Hair is NOT essential for our human survival. If you are losing hair, it means your body's metabolism has halted or slowed nutrients to feed your locks. When you enter a calories restrictive diet, you have major surgery or stress, your body gets on survival mode, and as mentioned hair is the first to go without necessary nutrients.
Continue to keep your protein and hydration high. Take all your vitamins and try to relax. It will start hair production and nutrients once it finds a balance. And you stressing about it might delay that balance.
✨Hugs!✨
I have meant to add this topic to my personal blog. I will look for the data to support information on hair nutrition and health.