12 March 2012

Protein facts

There have been many questions about proteins on the forum lately - how much should I eat? Why do I need it? What can I eat instead of red meat? What if I'm vegetarian?


“How much protein can/should I eat? What protein foods can I eat instead of red meat? What proteins can vegetarians eat? Which foods have a high protein content?”

These are just some of the questions that have popped up on the forum lately. As there seems to be quite a bit of Confusion about Protein among the public, I thought it a good idea to give you some facts about protein.

What are proteins?

Proteins are macronutrients, which humans need to eat together with the other macronutrients, namely carbohydrates, fats and dietary fibre. Like all the other macronutrients, proteins are basically made up of carbon, hydrogen and oxygen, but they are the only macronutrients that also contain nitrogen.

Basic structure

Proteins consist of ‘building blocks’ called amino acids. Amino acids are divided into ‘essential’ and ‘non-essential’ categories. Essential amino acids are those amino acids, which we humans are not able to synthesize in sufficient quantities to meet our daily needs and that must be supplied by the food we eat. Non-essential amino acids are manufactured in the human body in adequate quantities to meet our daily needs.

Essential amino acids

The following amino acids are classified as ‘essential’: threonine, tryptophan, histidine, lysine, leucine, isoleucine, methionine, valine and phenylalanine. The reason why I have listed these essential amino acids is to assist those readers who take protein supplements for various reasons (muscle building, supplementation during, or after wasting illnesses), to judge if the product they are using contains all the essential amino acids, or not. Check the labels of these products against this list if you want to determine if the product you have purchased is indeed a ‘complete’ protein supplement.

What foods contain ‘complete’ proteins?

‘Complete’ proteins are those that contain all the abovementioned essential amino acids and they are found in the following foods:

  • all types of meat - beef, mutton, pork, poultry, liver
  • all types of fish - fresh, canned or frozen
  • all types of milk - cow’s, goat’s and even exotic species like yak’s milk
  • dairy products - yoghurt, maas (sour milk), cottage cheese and all other types of cheese (Cheddar, Gouda, Feta, Roquefort, Emmenthal, etc)
  • eggs, especially the whites

What protein foods can be eaten instead of red meat?

Most people think that red meat is the only source of complete protein and that they will be losing out if they don’t like eating red meat or are unable to do so for personal, religious or health reasons (e.g. gout). The idea that red meat is the only, or the best source of protein is false. In nutritional terms the proteins found in milk and egg white are often classified as the ‘gold standards’ of high protein quality. So if you can’t, or don’t want to eat red meat, you need not worry that you will develop a protein deficiency. Just make sure that you drink milk and/or eat yoghurt, cheeses and eggs.

For those of you who can’t face red meat, fish and sea food are also excellent substitutes for meat, with the added benefit that fish contains omega-3 fatty acids and iodine. White fish is also less fattening than red meat, and contains less saturated fat.

Combining proteins

Protein foods derived from animals are usually expensive and many people cannot afford to eat even moderate quantities of meat or fish on a daily basis. If this applies to you, then you will be glad to know that eating other protein foods such as legumes (dry beans, peas, lentils, soya products) together with small quantities of animal proteins will still ensure that you are getting sufficient proteins to meet your needs. This is because plant proteins (which are partially ‘incomplete’) and animal proteins (‘complete’) complement each other when it comes to providing your body with the correct mix of amino acids. In fact, people who obtain most of their protein from plants combined with small quantities of animal protein (e.g. Toppers eaten with a bit of grated cheese), are usually healthier than people who eat only animal protein.

Advantages of plant protein

Despite the fact that plant proteins found in foods such as legumes, are lacking some of the essential amino acids, these foods are basically better for all round health than foods such as red meat. Plant proteins contain less fat, less atherogenic fat (atherogenic = causing clogged arteries/heart disease), no cholesterol, and plenty of dietary fibre and protective nutrients such as bioflavonoids. Lacto-ovo-vegetarians and people in rural communities, who have not changed to western eating habits, probably eat the healthiest diet on our planet. By eating predominantly plant foods combined with milk, dairy products and eggs, these people ensure that they are getting sufficient total protein, and sufficient ‘complete’ protein with all the added benefits bestowed by a diet rich in fibre, vitamins and minerals.

Conversely, diets that contain no animal protein whatsoever (e.g. vegan diets) can cause a deficiency in those essential amino acids and are not recommended for anyone with growth needs: infants, children, teenagers, pregnant and lactating women and individuals suffering from wasting diseases, such as HIV/AIDS, or cancer.

If you have any diet queries, post a question or message on DietDoc's forum

- (Dr I.V. van Heerden, DietDoc)

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