I've seen several articles and blurbs lately about how spinach is not all it's cracked up to be, as far as it's calcium levels go.
Here's the story. Spinach contains quite a bit of calcium. 1/2 cup of the stuff contains 122mg or so. That's been pretty good news, as 1/2 cup of spinach is like 10 calories... You'd have to drink a 1/2 cup of milk to get the same amount (and, more calories).
Now, calcium absorption comes into the story. Spinach has some compounds that bind to the calcium, decreasing your body's ability to absorb the mineral (calcium is a mineral). According to the University of Hawaii research scientists, you only absorb 6mg of that 122mg of calcium. So, go for the milk.
Here's just one of the little articles that I found; Is that Food REALLY a Good Source of Calcium? You get to read this one because it's available online. The others were in print magazines. Men's Health being one of them.
I understand the spirit of what they are saying and recommending. They just need to look at it from the other direction. They've come up with an elaborate method of replacing the calcium lost from the bones, rather than helping us to keep the calcium that we have.
They're forgetting the other critical role that spinach and other veggies play. Spinach keeps you from pissing the calcium that's already been absorbed, away! An acid/base imbalance forces our bodies to sacrifice it's calcium to combat blood acidosis. Why not stop the acid/base imbalance, rather than merely give our bodies more calcium to work with.
A couple weeks back, I posted this: The Big Calcium "Problem"
While milk, itself, is relatively close to neutral on the acid/base scale, cheese is a big offender. The irony is that cheese is often touted as a great source of calcium... Kinda reminds me of the American proverb "Give a man enough rope, he'll hang himself."