They've been studying our dna through samples for a really long time. Some have a MTHFR gene mutation, which causes the body to not be able to remove toxins as efficiently. Also reduces uptake of nutrients. Things like this definitely increase odds of having a terrible response. If there was a way to determine how many men vs women, I would bet there are more men having a negative response by percentage. Men usually have the genetic mutation more, and also are more negatively impacted by heavy metals.