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.
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 that humans are not able to synthesise 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.
The following amino acids are classified as ‘essential’: threonine, tryptophan, histidine, lysine, leucine, isoleucine, methionine, valine and phenylalanine.
Which foods contain ‘complete’ proteins?
‘Complete’ proteins are those that contain all the above-mentioned essential amino acids. 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
Which 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're vegetarian.
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.
If you're a lacto-ovo vegetarian, you needn't worry that you'll develop a protein deficiency. Just make sure that you drink milk and/or eat yoghurt, cheese and eggs.
Fish and seafood 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.
But protein foods derived from animals aren't ideal for all vegetarians.
If this is the case, you'll be glad to know that eating other protein foods such as legumes (dry beans, peas, lentils, soya products) along with small quantities of animal proteins will still ensure that you're getting sufficient protein 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. soya protein 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 lack 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 follow the healthiest diet on the planet.
By eating predominantly plant foods combined with milk, dairy products and eggs, these people ensure that they're 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.
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