"The UCLA researchers have found that a protein called sex hormone-binding globulin (SHBG) somehow lowers insulin resistance. Most coffee drinkers greatly increased levels of SHBG in the UCLA study. The people with higher SHBG were the ones who didn’t develop diabetes.
A 2009 study in The New England Journal of Medicine of over 800 women found that “higher plasma levels of SHBG were… associated with a lower risk of Type 2 diabetes.” The lowest SHBG group had twenty times the risk for Type 2 of the highest SHBG group."