Why is protein important?? From hair to fingernails, protein is a major functional and structural component of all our cells. Protein provides the body with roughly 10% to 15% of its dietary energy, and is needed for growth and repair.
Proteins are large molecules made up of long chains of amino acid subunits. Some of these amino acids are nutritionally essential as they cannot be made or stored within the body and so must come from foods in our daily diet.
Although all animal and plant cells contain some protein, the amount and quality of this protein can vary widely.
ANIMAL PROTEIN
Protein from animal sources contains the full range of essential amino acids needed from an adult's diet. But red meat, in particular, should be eaten in limited amounts due to the high level of saturated fat it contains, which may raise blood levels of 'unhealthy' LDL cholesterol.
A high intake of saturated fat can lead to an increased risk of cardiovascular disease and other related disorders. As an alternative source of animal protein, choose poultry, fish and shellfish.
The 2007 World Cancer Research Fund report recommended meat eaters limit their consumption of red meat to no more than 500g a week, with very little processed meat, as these have both been linked to certain forms of cancer.
Fish is a good source of animal protein. Oil-rich fish such as salmon, mackerel, herring, tuna, trout and sardines are all rich in omega-3 fatty acids, which help to reduce the risk of developing cardiovascular disease.
Shellfish is also a good source of protein and is low in fat.
Aim to eat a couple of portions of fish every week, with at least one portion being an oily fish.
"Advice for vegans and vegetarians"
Vegetarians rely on plant sources for their daily protein. Plants don’t contain the full range of essential amino acids and so are not as high in nutritional value as animal protein. But by eating a well-balanced diet that contains a variety of different foods, it's possible to consume the required amino acids, regardless of the time of day they’re eaten or in what combination within a meal.
Foods such as nuts, seeds, beans, pulses, vegetable protein foods and soya products all contain protein. There are also small amounts in grains and dairy products. Due to this variety of protein-rich foods available in the UK, protein deficiency is rare.
"How much is enough?"
Health professionals suggest men should eat 55.5g protein a day and women 45g. In practical terms, eating a moderate amount of protein - in one or two meals every day – should give you all the protein you need. Most people in the UK eat far more protein than they actually need.
"Serving size"
You should eat two to three servings of protein every day from both plant and animal sources. Here are some examples of one serving (about the size of a standard pack of playing cards):
- 100g boneless meat (e.g lean beef, lamb or pork)
- 100g boneless poultry (e.g chicken or turkey breast)
- 100g fish (e.g salmon, sardines or tuna)
- 2 medium eggs
- 3 tablespoons of seeds (e.g sunflower or pumpkin seeds)
- 3 tablespoons of nuts (e.g almonds or walnuts)
"Choosing the right protein"
If you can, choose to eat low-fat protein foods as these will help to:
- Keep your heart healthy
- Keep cholesterol low
- Minimize the risk of developing cardiovascular disease and other related disorders
"Protein and weight management"
High-protein diets are sometimes popular with people wanting to lose weight, and there have been many studies looking at the effect of such diets on weight loss.
Regardless of the composition of the diet, weight loss will only occur if you expend more energy through activity than your body produces from food.
Protein-rich foods tend to make people feel fuller than foods rich in carbohydrates or fat. This can have a knock-on effect on appetite, minimizing feelings of hunger, and helping to reduce overall energy intake.
Diets rich in protein at the expense of carbohydrates, for example, have been associated with slightly greater losses of weight in the short term compared with the recommended high-carbohydrate, low-fat eating plans. But after one year, studies have found there is no difference in weight loss between the two diets.
To control your weight it's important to find an eating pattern that suits your lifestyle and that you can sustain over a long period.
This article was last medically reviewed by the MRC Human Nutrition Research in July 2008.
First published in March 2001.
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