Didn't have one of those blogger logins, so I am sending a comment by
Oxalates reduce the absorption of calcium, but it works the other way
around as well: calcium reduces the absorption of oxalates and lowers
the risk of kidney stones.
"Dietary intake of calcium or dairy products has been shown to decrease
urinary oxalate excretion by limiting its intestinal absorption."
"The consumption of dark chocolate induced a significant increase in
mean urinary Oxalate not observed in the milk chocolate group."
Cooking high-oxalate foods with milk or cheese seems to be wise.
Spanakopita is one example of a food combination in traditional cuisine
that significantly blunts spinach oxalates (which are also quite
hight)... should work for amaranth as well.