Protein

Without protein you couldn’t exist – not only does it make up your muscles, nails and hair, but even your DNA is made from protein. But what is it and where does it come from?

We can build it

Proteins are chains, made up of various combinations of 20 amino acids – known as the ‘building blocks’ of protein. The chains are incredibly long and complex – every part of the chain has to be exactly right for the protein to do its job properly. The order and number of amino acids in the chain is what affects the protein’s role – whether it will become a hormone, an enzyme or part of a blood cell, for example.

Amino acids are found in all sorts of foods – both plant and animal sources.

Some amino acids can be manufactured by the body but there are eight that the body can’t make – these are called the ‘essential amino acids’.

One particular food may contain two or three of the essential amino acids, while another will contain two or three others. The more varied the diet, the better chance you have of obtaining building blocks for all the proteins.

Veggie heaven

Some people believe that vegetarians don’t eat enough protein. The truth is that protein is present in so many types of food that people in this country rarely suffer from deficiency, so a vegetarian with a varied, balanced diet will easily eat enough protein.

The reason for the confusion is down to what used to be known as the ‘quality’ of the protein. Animal sources of food, like meat or egg, contain all the essential amino acids we need, in about the right proportions (they provide a ‘complete’ protein), while plant foods usually do not (soya is an exception as it is a complete protein).

Vegetarian people simply need to eat a variety of different foods to obtain all the essential amino acids – beans on toast, for example, or rice and lentil dahl.

These types of meal are good alternatives for meat eaters, too – low in fat, high in fibre and full of vitamins and minerals, they make a cheap and tasty protein-rich meal.

Making muscles

Protein is essential for repairing the muscles used during exercise. Athletes need to eat more protein than other people to help repair and rebuild their muscles, which are worked so hard during intensive exercise.

Some athletes believe that they need to boost their dietary intake with protein shakes or supplements. However, this is completely unnecessary, as long as the athlete is eating a varied, balanced diet.

Gym-goers are also often told that protein supplements can help them but, in fact, protein is so widely available from food that taking extra is pointless.

The amount of protein we need varies with age, build and gender (men tend to need more than women). It's recommended that women should consume around 45g per day, while men should consume around 55g per day.

These examples should give you an idea of how easy it is to achieve the recommendations:

• Half a can of baked beans on two slices of wholemeal toast: 17g protein

• Small can of tuna on a baked potato with a salad: 40g protein

• Turkey strips stir-fried with mange-tout, beansprouts, peas and green peppers, served with brown rice: 39g protein

Can I eat too much protein?

After you’ve eaten protein-containing foods, the protein is broken down into its original building blocks – the amino acids – which are then used to create new proteins. But if there’s more protein than your body needs, some parts will be used as energy - or converted into fat! - and the rest will leave your body, via the kidneys, when you wee.

Research into whether a high protein diet causes damage to the kidneys has had mixed results. Certainly, a person who already has kidney disease of any sort should take care with their protein intake (ask your GP for advice). However, in people with healthy kidneys, it’s not thought that any damage is caused by eating lots of protein.

Protein contains calories so there’s a good reason to not eat excessive amounts if you’re watching your weight. The recommendation is that you shouldn’t eat more than 1.5g of protein per kg of body weight per day. This sounds complicated, but it’s not…

For example, a woman weighing 9 ½ stone (60kg) should avoid consuming more than 90g of protein a day (1.5g x 60kg).

Base your varied, balanced diet on around one-third carbohydrates (including potatoes) and one-third fruit and vegetables, with the final third divided between low fat milk and dairy products and meat, fish, eggs and non-meat sources of protein like beans and pulses. And don’t forget an occasional treat…!