Following oral administration in humans, 75% of resveratrol from suppliments is absorbed, possibly by transepithelial diffusion. However, oral bioavailability is low (<1%) due to rapid and extensive metabolism in the intestine and liver (Almeida, et al., 2009; Cottart et al., 2010)
As for the absorption rate when drinking red wine,
A total number of 25 subjects have been involved in the experiments and it was clearly demonstrated that resveratrol absorption after wine consumption is highly variable. The compound was found in the serum of roughly half of the subjects participating to the experiments, in free or in glucuronidated form and in very different concentrations. A further evidence emerging from the data is that the bioavailability of trans-resveratrol absorption associated to wine consumption is generally influenced neither by the meal nor by the kind and/or the quantity of lipids contained in the meal consumed. (Vitaglione, et al. 2005)
Almeida, L., Vaz-da-Silva, M., Falcão, A., Soares, E., Costa, R., Loureiro, A. I., Fernandes-Lopes, C., Rocha, J.-F., Nunes, T., Wright, L. and Soares-da-Silva, P. (2009) Pharmacokinetic and safety profile of trans-resveratrol in a rising multiple-dose study in healthy volunteers. Molecular Nutrition & Food Research, 53(1), S7—S15.
DOI: 10.1002/mnfr.200800177 PMID: 19194969
Cottart, C.-H., Nivet-Antoine, V., Laguillier-Morizot, C. and Beaudeux, J.-L. (2010). Resveratrol bioavailability and toxicity in humans. Molecular Nutrition & Food Research, 54(1), 7—16.
DOI: 10.1002/mnfr.200900437 PMID: 20013887
Vitaglione, P., Sforza, S., Galaverna, G., Ghidini, C., Caporaso, N., Vescovi, P. P., Fogliano, V. and Marchelli, R. (2005), Bioavailability of trans-resveratrol from red wine in humans. Molecular Nutrition & Food Research, 49(1) 495—504.
DOI: 10.1002/mnfr.200500002 PMID: 15830336