Do I Need To Combine Proteins In A Plant Based Diet? | The PNW Clinic

There is lots of misinformation about plant-based diets, and protein requirements.

Outdated beliefs lead many to believe that plant-based diets are low in protein.  A common question that get asked is do I need to combine proteins on a plant-based diet?

In this article, we discuss the idea of protein-combining, and the protein requirements for plant-based diets.

How do you get your protein on a plant-based diet?

A common question and scepticism posed to those following a plant-based diet is often something along the lines of ‘How do you get your protein?’. 

For many, there is a lack of public knowledge that plant-based diets can be nutritionally adequate (1) and it is very possible to meet these requirements even when excluding animal-based protein. 

Why do we need protein?

Protein is a vital macronutrient, essential for all aspects of human development, and the growth and repair of human cells (2). It drives metabolic reactions, maintains pH and fluid balance, transports and stores nutrients, and provides an energy source (3).

It is a fundamental building block of human bodies, and a core component of a balanced, healthy and sustainable diet. 

Common sources of protein in an omnivorous diet include meats and fish, legumes, dairy, seeds and nuts (2). 

Protein sources in a plant-based diet may include soy-based products, nuts, seeds, grains, pulses and legumes (4). 

The recommendations for the Australian population is a minimum of 0.84g/kilogram per day for adult men, and 0.75g/kilogram per day for women (5). For vegans and vegetarians, the recommendation is higher. 

For plant-based diets,  our plant-based dietitians recommend having a a diverse and varied diet. This ensures that a combination (6) of these various protein sources is achieved, and does not result in specific deficiencies. 

What Are Amino Acids?

Protein is composed of building blocks (2) called amino acids. Amino acids provide various functions throughout the human body – building new proteins, muscles and bones, enzymes and hormones. 

11 of these amino acids can be made by our bodies – these are called non-essential. 9 of these amino acids are essential, which means the body cannot make them and we need to eat these in our diet (4).

Animal-based sources are complete proteins. Complete proteins mean the food contains all the  essential amino acids in the right quantity our body needs.

Plant-based foods are often incomplete in one or a few acids and are called incomplete protein. A common amino acid they are deficient in is called lysine (7). 

This doesn’t make plant-based diets ‘bad’ or inadequate. This just means it is important to pay attention to the diversity of your diet. This is to make sure you are eating a range of amino acids.

There are some complete sources of plant protein, particularly soy products such as tofu, soy milk, soy yogurt, tempeh and chia seeds.

However, a diet consisting only of these foods poses its own nutritional limitations, and would be unsustainable. These can certainly be eaten with various other ‘incomplete’ sources. 

Meeting nutrient needs is possible! This can be done by combining various sources of these proteins, to build a rich and nourishing nutritional profile.

Do I need to eat two foods together to have complete proteins?

Protein-combining is a historic belief, which essentially believes that in order to achieve complete protein adequacy on a plant-based diet, various plant sources need to be consumed at the same time. 

Typically, it was encouraged to pair foods (8)  such as cereal with legumes, legumes with nuts, and cereals with nuts, in an effort to avoid deficiency of particular amino acids. 

This ‘myth’ was held for many years, however it has since been proven that a diet rich in diverse plant foods is inherently sufficient in amino acids (9). These foods do not need to be consumed at particular times. 

There is no specific detriment to combining proteins, however it is not necessary when one is consuming a variety of sources throughout the day. 

Strict adherence to this idea can present some challenges in enjoyment of food, and can cause food to become a chore – rather than enjoyment, nourishment and fuel for your body. 

It is recommended to work with a dietitian who is educated and knowledgeable surrounding plant protein and vegan diets – such as the plant-based dietitians at PNW clinic (10).

What Does The Research Say?

The current standpoint around whether to combine proteins essentially refers to the inclusion of various protein sources, ensuring that all amino acids are acquired through diet. 

Various studies have been conducted to this effect, with researchers creating an amino profile upon the basis of a specific animal product (7) and tailoring the plant-protein blend to meet these specific sources (egg white, cow milk, chicken). 

Common rhetoric in these studies found potato and pea proteins to be of the highest quality (11), and had success in creating plant-protein supplementations for targeted amino acids. 

For more complex proteins such as whey, a milk protein, it was found to require a more complex combination (7) of these plant-sources. 

The amino acids histidine, lysine, sulfur amino acids, isoleucine and leucine placed constraints on the building of complete profiles and are more difficult to replicate. 

However, this is attainable through specific tailoring and supplementation!

Example Meal Plan To Combine Proteins On A Plant-Based Diet

Each person has different food preferences! 

This means that each person’s day of eating will be unique, based on their requirements and enjoyment.

An example of a balanced, protein filled day of eating may look like: 

Breakfast 

Soy yoghurt bowl with granola, strawberries and banana

Lunch 

Smashed chickpea and avocado sandwich

Dinner 

Tofu curry 

Snacks 

Protein balls with fruit

Plant-based milo and soy milk

Roasted edamame 

Nut butter on wholegrain crackers

Do I Need To Combine Proteins On A Plant-Based Diet?

Dietitians and medical professionals have found that is is not essential to combine proteins on a plant-based diet.

Meeting protein needs is possible through following a diverse and varied plant-based diet.  A balanced plant-based diet is ‘combined’ by default. 

Pairing foods together, at the same time, is not necessary. 

If you are concerned about your protein intake, it can always be recommended to speak to an accredited practising dietitian such as the plant-based dietitians at The PNW Clinic (10). 

There are many ways to incorporate a diverse plant protein profile. Soybean products such as tofu, soy milk, yogurt and edamame are a fantastic source of complete plant protein. 

Consuming a wide variety of sources – pulses, seeds, grains and cereals, nuts, beans and legumes – can ensure a diverse amino profile is eaten.

As always, individuals are inherently complex and unique.

If you want to optimise your nutrition on a plant based diet, book in a free discovery call with the plant based dietitians at  Plant Nutrition Wellness (11). 

Article Written by Tara Finn and Reviewed by Kiah Paetz