Sure, here's a CDC report: https://www.cdc.gov/nutritionreport/pdf/Nutrition_Book_compl... as well as this secondary study that summarizes some of the findings https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4822995/.
Sure, here's a CDC report: https://www.cdc.gov/nutritionreport/pdf/Nutrition_Book_compl... as well as this secondary study that summarizes some of the findings https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4822995/.
Summary reference:
"The Nutrition Report has limitations. First, it does not cover information beyond biochemical indicators, such as dietary intake, supplement usage, hematologic measurements, and anthropometric body measurements, which are generally used together with the biomarker information to comprehensively assess nutritional status."
"forfeit insight into the association between variables unique to each individual biomarker"
In the end, what we are doing is using data to see if controlling for purity in supplementation improves people's definition of health. If we can control parameters (purity, vitamin active form, etc.), can we see those changes quantitatively rather than qualitatively.
Thanks for your inquiry.
I hope you find more studies, but the variables such as those mentioned above will make it very difficult to determine causation.