How to Figure Out if Something is a Good Source of Protein?

December 22, 2025 •

4 min read

According to a 2022 review, eating adequate amounts of protein is crucial for maintaining muscle mass and promoting muscle growth during strength training. But with so many options available, how can you figure out if something is a good source of protein for your needs? The answer goes beyond simply checking the gram count on the nutrition label.

Quick Summary

Beyond grams per serving, a food's protein quality is determined by its amino acid profile, digestibility, and nutrient density. Understanding these factors allows for informed choices when comparing animal versus plant-based proteins and assessing processed foods. Key metrics include the DIAAS and a protein-to-calorie ratio, ensuring all essential amino acids are met through a varied diet.

Key Points

Amino Acid Profile is Key: A good protein source contains all nine essential amino acids; these are called complete proteins, common in animal products and some plants like soy and quinoa.
Consider the 'Protein Package': Evaluate the food's overall nutrient density and protein-to-calorie ratio, not just the grams of protein. Lean whole foods are generally superior to processed options.
Digestibility Matters: How well your body can absorb protein is critical. Newer scoring systems like the DIAAS are more accurate than older ones like PDCAAS in determining bioavailability.
Variety is Crucial for Plant-Based Diets: If following a vegetarian or vegan diet, consuming a diverse range of plant proteins throughout the day, like beans and grains, ensures you get all essential amino acids.
Prioritize Whole Foods: Focus on whole, minimally processed protein sources such as lean meats, fish, eggs, dairy, legumes, and nuts to get the best nutritional benefits.
Check the Label Smartly: Use the simple hack of multiplying protein grams by 10 and comparing it to the total calories to quickly judge protein density in packaged foods.
Match Protein Choice to Goals: Choose different protein sources based on your health objectives. For rapid muscle recovery, whey is excellent; for sustained release, casein is effective.

Beyond the Grams: What Makes a Protein Source 'Good'?

When you scan a nutrition label, the protein content is the most visible metric, but it only tells part of the story. A truly 'good' protein source is defined by three key factors: its amino acid profile, its digestibility, and its nutrient-to-calorie ratio. High-quality proteins are rich in essential amino acids (EAAs), are easily digested and absorbed by the body, and are typically part of a nutrient-dense food package.

The Amino Acid Profile: The Complete vs. Incomplete Debate

Proteins are composed of amino acids, and our bodies require a specific set of nine essential amino acids that they cannot produce on their own. A "complete" protein source provides all nine of these essential amino acids in adequate amounts.

Complete proteins: Mostly from animal sources like meat, eggs, and dairy, but also some plant-based foods like soy and quinoa.
Incomplete proteins: Most plant-based foods, such as beans, nuts, and grains, are typically low in one or more essential amino acids.
Complementary proteins: By combining different incomplete protein sources throughout the day, you can get all the essential amino acids you need. The myth that they must be eaten at the same meal has been debunked. For example, a meal of beans and rice forms a complete protein.

Digestibility and Absorption: The Role of Protein Scores

The body's ability to break down and absorb amino acids is a crucial aspect of a protein's quality. While older systems like the Protein Efficiency Ratio (PER) exist, the most modern and accurate evaluation is the Digestible Indispensable Amino Acid Score (DIAAS).

DIAAS: This method measures the ileal digestibility of each individual essential amino acid, providing a more precise score of how much protein is truly available for the body's use. Foods with a DIAAS score of 1.0 or higher are considered high quality.
PDCAAS (legacy score): The older Protein Digestibility Corrected Amino Acid Score (PDCAAS) is less accurate because it uses fecal digestibility and caps its scores at 1.0, failing to differentiate between proteins that are very high quality.

Nutrient-to-Calorie Ratio: Getting the Most Out of Your Macros

To assess the quality of a processed food or protein supplement, consider the protein-to-calorie ratio. This helps you determine if the product is genuinely protein-dense or simply high in overall calories. A common rule of thumb is that if the protein grams multiplied by 10 is equal to or greater than the total calories, it is a high-protein food.

Comparison of Common Protein Sources


Protein Source	Amino Acid Profile	DIAAS (Approximate)	Additional Benefits
Whey Protein Isolate	Complete	High (often >1.0)	Fast absorption, high leucine content, supports muscle recovery
Eggs	Complete	High (often >1.0)	Contains healthy fats, vitamins, and minerals; highly bioavailable
Lean Beef	Complete	High	Excellent source of iron, zinc, and B vitamins
Greek Yogurt	Complete	High	Good source of calcium, contains both whey (fast) and casein (slow) proteins
Soy (Tofu/Edamame)	Complete	High (around 1.0)	Versatile plant-based option, good source of iron and calcium
Lentils/Beans	Incomplete*	Lower	High in fiber, affordable, nutrient-dense
Quinoa	Complete	Good (around 0.8)	One of the few complete plant-based proteins, gluten-free
Almonds	Incomplete*	Lower	Good source of healthy fats, vitamin E, and fiber

*Can be combined with other plant foods to create a complete protein source over the course of the day.

Practical Steps to Identify a Good Protein Source

Check the nutrition label: Start by looking at the grams of protein per serving. While not the only factor, it’s the most basic indicator.
Evaluate the protein-to-calorie ratio: For packaged foods, use the "protein grams x 10 vs. calories" trick to quickly gauge protein density.
Prioritize whole foods: Whole foods like lean meats, eggs, dairy, and legumes offer a complete nutritional package, including vitamins, minerals, and fiber, in addition to protein.
Look for complete sources: While a varied diet provides all EAAs over time, incorporating single-source complete proteins like eggs, soy, or quinoa is efficient.
Choose wisely based on dietary goals: If you are vegetarian, vegan, or have specific health goals like building muscle or managing weight, you can tailor your protein choices. For muscle growth, higher DIAAS and leucine content can be beneficial.
Consider digestibility: While DIAAS scores aren't always on the label, a general rule is that animal proteins are more readily digestible than most plant proteins. Mixing sources, however, improves the overall quality of plant-based diets.

Conclusion

Choosing a good source of protein is a layered decision that moves beyond just counting grams. By considering the amino acid profile (complete vs. incomplete), digestibility (DIAAS), and overall nutrient package, you can make smarter food choices. Prioritizing a variety of whole food sources, both animal and plant-based, and being mindful of protein density in processed items will help you meet your nutritional needs effectively.

For more information on protein quality, consider visiting the Food and Agriculture Organization of the United Nations website.

Frequently Asked Questions

A complete protein contains all nine essential amino acids that the human body cannot produce on its own. Incomplete proteins are missing or low in one or more of these essential amino acids.

No, it's a common misconception. As long as you eat a variety of protein sources throughout the day, your body can pool amino acids to form complete proteins.

One simple trick is to multiply the grams of protein per serving by 10. If the resulting number is equal to or greater than the total calories per serving, the food is considered high in protein.

The Digestible Indispensable Amino Acid Score (DIAAS) is a newer protein quality measure that accurately assesses the digestibility of individual amino acids in the small intestine. It is considered more accurate than the older PDCAAS, which uses cruder fecal digestibility and caps scores at 1.0.

Animal-based proteins are typically complete and more easily digestible. However, many plant-based sources like soy and quinoa are complete, and a diverse diet of plant foods can provide all necessary amino acids. Plant-based options can also be lower in saturated fat and offer more fiber.

Excellent examples include eggs, lean beef, chicken breast, fish like salmon, Greek yogurt, and whey protein.

Good plant-based sources include soy products (tofu, tempeh), quinoa, beans, lentils, nuts, seeds, and pea protein powder.

Yes, cooking and processing methods can influence protein digestibility. For example, excessive heat can make some amino acids less available for absorption.