What is Protein?
The word ‘protein’ refers to a type of molecule in food that can be broken down into amino acids.
The body needs twenty amino acids - as a biological machine it can create (or synthesize) eleven of these itself. However there are nine, called ‘essential amino acids’ that the body cannot create and has to gain through the consumption of food.
These ‘essential amino acids’ are: Tryptophan, Threonine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Valine and Histidine.
When we eat, the body breaks down the protein in food in order to create the amino acids that it needs.
Although most foods contain protein some foods are richer in some of the essential amino acids than others. Usually, therefore, foods need to be combined so that the body receives all the amino acids it needs on a daily basis – part of the reason that a varied, balanced diet is essential to us.
For example, if you ate only blueberries you may start to lack the Tryptophan, Lysine and Histidine that your body needs - introducing some meat and/or cheese into your diet would help to address these deficiencies.
What Protein Does for Us
Protein is the body’s building block. All of our organs, including the skin, are built from proteins, as are the muscles, hair and nails.
Many hormones are proteins, and, the immune system, digestive system and blood all rely on proteins to work correctly.
Protein is therefore an essential part of our diet, vital to development and correct functioning of the body. Protein is particularly important for children and adolescents - as they grow and develop into adults proteins are used to produce tissue. Protein is also particularly important for pregnant women (see our page Pregnancy and Wellness for more.)
If our diets contained no protein then our bodies would start to break down muscles in order to produce the protein it needs – our bodies are good at storing fats and some sugars but not good at storing proteins. It is therefore necessary to continually replace the protein that our bodies use.
Proteins need fuel in order to work – like a car needs fuel. Fuel is provided from the carbohydrates and fats in our diet. The production of amino acids in the body is also reliant on other nutrients especially B vitamins and zinc.
How Much Protein Do We Need?
The amount of protein that we need is dependent in part on our age, weight and levels of activity. Children and adolescents who are still growing and developing need proportionately more protein in their diets than adults. People with high levels of activity may need slightly more protein than those who lead more sedentary lifestyles – as protein is essential in building and repairing muscle and other tissues slightly more is needed for those actively trying to develop muscle.
To calculate roughly how much protein you need to consume daily: multiply your weight in kilograms by 0.8. The answer is the number of grams of protein you should consume every day.
Therefore if you weigh 100kg you should be consuming around 80grams of protein a day.
Many people on modern diets consume more protein than necessary. A simple way to think about protein intake is to think about protein-rich foods making up a quarter of your diet – with a further quarter being carbohydrates and the other half being fresh fruit and vegetables.
If we exercise more our appetites generally increase, so we eat more - the above ¼ protein rule still works as a general guideline - our protein intake would increase proportionately.
Food Rich in Protein
Although most food and drinks contain some protein, certain types of food are richer in protein than others.
The following list includes the food types that contain the most protein:
Most meats and poultry and are good sources of protein.
As meat can also be high in saturated fats, lean cuts of meat are better as they contain less saturated fat. Meat preparation is also an important factor in balancing protein intake and fats - for example, fried meat products contain protein but higher levels of saturated fats.
More on Fat - Good and Bad.
A piece of lean meat (beef, pork, lamb or chicken) about the size of a pack of playing cards will contain approximately 20 grams of protein.
Fish is also a good source of protein.
Salmon, trout, mackerel, sardines, pilchards, herring, kipper, eel and whitebait are termed oily fish, approximately 140 grams of oily fish will contain 20 grams of protein.
Other fish - cod, plaice, tuna and seafood like lobster and crab are also high in protein but usually in slightly lower quantities, about 150 grams of these fish types contain 20 grams of protein. Fish eggs, namely Roe and Caviar are also good sources of protein.
One large egg will contain about 6 grams of protein.
Eggs are an important source of protein to vegetarians, boiled and poached eggs are better than fried as they will contain less fat.
See our page: Cooking Fats and Oils to find out which are the healthiest cooking fats and oils to use - for frying an egg and other purposes.
Dairy products are also important sources of protein.
For example, 200ml (1 cup) of semi-skimmed (2%) milk contains about 8 grams of protein.
Protein comes from the milk and not fat in milk, skimmed and semi-skimmed milk have had much of their fat removed and therefore contain more protein per ml than whole milk (and more calcium too).
Other dairy products are good sources of protein, cheeses, yoghurt, fromage frais and sour cream. These products can also, however, be high in fat. Low fat alternatives usually have the same, if not slightly more, protein per gram than the full fat versions.
Beans are a good source of vegetable proteins, essential to vegans but also an important part of all well-balanced diets.
Mature soya beans contain nearly 40% protein; soya products such as soya milk and tofu are also good sources of protein. Many other types of beans - black beans, pinto beans, kidney beans, butter beans and lentils are all important sources of protein. Peanuts (which are actually beans and not nuts) contain almost 25% protein – peanut butter is therefore a good source of vegetable protein, although it can contain a lot of fat and salt.
Vegetarian and vegan alternatives to meat, like Quorn, also contain proportionately high levels of protein.
Nuts and Seeds
Many nuts and seeds contain protein; nuts and seeds are also a good source of many vitamins and minerals needed by our bodies.
Almonds, cashews, walnuts and pecan nuts are all relatively high in protein, as are sunflower, pumpkin and flax seeds.
Other Protein Sources
Marmite and other yeast extract spreads are high in protein content – about 25% protein.
Whole grains can be significant sources of protein in some diets, whole grains also contain high levels of beneficial complex carbohydrates. Protein rich whole grains include whole wheat and wheat bran, oats and oat bran, barley and brown rice.
Certain vegetables, especially asparagus, broccoli, Brussels sprouts, cauliflower and avocado are good sources of protein.
Finally, protein supplements are available – commonly powdered milk (whey) and soya based proteins are used to make protein rich drinks.
Amino acids are also available in pill form, either individually or combining two or more of the essential amino acids – such pills may be prescribed to patients who cannot, thorough various health complaints, synthesise the amino acids they need from protein.