Many recipes using frozen chopped spinach instruct one to thaw and squeeze out the water from the spinach. When I do this, how much nutrition I am squeezing out?
One way of looking at it is that nutrient density is increased due to the removal of water. Minerals will not have been drained away at any rate.
Example from nutritiondata.self.com:
water content, g per 100g Iron vitamin A Unprepared thawed spinach 90.2 1.9 11725 cooked drained 88.9 2.0 12061
I assume more nutrients are cooked away rather than squeezed but that was the data available.
When you squeeze the water 'out' you are really squeezing out the water on the outside of the spinach leaves, not the juice inside the spinach. You will get some green color but most of the moisture is just wash water.
I'd think this would have the same effect as overcooking. It'll probably be difficult to measure the amount of lost nutrients, but there will likely be nutrients lost.