Protein in a plant-based diet

All you need to know about the role of protein in a plant-based diet, from science to practice in helping people achieve their protein recommendation.

Summary

• Protein provides the building blocks for life and is an essential macronutrient for tissue growth, maintenance and repair as well as almost all biological processes.

• Proteins are made of building blocks called amino acids. There are 20 different amino acids but 9 are essential where we must eat them from food. These are all contained in both plant and animal protein sources.

• Those consuming plant-based diets tend to have lower total protein intakes, but this is not of concern in the context of overconsumption in developed countries when consuming sufficient energy and a variety of plant proteins.

• Moving towards an increased intake of plant protein has multiple benefits for population health through reduction of non-communicable disease. This is partly due to the high fibre and healthy fat content of plant-based foods.

• Plant protein sources use less land and water, emit less pollutants, less greenhouse gases and use less land versus animal protein, making them a crucial component of a sustainable dietary pattern for planetary health.

• Plant foods high in protein include soy and soy products such as tofu, tempeh, soy drinks and soy alternatives to yogurt, as well as peanuts, peas, pulses, nuts, seeds, mycoprotein and quinoa.

• Choosing protein from plant sources is beneficial for both people and planet.

• A key barrier to including more plant foods in the diet is a lack of knowledge of how to prepare and incorporate them into usual day-to-day patterns. Guidance on many easy meals ideas that can be made as part of a varied and flexitarian dietary pattern is important for supporting a plant-based dietary approach.

Introduction

Protein has long been a hot topic in nutrition science.

Alongside fat and carbohydrates, protein is a macronutrient that is required in relatively large quantities in our diet as it provides the building blocks for life.

Pie chart showing the percentage of protein required in a human diet

Protein molecules are made from chains of amino acids that are woven together in unique sequences, ultimately determining their structure and function. Of the 20 known amino acids, our bodies can synthesise 11, and these are referred to as non-essential amino acids (NEAA).

The remaining nine can only be sourced from our diet and are referred to as essential amino acids (EAAs). With countless combinations of the 20 amino acids available, proteins vary widely in their actions.

From tissue growth and repair to enzyme activity and immune function, proteins are involved in virtually every biological process and so are essential for sustaining life and optimal health.

Dietary protein is available from a variety of both plant and animal sources. Globally, most protein is sourced from plant foods such as wheat, maize and rice (57%), however since the 1970s, protein in Europe has been predominantly derived from animal sources such as meat, dairy and fish (55-60%)(1).

Protein requirements

Adequate protein intake can range from 10% to 35% of total energy intake. Daily recommendations are however based on an individual’s body weight.

Nitrogen balance studies suggest that the minimum requirement to maintain nitrogen balance, known as the average requirement, is 0.66g per kilogram of body weight per day (/kg/BW/day).

The daily recommended intake of protein for healthy European adults ranges from 0.8 to 0.83g/kg/BW/day for both men and women, allowing for the variability of protein needs among individuals.

Using these recommendations, a 75kg man would have a recommended intake of 60g protein per day, and a 60kg female would require 48g per day.

Children, athletes and pregnant or breastfeeding women have higher recommendations to allow for growth, tissue maintenance and milk production as shown in table 1.

Regarding older adults, EFSA states:”…the available data are insufficient to specifically determine the protein requirement in older adults and that at least the same level of protein intake as for young adults is required for older adults.

As sedentary older adults have a lower energy requirement the protein to energy ratio of this subgroup is higher than for younger adults(2).

Deutz and colleagues recommend healthy older adults to consume 1-1.2 g/kg/BW/day, and if combined with acute or chronic illness then up to 1.5g/kg/BW/day(3).

Table 1. Protein recommendations across population groups(2)

Protein consumption

Protein intake across Europe varies from 12 to 20% of energy intake. Table 2. presents data on total protein intakes in males and females in a variety of European countries.

Table 2. Daily protein intake across European adults(5)

There is a global trend towards over-consumption of protein. With a global average intake of 68g of protein per person per day, consumption is estimated at one third above the average adult daily requirement, with a growing share of this being animal-derived protein.

This is particularly prevalent in the world’s wealthiest regions, such as Europe, but expected to undergo the most growth in developing countries in years to come(6).

Despite the popular narrative that more protein is always better, high protein intakes can have a variety of detrimental effects, such as increased calcium excretion and reduced insulin sensitivity(7).

Table 3. Protein supply from plant and animals in Europe (g/capita/day)(8)

Protein timing

Protein is a key component of muscle mass, which in turn is vital for health, independence and functionality in ageing.

Muscle protein synthesis (MPS) is the process of incorporating amino acids into bound skeletal muscle proteins and inducing hypertrophy.

Studies have found that a 20g protein bolus following resistance exercise appears to maximally stimulate acute MPS, however studies have now found that to promote attainment and maintenance of peak muscle mass, the distribution of protein intake over a 12-hour period is also an important factor(9).

It has been found that both omnivorous and vegan diets can support comparable rested and exercised daily MPS rates in healthy young adults consuming a high protein diet(10).

Protein intakes across dietary patterns

Protein intake appears to have a positive relationship with the number of animal foods included, with meat eaters reaching 90g of protein daily, flexitarians achieve 67g protein daily and vegans achieving 64g(11). This data demonstrates that with and without animal foods, protein intake remains sufficient.

Plant proteins have been misleadingly referred to as ‘incomplete’ based on their varying amino acid profiles. This is because many plants do not all contain sufficiently high quantities of some amino acids if eaten in isolation, except for soy, hemp, buckwheat and quinoa.

Despite the concerns, all plants contain all amino acids but proportions will vary from one plant to another.

All amino essential amino acids will be obtained in sufficient quantities as long as there is enough energy and a variety of plant food types in the diet.

In addition, the term ‘high quality’ when referring to protein sources focuses solely on their quantity of essential amino acids and individual digestibility and does not take account of their place within a mixed diet, or their health or environmental impacts. This term is therefore of little relevance in developed countries(12).

Those at risk of not meeting protein requirements include those with a low calorie intake, those with higher requirements including older adults, athletes, pregnant and breast feeding women plus those consuming diets too high in ultra-processed foods ie crisps, cakes sweets, sugary cereals.

Plant protein and animal protein in a flexitarian diet

A move towards more plant proteins in a flexitarian-style diet is not of concern for protein sufficiency. In fact, due to the differing nutritional components of plants and animals, diets favouring more plant protein contain more fibre, beneficial phytochemicals and less saturated fat.

Changes toward increasingly plant-based diets on a population level would therefore reduce non-communicable disease risk factors, such as elevated LDL cholesterol and hypertension as well as improve gut microbial diversity and induce an anti-inflammatory effect.

These factors, amongst others, would contribute to lower disease burden with subsequent benefits for healthcare costs(7).

Another powerful motive to embrace plant protein is planetary health. Plant-based diets are more environmentally sustainable than meat-based diets, with lower greenhouse gas emissions and pollutants and significantly reduced requirements for valuable resources such as land and water.

Meat and dairy production processes currently use 83% of global farmland but supply just 18% of calories and 37% of protein(13).

Crops for direct human consumption are therefore a significantly more efficient and sustainable way to produce food. Reduced reliance on animal-based foods is essential to meet climate and environmental targets.

Driving behaviour change: ways to eat more plant protein

A key barrier to including more plant foods in the diet is a lack of knowledge of how to prepare and incorporate them into usual day-to-day patterns.

Guidance on many easy meals ideas that can be made as part of a varied and flexitarian dietary pattern is important for supporting a plant-based dietary approach.

These top plant protein sources provide good amounts of protein, with more fibre and less saturated fats and can therefore contribute to better health for people and planet.

• Tofu – 12g/100g

• Tempeh 21g/100g

• Pulses – 6-8g/100g

• Soya alternatives to milk - 3g/100ml

• Soya alternatives to yogurt – 4g/100ml

• Mycoprotein (known as Quorn®) 13g/100g

• Nuts – 20g/100g

• Seeds – 30g/100g

• Buckwheat 4g/100g

• Quinoa (dry) 4g/100g

Whatever dietary pattern you follow, there are many ways you can explore plant proteins.

You could:

• Try one fully plant-based day per week, for example a meatless Monday.

• Try one fully plant-based meal per day, for example a plant-rich breakfast.

• Swap half of your meat in meals with plant-based alternatives like lentils, beans or soy.

• Try adding extra plant foods to your diet, for example sprinkling some roasted chickpeas over a salad or topping your porridge with seeds and soya alternative to yogurt.

Meal ideas

Breakfast – Blueberry and almond porridge – 22g protein

Serve 50g of oats with 300ml soya drink, a handful of blueberries and a sprinkle of almonds.

Lunch – Falafel and hummus wrap – 12g protein

Spread 50g (2 tbsp) of hummus on a wholemeal wrap with slices of cucumber and baby spinach, top with 2-3 falafels before folding the sides over and tightly rolling it up.

Snack – Roasted chickpeas – 9g protein (per 100g)

Drain 1 tin (400g) of chickpeas and combine with 1 tbsp of olive oil, black pepper and curry powder. Spread evenly onto a baking tray and roast at 180°C for 25 minutes or until crispy. Shake the tray halfway through roasting.

Dinner – Tofu stir fry with vegetables and cashews – 30g protein

Fry 2 chopped spring onions, 1 grated garlic clove and a grated thumb sized piece of ginger in 1 tbsp of olive oil. Add vegetables of choice, for example peppers, bean sprouts, carrot strips and sliced cabbage, or a pre-chopped and mixed bag for ease for 4-5 minutes. Add 1 tbsp of soya sauce, a dash of lemon juice and 200g of marinated tofu pieces. Serve with 250g of cooked noodles (of choice) and top with a handful of cashews.

Protein content is approximate and may vary based on brands purchased.