We live in a society obsessed with protein consumption. More specifically, we live in a society that regards animal protein as superior to plant-based protein, which is an outdated and incorrect assumption.
When someone finds out I'm vegan, the first question is invariably ‘where do you get your protein?’. I usually reply with ‘from a balanced plant-based diet of whole grains, legumes, fruits, vegetables, nuts, and seeds’, which is almost always met with a quizzical raise of an eyebrow and a grunt which simultaneous means 'fair enough’ and ‘I don’t really believe you, but I don’t dare argue’.
Firstly, let me address the myth that foods are either ‘proteins' or ‘carbohydrates’ (carbs). In nature, it is incredibly rare to find a food that is made up of one single macronutrient, i.e. protein, carbohydrate or fat. Animal foods such as meat, fish and eggs usually contain both protein and fat, whereas dairy products contain all three macronutrients (protein, carbs and fat). Only in processed foods do we find foods composed of a single macronutrient. Oil, for example, only contains fats, and refined sugar only contains sugar (carbs).
All whole plant foods contain a combination of protein, carbohydrate and fat. Protein is ubiquitous in plant foods; even a large potato (which most people would classify as pure carb) contains 4g of protein, and just half a cup of rolled oats contains 5g of protein.
Labelling animal foods such as meat, fish and eggs as ‘a protein’ ignores the fact that they all come packaged with unwanted food components such as saturated fat, cholesterol, and haem iron - all of which are implicated in the progression of chronic diseases such as diabetes and heart disease. For example, red meat is touted as a good source of protein, iron and zinc, but consumption of red meat is also associated with an increased risk of bowel cancers.
Plant foods, on the other hand, in addition to being a source of protein are also packed with health-promoting components such as dietary fibre, phytochemicals and antioxidants.
Complete vs Incomplete protein
Proteins are made up of 20 different amino acids, which are the building blocks of proteins. There are 9 essential amino acids which can’t be synthesised in the body, and have to be supplied by our diet. Most plant proteins (but not all) are known as incomplete proteins, as they are lower in (but not devoid of) one or more essential amino acids than what our bodies require. This is of no consequence nutritionally, as the body has a short-term storage pool of essential amino acids which we add to and draw on throughout the course of the day. Eating a wide variety of plant-based foods such as whole grains, legumes, nuts, seeds, fruits and vegetables will ensure you’ll easily meet your amino acid requirements. The discovery of this storage pool debunked the concept of 'protein combining', which promoted eating plant foods with complementary amino acid profiles (such as legumes and grains) in the same meal in order to make a complete protein.
So if we know we can get the right type of protein on a plant-based diet (i.e. all the essential amino acids), how do we get enough protein on a plant-based diet?
Let’s start with how much protein the average woman needs, which is approximately 0.75g (the RDI for protein) to 1g per kilogram bodyweight. As the protein in plant foods is less 'digestible' due to their fibre content compared to animal foods (meat and dairy), it is generally recommended that people on plant-based diets aim for the 1g per kilogram bodyweight mark. As an example, a 60kg woman would require 60g of protein per day.
Another way of looking at it is by percentage of energy (kilojoules or calories), which should be around 15%, as a minimum, as protein-rich foods tend to also a good source of the minerals iron and zinc. The Australian government suggest an Acceptable Macronutrient Distribution Range (AMDR) for protein of 15%-25% of energy, which is to ensure requirements for other essential micronutrients (aside from protein) are also met.
If that same 60kg woman was eating around 7,000kJ each day, 15% of the energy as protein equates to 60g of protein (which is in line with the 1g per kilogram bodyweight recommendation).
Feel free to ask any questions (nutrition-related are preferred) in the comments section below.