It's become a fad for nutritionists to claim that oranges are better than orange juice, and they list numerous reasons - from added sugar in juice to better uptake of carotenoids, flavonoids and Vitamin C in whole oranges.

But how different are they? Unless you are someone on a nutrition website selling the lifestyle and health fad of the moment, not much. It is true that some juices have more sugar but that is offset by the biological fact nutrients in orange juice seem to be easier for the body to absorb from juice than when a person consumes them from unprocessed fruit. 

And there is convenience. It is better to have a health benefit from something than no health benefit at all.

Mechanical disruption of orange segments prior to digestion did not alter carotenoid BA, whereas pasteurization of the freshly squeezed juice slightly increased BA by 9–11%. Credit: DOI: 10.1021/jf505297t

Writing in Journal of Agricultural and Food Chemistry, Ralf Schweiggert, Julian Aschoff and colleagues note that oranges have nutrients such as carotenoids and flavonoids that, among other benefits, may potentially help lower a person's risk for certain cancers and cardiovascular disease.

If so, the sugar and convenience trade-off may be worth it and people should drink rather than not eat fruit. The team wanted to find out if they are getting the same nutritional benefits.  The researchers found that the production of pasteurized orange juice slightly lowered the levels of carotenoids and vitamin C but it significantly improved the carotenoid and vitamin C bioaccessibility - how much the body can absorb and use.

Juicing oranges cut flavonoid levels but the the remaining ones were much more bioaccessible than those in orange segments.

Citation: Julian K. Aschoff, Sabrina Kaufmann, Onur Kalkan, Sybille Neidhart, Reinhold Carle, and Ralf M. Schweiggert,  In Vitro Bioaccessibility of Carotenoids, Flavonoids, and Vitamin C from Differently Processed Oranges and Orange Juices [Citrus sinensis (L.) Osbeck], Journal of Agricultural and Food Chemistry 2015 63 (2), 578-587