The studies concluded that it was effective at providing vitamin A as part of a well-balanced diet that wasn't overly reliant on rice. The controversy is over its effectiveness in severely malnourished kids whose diet is mostly rice, since there's reason to believe its effectiveness - and indeed that of supplementation in general - in providing vitamin A ia heavily dependant on the quality of the rest of the diet.
To put it bluntly, proponents of golden rice have been arguing that it's worthwhile because it's just not realistic for poor families to include vegetables in their diets because of expense and logistical difficulties, whilst pointing to a study in which the participants were fed meat (amongst other ingredients) along with their golden rice to prove it works.
To put it bluntly, proponents of golden rice have been arguing that it's worthwhile because it's just not realistic for poor families to include vegetables in their diets because of expense and logistical difficulties, whilst pointing to a study in which the participants were fed meat (amongst other ingredients) along with their golden rice to prove it works.