There is a reason you get tired after eating - It's due to a portion of your blood in your body moving to your gut and bowel, leaving less for the rest of your body (brain, muscles etc) and slowing you down, making you sleepy(1)!
Whether is is healthy or not, it's neither here nor there. It can mess with your natural sleeping cycle, but it is also not good to deprive yourself of sleep. I feel the best advice I can offer is just to listen to your body and what feels right for you. We are all built slightly differently, so forcing yourself to adhere to other peoples norms certainly isn't good for you! There have been studies done showing it has very little impact on how well you learn (2).
My apologies for the shoddy response and references, I've put 2 basic sources in, if you have any further questions I will do my best to answer them and improve my referencing. A lot of my information comes from my degree and background (Medical Physics).
(1) - http://www.thejakartapost.com/life/2016/10/04/why-do-we-feel-sleepy-after-eating-a-meal.html?src=mostviewed&pg=/
(2) - A nap is as good as a night, https://www.nature.com/articles/nn1078#references