Study concludes that bioavailability of natural Beta-Carotene (Vitamin A) is the same as that of synthetic.
-Jordão Jr, Alceu A., and H. élio Vannucchi. "Improvement in vitamin A status with consumption of dark-green vegetables–a bioavailability study in rabbits." Nutrition research 23.3 (2003): 271-278. [Publication]
Clinical evaluation revealed comparable bioavailability for both natural and synthetic B vitamins.
Lindschinger, Meinrad, et al. "A randomized pilot trial to evaluate the bioavailability of natural versus synthetic vitamin B complexes in healthy humans and their effects on homocysteine, oxidative stress, and antioxidant levels." Oxidative medicine and cellular longevity 2019 (2019). [Publication]
Researchers find no difference in Vitamin C uptake between synthetic versus natural forms
-Carr, Anitra C., and Margreet Vissers. "Synthetic or food-derived vitamin C—are they equally bioavailable?." Nutrients 5.11 (2013): 4284-4304. [Publication]
Vitamin E bioavailability ratio of natural:synthetic is 1.3:1 in non-smokers and 0.9:1 in smokers.
-Lodge, John K. "Vitamin E bioavailability in humans." Journal of plant physiology 162.7 (2005): 790-796. [Publication]
Food folate bioavailability is actually lower than that of synthetic folic acid, however more studies need to be completed to understand this phenomenon as it relates to the entirety of the diet.
-Caudill, Marie A. "Folate bioavailability: implications for establishing dietary recommendations and optimizing status." The American journal of clinical nutrition 91.5 (2010): 1455S-1460S. [Publication]