Month: August 2023

Note: This article was originally posted on August 20, 2023, and was revised and reposted on November 2, 2025. It now includes the latest research on protein quality, amino acid bioavailability, and the Digestible Indispensable Amino Acid Score (DIAAS). References and recommendations for both plant and animal proteins have been updated for accuracy.

Some people are considering going “plant-based” for perceived health reasons or for ethical considerations, and while these are important, evaluating plant protein quality is also necessary. Assessing protein quality using the Digestible Indispensable Amino Acid Score (DIAAS) can help identify the best sources of protein for maintaining and building muscle.

A recent study found that essential amino acids from animal protein are more bioavailable than those from plant protein [1]. These findings are especially important for older adults who need to preserve muscle mass, and for active adults wanting to build or repair muscle.

Amino Acids and Bioavailability

Amino acids are the building blocks of protein, including muscle. There are twenty amino acids, divided into two groups: essential amino acids (EAA) and non-essential amino acids.

Bioavailability refers to the degree to which essential amino acids in food can be used by the body to build its own proteins [2], such as muscle tissue.

Essential amino acids, including leucine, must be consumed in the diet because the body cannot make them. Leucine plays a key role in muscle growth and repair by triggering mTOR signaling in muscle cells, which stimulates protein synthesis [3].

Dietary recommendations for older adults emphasize obtaining about 2.3 g of leucine per meal to support muscle growth [4], and around 3 g per meal to rebuild muscle after exercise [5].

Recent research suggests a practical target range of 2.5–3.0 g of leucine per main meal, roughly equivalent to 25–30 g of high-quality protein. This level best supports muscle protein synthesis in older adults and enhances recovery when paired with light resistance exercise — such as a breakfast of eggs or Greek yogurt.

Plant Protein vs. Animal Protein for Building Muscle

Plant proteins generally contain lower levels of leucine than animal proteins [6]. People choosing a more plant-based diet often rely on legumes like beans or lentils for protein. However, most legumes are incomplete proteins, meaning they lack one or more essential amino acids.

For example:

• Lentils contain about 0.7 g of leucine per half cup.

• Chickpeas contain about 0.42 g of leucine per half cup.

An older adult would need to eat more than 3 cups of lentils or 5½ cups of chickpeas at one meal to reach the 2.3 g leucine threshold needed to trigger muscle protein synthesis.

Is Plant Protein Equivalent to Animal Protein?

A randomized, investigator-blinded, crossover study was conducted with both young and older adults [1]. Researchers compared ounce-equivalents (oz-eq) of animal-based protein (lean pork or whole eggs) with plant-based protein (black beans or sliced almonds) in a mixed meal. The goal was to determine how efficiently the body uses amino acids from each source.

The Dietary Guidelines for Americans (DGA) defines ounce-equivalents to identify protein foods with similar nutritional content [7]. However, the researchers noted that the assumption of “equivalence” between these sources is questionable.

For instance, one ounce-equivalent of pork loin provides about 7 g of protein, while one ounce-equivalent of almonds provides only 3 g [1]. Beyond quantity, protein quality — the digestibility and bioavailability of essential amino acids — also differs substantially between these sources.

The Bioavailability of Plant Protein – Digestible Indispensable Amino Acid Score (DIAAS)

In 2013, the Food and Agriculture Organization (FAO) introduced the DIAAS method to replace the older PDCAAS system for assessing protein quality [9].

DIAAS measures how well individual essential amino acids are digested and absorbed at the end of the small intestine, giving a clearer picture of how well the protein supports the body’s needs.

High-quality proteins have a DIAAS ≥100, while scores of 75–99 are considered good, and <75 cannot make a quality protein claim [8].

• Most grains and legumes score below 75.

• Pea and soy protein range from 75–100.

• Animal proteins such as beef typically score well above 100 [10].

Although DIAAS provides a more accurate measure of protein quality, it has not yet been adopted for food labeling in Canada or the U.S. Implementation will require regulatory review and harmonized data across food categories. Until then, dietitians and consumers can use academic data to understand the real quality of different protein sources.

Plant Protein versus Animal Protein – What Studies Show

The recent trial found that meals containing animal-based proteins resulted in higher blood levels of essential amino acids compared with meals made from plant-based proteins — in both young and older adults [1].

Additionally, lean pork produced greater amino acid bioavailability than eggs, and no difference was found between black beans and almonds.

Researchers concluded that it is inaccurate to treat different protein sources as equivalent based on ounce-equivalents alone.

Final Thoughts

If you are an active adult wanting to build and repair muscle, or an older adult aiming to maintain strength, it’s essential to choose high-quality proteins that contain all essential amino acids — especially leucine. While the DGA lists one ounce of meat, one egg, 0.25 cups of beans, or 0.5 ounces of nuts as equivalent, this study shows they are not truly equivalent in quality or bioavailability.

If you are exploring a more plant-based lifestyle, understanding the science of protein bioavailability can help you make informed, health-supporting choices.

For those following a vegetarian or vegan diet for ethical or cultural reasons, combining complementary plant proteins and choosing higher-DIAAS options like soy or pea protein can help you meet your needs.

More Info

If you would like support ensuring that you or someone you love eats sufficient high-quality protein at each meal to trigger muscle synthesis, please reach out through the Contact Me form, available on the tab above.

To your good health,

Joy

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References

[1] Connolly G, Hudson JL, Bergia RE, Davis EM, Hartman AS, Zhu W, Carroll CC, Campbell WW. Effects of Consuming Ounce-Equivalent Portions of Animal- vs. Plant-Based Protein Foods, as Defined by the Dietary Guidelines for Americans, on Essential Amino Acid Bioavailability in Young and Older Adults: Two Cross-Over Randomized Controlled Trials. Nutrients. 2023; 15(13): 2870. https://doi.org/10.3390/nu15132870

[2] Gaudichon C, Calvez J. Determinants of Amino Acid Bioavailability from Ingested Protein in Relation to Gut Health. Curr Opin Clin Nutr Metab Care. 2021 Jan; 24(1): 55-61. doi: 10.1097/MCO.0000000000000708. PMID: 33093304; PMCID: PMC7752214. [https://pubmed.ncbi.nlm.nih.gov/33093304/]

[3] Norton LE, Layman DK. Leucine Regulates Translation Initiation of Protein Synthesis in Skeletal Muscle after Exercise. J Nutr. 2006 Feb; 136(2 Suppl): 533S–537S. doi: 10.1093/jn/136.2.533S. [https://www.sciencedirect.com/science/article/pii/S0022316622080956]

[4] Bauer J, Biolo G, Cederholm T, Cesari M, et al. Evidence-Based Recommendations for Optimal Dietary Protein Intake in Older People: A Position Paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013 Aug; 14(8): 542–59. doi: 10.1016/j.jamda.2013.05.021. [https://pubmed.ncbi.nlm.nih.gov/23867520/]

[5] Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016 Mar; 48(3): 543–568. doi: 10.1249/MSS.0000000000000852. Correction in Med Sci Sports Exerc. 2017 Jan; 49(1): 222. [https://pubmed.ncbi.nlm.nih.gov/26891166/]

[6] Berrazaga I, Micard V, Gueugneau M, Walrand S. The Role of the Anabolic Properties of Plant- versus Animal-Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review. Nutrients. 2019 Aug 7; 11(8): 1825. doi: 10.3390/nu11081825. PMCID: PMC6723444. [https://pubmed.ncbi.nlm.nih.gov/31394788/]

[7] U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025, 9th ed. Washington, DC: U.S. Government Publishing Office; 2020. Available from: https://www.dietaryguidelines.gov

[8] Herreman L, Nommensen P, Pennings B, Laus MC. Comprehensive Overview of the Quality of Plant- and Animal-Sourced Proteins Based on the Digestible Indispensable Amino Acid Score. Food Sci Nutr. 2020; 8(9): 5379–5391. https://doi.org/10.1002/fsn3.1809

[9] Food and Agriculture Organization of the United Nations. Dietary Protein Quality Evaluation in Human Nutrition (FAO Food and Nutrition Paper 92). Rome, Italy: FAO; 2013. Available from: https://www.fao.org/3/i3124e/i3124e.pdf

[10] Marinangeli CPF, House JD. Potential Impact of the Digestible Indispensable Amino Acid Score as a Measure of Protein Quality on Dietary Regulations and Health. Nutr Rev. 2017 Aug 1; 75(8): 658–667. doi: 10.1093/nutrit/nux025. PMCID: PMC5914309. [https://pubmed.ncbi.nlm.nih.gov/28969364/]

 

Copyright ©2023 BetterByDesign Nutrition Ltd.

LEGAL NOTICE: The contents of this blog, including text, images, and cited statistics, as well as all other material contained here (the ”content”), are for information purposes only.  The content is not intended to be a substitute for professional advice, medical diagnosis, and/or treatment, and is not suitable for self-administration without the knowledge of your physician and regular monitoring by your physician. Do not disregard medical advice and always consult your physician with any questions you may have regarding a medical condition or before implementing anything you have read or heard in our content.

 

 

 

Note: This article was originally posted on August 13, 2023, and was updated and reposted on November 25, 2025

Introduction

In the interest of time, many people throw a cup or more of fruit, some green veggies, and maybe some protein powder into a blender to make a smoothie for breakfast. But most people don’t realize how blending affects their blood sugar, gut microbiome, and how much food they eat.

Making a Smoothie

For people with challenges keeping blood sugar stable, or having pre-diabetes or diabetes, a smoothie made with fruit is something to reconsider. Pureed fruit affects blood sugar very differently from eating the same type and amount of fruit, whole and intact. 

Cellular versus Acellular Carbohydrate

Cellular carbohydrates come from whole, intact foods where the carbohydrate is still inside the cell wall. These foods take longer to digest and to be absorbed into the bloodstream than ground or pureed foods.

Carbohydrates that have been pureed, like fruit in a smoothie, or ground, like flour made from grain, are now outside their cell wall (acellular carbohydrate). As a result, pureed and ground foods are digested more quickly because the fiber that normally slows absorption is disrupted.

A Smoothie as “Pre-Chewed” Food

Most people think digestion begins in the stomach, but it starts in the mouth, when we chew food. As unappealing as it sounds, smoothies are “pre-chewed” food.

Drinking carbohydrates, rather than eating them, can result in spikes in blood sugar, affect gut bacteria, and can even impact how much food we eat due to hunger that follows a quick rise and then fall in blood sugar from the insulin response to quickly digested carbs.

Research shows that when fruit is pureed or juiced, blood glucose rises more rapidly and remains higher than when the same fruit is eaten whole [1]. This occurs because the blender has already broken down the cell walls, doing some of the work that chewing would normally do. For people with higher than ideal blood sugar, or pre-diabetes or diabetes, drinking a morning smoothie instead of eating the same foods intact can lead to a significantly different blood sugar response.

It is important to note that 60 g of whole fruit, 60 g of pureed fruit, and 60 g of juiced fruit all contain the same amount of carbohydrate and have similar Glycemic Index (GI) values. But the GI only tells us how quickly a food raises blood sugar, not how high blood sugar will go. Recent research also emphasizes that food structure, not just carbohydrate content, plays a critical role in blood glucose control [2].

Whole berries or fruit (cellular carbohydrate) are preserved within their cell walls until the digestive juices in the stomach begin to break them down. Once released, the carbohydrate is then absorbed mainly in the large intestine (colon).

Acellular carbohydrates, such as the fruit in smoothies, begin digestion in the small intestine rather than the colon. Early digestion of acellular carbohydrates can alter gut microbial fermentation and is thought to contribute to an imbalance in gut microbes (gut dysbiosis) or leaky gut (increased intestinal permeability) [3].

Drinking carbohydrate-containing foods, rather than eating them, may promote overconsumption and contribute to leptin resistance. Leptin is the hormone that signals us when we are hungry via a negative feedback loop. This feedback loop is thought to become dysregulated when we consume large amounts of acellular carbohydrates, such as pureed fruit. Leptin resistance occurs when the body fails to respond properly to leptin. Some research suggests that acellular carbohydrates alter leptin signaling, increase inflammation, and disturb the gut microbiota, which over time can blunt the body’s feedback loop that signals the brain that we are full [4].

Final Thoughts

Digestion begins in the mouth when we chew food, and there is a big difference between how whole, intact carbohydrates are absorbed and how blended smoothies are absorbed.

Smoothies are “pre-chewed food” that can disrupt blood sugar, alter our gut microbiome, and increase the total amount of food we consume.

Instead of throwing fruit, veggies, and protein powder into a blender, reach for half a cup of berries to put over top a cup of cottage cheese or plain Greek yogourt with a few spoons of hemp hearts, and grab a handful of snap peas or baby carrots. This quick, light meal that has the protein and leucine adults need to preserve their muscle mass — and there is no blender to clean afterwards!

More Info

I understand that not everyone who wants to eat healthy loves to cook. I am experienced at designing Meal Plans using readily available foods that require minimal preparation and little to no cooking. Whether you love to cook or prefer simplicity, I can help. You can learn more under the Services tab. 

To your good health, 

Joy

You can follow me on:

Twitter: https://twitter.com/jyerdile
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References

[1] Haber GB, Heaton KW, Murphy D, Legg NJ. Depletion and disruption of dietary fibre. Effects on satiety, plasma-glucose, and serum-insulin.Lancet. 1977 Oct 1;2(8040):679-82. doi: 10.1016/S0140-6736(77)90494-9. [https://pubmed.ncbi.nlm.nih.gov/71495/]

[2] Forde CG, Frank T, Leong C. Interrelations Between Food Form, Texture, and Matrix. Nutrients. 2022;14(4):731. doi:10.3390/nu14040731 [https://pmc.ncbi.nlm.nih.gov/articles/PMC9174310/]

[3] Stull AJ, Apolzan JW, Thalacker-Mercer AE, Iglay HB, Campbell WW. Liquid and solid meal replacement products differentially affect postprandial appetite and food intake in older adults. J Am Diet Assoc. 2008 Jul;108(7):1226-30. doi: 10.1016/j.jada.2008.04.014. PMID: 18589034; PMCID: PMC2556245. [https://pubmed.ncbi.nlm.nih.gov/18589034/]

[4] Spreadbury I. Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity. Diabetes Metab Syndr Obes. 2012;5:175-89. doi: 10.2147/DMSO.S33473. Epub 2012 Jul 6. PMID: 22826636; PMCID: PMC3402009. [https://pubmed.ncbi.nlm.nih.gov/22826636/]

 

 

Copyright ©2023 BetterByDesign Nutrition Ltd.

LEGAL NOTICE: The contents of this blog, including text, images, and cited statistics, as well as all other material contained here (the ”content”), are for information purposes only.  The content is not intended to be a substitute for professional advice, medical diagnosis and/or treatment, and is not suitable for self-administration without the knowledge of your physician and regular monitoring by your physician. Do not disregard medical advice and always consult your physician with any questions you may have regarding a medical condition or before implementing anything you have read or heard in our content.

 

 

Note: this article was originally posted on August 11, 2023, and has been updated and reposted on November 23, 2025.

Understanding Sarcopenia

The inability to retain muscle and strength associated with aging is called sarcopenia. Since adults lose approximately 1% of muscle mass each year after the age of thirty [1], knowing how to retain muscle as an adult is essential, even though the decline in strength normally only becomes noticeable by age fifty [2].

Muscle loss affects 5–13% of adults between sixty and seventy, and up to 50% of adults over eighty years of age have sarcopenia [2].

Not being able to retain muscle mass reduces activity levels, lowers quality of life, increases risk of falls, and worsens metabolic and bone health [3].

Most people have never paid close attention to the amount and quality of protein they eat, often choosing foods based on taste, cost, or ethical or religious reasons. These are important considerations, but they are not the only ones that matter.  As outlined in a previous article on protein for older adults, high-quality protein containing sufficient leucine is necessary for maintaining muscle [4], but not all protein foods are equal.

Amino acids are the building blocks of protein, including muscle. There are twenty amino acids, grouped as essential or non-essential. Essential amino acids, such as leucine, cannot be produced by the body in sufficient amounts and must be obtained through diet [5].

The leucine content of protein is critical because leucine triggers mTOR signaling in muscle, which stimulates muscle protein synthesis. For this reason, proteins consumed by older adults must contain enough leucine to support muscle maintenance and mobility[5].

Plant proteins generally contain lower levels of leucine compared to animal proteins [7]. Grains such as wheat contain less than 7% leucine [6], and even quinoa, considered a “complete protein,” contains only 4.5% leucine [6]. People who want a more plant-based diet may turn to legumes (“beans”), but these are usually incomplete proteins, meaning that they are missing some essential amino acids, and generally low in leucine. Even soybeans, a complete protein, contain only about 8% leucine [6].

Dietary recommendations for older adults emphasize a minimum of 20–30 g of protein per meal, with at least 2.3–3 g of leucine per meal, to effectively stimulate muscle protein synthesis [7][8].

To recover lost muscle mass, the recommended intake is 3 g of leucine at each of three meals, along with 25–30 g of protein per meal [7][8].

Protein Sources to Help Retain Muscle 

Animal proteins are highly bioavailable, complete proteins, and the richest sources of leucine. One cup of low-fat (1%) cottage cheese contains approximately 2.9 g of leucine, enough for a full meal. A cup of plain yogurt contains roughly 1.3 g, and a cup of Greek yogurt provides about 1.2 g. Only 3 oz (85 g) of ground beef or pork contains ~1.8 g, and the same amount of chicken breast provides about 2.25 g — all close to the per-meal leucine target for older adults [9].

Soybeans, a complete plant-based protein, contain only 0.28 g of leucine per half-cup, and firm tofu, a concentrated form of soy protein, provides approximately 0.73 g per 3 oz (85 g). To reach the minimum leucine threshold from firm tofu, an older adult would need to eat about ¾ pound, which may exceed their typical appetite [9].

Incomplete plant proteins, such as lentils, contain 0.7 g of leucine per half-cup, and black beans contain 0.61 g per half-cup. This means an older adult would need to consume more than 3 cups of lentils or black beans, or 5½ cups of chickpeas (0.42 g leucine per half-cup), to meet the minimum leucine requirement per meal [9]

Older adults who want to eat a more plant-based diet need to ensure they consume adequate, highly bioavailable protein rich in leucine to maintain their muscle mass. A practical approach is to “prioritize protein” at each meal [8].

[NOTE: A recent article explains differences in protein bioavailability between plant-based and animal-based sources.]

Prioritize Protein to Retain Muscle 

“Prioritizing protein” means first deciding which protein you will eat at a meal, and then building the rest of the meal around that. For older adults, the protein chosen should provide 25–30 g of highly bioavailable protein and 2.3–3 g of leucine per meal [7].

For breakfast, choosing high-leucine proteins such as 1 cup of cottage cheese or 1 cup of plain Greek yogurt will provide enough protein and leucine to meet the minimum target. In contrast, 2 eggs contain only 12 g of protein and ~1.2 g leucine, which is less than half of the recommended per-meal leucine for older adults [9].

For lunch, 4 oz (113 g) of canned tuna provides about 4 g of leucine and 21 g of protein, and 3 oz (85 g) of cooked chicken breast provides 2.4 g of leucine and 26.5 g of protein. To increase leucine further, you can add 1 oz (28 g) of pumpkin seeds (~0.7 g leucine) or 1 oz (28 g) of sunflower seeds (~0.46 g leucine) to a salad [9].

For dinner, steak is one of the richest sources of leucine, with 4 oz (113 g) providing ~3.4 g, although cost may be a consideration. More budget-friendly options for those who don’t avoid it for religious reasons would be 4 oz (113 g) of pork chops (~27 g protein, 2.5 g leucine) or 4 oz of ground beef (~16 g protein, 2.5 g leucine). If there is a slight shortfall, the protein content of the meal can be boosted by adding a small serving of Greek yogurt [9].

Final Thoughts…

The quality of life and overall health of older adults depend on staying active, which requires adequate muscle mass. Preventing sarcopenia requires consuming sufficient high-quality protein that contains all essential amino acids, including an adequate amount of leucine to stimulate muscle growth.

Since muscle mass is lost at an estimated rate of 1% per year after age thirty, the choice of protein at each meal is crucial for maintaining strength and mobility. 

For those who would like help, we offer the Healthy Aging Package, which helps ensure that middle-aged and older adults eat sufficient protein and leucine at each meal to maintain their muscle and bone mass as they age.

To your good health, 

Joy

You can follow me on:

Twitter: https://twitter.com/jyerdile
Facebook: https://www.facebook.com/BetterByDesignNutrition/

 

References

1. Keller K, Engelhardt M. Strength and muscle mass loss with aging process. Age and strength loss. Muscles, Ligaments and Tendons Journal. 2013;3(4):346-350. [https://pmc.ncbi.nlm.nih.gov/articles/PMC3940510/]
2. von Haehling S, Morley JE, Anker SD. An overview of sarcopenia: facts and numbers on prevalence and clinical impact. J Cachexia Sarcopenia Muscle. 2010 Dec;1(2):129–133. doi:10.1007/s13539-010-0014-2. Epub 2010 Dec 17. PMID: 21475695; PMCID: PMC3060646 [https://pmc.ncbi.nlm.nih.gov/articles/PMC3060646/]
3. Fielding RA, Vellas B, Evans WJ, et al. Sarcopenia: an emerging public health problem. StatPearls. 2021. [https://www.ncbi.nlm.nih.gov/books/NBK560813/]
4. Szwiega S, Pencharz PB, Rafii M, et al. Dietary leucine requirement of older men and women is higher than current recommendations. Am J Clin Nutr. 2020;113(2):410–419. doi:10.1093/ajcn/nqaa323 [https://pmc.ncbi.nlm.nih.gov/articles/PMC7851820/]
5. Cruz-Jentoft AJ, Baeyens JP, Bauer JM, et al. Sarcopenia in older people: European consensus on definition and diagnosis. J Gerontol A Biol Sci Med Sci. 2010;65A(3): 101–116. doi:10.1093/gerona/glp018 [https://pubmed.ncbi.nlm.nih.gov/20392703/]
6. Guo Y, Fu X, Hu Q, Chen L, Zuo H. The effect of leucine supplementation on sarcopenia-related measures in older adults: a systematic review and meta-analysis of 17 randomized controlled trials. Front Nutr. 2022;9:929891. doi:10.3389/fnut.2022.929891 [https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.929891/]
7. Tanaka T, Simonsick E, Ferrucci L, et al. Leucine intake and risk of impaired physical function and frailty in older adults. J Gerontol A Biol Sci Med Sci. 2022;78(2):241–247. doi:10.1093/gerona/glac219 [https://pubmed.ncbi.nlm.nih.gov/36107140/]
8. MDPI Nutrients. Beneficial effects of leucine supplementation on sarcopenia: a systematic review. Nutrients. 2019;11(10):2504. doi:10.3390/nu11102504 [https://www.mdpi.com/2072-6643/11/10/2504]
9. USDA FoodData Central. Leucine content of common foods. U.S. Department of Agriculture, Agricultural Research Service. https://fdc.nal.usda.gov. Accessed [November 23, 2025].

 

 

Copyright ©2023 BetterByDesign Nutrition Ltd.

LEGAL NOTICE: The contents of this blog, including text, images, and cited statistics, as well as all other material contained here (the ”content”), are for information purposes only.  The content is not intended to be a substitute for professional advice, medical diagnosis, and/or treatment, and is not suitable for self-administration without the knowledge of your physician and regular monitoring by your physician. Do not disregard medical advice and always consult your physician with any questions you may have regarding a medical condition or before implementing anything you have read or heard in our content.