Is Soy Milk a complete protein?

In this brief article, we will address the query: “Is Soy Milk a complete protein?”. Additionally, we will cover the process to obtain soy milk and its composition; the possible health benefits and risks associated with its consumption; and finally, a brief comparison with cow’s milk and some recipes to incorporate it in your diet.

Is Soy Milk a complete protein?

No, Soy Milk and soybean do not have all amino acids, they are lacking sulfur containing amino acids like Histidine, Cysteine, Methionine, and Tryptophan (1,2).

Which food items are considered a complete protein?

All animal foods are considered complete proteins. This is because foods like meats, milk, eggs, and fish all have essential amino acids (those your metabolism can synthesize) (3).

Regarding Soy Milk, it contains very low quantities of Histidine, Cysteine, Methionine, and Tryptophan (2). You can see the content of essential amino acids of Soy Milk in the following table:

Amino acidContent (%)

* Adapted from Reynaud et al. (2).

What is Soy Milk, and how is it obtained?

Soy Milk is a cow’s milk alternative originated in Asia and adopted in the rest of the world. Because it does not contain lactose, cholesterol, and is plant-based, it is appreciated by people with lactose intolerance, hypercholesterolemia, and vegetarians (4). 

To obtain Soy Milk, you just have to soak the soybeans, then grind the soaked seeds, filtering to remove the solids, and boil the Milk. The food industry uses the same process, but on a larger scale, and they add other ingredients like sugars, preservatives, vitamins, and minerals (4).

What can you eat along with soy milk to have a complete protein?

To complement the protein of soy milk you could combine it with foods containing complete proteins, for example, eggs or yogurt. Another option is to add a cereal, like oats, to complement the missing amino acids in Soy Milk (3); but going for an animal-based protein could be the best option!

What are the health benefits of Soy Milk?

The health benefits of Soy Milk are varied, for example, it could help (if consumed with moderation) prevent some types of cancer and promote bone and gastrointestinal health (5-9). 

Soybean and Soy Milk contains some molecules called isoflavones; after your body digest those isoflavones, they become “active” and can exert a potent antioxidant effect that is responsible for protecting you against breast or prostate cancer (5,6)

Soy isoflavones and proteins contained in Soy products could provide your body with the building blocks necessary to prevent osteoporosis; however, the available evidence only suggests this is true in women, but it has not proven in men yet (7,8).

Another interesting role of Soy Milk isoflavones is that they are anti-inflammatory. If you suffer from bowel inflammation, Soy Milk isoflavones could help to alleviate the inflammation on your intestine (9). 

What are the potential health risks of Soy Milk?

There are not too many health risks about consuming Soy Milk. The only risk is an anaphylaxis or allergic reaction if you are allergic to soy’s proteins (10). 

What is better between Cow Milk and Soy Milk?

If you are looking for a good protein source, cow’s milk is definitely a better option. It contains complete proteins with a high bioavailability (your body can digest it and absorb it) (11,12).

However, if you can not consume cow’s milk for any reason, you can prioritize Soy Milk in your diet in combination with other foods to achieve your protein requirements (3). 

Please take into account that substituting cow’s milk with soy milk (or any other vegetable milk) is not recommended for children! This kind of intervention should always be prescribed by a pediatrician (13, 14). 

How to Incorporate Soy Milk into Your Diet

The most common way to incorporate Soy Milk in your diet is with smoothies or beverages, however, you can spice up your options with all the recipes in this BBC website. There you can find breads, desserts, ice creams, pancakes, and more.


In this brief article, we addressed the query: “Is soy Milk a complete protein?”. Additionally, we presented the process to obtain soy milk and its composition; the possible health benefits and risks associated with its consumption; and finally, a brief comparison with cow’s milk and some recipes to incorporate it in your diet. 


  1. Qin P, Wang T, Luo Y. A review on plant-based proteins from soybean: Health benefits and soy product development. J Agric Food Res, 2022;7(100265):100265.
  1. Reynaud Y, Buffière C, Cohade B, Vauris M, Liebermann K, Hafnaoui N, et al. True ileal amino acid digestibility and digestible indispensable amino acid scores (DIAASs) of plant-based protein foods. Food Chem, 2021;338:128020.
  1. Day L. Proteins from land plants – Potential resources for human nutrition and food security. Trends Food Sci Technol, 2013;32(1):25–42
  1. Li Y-T, Chen M-S, Deng L-Z, Liang Y-Z, Liu Y-K, Liu W, et al. Whole soybean milk produced by a novel industry-scale micofluidizer system without soaking and filtering. J Food Eng, 2021;291(110228):110228.
  1. Tan M-M, Ho W-K, Yoon S-Y, Mariapun S, Hasan SN, Lee DS-C, et al. A case-control study of breast cancer risk factors in 7,663 women in Malaysia. PLoS One, 2018;13(9):e0203469.
  1. Chatterjee C, Gleddie S, Xiao C-W. Soybean bioactive peptides and their functional properties. Nutrients, 2018;10(9):1211.
  1. Rizzo G, Baroni L. Soy, soy foods and their role in vegetarian diets. Nutrients, 2018;10(1):43. 
  1. Valtueña S, Cashman K, Robins SP, Cassidy A, Kardinaal A, Branca F. Investigating the role of natural phyto-oestrogens on bone health in postmenopausal women. Br J Nutr, 2003;89 Suppl 1(S1):S87-99. 
  1. Al-Nakkash L, Kubinski A. Soy isoflavones and gastrointestinal health. Curr Nutr Rep, 2020;9(3):193–201.
  1. Vallath A, Shanmugam A, Rawson A. Prospects of future pulse milk variants from other healthier pulses – As an alternative to soy milk. Trends Food Sci Technol, 2022;124:51–62.
  1. Scholz-Ahrens KE, Ahrens F, Barth CA. Nutritional and health attributes of milk and milk imitations. Eur J Nutr, 2020;59(1):19–34.
  1. Walther B, Guggisberg D, Badertscher R, Egger L, Portmann R, Dubois S, et al. Comparison of nutritional composition between plant-based drinks and cow’s milk. Front Nutr, 2022;9:988707.
  1. Verduci E, Di Profio E, Cerrato L, Nuzzi G, Riva L, Vizzari G, et al. Use of soy-based formulas and cow’s milk allergy: Lights and shadows. Front Pediatr, 2020;8:591988.
  1. Collard KM, McCormick DP. A nutritional comparison of cow’s milk and alternative milk products. Acad Pediatr, 2021;21(6):1067–9.

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