Protein is a hot-button topic when it comes to plant-based diets. As a dietitian who specializes in plant-based nutrition and performance nutrition, it is something I find myself talking about almost every day.
So I figured, why not break it all down in one blog post? So this is your one-stop shop guide to protein on a plant-based diet.
Let’s go through it all!
What Is Protein?
Protein is required by the body to grow and repair cells. Protein is made of building blocks called amino acids.
There are 20 amino acids that combine together in different ways to create different types of proteins. Nine of the 20 amino acids are considered essential, meaning that our bodies cannot produce them and we must get them through our diet.
Of these nine essential amino acids, three of them are all called branched-chain amino acids (BCAAs). These include leucine, isoleucine and valine. Leucine has a particularly important role in muscle protein synthesis.
What Are Plant-Based Sources Of Protein?
Good sources of plant-based protein include soy foods such as tofu, tempeh, edamame, and textured vegetable protein as well as seitan and some mock meats.
Legumes such as beans, lentils, and chickpeas can also be good sources of protein to include in your diet. But if your protein requirements are high, it could be difficult to reach your target using legumes as a predominant source of protein. Legumes are quite starchy and have a fairly high carbohydrate content as well as protein.
It is a similar case for nuts and seeds. Whilst they can contribute to your daily protein intake, due to their high-fat content, they are not very efficient sources of protein.
We will cover protein efficiency a little more down below.
Plant-Based Protein Requirements
General protein recommendations for nonathletic populations are around 0.8g of protein per kg body weight. On the other hand, recommendations for athletes and active people vary between 1.4g/kg and even up to 3g/kg body weight depending on training, levels of muscle mass, and goals.
What is interesting to note is that protein requirements for vegans are often 10-20% more than non-vegans. This is due to the differences in protein quality and digestibility of plant-based proteins versus animal-sourced proteins.
There are several factors that make up the protein quality of food but the two main things researchers will look at are:
- The protein digestibility – this takes into account how much protein is absorbed from the total protein quantity of foods
- The amino acid score or profile – this measures the essential amino acid content present in a protein and the protein is rated based on the most limiting amino acid
In research, these are measured through the Digestible indispensable amino acid score (DIAAS) or the protein digestibility-corrected amino acid score (PDCASS).
You can see in the table below that plant-based food will typically have a lower score using both of these tools of protein quality assessment.
Plant-based proteins are less digestible than animal proteins. This could be due to several reasons including
- The difference in protein structure – plant-based proteins have a protein structure that is more resistant to proteolysis (protein breakdown into amino acids) than animal proteins
- Plant proteins contain non-starch polysaccharides or fibers – this also impedes the access of enzymes to proteins and reduces proteolysis
- Plant-based foods contain antinutritional factors including phytic acid, tannins, and protease inhibitors which can reduce protein bioavailability in numerous ways
Some processing techniques can increase protein digestibility in plant-based foods. For example, the phytic acid content found in nuts and seeds, as well as grain foods, can be reduced by soaking, sprouting, and germination of food.
Moreover, protease inhibitors present in cereals and legumes can be significantly reduced by cooking with heat. Heat-treated plant-based protein sources had 18% higher digestibility than unprocessed sources.
For example, let’s take a look at the protein digestibility of several soy products. Research has shown that soy protein isolate has a similar protein digestibility to whey protein isolate but edamame beans (the whole soybean) have a much lower protein digestibility. Tofu, being more processed than edamame but less processed than soy protein isolate has a protein digestibility somewhere in between.
This isn’t to say that you should always go for more processed sources of protein but to emphasize the fact that protein digestibility varies a lot between plant-based foods. Whole foods often offer a far greater benefit from a vitamin and mineral perspective. However, you will need more protein in total because not all the protein is being absorbed as well as if you were having animal-based proteins.
Plant-based proteins are often described as “not complete proteins” due to their often being a limited amount of particular essential amino acids.
For example, wheat protein, although abundant in methionine and tryptophan, is lacking in lysine. Legume protein, however, is lacking in methionine and tryptophan but abundant in lysine.
Plant proteins are lower in essential amino acids than animal proteins. The limiting amino acid problem can be solved through protein complementation. This means combining two protein sources that complement each other’s limiting amino acids.
Using our previous examples, baked beans (a legume) on toast (grain food) would together provide a much better amino acid profile than one of those foods by themselves.
For the general population, this protein complementation can occur across the day by having a wide range of protein foods. However, for athletes looking to optimize muscle protein synthesis as an athlete or active person, it is likely to be beneficial to complement proteins over 3-5 meals over the course of the day.
Soy foods are an exception to this protein-combining rule and are arguably the best plant protein.
Studies have shown that amongst the plant protein sources, soy foods have the most similar amino acid profile to animal products.
Soy protein isolate, in particular, has been shown to have an equal value to whey protein isolate
Efficient sources of protein have at least 12g of protein per 100 calories. This is a bit of an arbitrary line to draw but it can make identifying good versus poor sources of protein a lot more simple. Examples of efficient protein sources include tofu, textured vegetable protein, seitan, and protein powder.
The fewer calories you have to meet your protein requirements the more emphasis you will have to put on those very efficient protein sources.
Comparing plant-based protein sources to animal-based protein sources, it can be more difficult to reach protein requirements but also far from impossible.
For example, 100g of chicken breast contains 20g of protein for 100 calories and most lean meats will have roughly the same level of efficiency. Except for protein powder, there isn’t any plant-based protein source that is quite that efficient.
Although if you have a relatively high-calorie budget and/or lower protein requirements, this shouldn’t be too much of an issue.
The issue arises when your calorie budget is on the small side and your protein requirements are moderate to high. Depending on you as an individual and your goals, this can be highly variable.
Examples Of High Protein Snacks
Examples Of High Protein Meals
A Word On Mock Meats
If you are plant-based & have high protein requirements, tofu & beans gets really old, really quickly. Plant-based meats can be a great way to add variety & avoid flavor fatigue.
But plant-based meats are not all created equal. Some are better than others! I recommend looking for plant-based meats that meet the following criteria…
- >12g of protein per 100kcals
- <2g of saturated fat per 100g (so not heavy on the coconut or palm oil)
My Nice To Haves
- Made from a nutrient-dense source of protein like soybeans or peas/ legumes
- <400mg of sodium per 100g
- Fortified with iron or zinc or naturally rich in these minerals
Plant-based meats exist on a spectrum ranging from “protein efficient, nutrient-rich meat alternatives” to “tasty but not super nutritious, sometimes foods”. So just choose your products wisely.
I hope this guide was helpful! If you want to hear more about protein on a plant-based diet and see some more high-protein meal ideas, check out my Instagram @plantstrong_dietitian!