What is protein and why do we need it in our diet?

Protein is an important macronutrient in our diet which is key for maintaining and building muscle. Protein sources can vary depending on our diet and the amount we need can change depending on our weight and our exercise goals.

We take a look at what protein is, the types and how much we need in our diets.

What is protein?

Proteins are known as the building blocks of life as they break down into amino acids that help the body grow and repair.¹

Some amino acids can be made by our bodies, but some can't and so we must get them from food.

Muscle accounts for around half of the protein in the body but other forms of protein include:

• hormones controlling growth and appetite,
• collagen which makes up our skeleton, nails and hair,
• enzymes that break down our food,
• and haemoglobin which carries oxygen in the blood.

Types of protein

There are 9 amino acids that can’t be produced by the body, and these are known as essential amino acids. If a food contains all the essential amino acids, it is called a complete protein.

If a food lacks one or more of the essential amino acids, it’s an incomplete protein. Incomplete proteins are not worse or lower quality proteins, it just means an amino acid the body can't make is missing.

Some examples of complete protein sources are:

• animal products (meat, eggs, dairy),
• soy protein,
• quinoa,
• and Quorn.

Some examples of incomplete protein sources are:

• legumes (beans, peas, lentils),
• nuts and seeds,
• wholegrains,
• and vegetables.

If your preferred diet consists of more incomplete proteins, pairing foods together helps ensure you get all the essential amino acids your body needs.

For example, beans on toast pairs together grains and legumes which gives you a complete protein source. You don’t need to do this with every meal, as long as you include a variety of protein sources throughout the day or week.

How much protein do I need?

The Reference Nutrient Intake (RNI) for daily protein for adults is 0.75g per kg of body weight.²

For the average woman, this is 45g, or 55g for men. That’s about two portions of meat, fish, nuts or tofu per day. As a guide, a protein portion should fit into the palm of your hand.³

However, individual protein requirements will change depending on our individual needs and goals. For example if the goal is weight loss, the National Academy of Sport Medicine recommends 1.6-2.2g per kg body weight.⁴ This is because protein helps to increase the satiety of food which can help you feel fuller for longer.

Average amount of protein in common foods

Protein content in grams (g) is based upon per 100g:

• Chicken breast (grilled, without skin) – 32.0g
• Pork chop (lean, grilled) – 31.6g
• Tuna (canned in brine) – 24.9g
• Salmon (grilled) – 24.6g
• Cod (baked) – 23.9g
• Prawns (cooked) – 15.4g
• Eggs (whole, boiled) – 14.1g

Dairy

• Whole milk – 3.4g
• Semi-skimmed milk – 3.5g
• Skimmed milk – 3.5g
• Cheddar cheese – 25.4g
• Reduced-fat cheddar – 27.9g
• Plain Greek-style yogurt – 5.7g
• Plain low-fat yogurt – 4.8g

Plant protein

• Red lentils (boiled) – 7.6g
• Chickpeas (canned) – 7.2g
• Tofu (steamed) – 8.1g
• Kidney beans (canned) – 6.9g
• Baked beans – 5g
• Rice (easy cook, boiled) – 10.9g
• Pasta (dried cooked) – 4.8g⁵

Protein forms part of eating a nutritionally balanced diet which has many health benefits, such as reducing the risk of diabetes, heart disease and some cancers.⁶

Combined with other healthy lifestyle habits, such as better sleep, moving more, and drinking plenty of water, diet is the foundation to building and maintaining good overall health.

References

1. Protein: what you need to know – British Heart Foundation
2. Eating well for exercise – British Nutrition Foundation
3. How much protein do I need? – British Heart Foundation
4. Protein and Weight Loss – NASM
5. Protein in the diet – British Nutrition Foundation
6. Why do I need a balanced diet? - British Nutrition Foundation