What are the Health Benefits of Brown Rice Protein?
If it seems to you that more and more people are developing food allergies or intolerances—especially gluten intolerance—then your observations are correct. In scientific circles, it is generally accepted that food allergy prevalence has been increasing in recent decades, particularly in westernized countries. 
Eight foods account for 90% of all food-allergic reactions: milk, eggs, peanuts, tree nuts (e.g., walnuts, almonds, cashews, pistachios, pecans), wheat, soy, fish, and shellfish. 
Brown Rice Protein High Allergenic Potential: The Problem with Milk-Based Proteins
This increased prevalence of allergies can present problems for certain kinds protein powders. This is especially true of highly popular milk-based proteins—such as whey and casein—both of which have the potential to elicit reactions from anyone a dairy or lactose allergy.
Because these milk-based proteins have been the “go-to” option for body-builders, athletes, and a growing variety of individuals who want to build or maintain muscle while losing fat, we’ve experiences a serious gap in evidence-based and hypoallergenic protein options for.
This is where rice protein may provide a solution.
Rice is generally considered to be hypoallergenic —which doesn’t mean non-allergenic, but rather that it has a low potential for allergic reactions.  In any case, as a hypoallergenic, protein-containing food, it serves as an ideal source for extracting protein for a protein powder.
High Quality Brown Rice Protein
Naturally, that leads to the question, “Am I settling for less when I use rice protein instead of whey protein—is it a less effective protein in general, and will it be less effective for building muscle?”
The short answer is no—but an explanation is in order.
There are those concerned that, due to lower levels of the amino acid lysine, rice protein is not a complete protein (i.e. provides adequate amounts of all the essential amino acids).   While it is true that rice protein has less lysine, this is not necessarily a real problem.
First, any plant-based protein is going to have one or more amino acids that it provides less of than an animal-based protein. Second, brown rice protein contains approximately 78% protein by weight with 36% essential amino acids and 18% branched-chain amino acids. This is similar to published values for soy protein isolate, which is considered to be reasonably complete for a plant-based protein. 
Of course, the actual amount of amino acids that gets absorbed into the blood stream is arguably far more important than approximate percentage protein or percentage amino acids.
In a double-blind crossover study  that compared blood concentrations of amino acids when subjects consumed rice protein isolate to when they consumed whey protein – researchers found that there was no statistically significant difference is the total amino acid concentration in the blood when comparing rice protein isolate to whey protein isolate.
Rice Protein’s Effect on Body Composition
And even more important than amino acid absorption is the actual effect of rice protein on body composition. This was examined to two different studies.
The first was a randomized, double-blind, placebo-controlled clinical trial,  in which 24 healthy, college-aged, resistance-trained participants received either 48 g of rice or whey protein isolate for eight weeks, immediately following training on training days. The results showed that rice protein isolate decreased fat-mass and increased lean body mass, skeletal muscle hypertrophy, power and strength comparable to whey protein isolate.
The second study included 11 healthy, male elite level mixed martial artists, who received either 75 g of protein from whey protein isolate or rice protein isolate per day, with at least 25 g of protein ingested after the first training session of the day. The results were that, after six weeks, there were no significant difference between the whey protein isolate and rice protein isolate groups with regard to body weight, fat-free mass, and fat mass, although percentage body fat trended toward a greater reduction in the rice protein isolate group.
Allergies to milk and milk proteins—including whey and casein—are common. Brown rice protein presents an excellent alternative, with an amino acid profile similar to soy protein, an absorption of total amino acids similar to whey protein isolate, and studies that have demonstrated that rice protein can be as effective as whey protein with regard to fat-mass, lean body mass, skeletal muscle hypertrophy, power and strength.
 Tang ML, Mullins RJ. Food allergy: is prevalence increasing? Intern Med J. 2017 Mar;47(3):256-261.  U.S. Food & Drug Administration. Food Allergies: What You Need to Know. Page Last Updated: 02/08/2018. Retrieved June 25, 2018 from https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm079311.htm.  Michelet M, Schluckebier D, Petit LM, Caubet JC. Food protein-induced enterocolitis syndrome - a review of the literature with focus on clinical management. J Asthma Allergy. 2017 Jun 27;10:197-207.  Moro GE, Warm A, Arslanoglu S, Miniello V. Management of bovine protein allergy: new perspectives and nutritional aspects. Ann Allergy Asthma Immunol 2002;89(6 Suppl 1):91-6 [review].  Murata K, Nishikaze M, Tanaka M. Nutritional quality of rice protein compared with whole egg protein. J Nutr Sci Vitaminol (Tokyo) 1977;23:125-31.  MacLean WC Jr, Placko RP, Graham GG. Postprandial plasma free amino acid changes in preschool children consuming exclusively rice protein. J Nutr 1979;109:1285-9.  Kalman DS. Amino Acid Composition of an Organic Brown Rice Protein Concentrate and Isolate Compared to Soy and Whey Concentrates and Isolates. Foods. 2014 Sep; 3(3): 394–402.  Purpura M, Lowery RP, Joy JM, De Souza EO, Kalman DS, et al. (2014) A Comparison of Blood Amino Acid Concentrations Following Ingestion of Rice and Whey Protein Isolate: A Double-Blind Crossover Study. J Nutr Health Sci 1(3): 306. doi: 10.15744/2393-9060.1.306  Joy JM, Lowery RP, Wilson JM, et al. The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutr J. 2013; 12: 86.  Kalman D, Escalante A. P34 The body composition effects of extra protein in elite mixed martial artists undergoing frequent training over a six-week period. JISSN. 2017;14(Suppl 2):31.