Since sperm makes up only one percent of semen, the answer would be that there is no harm at all in consuming it, although its obvious the purpose of it is not to be consumed but for the procreation...
as per my experience drinking own sperm is not good it create problem mild gastitis in your liver then you not feel hunger you feel burn in your stomach so do not drink your sperm
The amount of nutrition is so small it would make no difference. Just keep a healthy diet and exercise if you want to be healthy. Drinking semen will not make it. And there is always a risk for STI's.