For athletes ingesting supplemental protein, whey is thought to be preferable to plant-based supplements. This is due in part to whey’s superior concentration of leucine, the essential amino acid that makes a strong contribution to muscle protein synthesis (MPS).
For vegetarian athletes or those with dairy sensitivities, rice protein is sometimes used as an alternative to whey. In low doses, the leucine content of rice protein may not be adequate to stimulate MPS. But what about higher doses?
In research on the effects of leucine dose and MPS, there appears to be no beneficial effect of ingesting more than 2-3g. With high doses of rice protein (48g), the leucine concentration would theoretically be sufficient for impacting strength and MPS.
To examine this, Joy et al. (2013) selected 24 male college students with a history of resistance training and randomly assigned 12 to a rice protein condition and 12 to a whey protein condition. All participants engaged in a structured resistance training programs 3 times a week for 8 weeks.
After training, participants ingested 48g of whey (5.5g leucine) or rice protein (3.8g leucine). All participants agreed to discontinue use of other supplements and follow individualized diet plans of 25% protein, 50% carbohydrate, and 25% fat. At the end of 8 weeks, both groups experienced significant
- increases in lean mass
- decreases in body fat
- increases in 1RM bench press and leg press
- increases in power on a cycle ergometer
There were no differences between the rice protein and whey protein groups in any of the outcome measures.
The data indicate that the limitations of rice protein demonstrated in earlier studies can be overcome by increasing the dose. It should be noted, however, that 48g of rice protein is a large amount to ingest at one time. It will be interesting to see whether lower doses of rice protein combined with supplemental leucine have the same effect observed in this study.
Source: Joy et al. (2013). The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutrition Journal, 12.