Do Beans and Oatmeal Make a Complete Protein?

December 11, 2025 •

3 min read

According to the Academy of Nutrition and Dietetics, the misconception that plant-based foods must be combined in the same meal to form a complete protein has been disproven for decades. The question is, do beans and oatmeal make a complete protein? Yes, they do, but not necessarily in the way people think.

Quick Summary

Beans and oatmeal, when combined, create a complete protein because beans provide lysine and oats supply methionine. You don't have to consume them in one meal. Eating a variety of plant-based foods throughout the day is sufficient to obtain all essential amino acids.

Key Points

Completeness through Combination: Beans and oatmeal complement each other's amino acid profiles, providing all nine essential amino acids when consumed within the same 24-hour period.
Dispelling the Myth: The idea that beans and oatmeal must be eaten together to form a complete protein is incorrect. The body's amino acid pool allows for variety throughout the day.
Rich in Fiber: Combining beans and oatmeal creates a meal rich in soluble and insoluble fiber, promoting heart health and improved digestion.
Nutrient Synergy: Beans provide essential lysine, while oats offer ample methionine, filling the nutritional gaps in each other's protein content.
Dietary Diversity: Focus on a varied whole-food, plant-based diet to meet all essential amino acid requirements.
Delicious Meal Combinations: Include beans and oats in meals like overnight oats with beans, bean burritos with oat tortillas, or oat groats with black beans.

Understanding Complete vs. Incomplete Proteins

Proteins are essential for human health and are key in building and repairing tissues. Proteins are made of amino acids. There are 20 amino acids, and nine are considered 'essential' because the body cannot produce them and must get them from the diet. A complete protein has all nine essential amino acids in sufficient quantities. Most animal products, such as meat, dairy, and eggs, are complete proteins.

Most plant-based foods are "incomplete proteins," as they are low in or missing one or more of these essential amino acids. For example, grains like oatmeal are typically low in lysine, while legumes like beans are low in methionine and tryptophan. By combining different plant foods with different amino acid profiles, you can get all the necessary building blocks for a complete protein.

The Complementary Protein Myth

The idea that plant-based eaters must carefully combine specific proteins at every meal was a popular guideline for years. Modern nutritional science has debunked this strict approach. The human body has an "amino acid pool" that can store and use essential amino acids consumed throughout the day. As long as you consume a variety of protein sources over a 24-hour period, the body will have everything it needs to form complete proteins. The strict meal-by-meal combining rule is unnecessary for those on a plant-based diet.

The Power Pairing: Beans and Oatmeal

Given that oats are a grain and beans are a legume, they fit the complementary protein model.

Oats: Excellent source of methionine, a sulfur-containing amino acid.
Beans: Abundant in lysine, an essential amino acid that is the limiting factor in most grains.

By consuming these two food groups within the same day, the body receives all nine essential amino acids. This pairing also has health benefits beyond protein synthesis, including high fiber content, which can improve heart health and digestion. The specific bean and oat varieties don't matter much as long as you maintain a varied intake.

Comparison of Amino Acid Profiles: Oats vs. Beans


Feature	Oats (Grain)	Beans (Legume)
Protein Type	Incomplete	Incomplete
Limiting Amino Acid	Lysine	Methionine
Complementary Amino Acid	High in Methionine	High in Lysine
Other Nutrients	Beta-glucan fiber, iron, magnesium	Dietary fiber, folate, potassium
Ideal Pairing	Combined with legumes like beans	Combined with grains like oatmeal

Practical Ways to Combine Beans and Oatmeal

For those looking to intentionally pair these complementary foods, there are many delicious and simple ways. A simple rule is to incorporate both a legume and a grain into your meals throughout the day.

Meal Ideas for Beans and Oats

For Breakfast: Overnight oats with mashed white beans mixed in, providing a boost of fiber and protein. Top with fruit and nuts.
For Lunch: A bean and oat flour tortilla burrito is an excellent option.
For Dinner: Serve black beans and brown rice alongside a topping of oat groats.
Snack Time: Enjoy hummus (made from chickpeas, a legume) with oat crackers or a handful of roasted chickpeas and oatmeal cookies.

The Importance of Dietary Variety

While the beans and oatmeal combination is a great way to ensure a complete protein, a varied diet is most important. Relying on a single complementary pair ignores the range of nutrients other plant foods offer. The key is to eat a variety of whole, unprocessed plant foods throughout the day, so you will naturally receive all the essential amino acids you need. The misconception that vegans and vegetarians are at risk of protein deficiency has been disproven, provided they are consuming enough calories.

Conclusion

Yes, beans and oatmeal make a complete protein, but the practice of requiring them in the same meal is no longer supported by nutritional science. Beans provide the lysine that oats lack, while oats supply the methionine that beans are limited in, forming a comprehensive amino acid profile when consumed within the same day. This plant-based pairing offers a healthy and fiber-rich way to meet protein needs. A diverse, whole-food plant-based diet will allow you to obtain all essential amino acids and experience the many health benefits that accompany it.

Authoritative research from sources such as the American Heart Association confirms that plant protein combining is not necessary meal-by-meal, so long as a varied intake is achieved throughout the day.

Frequently Asked Questions

Beans are categorized as an incomplete protein because they contain lower amounts of the essential amino acid methionine compared to animal sources. However, they are rich in lysine, which many grains lack.

Oatmeal is considered an incomplete protein because it is low in the essential amino acid lysine. It is, however, a good source of methionine, which complements the amino acid profile of beans.

No, you do not need to eat them in the same meal. The human body maintains an amino acid pool and can combine essential amino acids from different foods consumed throughout the day to form complete proteins.

The concept of complementary proteins is relevant in understanding how different plant foods offer a full range of amino acids. However, the original premise that you must combine them at each meal has been scientifically debunked.

Yes, a few plant-based foods are considered complete proteins, including quinoa, soy products (tofu, tempeh), chia seeds, and hemp seeds.

Other examples include rice and lentils, hummus (chickpeas and sesame seeds) with pita bread, and a peanut butter sandwich on whole wheat bread. Combining any legume with a grain, nut, or seed generally creates a complete protein.

For most people consuming enough calories from a varied, whole-food plant-based diet, protein deficiency is highly unlikely. If you have concerns, speaking with a registered dietitian can provide personalized guidance.