Oryzatein® Rice Protein Absorption Kinetics Compared to Whey Protein

Full Manuscript Published October 2014Journal of Nutrition and Health Sciences


While many athletes or bodybuilders look to “fast” (rather than “slow”) absorbing proteins after their workout to optimize muscle gains, there has been no conclusive data about the advantage of one over the other for stimulating muscle protein synthesis (MPS).  Nonetheless, some research suggests that differences in rate of absorption of different proteins can affect the amplitude and possibly duration of MPS especially after resistance exercise. The purpose of the study was to evaluate the concentration of amino acids in the bloodstream after administration of rice protein or whey protein.


After a 12 hour overnight fast, 10 trained male subjects were randomly assigned to receive either 48 grams of rice protein isolate (RPI) or whey protein isolate (WPI) in a double-blind, crossover design, separated by a washout period of 7 days. Blood draws were taken immediately prior to and at 1, 2, 3, and 4 hours following consumption of WPI or RPI.


1) Significant differences seen between RPI and WPI for Tmax:

  • Total amino acids peaked in the bloodstream at 93 +/- 4 min for RPI and 69 +/- 3 min for WPI
  • Essential amino acids peaked in the bloodstream at 87 +/- 7 min for RPI and 67 +/- 4 min for WPI
  • Non-essential amino acids peaked in the bloodstream at 97+/- 4 min for RPI and 71 +/- 5 min for WPI

2) No significant differences detected for AUC (area under the curve) between RPI and WPI

3) No significant differences detected for Cmax between RPI and WPI

4) On an individual amino acid basis, WPI was faster or equal for all amino acids with the exception of leucine, which peaked in the blood faster in the RPI group


Oryzatein® rice protein may be considered a medium to slow absorbing protein which is in line with other non-meat/non-dairy proteins.  Nonetheless, faster leucine absorption from RPI may indicate why RPI supplementation supported gains in muscle, power and strength as good as whey in the first rice versus whey study published June 2013.


RPI showed a non-significant 6.8% lower total amino acid concentration in the blood based on AUC when compared to WPI. Time to reach peak concentrations was slower with RPI in comparison to WPI, with the exception of leucine, a key amino acid in MPS.