One of the three types of macronutrients we get from our diet is protein, which comprises of chains of subunits called amino acids. We need these amino acids to fulfil many vital physiological functions, such as the growth and repair of tissues and the formation of enzymes and hormones.
It’s often said that we eat more protein than we need. However, this simply isn’t the case. The recommended daily intake for protein is 0.8g per kilogramme of ideal body weight, but some researchers insist this is too little for optimal health. Evidence now considers a daily protein intake as high as 2.4g per kilogramme of ideal body weight may be more beneficial to individuals who are active or trying to lose weight.[1] An increased protein intake is also recommended for older people as it can also help to prevent age-related muscle loss.[2]
Before we look into the best protein sources, we need to explore why some protein sources are not considered equally valuable nutrition-wise.
Protein quality: animal vs. plant protein
As we mentioned at the beginning, amino acids are essential for our health and wellbeing, with nine of them considered essential despite not being produced in our bodies. Despite this, we can source these amino acids through our diet.
All nine essential amino acids can only be found in complete proteins, which are in all animal-based protein sources. On the other hand, plant-based proteins usually lack at least one of essential amino acid.
For example, beans do not contain the amino acid methionine, while nuts do not consist of enough lysine. This is the reason why vegetarians and vegans must find their protein from a wider range of sources to guarantee they are getting the full spectrum of essential amino acids.
Scientists have established a system named the Digestible Indispensable Amino Acid Score (DIAAS) to evaluate the protein standard that considers the essential amino acid profile alongside its digestibility. [3]
Sources of animal-based protein are more bioavailable, which means they have amino acids which our bodies can more easily absorb. Due to the complex structure of plant-based proteins, they are harder for us to digest. Vegetarians and vegans have to consume a further 10-30g of protein each day to get the same amount as someone who is omnivorous.[4]
The best sources of protein
Chicken, turkey, beef, pork and lamb are all great sources of complete and bioavailable protein. Chicken breast and pork loin are both leaner cuts of meat and contain more protein per volume. Additionally, meat is an excellent source of zinc, selenium, iron and B vitamins.
Protein per 100g:
Chicken breast – 31g
Chicken thighs – 24g
5% beef mince – 21g
20% beef mince – 17g
Sirloin steak – 20g
Pork loin – 21g
Pork belly – 9g
Eggs are packed with efficient and bioavailable protein, most of which can be found in the egg white although the yolk also contains B vitamins and vitamin A.
Protein per 1 Egg – 6g
Seafood and fish are rich in protein, especially leaner fish. It would be best if you tried to include fatty fish like salmon, sardines and mackerel into your diet at least once a week because they contain omega-3 fats. Besides this, fatty fish is also great for vitamin D and B.
Protein per 100g:
Salmon – 20g
Mackerel – 19g
Sardines – 20g
Cod – 31g
Seabass – 18g
Prawns – 25g
As another complete source of protein, dairy ranks high on the DIAAS scale. Cottage cheese and Greek yoghurt are particularly high in protein, while cheese has a more modest amount of protein per serving. Most dairy foods are also rich in calcium, potassium, phosphorus, and vitamins A, D and B12, while full-fat dairy usually contains more of the nutrients.
Protein per 100g:
Full-fat Greek yoghurt – 6g
Full-fat natural yoghurt – 4g
Cottage cheese – 11g
Whole-fat milk – 4g
Fresh mozzarella – 22g
Feta cheese – 14g
Cheddar – 25g
Parmesan – 38g
Tofu is traditionally consumed in Southeast Asia and by those with a plant-based diet. The curd is made from soybeans, one of the only plant-based protein sources containing all essential amino acids. Due to this, tofu is the best plant-based complete protein. However, tofu is not as easily-digestible as the protein found in meat, fish, eggs and dairy.
Tofu is also crammed with minerals including iron, zinc, potassium, selenium and magnesium and contains fewer carbohydrates than other plant-based sources, meaning it can be a great addition to any low carb diet.
Protein per 100g of tofu – 8g
Chickpeas, green peas, kidney beans, black beans, butterbeans and lentils are another great source of plant-based protein. While beans and pulses do not contain all essential amino acids, they are an excellent source of fibre, and also contain nutrients such as folate, iron, magnesium and potassium. Due to having an incomplete amino acid profile, those who follow a vegetarian or vegan diet should include nuts and seeds alongside beans and pulses to ensure they receive all the essential amino acids.
Protein per 100g:
Chickpeas – 7g
Green peas – 5g
Kidney Beans – 7g
Butterbeans – 8g
Lentils – 8g
Nuts and seeds are another excellent way to increase the amount of protein in your diet. As with beans and pulses, nuts and seeds are best consumed alongside other protein sources because they are lacking in one of the essential amino acids. While being a great source of healthy fats, nuts and seeds also contain magnesium, potassium, zinc and B vitamins.
Protein per 100g:
Almonds – 21g
Peanuts – 26g
Walnuts – 15g
Cashew nuts – 18g
Brazil nuts – 14g
Sunflower seeds – 21g
Chia seeds – 17g
Sesame seeds – 18g
Flaxseed – 18g
References
Longland TM, Oikawa SY, Mitchell CJ, Devries MC, Phillips SM. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. The American Journal of Clinical Nutrition. 2016;103(3):738-46. Baum JI, Kim I-Y, Wolfe RR. Protein Consumption and the Elderly: What Is the Optimal Level of Intake? Nutrients. 2016;8(6):359. Berrazaga I, Micard V, Gueugneau M, Walrand S. The Role of the Anabolic Properties of Plant- versus Animal-Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review. Nutrients. 2019;11(8):1825. Ciuris C, Lynch HM, Wharton C, Johnston CS. A Comparison of Dietary Protein Digestibility, Based on DIAAS Scor
