Rice Protein - Composition and Amino Acids
Rice protein powder is gluten-free. It is also an allergen-free plant protein. 6.
Rice protein powder is a dietary supplement that cannot replace a balanced diet. The intake of protein powders should be tailored to individual physical needs and goals – see protein requirements, protein deficiency, and protein excess.
Plant Protein Compounds
The main plant protein compounds (protein fractions) in rice protein are 75% glutelin, 15% globulin, 6% albumin, and 3% prolamins. 7 8. These fractions consist of various proteins. Proteins are composed of different amino acids, which ultimately determine the protein quality.
Compared to commercially available rice (7.5 g), rice bran already contains more protein at 13.3 g per 100 g.
Rice protein isolate typically contains between 77% and 82% protein. The protein powder is characterized by relatively high levels of methionine and cysteine.
Percentage distribution of amino acids 9:
Limiting Amino Acids
Most plant-based foods lack at least one essential amino acid 10 11. These are called limiting amino acids. In rice protein, the limiting amino acids are lysine, threonine, and isoleucine 12 13 14. In the scientific field, proteins that lack one or more amino acids are referred to as incomplete proteins 15 16. Foods with incomplete proteins contain all essential amino acids, but not in the correct proportion for the human body to form proteins 17. However, the body stores the amino acids already consumed in an amino acid pool until the missing ones are obtained through food 18. Therefore, combining different protein sources is not necessary.
Since rice lacks some essential amino acids, its PDCAAS value is correspondingly low at 0.47 19. The PDCAAS method can be used to determine the protein quality of a food or dietary product. The value takes into account the digestibility of amino acids and the amino acid profile of the food. The maximum value is 1.0. No PDCAAS value for rice protein was found.
Rice protein is easily digested by the body. 96.66% of rice protein isolate is digested in the body 20. Digestive discomfort is highly unlikely.
Rice Protein and Soy Protein - Comparison
A study examined two rice protein powders, one concentrate and one isolate 23. The following average values were determined: 78% protein, 36% essential amino acids, and 18% BCAA (branched-chain amino acids). The scientific findings suggest that rice protein powder could be used instead of other protein isolates (such as soy protein or animal-derived: whey) without having to sacrifice essential nutritional value.
Other scientists share a similar view. According to their opinion, rice protein could also be a valuable source of plant-based protein that can be used as an alternative to soy protein. 24. In their studies, the levels of essential amino acids were higher than soy protein isolate. Additionally, rice protein had a digestion rate of 96.66% compared to soy protein's 91.41%.
Rice Protein vs. Whey
In 2013, a study lasting over eight weeks was published online, demonstrating the effectiveness of rice protein isolate compared to whey protein in muscle mass building 25. Rice protein achieved the same results as whey in supporting muscle growth when combined with strength training. The 24 study participants, divided into two groups and training three times a week, consumed high amounts of protein (48g) immediately after exercise. Both the rice protein and whey protein groups were able to reduce body fat percentage and increase muscle size and strength. The researchers deliberately chose a high protein amount (48g) to ensure the leucine content reached a level where muscle protein synthesis is triggered – optimal range: 1.7 to 3.5g of leucine in a protein meal 26. Out of the 48g of rice protein used, 3.8g was leucine.
Compared to quickly digested whey proteins, rice proteins are processed by the body at a moderate speed 27. Additionally, the amino acid appearance in the blood is 6.8% lower compared to animal-derived protein powder.
Single-Component and Multi-Component Protein Powders
Rice protein is available as a single-component protein powder (isolate) or in combination with other plant-based protein sources as a multi-component protein powder (blend). In most cases, digestive enzymes are artificially added to multi-component protein powders to increase amino acid appearance in the blood 28.
Using Rice Protein
Typically, rice protein is consumed as a protein shake with water or plant-based drinks. Rice protein powder also pairs well with smoothies due to its mild, slightly sweet taste.
Rice protein can also be combined with other protein powders to enhance the amino acid profile. Hemp protein, lupine protein, and pea protein are additional vegan protein powders that can be used for this purpose. The resulting multi-component protein powder will have an improved amino acid profile.