The Science

Protein is an essential part of our diet. It being present in all parts of the body, from your bones and skin, to your hair and nails, and is needed for the repair and building of muscles and organs. It can also serve as a fuel source and helps with various tasks around the body. Hemoglobin, for instance, the carrier of oxygen in the blood, is a protein.

Proteins are formed from 22 types of amino acids. Nine are “essential” as they cannot be synthesized by our body and must be gained through diet. A type of food that contains all nine is referred to as a complete protein source. Six are “non-essential”, meaning they can be synthesized in sufficient quantities in the body. A further six are considered “conditionally essential” as they may be synthesized under certain conditions but ought to be ingested in the food that you eat. The remaining amino acid is unnecessary in our diet. During digestion the proteins in our food are broken down in the stomach, so that the essential amino acids can be absorbed in the small intestine.

However unlike other macronutrients protein is not stored by the body. Once the amino acids have been utilized by the body, the surplus is degraded or lost in body excretions, employed directly as a source of energy or are converted to carbohydrate or fat. Therefore a continuous supply of dietary amino acids (in the form of protein) is required to replace these losses on a daily basis.

Protein is acquired from both plants and animal sources, but there are some differences as two of the essential amino acids are poorly represented in most plant proteins. Understanding the differences between plant and animal proteins is important for anyone who wants to ensure that their diet is healthy.

Your Meat and Veg

Your diet should consist of complete protein sources, which contain all nine essential amino acids. Many believe this is only possible with meat, and if a vegan or vegetarian, you must take supplements to obtain all the required amino acids. It is true that most foods that provide a complete protein source are animal based; such as red meat, fish, eggs, poultry, dairy cheese and dairy yoghurt. There is however some plant based complete proteins such as quinoa and chia seeds. Nevertheless the vast majority of vegan foods on their own are not complete proteins, although it isn’t important to get all essential amino acids in every single meal. You just need to have all 9 across a day.  Remember too that some sources of plant protein may take longer for the body to digest and use.

For example, meat (as in muscle tissue of an animal), consists of roughly 20% protein. This means that if consuming a 300 gram steak you are getting around 60 grams of protein (around the recommended daily allowance). According to the USDA nutrient database, 1 cup (at 185 grams) of cooked quinoa contains 8.14 grams of protein or 13 grams per 300 grams. Therefore to get your daily allowance of protein from this source you would need to eat 7 cups, or 1.3 kilograms of quinoa.

When choosing between plant and animal sources of protein, it is important to factor in the other nutrients that the foods provide also. Certain sources of animal protein can contain high levels of heme iron and vitamin B-12, lacking in plants, while some plant-based foods contribute fibre and is low in fat.  In general, the best way to cover a person’s dietary needs is to eat a wide variety of foods.

Enough or Not Enough

Simply getting enough protein in the diet may be more important than focusing on the kind of protein you are eating. Research notes that the amount of protein is more important than the type. Nutritional Guidelines suggest the DRI (Dietary Reference Intake) is 0.8 grams of protein per kilogram of body weight. This amounts to: 56 grams per day for the average sedentary man and 46 grams per day for the average sedentary woman for normal needs. Nevertheless at times you may need to consider the need for more or less protein in your diet.

Athletes and heavy exercisers should consume 2.2-3.4 grams of protein per kilogram to increase muscle mass and continual repair.  At these times a formulated protein may be beneficial. Whey protein is created as a milk or cheese bi-product and is considered a complete protein.  Many athletes turn to whey protein for building muscle as this type of protein is easier for the body to break down and absorb.

If wanting to lose weight, protein can aid getting lean mass and helps in maintaining that “full” feeling longer. Roughly 1.8 – 2.9 grams of protein per kilogram of body weight, daily, is a suggested amount to provide satiety while still preserving weight loss.

In Summary

For many people, the choice between animal and plant proteins involves a range of considerations.

Rather than focusing on a single type of protein, it may be better to focus on eating a wide variety of foods. This can help ensure that a person gets a healthful balance of amino acids and other vital nutrients.