<But recently I read The Schwarzbein
 Principle (yes I know it's just another low carb  book) and she claims that
 for many people low carb dieting induces too low insulin levels. She
doesn't
 define how low is too low but she claims that too low insulin levels are
 even more dangerous than too high. >

here is the truth: ingestion of protein stimulates insulin AND glucagon.
net result is blood sugar stays level.
carbs stimlate insulin only. net result chaos.

most diet books are written by liars. assume they are telling fibs
then see if you can prove your assumption wrong.

andrew