A very small trial involving 10 healthy males aged 18 to 35 found that drinks made from 200g and 400g of frozen raspberries produced improved blood vessel function when tested after 2 hours and after 24 hours.
Istas, G. Feliciano, R. Weber, T. Garcia-Villalba, R. Tomas-Barberan, F. Heiss, C. Rodriguez-Mateos, A. Plasma urolithin metabolites correlate with improvements in endothelial function after red raspberry consumption: a double-blind randomized controlled trial. Archives of Biochemistry and Biophysics. May, 2018.