Which Lentils Have All Amino Acids? Dispelling the Complete Protein Myth

November 28, 2025 •

3 min read

While lentils are a nutritional powerhouse packed with protein and fiber, a common misconception is that a single type contains all the essential amino acids. This is a myth, as no one variety of lentil on its own provides a complete amino acid profile. However, this is easily remedied by understanding the concept of complementary proteins.

Quick Summary

Lentils are not complete proteins because they are low in certain amino acids like methionine. To get a complete amino acid profile, lentils should be combined with complementary foods, such as grains, throughout the day.

Key Points

Incomplete Protein: No single variety of lentil contains all nine essential amino acids in sufficient quantities, making them an incomplete protein.
Methionine Deficiency: Lentils are typically low in the sulfur-containing amino acids methionine and cysteine.
Complementary Pairing: To form a complete protein, lentils should be combined with other food sources like grains, which are high in methionine.
Same-Day Consumption: Complementary proteins do not need to be consumed in the same meal; your body can combine amino acids from different meals throughout the day.
Complete Plant Proteins: Quinoa and soy are examples of plant-based foods that are complete proteins on their own.
Enhanced Absorption: Soaking lentils and cooking with Vitamin C can improve digestibility and nutrient absorption.

Understanding the Myth of Lentil Complete Proteins

Protein is made up of 20 amino acids, 11 of which are non-essential (produced by the body) and 9 are essential (obtained through diet). A complete protein contains all nine essential amino acids in adequate amounts. While animal products are complete proteins, most plant-based foods, including all varieties of lentils, are incomplete proteins as they are low in one or more essential amino acids.

Lentils are particularly low in the sulfur-containing amino acids, methionine and cysteine. This means that consuming lentils alone will not provide a complete protein intake, a point often misunderstood by those following plant-based diets.

The Importance of Complementary Proteins

To obtain a complete protein from plant sources like lentils, combining them with other foods that provide the missing amino acids is necessary. These are called complementary proteins. It's important to note that these combinations don't need to happen in the same meal; the body can utilize amino acids from different foods consumed throughout the day. However, eating them together can be beneficial for specific goals.

Common Complementary Protein Combinations:

Lentils and Rice: A traditional pairing where rice supplies the methionine lacking in lentils, and lentils provide the lysine that rice is lower in.
Lentils and Whole Wheat Bread: The whole grains complement the amino acid profile of the lentils.
Lentils and Nuts/Seeds: Combining lentils with additions like sunflower seeds or walnuts creates a complete protein.

What About Other Plant-Based Complete Proteins?

While lentils need pairing, several other plant-based foods are complete proteins on their own:

Quinoa: A pseudocereal containing all nine essential amino acids.
Soy Products: Tofu, tempeh, and edamame are complete protein sources.
Buckwheat: Another pseudocereal that provides complete protein.
Hemp Seeds: Known for their nutritional value and status as a complete protein source.

Amino Acid Comparison: Lentils vs. Other Proteins

This table shows a typical amino acid comparison (in grams per 100g of dry protein) between lentils, a complete plant protein (soy), and an animal protein (chicken) to highlight the relative deficiency in lentils:


Amino Acid (g/100g)	Lentil Protein (Avg)	Soy Protein Isolate (Avg)	Chicken Breast (Avg)
Methionine	0.9	1.3	2.5
Cysteine	1.1	1.3	4.7
Tryptophan	0.8	1.4	0.35
Lysine	6.7	6.4	3.02
Leucine	7.2	7.5	2.72
Valine	4.1	4.4	1.73

Note: Values are averages and can vary. The table demonstrates lentils' lower levels of methionine and cysteine.

Can Combining All Lentils Create a Complete Protein?

No. Since all types of lentils (red, green, brown) have a similar deficiency in methionine and cysteine, mixing them won't provide a complete protein. The key is to combine lentils with different food groups, such as grains, nuts, or seeds.

How to Maximize Protein Absorption from Lentils

Preparation can also impact nutrient availability. Soaking lentils before cooking may improve digestibility. Cooking lentils with Vitamin C sources, like bell peppers or tomatoes, can enhance iron absorption.

Conclusion: Strategic Pairing for Optimal Nutrition

To summarize, no single lentil variety provides all essential amino acids, making them incomplete proteins individually. However, this is easily addressed by pairing lentils with complementary foods like grains, nuts, or seeds. This approach ensures a complete protein intake, allowing those on plant-based diets to fully benefit from lentils' nutritional value. Smart food combinations are crucial for unlocking the full potential of this versatile legume.

Here is a useful guide on complementary proteins from Real Simple.

Frequently Asked Questions

No, this is a common misconception. Lentils are an excellent source of protein for vegetarians and vegans. While they are not a complete protein on their own, they can be easily combined with other plant foods to provide all the essential amino acids needed.

Lentils are primarily low in methionine and cysteine, two sulfur-containing essential amino acids.

No, since all lentil varieties share a similar amino acid deficiency (low methionine), simply mixing different types will not create a complete protein. They must be combined with a complementary food source like grains or seeds.

You can make lentils a complete protein by pairing them with grains, nuts, or seeds. Classic examples include eating lentils with rice, or adding nuts and seeds to a lentil salad.

No, it is a common myth that complementary proteins must be consumed in the same meal. Your body maintains a pool of amino acids, and as long as you eat a varied diet throughout the day, your body can create complete proteins.

A classic example is a lentil and rice pilaf, a dish where the amino acid profile of the rice complements that of the lentils to create a complete protein. Another option is a lentil soup served with whole-grain bread.

Yes, some plant-based foods are considered complete proteins, including quinoa, soybeans (and products like tofu and tempeh), hemp seeds, and buckwheat.