My son just turned 7 months old and still nurses. I would say I'm the last few weeks he has started…

My son just turned 7 months old and still nurses. I would say I'm the last few weeks he has started to grunt during feedings... he doesn't cry or seem to be in any pain but I was curious as to why all of a sudden he is grunting? He also straightens out his whole body while he does it... should I be concerned?