Proteins are composed of amino acids
Proteins are made up of building blocks called amino acids. There are about 20 various amino acids that link usually in different combinations. Your body uses them to make new proteins, such as muscle and bone, and other compounds such as enzymes and hormones. It can also use them as an energy source.
Nutritional value of protein
The nutritional value of a protein is measured by the number of essential amino acids it contains.
Different foods contain different amounts of basic amino acids:
- Animal products (such as chicken, beef, fish, and dairy products) have all of the required amino acids and are known as ‘complete’ protein (or ideal or high-quality protein).
- Soy products, quinoa, and the seed of a leafy green called amaranth (consumed in Asia and the Mediterranean) also have all of the necessary amino acids.
- Plant proteins (beans, lentils, nuts, and whole grains) usually lack at least one of the required amino acids and are considered ‘incomplete’ proteins.
People following a strict vegetarian or vegan diet require to choose a variety of protein sources from a mixture of plant foods every day to make sure they get a sufficient mix of essential amino acids.
If you follow a vegetarian or vegan diet, as long as you eat a wide variety of foods, you can normally get the protein you need. For instance, a meal including cereals and legumes, such as baked beans on toast, provides all the required amino acids found in a typical meat dish.
Some food sources of dietary protein include:
- Poultry: chicken, duck, turkey, emu, goose, bush birds
- Lean meats: beef, lamb, veal, pork, kangaroo
- Fish and seafood: fish, crab, lobster, prawns, mussels, oysters, scallops, clams
- Dairy products: yogurt, milk, cheese
- Nuts and seeds: pine nuts, walnuts, almonds, macadamias, cashews, pumpkin seeds, hazelnuts, sesame seeds, sunflower seeds
- Legumes and beans: all beans, chickpeas, lentils, split peas, tofu.
Some cereal-based and grain products are also sources of protein but are commonly not as high in protein as meat and meat alternative products.
How to get your protein needs
Your regular protein needs can easily be met by following the Australian Dietary Guidelines.
The two main food groups that contribute to protein are:
- ‘lean meat and poultry, fish, eggs, tofu, nuts and seeds, and legumes/beans’ group
- ‘milk, yogurt, cheese.
As part of a healthy diet, the Guidelines suggest appropriate serves per day from each of the five food groups.
The human body can’t store protein and will excrete any excess, so the most effective way of meeting your daily protein requirement is to eat small amounts at every meal.
Daily suggested serves of ‘lean meat and poultry, fish, eggs, tofu, nuts and seeds, and legumes/beans’ and ‘milk, yogurt, cheese and/or alternatives (mostly reduced fat)’ for adults
|Person||Recommended average daily number of serves of lean meat and poultry, fish, eggs, nuts and seeds, and legumes/beans||Recommended average daily number of serves of milk, yogurt, cheese and/or alternatives (mostly reduced fat)|
|Men aged 19–50 years||3||2 1/2|
|Men aged 51–70 years||2 1/2||2 1/2|
|Men aged 70+ years||2 1/2||3 1/2|
|Women aged 19–50 years||2 1/2||2 1/2|
|Women aged 51–70 years||2||4|
|Women aged 70+ years||2||4|
|Pregnant women||3 1/2||2 1/2|
|Lactating women||2 1/2||2 1/2|
Standard serving size of ‘lean meat and poultry, fish, eggs, nuts and seeds, and legumes/beans’ is one of:
- 65g cooked lean meats such as beef, lamb, veal, pork, goat or kangaroo (about 90 to 100g raw)
- 80g cooked lean poultry such as chicken or turkey (100g raw)
- 100g cooked fish fillet (about 115g raw weight) or one small can of fish
- 2 large eggs
- 1 cup (150g) cooked dried beans, lentils, chickpeas, split peas or canned beans (preferably with no added salt)
- 170g tofu
- 30g nuts, seeds, peanut or almond butter or tahini or other nut or seed paste (no added salt).
A serve of ‘milk, yogurt, cheese and/or alternatives (mostly reduced fat)’ could include:
- 250ml (1 cup) fresh, UHT long life, reconstituted powdered milk or buttermilk
- 120ml (1/2 cup) evaporated milk
- 200g (3/4 cup or 1 small carton) yogurt
- 40g (2 slices) hard cheese such as cheddar
- 120g (1/2 cup) ricotta cheese.
Getting more protein into your day, naturally
If you’re looking for ways to get more protein into your diet, here are some suggestions:
- Try a peanut butter sandwich. Remember to use natural peanut butter (or any other nut paste) with no added salt, sugar, or other fillers.
- Low-fat cottage or ricotta cheese is high in protein and can go in your scrambled eggs, casserole, mashed potato, or pasta dish. Or spread it on your toast in the morning.
- Nuts and seeds are fantastic in salads, with vegetables and served on top of curries. Try toasting some pine nuts or flaked almonds and putting them in your green salad.
- Beans are great in soups, casseroles, and pasta sauces. Try tipping a drained can of cannellini beans into your favorite vegetable soup recipe or casserole.
- A plate of hummus and freshly cut vegetable sticks as a snack or hummus spread on your sandwich will give you easy extra protein at lunchtime.
- Greek yogurt is a protein-rich food that you can use throughout the day. Add some on your favorite breakfast cereal, put a spoonful on top of a bowl of pumpkin soup, or serve it as a dessert with some fresh fruit.
- Eggs are a versatile and easy option that can be enjoyed on their own or mixed in a variety of dishes.
Getting too little protein (protein deficiency)
Protein deficiency means not getting enough protein in your diet. Protein deficiency is rare in Australia, as the Australian diet generally includes far more protein than we actually need. However, protein deficiency may occur in people with special requirements, such as older people and people following strict vegetarian or vegan diets.
Symptoms of protein deficiency include:
- wasting and shrinkage of muscle tissue
- oedema (build-up of fluids, particularly in the feet and ankles)
- anaemia (the blood’s inability to deliver sufficient oxygen to the cells, usually caused by dietary deficiencies such as lack of iron)
- slow growth (in children).
Protein – maintaining muscle mass as you age
From around 50 years of age, humans begin to gradually lose skeletal muscle. This is known as sarcopenia and is common in older people. Loss of muscle mass is worsened by chronic illness, poor diet, and inactivity.
Meeting the daily recommended protein intake may help you maintain muscle mass and strength. This is important for maintaining your ability to walk and reducing your risk of injury from falls.
To maintain muscle mass, it’s important for older people to eat protein ‘effectively’. This means consuming high-quality protein foods, such as lean meats.
Protein shakes, powders, and supplements
Protein shakes, powders and supplements are unnecessary for most Australians’ health needs. According to the most recent national nutrition survey, 99% of Australians get enough protein through the food they eat.
Any protein you eat on top of what your body needs will either be excreted from your body as waste, or stored as weight gain.
The best way for you to get the protein you need is to eat a wide variety of protein-rich foods as outlined in the Australian Dietary Guidelines, as part of a balanced diet. But if you are still interested in using protein shakes, powders and supplements, talk to your doctor.
Protein and exercise
Soon after exercising, it’s recommended that you have a serve of high-quality protein (such as a glass of milk or tub of yogurt) with a carbohydrate meal to help maintain your body’s protein balance. Studies have shown this to be good for you, even after low to moderate aerobic exercise (such as walking), particularly for older adults.
People who exercise vigorously or are trying to put on muscle mass do not need to consume extra protein. High-protein diets do not lead to increased muscle mass. It’s the stimulation of muscle tissue through exercise, not extra dietary protein, which leads to muscle growth.
Studies show that weight-trainers who do not eat extra protein (either in food or protein powders) still gain muscle at the same rate as weight-trainers who supplement their diets with protein.
Very high protein diets are dangerous
Some fad diets promote very high protein intakes of between 200 and 400g per day. This is more than five times the amount recommended in the Australian Dietary Guidelines.
The protein recommendations in the Guidelines provide enough protein to build and repair muscles, even for bodybuilders and athletes.
A very high-protein diet can strain the kidneys and liver. It can also prompt excessive loss of the mineral calcium, which can increase your risk of osteoporosis.