(This is the third post in the Dieting Basics series.)
What are proteins?
Proteins are used for growth and reparation in the body. They are essential for almost all day-to-day metabolic processes, from digesting food to transporting oxygen around the body. They’re also needed to produce antibodies to fight off disease and infection.
Proteins are made of up amino acids – there are 20 different amino acids found in proteins of various sources. When the protein we eat is digested, it’s broken down into individual amino acids which are then reformed into new proteins for use by our body.
A gram of protein contains 4 kilocalories.
What’s the difference between essential and non-essential amino acids?
The 20 types of amino acid in the protein we eat are divided into essential and non-essential amino acids.
The 8 essential amino acids can’t be produced by our body and have to come from the food we eat. The 12 non-essential amino acids can be manufactured by our body.
However, this doesn’t mean we only need to eat essential amino acids: the non-essential ones are just as important, as the body needs them in order to form new proteins.
(Note that two of the 12 non-essential amino acids are essential for babies, who can’t produce them: this is why you’ll sometimes see the figure “10 essential amino acids” or “8/10 essential amino acids”.)
What are complete and incomplete sources of protein?
A “complete” source of protein is a food that contains all 8 of the essential amino acids. All animal sources (such as meat, fish, dairy products and eggs) are complete proteins. “Incomplete” sources of protein contain some, but not all, of the essential amino acids.
If you’re vegetarian or vegan, you can still get all your essential amino acids by combining different sources of protein: baked beans on wholemeal bread is an easy example! Soybeans are the only food from a plant source considered be a “complete” protein in a single food.
Am I eating enough protein?
It’s very rare for people in the developed world to suffer protein deficiency. If you eat meat, you’re almost certainly getting plenty of protein. A single chicken breast contains 40g of protein – compare this with the RDA (recommended daily allowance) for an adult woman of 50 grams and for an adult man of 63 grams, and you can see that it’s easy to exceed this target.
Even if you’re vegetarian, you might be surprised how much protein there is in foods often considered to be just “carbohydrates” – wholemeal bread and rice contain reasonable amounts of protein. Dairy products such as cheese and milk are obviously good sources, as are beans and pulses.
Eating too little protein can make you feel tired and run-down, and the condition of your skin and hair will suffer. If you’re recovering from illness or exercising regularly, you may need to eat extra protein.
Am I eating too much protein?
Too much protein can be just as dangerous as too little – and is more of a risk for many people. The body can’t store extra protein, so eating too much means it will be converted to glucose by the liver and either used up as energy or stored as fat. Protein-rich foods contain high levels of nitrogen, which the kidneys and liver have to remove from the body – overworking these organs can damage them. Excessive protein also promotes the loss of calcium from bones, which can lead to osteoporosis.
Even if you’re weight training, you almost certainly don’t need to buy expensive protein bars or shakes. And if most of your day consists of sitting at a desk, you’re likely to be getting more than enough protein to keep your body in good shape.
It’s safest to follow a diet which consists mainly of carbohydrates (about 55-60% of your calories should come from carbs), with protein making up about 15-20% of your total calorie intake.
What foods are good sources of protein?
All meat and dairy products contain plenty of protein – and they are complete sources, so you’ll get all the essential amino acids. However, some choices are better for dieters than others: these “lean proteins” are ones which don’t come with much fat:
- Skinless chicken breasts
- Wafer-thin ham
- Cottage cheese
If you’re vegetarian, you need to make sure you’re eating foods containing the different essential proteins. This usually happens naturally as part of a balanced diet. To combine proteins, just make sure you have the following in your meal:
- Bread, cereals or grains (eg. pasta, breakfast cereal, bread, noodles)
With a food from one of the following three groups:
- Legumes (peas, beans and lentils)
- Vegetables (including potato)
- Nuts and seeds
But remember that you don’t need to eat all the essential amino acids at the same time – so long as you eat a range of foods over a period of a few days, you should be getting plenty of protein and all the essential amino acids that you need.
As you can see, it’s easy to get all the protein and amino acids that you need. Don’t be fooled into believing that you need to follow an expensive high-protein diet to lose weight – you don’t, and you’ll risk damaging your liver and kidneys.
If you missed part two of the Dieting Basics series, find it here: Fats – mono, poly, trans – which are good? … and make sure you get the rest of the series by subscribing to The Office Diet in your feed reader.
(Image above by rexipe)