A high-protein diet typically conjures up images of jacked-up bodybuilders cracking raw eggs into their mouths and having slabs of steak for breakfast, but does it have to be this way?

It is true that meat and dairy products are particularly good sources of protein, but the negative environmental impacts of these foodstuffs are now widely recognised.

So how hard would it be to maintain a high-protein diet without meat and dairy?
Meat alternatives have really taken off in the last few years, but are these products any good nutritionally?
Are the high-protein alternatives competitive with meat and dairy protein in terms of cost and flavour?
And how much carbon could I save by swapping to low-carbon protein alternatives?

My Low Carbon Lent was spent taking an exploratory dive into the world of protein alternatives and seeking answers to these questions.

Why protein?

Protein is a macronutrient that we need for growth, repair, and maintenance in the body, especially for bones and muscles. The average adult needs around 0.75g protein per kg of body mass each day, but this rises to 1.2-2.0g for individuals undertaking vigorous physical activity or a strength-based training programme (athletes, bodybuilders etc)¹.

There are now a wide range of low-carbon, high-protein alternatives to traditional meat, such as insects, mycoprotein (Quorn), algae and lab-grown meat – not to mention existing plant-based protein options such as soya, beans, peas, and nuts. The market for these alternative products has exploded in recent years, which has piqued my interest, but I also had a couple of personal reasons for this investigation:

I did Veganuary a few years ago and was shocked to find that my protein levels were way below what they should be.
I’ve been doing a lot of strength training recently and to reach the high levels of protein intake recommended to support this, I’ve actively been eating more meat (blasphemy, I know).

During my Low Carbon Lent, I flipped between vegan, vegetarian and low-carbon carnivorous diets whilst attempting to maintain 125g protein intake a day². Along the way, I tried out some weird and wonderful alternative proteins which I have reviewed below.

Environmental impacts

But firstly, how bad are the carbon impacts of meat and dairy products? And how good are the high-protein alternatives? For a fair comparison, this must be assessed on a per unit of protein basis. Thankfully, there have been numerous studies which have done exactly that³ ^, ⁴ ^, ⁵.

The above chart from Our World in Data plots the expected CO2 equivalent emissions from a variety of sources on a per 100g of protein basis⁴. Cows and sheep top the list: these are “ruminant” animals that have a unique digestive system that causes them to belch out methane (in even greater quantities than their flatulence⁶). The GHG impact of meat from small, non-ruminant animals, such as chicken and turkey, is much lower than that of beef and lamb.

The beef impact is clearly shocking, but what also surprised me is the impact of milk and cheese. A vegetarian diet is often seen as a lower carbon alternative to a carnivorous one, but on a per unit of protein basis, these dairy products are worse than pig and poultry meat. I’ve recently been eating a lot of high-protein yoghurts (which are actually a form of cheese) as they offer high amounts of protein in a low-fat, low-calorie product. These yoghurts are seemingly harmless, but the above chart suggests I’d be better off substituting them for chicken.

As expected, the impacts of the plant-based protein sources are relatively small, with nuts having an impact 192 and 16 times less on a per unit protein basis than beef (beef herd) and eggs respectively.

Another key metric of environmental impact is land use. Extensive land use has a major impact on the earth’s environment as it reduces wilderness, threatens biodiversity, and contributes to deforestation. In fact, meat production is the single greatest cause of deforestation globally, with about half of the world’s habitable land used for this purpose⁷. Our World in Data has also compiled data on the land use (in m²) of various protein sources on a per 100g of protein basis⁴.

It’s a similar story to carbon emissions, the ruminant animals (cows and sheep) top the list by a substantial margin, with the dairy products of cows (milk and cheese) following behind. Interestingly, two of the lowest carbon proteins (nuts and pulses) are middle of the list in terms of land use, with an impact comparable to poultry meat. The disparity between the lowest impact protein and the highest is comparable to that seen in the carbon emissions analysis, with farmed prawns (2m²) requiring 93 times less space than lamb and mutton (185m²).

High-protein, low-carbon alternatives

Recognition of the high environmental impact of meat and dairy products has driven the emergence of high-protein alternatives. Some of these alternatives (such as plant-based) are packaged up as meat substitutes in an attempt to replicate meat in terms of look and texture; some have similar levels of protein to meat, but some do not. These high-protein alternatives were summarised into six groups and the potential environmental impacts were assessed in a study by the University of Oxford in 2021³. A summary of these alternatives is shown in the table below.

The University of Oxford study provides ranges of land use requirements and GHG emissions (assuming the use of zero-emission energy) per 100g of protein for these alternative proteins; poultry meat is provided as a comparison. As per the Our World in Data analysis, the land-use impacts of poultry and plant-based proteins are comparable, but plant-based protein has a much lower range of GHG emissions. The land use requirements of the other alternatives are lower than the plant-based protein. An important caveat to add to this analysis is that plant-based protein sources that are processed and packaged up as meat substitutes could have environmental impacts significantly greater than in their unprocessed form. Santo et al demonstrated that the processed plant-based meat substitutes could have 1.6-7 times higher environmental impact than less processed plant protein sources¹¹. The GHG emissions of bacterial protein and cultivated (lab-grown) meat can be negligible, provided they are powered by zero-emission energy.

High-protein alternative reviews

As well as being economically comparable to traditional protein sources, these alternative proteins will also need to perform on taste and appeal to be widely accepted by consumers. Throughout my Low Carbon Lent, I tried out some of these alternatives. Here are some of my opinions, although taste is of course, subjective.

Spirulina (algae, 66% protein)

Spirulina comes in tablet and powder form. At a whopping 66g of protein per 100 grams, its protein content is comparable to traditional protein powders. The powder can be added to several different recipes to increase its protein content. I added it to a smoothie and the spirulina made it taste significantly worse. Not to mention that the super dark green powder seemed to stain everything it touched. Sorry spirulina - not for me.

Richmond meat-free bacon (plant-based, 12% protein)

It’s amazing how many meat products have now been replicated using alternative protein sources – bacon was not one that I thought could be pulled off successfully. However, Richmond has done a good job of putting together these bacon rashers using a mixture of soya and wheat protein. They look somewhat similar to bacon, and when they are cooked, they give off a smell which is not too dissimilar from that wondrous meaty aroma. The texture is quite different - it's super synthetic and plasticky - but I kind of like it. I’d happily eat this product again, though I don’t think it would quite satisfy a strong craving for some real bacon.

Eat Grub roasted crickets (insects, 44% protein)

These little roasted crickets are a surprising winner for me, they taste great (like eating crisps) and because they have been roasted, they bear only a small resemblance to their original insect form, thereby reducing the ick factor. However, they are very high in salt, only come in small 15-gram packets and are not cheap (£15 for 10 small packets at the time of writing). At 44g of protein per 100g, these have a protein content of almost double that of traditional meat. If the cost of this product could be reduced (which it hopefully should if the market develops) and if they could be made to taste great with less salt, this could be a great protein alternative.

Quorn mince (mycoprotein, 13% protein)

Quorn mince is widely available and well known. It doesn’t have the highest protein content (13%), but it is low in fat and calories. The texture is not too dissimilar to real beef mince and its price is comparable. It doesn’t taste quite as good as the real thing, but that would be expected from a lower-fat product. Substituting real mince with Quorn mince in a meal such as a chilli con carne, where the flavour is masked, is an easy low-carbon win.

Vivera vegan kebab (plant-based, 15% protein)

Yep, you read that right, Vivera have replicated the infamous late-night snack using soya protein, and surprisingly, it tastes great. However, it has a significant amount of fat and salt (probably why it tastes so good), and its protein levels are not that high (15% protein). So, it’s not exactly the healthiest means of protein intake, but it offers a means to indulge yourself with a lower carbon impact than the real thing. Don’t knock it until you try it.

Sadly, I didn’t manage to test out any bacterial protein or cultivated meat. Bacterial protein is still under research. Cultivated meat is now available in a few restaurants around the world, but only Singapore has approved its sale in supermarkets.

Conclusions

Here are my five key takeaways from my high-protein, low-carbon lent endeavour:

1 Minimise or eradicate ruminant meat

Beef’s carbon impact is difficult to justify, even when considering its high nutritional value, and both cows and sheep have high land use impacts. The minimisation of ruminant meats from our diets is therefore an easy win, even for us carnivores who can simply swap to other meats such as chicken and turkey.

2 Vegetarians be aware - dairy products have a high impact

When considering that milk and cheese are the products of the most environmentally impactful animal (cows), it shouldn’t be such a revelation that these foodstuffs themselves come with a high environmental cost, but the impact of these sources of protein took me by surprise.

3 If vegan, take active measures to achieve your protein levels

I had no trouble reaching my protein goal under a vegetarian diet (mostly due to the existence of high-protein yoghurts), but the vegan days were more difficult. It's certainly possible to have a high-protein vegan diet, but I found that it took a significant amount more effort.

4 I’m excited by the potential of cultivated meat

Whilst great progress has been made in developing plant-based meat substitutes that replicate the taste and texture of real meat, they still don’t taste quite as good as the real thing. Cultivated meat could offer a chemically identical product without the environmental impact and the moral complications of animal slaughter.

5 Philosophical questions ahead for vegans and vegetarians

The rationale behind these dietary regimes is often due to animal welfare or environmental concerns. But with the advent of cultivated meat, which could eradicate both issues whilst providing an identical product to real meat, what would it mean to be vegetarian or vegan in an age of zero impact meat?

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