"It seems that people have this warped idea of vegans being malnourished and weak," Dr Strydom said in March.
"We want to prove that vegans can do anything and more."
Humans evolved as omnivores.
Many people, I'm certain, have noticed the pale quality of vegetarians/vegans. That paleness indicates suboptimal health. I'm not surprised that they could not handle the low oxygen and pressure present at high altitudes. Carrying extra oxygen bottles only helps a little--at high altitudes, the blood simply cannot carry enough oxygen, even when breathing a pure oxygen atmosphere. That is why airplanes are pressurized to simulate lower altitudes.
I would hypothesize that vegans have a lower carrying capacity for oxygen, which becomes critical at altitudes lower than what people who eat normal diets can tolerate. It would be an interesting physiological study to carry out.
Well, you have 2 data points already!