Read the methods section of the study. > The issue with this is that the amount of vitamin D someone might take is correlated with how much sun exposure is ava

Read the methods section of the study. > The issue with this is that the amount of vitamin D someone might take is correlated with how much sun exposure is available. And the amount of available sun exposure can impact what is considered a little / a lot to each person. That could be case but not necessarily in this study.