Is Soy a Carbohydrate, Lipid, or Protein?

November 12, 2025 •

2 min read

According to the USDA, 100 grams of raw mature soybeans contains 36.5 grams of protein, 30.2 grams of carbohydrates, and 19.9 grams of fat. This dispels the myth that soy can be neatly categorized into a single macronutrient group, as it is a rich source of all three: protein, lipids, and carbohydrates.

Quick Summary

Soybeans are not a single macronutrient but contain significant amounts of protein, lipids (fats), and carbohydrates, making them a well-rounded food. Their nutritional composition varies based on processing, offering a versatile dietary source of high-quality protein, fiber, and healthy fats.

Key Points

Complete Protein: Soybeans are one of the few plant-based foods that provide a complete protein, containing all nine essential amino acids.
Rich in Healthy Fats: Classified as an oilseed, soy contains significant amounts of healthy polyunsaturated and monounsaturated fats, including omega-3s.
Source of Fiber: Whole soybeans are a good source of dietary fiber, which aids digestion and promotes gut health.
Contains All Macronutrients: Soy is not just one macronutrient but a balanced source of protein, lipids, and carbohydrates, making it a well-rounded food.
Health Benefits: The nutritional profile of soy, including its phytoestrogens, isoflavones, and fiber, is associated with benefits such as lower cholesterol and heart health.
Versatile Processing: The ratio of macronutrients can change based on the soy product, from whole beans to highly refined soy protein isolate.

The Multifaceted Nutritional Profile of Soybeans

Soybeans are a versatile legume known for their diverse nutritional profile, offering a balanced mix of proteins, fats, and carbohydrates, along with essential vitamins and minerals. Understanding this composition is important for those incorporating soy into their diet, particularly in plant-based eating.

Soy as a Complete Protein Source

Soy stands out as a high-quality protein source, considered complete because it contains all nine essential amino acids. The protein content typically ranges from 36–56% of their dry weight. Soy protein is available in various forms with differing protein concentrations:

Soy Flour: Used as a protein fortifier in baking.
Soy Protein Concentrate: Contains 65-70% protein after removing water-soluble carbohydrates.
Soy Protein Isolate: A highly refined form with over 90% protein, used in supplements and dairy alternatives.

Soy as a Source of Lipids and Essential Fatty Acids

As an oilseed, soybeans contain about 18% fat by dry weight. This fat is primarily composed of heart-healthy polyunsaturated and monounsaturated fatty acids. Soybeans are rich in linoleic acid (an omega-6) and alpha-linolenic acid (an omega-3) and are low in saturated fat and cholesterol-free compared to many animal products.

Soy and Its Carbohydrate Content

Approximately 30% of the dry weight of soybeans is carbohydrates. A significant portion is dietary fiber, beneficial for digestive and gut health. Soybeans also contain oligosaccharides like raffinose and stachyose, which can act as prebiotics but may cause gas in some individuals. Whole soybeans have a low glycemic index.

Nutritional Comparison: Whole Soybeans vs. Soy Protein Isolate

Processing significantly alters the macronutrient profile. The table below compares the approximate nutritional content of 100 grams of raw whole soybeans and soy protein isolate.


Nutrient	Raw Whole Soybeans	Soy Protein Isolate
Protein	36.5 g	>90 g
Fat	19.9 g	<1 g
Carbohydrate	30.2 g	<10 g
Fiber	9.3 g	0 g
Minerals	Present	Reduced

This shows how isolate processing increases protein concentration while reducing fats and carbohydrates.

Bioactive Compounds in Soy

Soybeans contain beneficial bioactive compounds like isoflavones, which are linked to reducing the risk of heart disease and certain cancers. Saponins may help lower cholesterol, and lunasin is being studied for potential cancer-preventive properties.

The Versatility of Soy

Soy's diverse composition allows for wide use in food, from whole edamame beans to refined protein isolates. It's a key protein source in vegan and vegetarian diets, providing essential protein, healthy fats, and fiber. Processing can also reduce antinutritional factors. For more on bioactive compounds, refer to publications from IntechOpen.

Conclusion

In summary, classifying soy solely as a carbohydrate, lipid, or protein is inaccurate. Soybeans are a rich source of all three macronutrients, serving as a high-quality complete protein source, providing healthy polyunsaturated fats, and offering beneficial fiber and carbohydrates. The specific macronutrient balance varies depending on the processing of soy products.

Frequently Asked Questions

Yes, soy is an excellent and versatile protein source for vegetarian and vegan diets because it is a complete protein, containing all nine essential amino acids necessary for the body.

Yes, soybeans contain carbohydrates. While known for its protein, a significant portion of the soybean's composition is made up of carbohydrates, including dietary fiber.

The fat in soybeans is primarily healthy, unsaturated fat. It is particularly rich in polyunsaturated fats like linoleic acid and alpha-linolenic acid, and contains very little saturated fat.

Soy protein concentrate typically contains 65-70% protein by weight, while soy protein isolate is more refined and contains over 90% protein by weight, with most of the fats and carbohydrates removed.

Yes, consuming soy foods as part of a balanced diet may be beneficial for heart health. Soy protein has been linked to lowering LDL ('bad') cholesterol levels and improving other cardiovascular disease risk factors.

Some people may experience gas and bloating from soy due to its oligosaccharide content, a type of carbohydrate. These can be fermented by gut bacteria, but this fermentation also produces beneficial compounds for gut health.

The primary macronutrient in soybeans is protein. However, raw soybeans also contain a substantial amount of carbohydrates and fats, making them a nutritionally dense food.