Which is better, plant or animal protein?
Vegans swear by their diet, while carnivores won’t give up the position that animal protein is the gold standard.
Which type of protein should you be eating, and do you really need to worry about the differences between plant and animal proteins?
Let’s take a look.
What are proteins?
Proteins consist of intricate chains of amino acids, with their structures and arrangement resembling the following illustration:
When we eat a protein food, the proteins look like the image on the far right. Once the protein is digested, we get individual amino acids – the image on the far left.
There are 9 essential amino acids and 11 non-essential, that are located primarily in our skeletal muscle (~40%), and body organs (~25%), with the remainder in our skin and blood (~ 35%). Essential amino acids must be obtained from food; however, our bodies can make non-essential amino acids.
Whether they come from animals or plants, the amino acids are the same. For example, the structure of the essential amino acid valine, which is found in cheese, soy, meats, vegetables, and fish keeps its same structural form for both animal and plant proteins.
You may have heard of the term ‘complete protein.’ A complete protein food is one that contains all 9 essential amino acids. We have to get these aminos in our diet, because our bodies can’t produce them. The 9 essential amino acids are: phenylalanine, valine, threonine, methionine, tryptophan, histidine, isoleucine, leucine, and lysine.
The other 11 amino acids can be made by our bodies, and therefore don’t need to be consumed in our diet.
The reason animal proteins are often called “complete”, and some plant proteins are called “incomplete” is because of the combination of specific amino acids they contain, not because the amino acids themselves are any different.
A protein that’s incomplete isn’t ‘missing’ an amino acid; it just means that one of its amino acids is present in short supply, which can affect the synthesis of protein in the body.
Steak and soybeans both contain all 9 of the essential amino acids, but peanuts (low in lysine) or black beans (limited in lysine and leucine) do not.
Quinoa, buckwheat, Ezekiel bread, and soybean products including tofu, edamame beans, and tempeh, are all complete protein foods on their own. Pairing an incomplete protein, such as chickpeas or black beans, with a grain, seed or nut will form a complete protein. For example, black beans paired with rice, hummus with pita bread, or peas with rice would create a complete protein.
We used to think that incomplete proteins needed to be eaten together to form complete proteins in the same meal; now, we know that as long as we eat a variety of protein sources (and therefore, amino acids) throughout the day, we don’t have to worry about combining our proteins.
FYI: Pistachios are the only nut that is a complete protein!
When we eat protein-containing foods, our bodies start digesting the proteins in the stomach, where they are denatured, or taken apart. The end product is peptides and free amino acids.
These peptides (short chains of amino acids) and free amino acids are absorbed from the gut into the bloodstream. Our liver is the primary site for post-meal amino acid uptake.
What do proteins do in the body?
The functions that proteins serve in our bodies are seemingly endless – they are catalysts for chemical reactions, they are messengers, buffers, fluid balancers, immuno-protectors, acute phase responders, transporters for cell membranes, as well as blood (albumin, iron, vitamin A to name a few), and of course, they play a huge role in the structural elements of contractile (cardiac, smooth, and skeletal muscles) and fibrous proteins (collagen, elastin, blood vessels, tendons, hair, nails, etc.).
We can’t carry out basic daily functions without a steady stream of protein.
How much protein should we eat?
I wrote about this in my post How Much Protein Do We Need Every Day?
While official (and fairly ancient IMO) recommendations around protein remain at 0.8-1.0 grams per kilogram of body weight per day, current research around protein indicates that ideal protein consumption for healthy, physically active adults lies around 1.2-2.0 grams/kilogram/day. That’s a huge difference, and it’s one I support (along with the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine.
It’s always important to remember that dietary guidelines and RDAs for nutrients were developed to reflect nutrient amounts required to avoid deficiency, not necessarily to optimize health. So, while we can live on 0.8-1.0 grams of protein per kilogram per day, it may not be ideal for muscle maintenance and building. These things become even more important as we age.
Animal vs Plant protein – which is better?
Because protein per serving is higher with most animal foods, you may need to eat more plants to get the same amount. With the exception of soy and pea proteins, plant proteins may also be less bioavailable to the body, but eating complete plant proteins, as well as cooking and processing, can change this so the difference is basically insignificant.
While vegan diets may result in micronutrient deficiencies if you aren’t careful, the diet can absolutely be adequate and complete, even in athletes. Please don’t ask vegans how they get enough protein…it’s annoying.
High-quality plant proteins will provide fiber and phytonutrients whereas meat protein will be void of both.
On the other hand, meat protein provides B12 that plants cannot, and the iron in animal foods is more bioavailable than the iron in plant foods.
Chicken is source of protein, as well as B12 and iron.
It is possible to get everything you need from a complete plant-protein diet; initially, it takes a little more planning and effort than it would take for a meat-protein diet, but a lot of that comes from the fact that meat is so widely used and readily available in our society. Once you get used to incorporating plant proteins daily, you realize it can be just as easy.
While there have been some great steps made at introducing more convenient plant-based options, it’s important to be aware that a lot of them are ultra-processed and contain high amounts of sodium and sauces. They also tend to be expensive.
The quality of a protein is measured in how much of the protein in the food gets absorbed.
The DIAAS – Digestible Indispensable Amino Acid Score is a newer way to measure protein quality, whereas the PDCAAS – Protein Digestibility Corrected Amino Acid Score is a bit older.
The PDCAAS compares the essential amino acid content of a food to what our bodies require. The DIAAS measures the digestible ratio of amino acids in a food.
Both measures are controversial. As a dietitian, I don’t think there’s a use for these metrics in everyday life. As long as we eat a variety of protein foods, we shouldn’t need to drill them down into absorption rates.
Animal vs plant protein comparison
Let’s compare a serving (4oz) of ribeye with chicken breast, salmon, and tofu – the amount of protein, and saturated fat, are not the same. Preparation and packaging method, (fried, baked, type and amount of oil used, if any) if applicable, also contribute substantially.
|4 oz steak
|4 oz chicken breast
|4 oz salmon
|4 oz of tofu
While a piece of steak and a piece of salmon both provide excellent protein, one contains high amounts of saturated fat, while the other contains omega-3 fatty acids, EPA, and DHA. Tofu is the only protein source on the chart that contains any fiber (and phytonutrients).
Red meat is associated with higher risk of CVD and many cancers. This doesn’t mean eating red meat is going to give you cancer or a heart attack, but high consumption, along with other lifestyle and genetic factors can put you at a higher risk over your lifetime.
This also doesn’t mean we need to avoid red meat all the time, and it doesn’t mean we should eat salmon every day either. I always recommend a variety of protein foods to people who are omnivores. I love a plant-forward diet for pretty much everyone, meaning, eat as many plants as you are able.
The bottom line is that regardless of protein origin, we should individualize our diet while considering taste preferences as well as health needs. Any diet (meat eater, vegan, vegetarian, etc.) can be deficient in essential nutrients, so one diet isn’t ‘better’ than the other.
Environmental impact of animal and plant proteins
Both plant and animal proteins have negative effects on the environment, but the majority of research suggests that the effects of plant proteins are fewer. Although there is such a thing as sustainability in meat farming. Cattle can upcycle the food we can’t eat, into bioavailable nutrients. Many cattle and lamb producers, especially those in Australia, are working to make their farms climate-neutral and to use significantly less water than they used to.
The Intergovernmental Panel on Climate Change (IPCC) describes plant-based diets as a major opportunity for lessening and adapting to climate change and provides a policy recommendation to reduce meat consumption when possible.
The Double Pyramid consists of two pyramids the Food Pyramid and the Environmental Pyramid. The Food Pyramid is based on the principles of the Mediterranean diet, with plant-based foods forming the base and limited consumption of animal products higher up. The Environmental Pyramid represents the environmental impact of different foods, with the most environmentally damaging foods at the top and mirroring the order of the Food Pyramid. This arrangement emphasizes the inverse relationship between nutritionally recommended foods and their environmental impact.
The double pyramid shows that the foods offering the greatest nutrition benefits such as vegetables, grains, legumes, and fruit, are those with the lowest environmental impact, while the foods that should be consumed in moderation for health reasons, such as red and processed meats, are those with the highest impact.
The study that was done looked into comparing those on a lacto-ovo vegetarian menu, a vegan menu, and an omnivorous menu. The menus were all balanced from a nutritional viewpoint. The results showed that both the vegetarian and vegan diets had lower environmental impacts compared to the omnivores diet.
The methodology used to assess the environmental impact was through the life cycle assessment (LCA) which considered carbon footprint, water footprint and ecological footprint.
The article emphasizes the important of raising public awareness about the environmental and nutritional impacts of food choices. The Double Pyramid Model does encourage the consumption of more plant based foods and the reduction of meat and animal products for both health and environmental reasons.
There are still gaps in the data, however the Double Pyramid model is a great tool to promote awareness about the relationship between healthy diets and environmental sustainability.
Overall, optimal protein sources vary from person to person based on individual preferences and needs. The most suitable protein options for you should ideally possess the following qualities.
- Eat a variety of proteins. If you choose a vegan diet, be mindful of micronutrients such as B12 (you’ll need supplementation) and calcium.
- Enjoyable: Consuming protein sources that are enjoyable and appealing to your taste, facilitating consistent consumption over time.
- Diversity: Incorporating diversity in protein-rich foods is essential. This diversity not only addresses your protein intake but also ensures you obtain a wide spectrum of other vital nutrients such as fiber and phytonutrients!