What is Biological Value (BV)?
Biological Value (BV) is a metric that assesses protein quality based on how efficiently the body utilizes it for growth and repair. It measures the proportion of absorbed protein incorporated into the body's proteins. A higher BV indicates more readily usable protein, determined by nitrogen intake versus excretion. BV depends significantly on a protein's amino acid profile, especially the nine essential amino acids (EAAs), with the lowest quantity of any EAA being the "limiting amino acid" that restricts the overall BV.
For many years, whole egg protein, containing all essential amino acids in optimal proportions for human needs, has served as the benchmark for BV, assigned a score of 100. All other food proteins are measured against this standard.
The highest BV food: Eggs versus whey protein
The question of what food has the highest BV involves comparing natural foods with processed supplements. While eggs are the 100-point standard, some protein powders can be more efficient due to advanced processing. For example, whey protein concentrate can achieve a relative BV of 104 when compared to eggs.
Whey protein
Whey is a fast-digesting milk-derived protein rich in branched-chain amino acids (BCAAs), which are vital for muscle protein synthesis. Its quick absorption makes it popular for post-workout recovery. Whey protein isolates, further processed to remove fat and lactose, can have an even higher BV than concentrate.
Egg protein
As the benchmark, egg protein offers a complete amino acid profile. Unlike the rapid absorption of whey, egg protein provides a moderate release of amino acids, making it suitable for a sustained protein supply. Eggs also offer a comprehensive nutritional package with vitamins, minerals, and healthy fats.
Comparison of protein sources by Biological Value
A table comparing protein sources by Biological Value can be found on {Link: Wikipedia https://en.wikipedia.org/wiki/Biological_value}. This table ranks sources like whey protein, whole egg, cow's milk, fish, quinoa, beef, soybeans, rice, and beans/legumes based on their relative BV, completeness, and key nutritional benefits.
Maximizing protein quality from plant-based foods
Most plant proteins are considered "incomplete" due to lacking sufficient levels of one or more essential amino acids. However, a varied intake of plant-based foods throughout the day can provide a complete amino acid profile.
This is known as protein complementation. By combining different plant sources, the amino acid strengths of one food compensate for the weaknesses of another. For instance, legumes are low in methionine and cysteine, while grains often lack lysine. Combining them, such as rice and beans, creates a complete protein with high BV.
Some plant-based foods are complete proteins on their own, including:
- Quinoa: A grain-like seed and complete protein source.
- Soy Products: Tofu, tempeh, and edamame contain all essential amino acids.
- Buckwheat: This seed is another excellent complete protein source.
- Hemp and Chia Seeds: Both are complete plant-based proteins.
Other metrics for protein quality and BV's limitations
BV is a known metric but has limitations, particularly not accounting for protein digestibility. Other scoring systems are now widely used by health authorities.
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
Adopted by the WHO and FDA, PDCAAS corrects the amino acid score based on digestibility. Scores range from 0 to 1.0, with scores over 1.0 truncated to 1.0. Egg, whey, and soy protein all score 1.0 on this scale.
Digestible Indispensable Amino Acid Score (DIAAS)
The FAO recommends DIAAS, which improves upon PDCAAS by measuring amino acid digestibility at the end of the small intestine, a more accurate method. Unlike PDCAAS, DIAAS does not truncate scores at 100%, allowing some proteins like eggs to score slightly above 100.
Practical steps for a balanced protein intake
Optimizing protein intake is best achieved through a varied diet, not just focusing on BV. Key steps include:
- Diversify sources: Eat a range of proteins, including lean meats, eggs, dairy, and various plant foods.
- Combine plant proteins: Vegetarians and vegans should pair different plant foods for a full spectrum of essential amino acids.
- Choose lean options: Opt for leaner cuts of animal proteins to manage saturated fat.
- Consider the "protein package": Evaluate the overall nutritional value of food, not just protein. Healthy sources offer additional benefits like omega-3s in fish or fiber in lentils.
Conclusion
While eggs and some whey supplements top the list for BV, optimal nutrition comes from a varied diet. Consuming diverse protein sources ensures all essential amino acids are met. Plant-based diets can achieve high BV through complementary proteins, while omnivores benefit from mixing animal and plant sources. A balanced intake from various sources is more effective for long-term health than focusing on a single metric or food.
What food has the highest BV? A Quick Review
A quick review of protein quality and BV includes points such as eggs being the natural benchmark, whey protein supplements often scoring highest, the difference between animal and plant proteins, the importance of complementary proteins, and the existence of other protein metrics like PDCAAS and DIAAS. It emphasizes that diet variety is key for optimal nutrient intake.
FAQs
Q: What is the difference between BV and PDCAAS? A: BV measures nitrogen retention with eggs as a reference. PDCAAS is a newer metric correcting amino acid scores for digestibility, used by the FDA and WHO.
Q: Can a BV score be higher than 100? A: Yes, on a relative scale. With egg protein set at the 100% benchmark, more efficiently utilized proteins like whey concentrate can score over 100.
Q: Which plant-based food has the highest BV? A: Quinoa is among the highest-BV plant foods, containing all nine essential amino acids. Soy products are also complete proteins.
Q: What are some good examples of complementary proteins? A: Examples include rice and beans, hummus with pita, and lentils with buckwheat. These combinations provide a complete amino acid profile.
Q: Do I need to combine proteins at every meal? A: No. Eating a variety of protein sources throughout the day ensures your body gets all essential amino acids.
Q: Is BV the most important factor when choosing a protein source? A: No, BV is one factor, but the overall nutritional profile, including vitamins, minerals, and fat content, is also crucial. A balanced, varied diet is generally more beneficial.
Q: How does cooking affect the biological value of eggs? A: Cooking eggs improves their BV by breaking down protease inhibitors, enhancing protein digestibility and absorption.
