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Biological Value or BV is a common method for measuring protein quality and biological utilization rates of protein for human and animal consumption. The method relies on nitrogen retention as an indicator of protein quality. Unlike carbohydrates and fats all protein contains nitrogen. Scientists trace nitrogen as it enters the body through protein intake and measure the amount that is retained. Since protein is used in the construction of bodily cells the more protein that is retained indicates a higher level of biological utilization of the particular protein. The more nitrogen that is excreted as urine and fecal matter the less utilizable the particular kind of protein.

The number is expressed as a score with 100 being the threshold. The number progressively lowers as more is consumed, while the protein's score is based on its consumption in a fasted state.

Humans

The now accepted method tested in humans for protein utilization is biological value of protein. Egg protein scored the highest number of 100 to serve as a measuring stick. Whey protein has subsequently been found to have the highest known biological value of any protein in humans. Whey scored a 104 in its basic form relative to the original 100 egg scale. Further testing validated, the biological value of protein for whole eggs is 100 and 104 for whey.

Animals

The Biological Value method is also used for analysis in animals such as cattle, poultry, and various laboratory animals such as rats. It was used by the poultry industry to determine which mixtures of feed were utilized most efficiently by developing chicken. Although the process remains the same, the biological values of particular proteins in humans differs from their biological values in animals due to physiological variations.

Advantages

The BV is superior to both the PER and the PDCAAS for the measurement of protein utilization in humans.

The table below shows the Biological Value rating of various proteins.

• Isolated Whey: 104
• Whole Egg: 100
• Cow’s Milk: 91
• Egg Whites: 88
• Fish: 83
• Casein: 80
• Beef: 80
• Chicken: 79
• Soy: 74
• Wheat Gluten: 54
• Kidney Beans: 49

Methodology

Since the method measures only the amount that is retained in the body critics have pointed out what they perceive as a weakness of the biological value methodology. Critics have pointed to research that indicates that because whey protein isolate is digested so quickly it may in fact enter the bloodstream and be converted into carbohydrates much more rapidly than was previously thought possible. They claim that when the human body consumes whey protein it is absorbed so rapidly that most of it is sent to the liver for oxidation. Hence they believe the reason so much is retained is that it is used for energy production not protein synthesis. This would bring into question whether the method defines which proteins are more biologically utilizable.

References

1. Protein Fundamentals - Part 3 Quality Determinants by Donald G. Snyder, Ph.D. This article is sponsored by Proper Nutrition, a proprietary company
2. LE Magazine October 1998 Unlocking the Secrets to Health & Fitness.
3. Turning Up The Heat Newsletter: Evaluating the Quality of Common Protein Sources by Cheri A. Lynn.
4. Recent developments in protein quality evaluation by Dr E. Boutrif.
5. .

• Proteins
• Nutrition