Understanding Protein: Bioavailability, Supplements, & Enhancing Intake
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In last week’s article, I explored the crucial role protein plays in supporting our health as we age—particularly its impact on muscle preservation, immune function, and overall vitality. I also touched on the challenges of meeting protein needs from plant-based sources, especially when it comes to getting enough leucine, an amino acid essential for muscle maintenance. For many, this leads to an unintended increase in carbohydrate consumption as they try to satisfy hunger and energy needs, creating a dietary imbalance that can be hard to navigate.
In this week’s article, I’m going to build on that conversation by exploring a concept known as the Protein Leverage Hypothesis. This theory suggests that our bodies may be hardwired to prioritize protein intake above all other nutrients. We’ll explore how this hypothesis relates to modern dietary trends and delve into bioavailability—the key factor that determines how effectively our bodies utilize the protein we consume. Additionally, I’ll guide you through calculating your individual protein needs. We’ll focus on ensuring you’re getting all nine essential amino acids, with a special emphasis on meeting your leucine requirements in each meal to effectively stimulate muscle protein synthesis.
Finally, I’ll walk you through the world of protein supplements, from whey to pea protein, and help you understand when and how Branched-Chain Amino Acids (BCAAs) and free amino acids can support muscle recovery and overall health. Whether you’re a vegetarian, pescatarian, or omnivore, understanding these concepts will help you make better, more informed choices about your protein intake. By the end of this article, you’ll have the tools to fine-tune your protein consumption, ensuring that it supports your goals, whether that’s preserving muscle, supporting immune function, or simply improving your overall energy levels.
The Protein Leverage Hypothesis
The Protein Leverage Hypothesis suggests that our bodies instinctively prioritize protein, driving us to consume more food until our protein needs are met. When those needs are not fulfilled—particularly from sources with lower bioavailability—our bodies compensate by increasing the intake of other macronutrients, mainly carbohydrates and fats.
To better understand this, consider the experience of eating a steak or a piece of salmon. It’s difficult to overeat these protein-rich foods. Your body reaches fullness quickly because it’s receiving the protein it craves. The dense, high-quality protein from animal sources satisfies hunger in a way that carbohydrates alone cannot. That’s why we tend to stop eating when we've had enough—our bodies signal satisfaction once protein needs are met.
In contrast, plant-based meals, though rich in fiber, vitamins, and minerals, often fall short in protein or offer protein that is less bioavailable. Even a satisfying plant-based meal may leave you with a subtle sense that something is lacking—not due to its volume, but because it hasn’t met your body’s protein needs. This unmet need can drive cravings for calorie-dense foods, such as starches, fats, and processed snacks, leading many on plant-based diets to unknowingly consume excess calories in an effort to fill the gap.
Ancestral Roots, Modern Consequences
Although we live in a modern, food-abundant world, our physiology is still adapted to the conditions of our hunter-gatherer ancestors. Genetic and anthropological research shows that more than 99% of our evolutionary development occurred before the rise of agriculture, and our genome has changed relatively little since. In this context, we remain biologically tuned to a world in which energy was limited, and protein—critical for survival—was not always easy to come by.
In that ancestral environment, protein was the most precious macronutrient. It supported immune function, muscle repair, reproduction, and overall vitality. Because it wasn’t always available in sufficient quantities, our bodies evolved a regulatory mechanism that prioritized protein acquisition. When intake fell short, we instinctively consumed more food—particularly calorie-dense sources like fats and carbohydrates—until our protein needs were satisfied. This is the basis of the Protein Leverage Hypothesis, originally proposed by Simpson and Raubenheimer, and observed across a variety of species, including humans.
In the modern food environment, this once-adaptive trait has become a liability. Highly processed foods—low in protein but rich in refined sugars, starches, and industrial fats—are now abundant. Many people, still governed by this protein-seeking drive, consume excess calories without ever meeting their body’s actual nutritional needs. This mismatch between our biology and our environment may help explain the rise of obesity, metabolic syndrome, insulin resistance, and cardiovascular disease.
The consequences are even more pronounced with age. As the body’s efficiency in metabolizing protein declines—a phenomenon known as anabolic resistance—the need for high-quality, bioavailable protein becomes greater.
Protein Bioavailability: Why It Matters
When it comes to protein, bioavailability is everything—it’s not just about how much protein you eat, but how well your body can use it. Many people think that eating 20 grams of protein means their body gets 20 grams of protein, but that’s not always the case! Protein bioavailability is about how easily your body can digest, absorb, and use the protein you consume. Unfortunately, food labels don’t show you this.
What Is Protein Bioavailability?
Protein bioavailability is a measure of how well your body can digest, absorb, and use the protein you consume. Animal proteins—like meat, eggs, and dairy—are considered highly bioavailable because they contain all nine essential amino acids in the right proportions and are structurally similar to the proteins in our own bodies, making them easy to break down and use for muscle repair, immune support, and other vital functions.
In contrast, plant proteins often have lower bioavailability. They may be missing one or more essential amino acids (making them “incomplete”), and they contain natural anti-nutrient compounds like fiber, phytates, oxalates, and lectins that can interfere with nutrient absorption. As a result, your body absorbs and uses less of the protein from plant sources, even if the total grams look the same on a nutrition label.
What Is DIAAS and Why Should You Care?
To measure how bioavailable a protein is, we use DIAAS (Digestible Indispensable Amino Acid Score). It’s the best way to see how much of the protein your body can actually use.
Here’s why you should care: Even though a food label might say “20 grams of protein,” if it comes from a plant source like lentils, your body may only be able to use about 11 grams of that protein. DIAAS tells you exactly how much protein is useful. And plant-based protein often doesn’t score well.
Animal vs. Plant Proteins: The Key Differences
Animal proteins are highly bioavailable and score well on the DIAAS scale. For example:
🥚 Eggs: DIAAS ~1.13 (almost all the protein is usable)
🐟 Fish: DIAAS ~1.08
🥩 Beef: DIAAS ~1.10
Plant proteins, on the other hand, tend to score much lower, meaning your body doesn’t get as much out of them:
🫘 Lentils: DIAAS ~0.58 (only about 58% of the protein is usable)
🌾 Rice protein: DIAAS ~0.37–0.42
🌱 Soy protein: DIAAS ~0.84
🌰 Pea protein: DIAAS ~0.62
These scores mean that when you eat these plant-based proteins, you’re not getting anywhere near as much usable protein as you think you are!
The Food Label Problem: Lying by Omission
Protein content on food labels is one of the great nutritional sleights of hand. “20 grams per serving” may sound substantial—but it tells you nothing about how much your body can actually absorb and utilize. This omission is misleading, particularly for those following plant-based diets.
As DIAAS scoring demonstrates, most plant proteins are far less bioavailable than animal-based ones, yet this crucial information is completely absent from food labels.
This lack of transparency leaves consumers with a false sense of security, believing they are meeting their protein needs when, in reality, their bodies are not absorbing the nutrients they think they are. The result? Nutritional deficiencies that can undermine health over time—muscle loss, energy depletion, and metabolic imbalances.
The time has come for a fundamental overhaul of food labeling. Labels must go beyond simply listing protein grams and reflect the true biological reality: how complete, digestible, and effective that protein really is. People deserve to know the full picture, not a curated narrative. Food companies must provide clear, science-backed information that allows consumers to make truly informed decisions about their health.
A Day of High Protein Eating: How to Calculate Your Needs
Regardless of dietary preference, it's essential for everyone to prioritize complete and bioavailable proteins. While animal-based proteins naturally fulfill these needs, vegetarians and vegans must thoughtfully combine plant-based sources to ensure they meet these requirements. Admittedly, paying attention to protein intake and learning how to calculate it may feel overwhelming at first, but once you become familiar with the process, it will soon feel like second nature.
Step 1: Determine Your Protein Requirements Based on Ideal Body Weight
To calculate exactly how much protein you need per day, start by determining your ideal body weight in Kilograms (i.e. your healthy target weight). Protein needs also vary depending on your age and lifestyle, with older adults and individuals recovering from injury or illness requiring more protein than younger people.
▶ For younger adults (18-35 years):
Aim for 0.8 to 1 gram per kilogram of ideal body weight.
Example: If your ideal body weight is 70 kg (154 lbs), your protein intake should be 56–70 grams.
▶ For older adults (35+ years):
As we age, protein requirements increase to help preserve muscle mass and support metabolic function. Aim for 1.2 to 1.6 grams per kilogram of ideal body weight.
Example: For a 70 kg person, this would mean 84–112 grams of protein daily.
▶ For athletes or those recovering from illness/injury:
Protein needs increase for those engaging in intense physical activity or recovering from injury or illness. These individuals should aim for 1.5 to 2 grams per kilogram of ideal body weight.
Example: For a 70 kg person, this would mean 105 to 140 grams of protein daily.
Step 2: Factor in Leucine for Optimal Muscle Health
As we explored in last week's article, ensuring each meal contains at least 2 grams of leucine is crucial for effectively stimulating muscle protein synthesis. Leucine plays a pivotal role in metabolic health and recovery. I encourage you to familiarize yourself with the leucine content of the foods you regularly consume. Animal-based proteins—such as eggs, meat, fish, and dairy—naturally provide higher levels of leucine, making them particularly valuable for older adults, athletes, and those recovering from illness.
Step 3: Spread Protein Across Meals
For optimal muscle maintenance and overall health, try to distribute your protein intake evenly across your meals. Ideally, each meal should contain at least 20–30 grams of high-quality protein. This helps ensure that your body is efficiently using the protein you consume for muscle repair and other bodily functions.
💡 Fun Fact:
The global protein powder market is projected to reach over $32 billion by 2027—but most people still aren't sure which type is right for their body, goals, or sensitivities. Personalized guidance makes all the difference.
Protein Supplements: Bioavailability, Tolerance, and Quality
When it comes to meeting your protein needs, supplements can offer a practical solution, especially for those with increased requirements, limited dietary preferences, or busy lifestyles. Not all protein powders are created equally, and choosing the right one is key to ensuring that your body gets the most benefit. Here’s an overview of some of the most common protein supplements:
Whey
Whey protein is a high-quality, complete protein with exceptional bioavailability, meaning it’s easily absorbed and utilized by the body. It’s particularly rich in leucine. However, while it is highly beneficial, some people experience adverse reactions, especially those who are lactose intolerant, or histamine intolerance, which may cause symptoms such as sneezing, headaches, or skin irritation.
If you choose whey protein, it's crucial to opt for organic, grass-fed whey protein when possible. Non-organic, conventionally produced whey can come from cows treated with growth hormones and antibiotics, which may have negative long-term effects on health. Organic, grass-fed whey offers a cleaner, more natural source of protein, free from harmful chemicals and better for overall health.
Egg White
Egg white protein is another excellent source of complete, highly bioavailable protein. It is particularly low in fat and calories, making it ideal for supporting muscle growth without excess calories. However, it’s important to be cautious of egg allergies, which can limit this option. As with whey, when choosing egg white protein, prioritize organic or pasture-raised eggs to avoid eggs from chickens that may have been exposed to antibiotics or synthetic hormones. Organic eggs come from hens raised on a natural, omnivorous diet (chickens are not vegetarian!) and free from harmful chemicals, making them a healthier choice for those seeking a high-quality protein source.
Hydrolyzed Beef
Hydrolyzed beef protein is made by breaking down beef into smaller, more easily digestible peptides. This type of protein offers good bioavailability and can be a solid choice for those looking for a non-dairy, non-plant protein. However, similar to whey protein, hydrolyzed beef protein can cause histamine-related issues for those who are sensitive. Additionally, the taste and texture might be less appealing for some. Like with any protein source, it’s important to consider individual tolerance and choose a supplement that works for you.
Collagen
Collagen supplements have garnered significant attention for their potential benefits to skin elasticity, joint integrity, and even muscle maintenance—particularly when paired with resistance training. Emerging research also highlights improvements in skin hydration and bone density, especially in aging populations. However, it’s important to recognize that collagen is not a complete protein; it lacks several essential amino acids and therefore cannot replace high-quality sources like meat, eggs, dairy, or fish. Additionally, because collagen is rich in hydroxyproline, it may be metabolized into oxalates in some individuals. High oxalate loads can deplete sulfur, a mineral that is essential for joint health, meaning that for some, excess collagen may ironically work against its intended purpose. When used thoughtfully, collagen can be a valuable addition to a nutrient-dense diet, but—much like plant protein—it should be viewed as a complement, not a substitute, for complete, bioavailable protein.
Soy Protein Isolate
Soy protein isolate is a complete protein, meaning it contains all nine essential amino acids. It’s a go-to option for vegans and vegetarians, providing a plant-based alternative to animal proteins. However, not all soy protein is created equally. Much of the soy on the market is genetically modified (GMO). Therefore, when choosing soy protein, it’s crucial to select organic.
In addition, soy is known to contain high levels of oxalates, which can be problematic for sensitive individuals. Furthermore, soy contains phytoestrogens, plant compounds that mimic estrogen in the body. While the effects of phytoestrogens on human health are still debated, some studies suggest that they could have a disruptive effect on hormone balance, particularly in highly concentrated forms such as protein powders.
Pea
Pea protein is a popular hypoallergenic, easily digestible plant-based option, often favored for those avoiding dairy or soy. However, it has lower bioavailability than animal-based proteins, meaning it is not absorbed and utilized as efficiently by the body. One of its main limitations is its incomplete amino acid profile, particularly its low leucine content. Relying too heavily on pea protein will hinder your ability to build or maintain muscle mass.
Another concern is heavy metal contamination. Studies, including one by the Clean Label Project in 2018, have found that many plant-based protein powders, including those made from peas, can contain toxic metals such as lead, cadmium, and arsenic. These contaminants can pose serious health risks, particularly with long-term exposure. Choosing reputable brands that undergo third-party testing is essential to ensure the safety and purity of these products.
Hemp
Hemp protein is another plant-based option known for its fiber and healthy lipid profile. While it offers nutritional benefits, its lower bioavailability limits its effectiveness. Though hemp contains all nine essential amino acids, its leucine content is insufficient to maximize muscle protein synthesis, which makes it sub-optimal for those focused on muscle growth or repair.
Hemp protein also shares concerns with pea protein regarding heavy metal contamination. Hemp plants, due to their nature, can absorb toxins from the soil, including cadmium, lead, and arsenic. As with pea protein, it's crucial to select hemp protein products that have undergone third-party testing for contaminants to ensure the product’s purity and safety.
BCAAs & Free Amino Acids: What You Need to Know
BCAAs (branched-chain amino acids)—specifically leucine, isoleucine, and valine—are a subset of essential amino acids that are directly involved in muscle protein synthesis. This makes BCAAs particularly useful for athletes, bodybuilders, or anyone looking to optimize recovery and muscle growth. They can help prevent muscle breakdown during intense exercise, and there's strong evidence supporting their role in reducing muscle soreness (delayed onset muscle soreness, or DOMS) after workouts. For older adults, BCAAs can be beneficial in combating sarcopenia (age-related muscle loss) by supporting muscle maintenance and function, which is crucial for preserving mobility and strength.
What makes BCAAs stand out is their cleaner composition compared to typical protein powders. BCAAs are often sold as pure, isolated amino acids, without the added fillers or artificial ingredients that can be present in many protein powders.
On the other hand, free amino acids are a more comprehensive supplement, providing the full spectrum of essential amino acids required for various bodily functions beyond muscle building. While BCAAs focus primarily on muscle repair and recovery, free amino acids are absorbed and utilized by the body for a broader range of needs, including immune function, enzyme production, hormone regulation, and tissue repair. They can be especially beneficial for individuals with dietary restrictions—such as vegetarians, vegans, or those with food intolerances—who may struggle to obtain a complete amino acid profile from diet alone. Unlike BCAAs, which focus on muscle, free amino acids help maintain overall protein balance in the body, making them particularly helpful for people looking to support immune health, recovery from injury, or other repair processes.
Similar to BCAAs, free amino acids are often purer than many protein powders, providing a direct and highly bioavailable source of the essential building blocks your body requires—free from the added sugars, calories, and fillers commonly found in some protein supplements.
From Knowledge to Action: Let’s Build Your Health Strategy Together
Throughout this article, we explored the pivotal role protein plays in maintaining health, especially as we age. We looked at how protein supports muscle preservation, immune function, and energy, and examined the Protein Leverage Hypothesis, which suggests our bodies are naturally driven to prioritize protein intake. We discussed the challenges of meeting protein needs—particularly on plant-based diets—and why bioavailability matters when choosing your protein sources. From understanding DIAAS scores to calculating your individual protein requirements, we covered how to ensure you're getting enough of the right kind of protein—especially leucine—to support optimal muscle synthesis and vitality. Finally, we explored various protein supplements, their pros and cons, and how to make informed choices based on your personal health needs.
If you're reading this and feeling a bit overwhelmed—or unsure how to apply this information to your unique biology, health history, or lifestyle—you’re not alone. Protein needs can be deeply individual, and if you’re dealing with immune challenges, frequent infections, gut issues, food sensitivities, or lingering fatigue, it’s essential to look beyond the surface and understand the full picture.
As a functional nutrition practitioner, I specialize in helping people uncover the root causes behind their health concerns and create sustainable, personalized strategies to restore balance and resilience. If you’re someone who has struggled with a restrictive diet, or you’re an ex-vegan or vegetarian considering the reintroduction of animal foods and looking for a thoughtful, supportive approach—I’d love to help!
✨ The Better Health Bundle is a great place to start. It includes a consultation, a review of one functional lab test of your choice, a comprehensive blood panel analysis, and an in-depth look at your medical history and current symptoms. It’s a powerful, one-time deep dive for those who want clarity and direction without committing to a long-term program.
🌿 For those who are ready to go further and truly regain their vitality, I offer Reclaim Your Resilience—a high-touch, 4-month coaching program designed to help you uncover hidden imbalances, implement practical changes, and restore lasting health. This program is ideal for those who are tired of quick fixes and are ready to invest in a transformative journey toward greater energy, immunity, and clarity.
Whether you're just getting started or ready to go all in, I'm here to meet you exactly where you are—with compassion, clinical insight, and a plan that’s tailored to you. Contact me here to learn more and book your session.
Let’s build your foundation for lasting health—together.
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Volpi, E., Campbell, W. W., Dwyer, J. T., et al. (2013). Is the optimal level of protein intake for older adults greater than the Recommended Dietary Allowance? The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 68(6), 677–681.
Moore, D. R., Churchward-Venne, T. A., Witard, O., et al. (2015). Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 70(1), 57–62.
van Vliet, S., Burd, N. A., & van Loon, L. J. C. (2015). The skeletal muscle anabolic response to plant- versus animal-based protein consumption. The Journal of Nutrition, 145(9), 1981–1991.
Clean Label Project. (2018). Protein Powder: Heavy Metals Report.
Rutherfurd, S. M., Fanning, A. C., Miller, B. J., & Moughan, P. J. (2015). Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. The Journal of Nutrition, 145(2), 372–379.
Wolfe, R. R. (2017). Branched-chain amino acids and muscle protein synthesis in humans: Myth or reality? Journal of the International Society of Sports Nutrition, 14(1), 30.
