on the
button on the bottom right of your original post and then click the
button below your message.