vitamin C is the only nutrient degraded significantly. And it's not "leached" lol
here's "The Spanish Study" lol
https://zero.sci-hub.se/2083/62a036b8d7cb6af64300f4ff716d07e8/10.1021@jf071680t.pdf?download=true
Discussion
Conclusion: "In general, the losses during the cooking treatments of the human health-related compounds (phenolics, glucosinolates, and minerals) were mainly due to leaching into the cooking water. Therefore, we could conclude that losses of phytochemicals would be prevented with shorter cooking times and avoiding cooking with water, even if this last treatment could make the texture unacceptable for some consumers."