Is Tomato a Complete Protein? Demystifying Plant-Based Nutrition

January 7, 2026 •

4 min read

While tomatoes contain protein, they are not a complete protein source, as they lack sufficient amounts of certain essential amino acids. A complete protein must contain all nine essential amino acids in adequate proportions for human bodily needs.

Quick Summary

This article explains why a tomato is not a complete protein and details the essential and non-essential amino acids it contains. It clarifies how to combine plant-based foods to create a balanced amino acid profile and covers the nutritional benefits beyond just protein.

Key Points

Incomplete Protein: A tomato is not a complete protein source because it is low in certain essential amino acids.
Low Protein Content: Tomatoes contain a low amount of total protein, typically less than 1 gram per 100g.
Complementary Combining: Pairing tomatoes with other plant foods like legumes or grains can help create a complete protein profile over the course of a day.
Rich in Antioxidants: Tomatoes are an excellent source of lycopene, a potent antioxidant linked to reduced risk of heart disease and certain cancers.
Full of Vitamins and Minerals: They are packed with beneficial nutrients, including Vitamin C, Vitamin K1, potassium, and folate.
Varied Diet is Key: For plant-based diets, consuming a wide variety of foods throughout the day is the modern recommendation for ensuring all essential amino acids are met.
Cooking Increases Lycopene: The body can better absorb lycopene from cooked tomatoes, especially when consumed with a source of fat.

Understanding Complete vs. Incomplete Proteins

For a food to be considered a complete protein, it must contain all nine essential amino acids in sufficient quantities. Essential amino acids are those our bodies cannot synthesize on their own and must obtain from food. Animal products like meat, eggs, and dairy are classic examples of complete proteins. In contrast, most plant-based foods are considered incomplete proteins because they contain all nine essential amino acids, but are low in one or more of them. This was once a source of concern for people on plant-based diets, but modern nutritional understanding shows that a varied diet throughout the day provides all the necessary amino acids, without needing to combine them in every meal.

The Amino Acid Profile of a Tomato

Tomatoes, while a healthy and nutritious food, are not a significant source of protein, containing only about 0.9 grams per 100 grams. Furthermore, they are an incomplete protein. While research shows tomatoes contain essential amino acids, they are deficient in several, including methionine, isoleucine, leucine, lysine, and valine. The total amino acid content is also relatively low. However, this does not diminish their overall nutritional value. The human body is highly efficient at combining amino acids from various sources eaten throughout the day to meet its protein needs.

Combining Tomatoes with Other Plant Foods

For individuals on a plant-based diet, pairing tomatoes with other complementary foods can easily create a complete protein meal. This practice of combining plant foods, historically thought to be necessary at every meal, is now understood to be effective over the course of the day.

Tomatoes and Lentils: A lentil soup with a tomato base is a classic combination. Lentils are rich in some amino acids that tomatoes lack, and vice versa. This pairing provides a full spectrum of essential amino acids.
Tomatoes with Rice and Beans: A staple in many cuisines, the combination of rice and beans creates a complete protein. Adding tomatoes not only enhances flavor but also provides vitamins and antioxidants.
Tomatoes with Nuts and Seeds: A salad with tomatoes, paired with nuts and seeds, is a simple way to combine different amino acid profiles. Adding pumpkin seeds, for instance, can help fill in gaps.

Beyond Protein: The Nutritional Power of Tomatoes

Tomatoes offer a host of other nutritional benefits that are just as important as their protein content. They are a valuable source of essential vitamins, minerals, and antioxidants.

Antioxidant Powerhouse: Tomatoes are a rich source of lycopene, a potent antioxidant responsible for their red color. Lycopene has been linked to a reduced risk of certain cancers and improved heart health. Cooking tomatoes and consuming them with a source of fat, like olive oil, enhances the body's absorption of lycopene.
Rich in Vitamins: Tomatoes are excellent sources of Vitamin C, Vitamin K1, potassium, and folate. These vitamins and minerals play crucial roles in blood clotting, bone health, tissue growth, and cell function.
Fiber Content: Tomatoes contain both soluble and insoluble fiber, which is important for digestive health and can help prevent constipation.

Comparison: Tomatoes vs. Complete Plant-Based Proteins


Feature	Tomato (Incomplete Protein)	Quinoa (Complete Protein)	Tofu (Complete Protein)
Protein per 100g (Approx.)	0.9 g	4.4 g	8-10 g
Complete Amino Acid Profile?	No (deficient in several essential AAs)	Yes	Yes
Primary Function	Antioxidants (lycopene), Vitamins, Minerals	Protein, Iron, Magnesium, Fiber	Protein, Calcium, Iron
Preparation	Can be eaten raw or cooked, often part of dishes	Cooked like a grain, versatile for salads, bowls	Versatile ingredient for baking, grilling, sautéing
Best Paired With...	Nuts, seeds, legumes, whole grains to complete protein	Any other foods, complements a variety of flavors	Grains, vegetables, other ingredients

Conclusion: The Role of Tomatoes in a Balanced Diet

While the answer to "Is tomato a complete protein?" is definitively no, this fact should not diminish its place in a healthy diet. Tomatoes are a powerhouse of essential vitamins, minerals, and powerful antioxidants, especially lycopene. The concept of complementing proteins over the course of a day, rather than in a single meal, makes it easy for those on plant-based diets to meet their protein requirements. Tomatoes, combined with a variety of other protein-rich plant foods like legumes, grains, and nuts, provide all the essential amino acids needed for a complete and balanced nutritional intake. Incorporating them into your meals adds not only flavor but a substantial boost of vital nutrients that support overall health, from heart function to fighting free radicals.

Here is some guidance on building healthy vegetarian meals from the Physicians Committee for Responsible Medicine.

Frequently Asked Questions

No, it is a misconception that all complementary proteins must be eaten in the same meal. The body can effectively combine amino acids from various foods eaten throughout the day to meet its protein needs.

A complete protein is a food that contains all nine essential amino acids that the human body cannot produce on its own. Animal-based products are typically complete proteins, while most plant-based foods are considered incomplete.

A vegan or vegetarian can ensure they get all essential amino acids by eating a varied diet that includes a wide range of plant-based protein sources, such as legumes, whole grains, nuts, and seeds throughout the day.

Some notable plant-based foods that are complete proteins include quinoa, soy products (like tofu, tempeh, and edamame), buckwheat, and hemp seeds.

Processing, such as cooking tomatoes into sauces or paste, concentrates the protein and other nutrients. For example, tomato puree has significantly more protein per cup than a raw tomato.

While small in quantity, the protein in tomatoes is beneficial as part of a balanced diet. Its greatest value, however, is in its contribution to the body's overall pool of amino acids when combined with other plant foods.

Tomatoes are a fantastic source of antioxidants, particularly lycopene, which protects against cellular damage. They are also rich in vitamins C and K, potassium, and fiber.