Answer: Coconut Water

When there were shortages of IV fluid during the second World War, English doctors found a source in the unlikeliest of places: young, immature coconuts. The fluid found inside the hollow coconut chamber, the coconut water, is a surprisingly good substitute, as it’s nearly identical to human blood plasma: it’s nutritive, sterile, and contains various minerals and amino acids.

After the war was over, doctors largely abandoned the practice of using coconut water, both because there were no longer shortages and because of concerns over the high calcium and potassium content of the coconut water–a transfusion could potentially throw the salt balance off in the body and cause further complications. A study conducted in 1999 on both human and canine subjects showed that coconut water did indeed cause elevation of calcium and potassium in the patient’s blood, but the effect was temporary and did not lead to the predicted drop in blood salinity.