Proteins are large molecules composed of chains of amino acids in a specific order. They are held together by peptide bonds (proteins are also called polypeptides).
Proteins are important for growth and repair. They are required for the structure, function, and regulation of the body’s cells, tissues, and organs.
Each protein has unique functions.
Proteins are included in:
- The cell membranes
- Cellular structures (skin, hair, muscle, bone)
- Blood Components like haemoglobin
- Other structures that are carriers within the bloodstream, such as albumin
Albumin is the most common protein in the blood and is responsible for the transport of other proteins and molecules in the blood.
Globulin’s are also common proteins that are effective in the immune response. Our antibiotics are made from proteins.
On a macroscopic level, proteins make up the bulk of muscle tissue and can be found in most human tissue.
Non-structural proteins are perhaps as vitally important as the structural ones. These include enzymes, proteins that are catalysis which help a reaction take place, to make whatever biochemicals the body needs.
There are also digestive enzymes. These are the proteins in the human digestive tract that break down food, from proteins to fats and carbohydrates, into their component parts so they can be effectively absorbed by the small intestines.
Enzymes generally operate within a very narrow pH range and most of them work best in the pH of the human body.
However, the protein enzymes that work in the stomach, for example most operate at very low pH ranges.
The Roles of Enzymes
Most enzymes in the body are very specific and do only on particular job.
There are enzymes that break down chemical bonds, those that reconnect chemical bonds and those that help to package into their proper shape so they can be transported to where they are needed. Other proteins do the transporting.
Amino Acids: Essential and Non-essential
There are around 100,000 different proteins found in the human body and each of them is made from a different combination of just 20 different amino acid building blocks.
- A monomer is simply the basic unit of a protein, carbohydrate or fat. For example, the monomer for a fat is a fatty acid and the monomer for carbohydrates is the simple sugar. For proteins, it is the amino acid.
- In organic chemistry, an amino acid consists of the chemical H2NCHROOH, where the R group is an organic component. The R group defines the amino acid and is unique to each amino acid.
Pictorially, the structure of the amino acid looks like the following chemical structure:
There are two basic types of amino acids:
- The non-essential amino acid which is an amino acid that can be built by the body when necessary.
- The essential amino acid, which cannot be made by the human body and which must be eaten in the diet in order for the body to have it.
Let’s take a look at a list of these amino acids:
- Aspartic acid
- Glutamic acid
Essential amino acids are considered essential to the diet.
Five more are considered conditionally essential, meaning that in most people they are not required in the diet but in some populations who don’t make them in sufficient amounts, they are essential.
Besides the standard twenty amino acids, there are non-essential amino acids sometimes used in protein structures.
Sources of Protein
As a nutritional advisor, you should know how much protein is required from/in the clients diet, and which the best sources of protein are.
The average adult requires fifty grams of protein per day except in cases of pregnancy and body building, when the protein requirements are higher. Protein requirements may also vary according to health status and may be affected by digestive and absorptive capacity.
One way to determine the minimum amount of protein a person needs in their diet each day is to use the following formula:
How to Calculate Your Protein Needs
1. Weight in pounds divided by 2.2 = weight in kg
2. Weight in kg x 0.8-1.8 gm/kg = protein gm.
Use a lower number if you are in good health and are sedentary (i.e., 0.8). Use a higher number (between 1 and 1.8) if you are under stress, are pregnant, are recovering from an illness, or if you are involved in consistent and intense weight or endurance training.
Example: 154 lb male who is a regular exerciser and lifts weights
154 lbs/2.2 = 70kg
70kg x 1.5 = 105 gm protein/day
This represents the minimum recommended daily allowance for a given person needing protein in their diet.
All protein must be gained from food sources (unless the client is taking supplements). Lets take a look at food sources of protein.
Food Sources of Protein
The main sources of protein in the diet are:
- Meat (beef,pork, lamb)
- Poultry (chicken, turkey)
- Dairy (milk, cheese, yogurt)
- Pulses (beans, peas, lentils)
- Nuts or Seeds
Meat is a great source of protein.
Most beef cuts contain about seven grams of protein for each ounce you eat.
A chicken breast is similarly high in protein, with as much as thirty grams. An average chicken thigh contains 10 grams of protein.
Fish has slightly less protein at 22 grams of protein for a fish fillet about 100 grams in weight.
Pork is also slightly less in protein with about 22 grams of protein per pork chop or 19 grams of protein for 3 ounce serving of ham.
Eggs and Dairy
Eggs and dairy are good sources of protein, especially for vegetarians who eat eggs and dairy products. An egg has six grams of protein in it and a cup (8floz/250ml) of milk contains 8 grams of protein.
Cheeses have protein in them as well. Cottage cheese has 15 grams of protein per half cup and medium cheese like cheddar cheese and Swiss cheese contains about 7 grams of protein per ounce.
Pulses (or legumes) – Beans, Peas, Lentils
For vegetarians who don’t eat dairy or eggs and vegans who avoid all animal products, pulses are good sources of protein. Half a cup of tofu contains around 20 grams of protein, and soya milk contains 6 – 10 grams of protein per cup.
Beans like black beans, kidney beans and pinto beans contain around 8 grams of protein per half cup of cooked beans. Chick peas also have 8 grams per cup and lentils around 9 grams.
Soya beans, when cooked, contain about 14 grams or protein per half cup, while split peas contain about 8 grams of protein per half cup.
Another good source of protein is quinoa, a grain like food that resembles couscous. The can be added to salads, stew etc. There are also quinoa breakfast cereals which make good alternatives to regular cereals such as rice crispies etc.
Nuts and Seeds
Nuts and seeds are also rich in protein.
Peanuts contain 9 grams of protein per quarter cup serving. A table spoon of peanut butter has 4 grams. The peanut is not a true nut, but is a pulse as it grows in pods.
Almonds and cashews contain six to eight and five grams of protein per one quarter cup serving, respectively.
Pumpkin seeds are an excellent choice for protein, especially in vegetarians, as 100 grams of pumpkin seeds contain 29 grams of protein.
Those wishing to augment their diet with protein supplements have a wide variety to choose from. Many protein supplements are drinks made from whey powder.
Whey is classed as a complete protein, meaning that it contains all of the essential amino acids a person needs to live. Most whey powders contain about 6.5 percent protein by weight.
There are also ion exchange protein powders which are more concentrated than ordinary whey proteins but lack some of the essential nutrients the body needs.
For those who wish to avoid dairy products, protein supplements made from soy or pea power are also available. Soy is a complete protein.
Creating Complete Proteins
All meat, fish, eggs and dairy sources of protein are complete proteins; that is they contain all of the essential amino acids the needs.
Vegetable sources of protein, such as grains, legumes and nuts or seeds contain incomplete proteins which can be made complete when mixed with complementary protein sources. Grains can be combined with legumes, legumes with nuts and seeds.
Some examples of combinations of incomplete proteins to make complete proteins include:
- Peanut butter on wholewheat bread
- Peanut butter on rice cakes
- Humus made from chickpeas and sesame paste
- Trail mix with peanuts and sunflower seeds
- Rice and beans
- Bean soup with a wholewheat roll
- Vegetable stir-fry with tofu, served with rice or pasta
- Vegetarian chili with wholegrain bread
These are ways to provide complete proteins to vegans and vegetarians who don’t eat meat, eggs, milk or cheese. More care is required to get enough protein in the diet, but it is possible and the choices of foods are extensive.
Protein’s Role In The Diet
Protein is an essential nutrient in the human diet and we can’t live without it. As a good nutritionist you will look at a person’s situation, assess their dietary needs or protein and educate them on getting enough protein on a daily basis.
Sample menus can help educate an individual on how to get protein in their daily diet. The problem becomes more complex when the client is a vegetarian or when they are a bodybuilder and need alternative sources of protein.
Let’s look at the situation of a regular individual who weighs 100kg and lives a relatively sedentary lifestyle.
Using the formula that we discussed earlier, we get a dietary recommendation 120 – 150 grams of protein.
How can we instruct this person to get that amount of protein in their diet?
Start off with three boiled eggs and 3/4 cup of cottage cheese. That adds up to 42 grams of protein in the diet.
Have a tuna sandwich on wholewheat bread. This adds up to another 34 grams of protein.
Eat a handful of peanuts for another 9 grams of protein. So far, we’ve accumulated nearly 85 grams of protein.
Have 5 Ounces of fish along with some pasta and peanut sauce. This should add up to about 50 grams of protein with a daily total of about 125 grams of protein.
There are different types of vegetarians and they can be classified by what they choose to eat.
- A pescatarian is a vegetarian whose only meat source is fish
- Lacto-vegetarian eats dairy products but not eggs
- An ovo-vegetarian eats eggs but does not eat meat or dairy products
- Lacto-ovo-vegetarian does’t eat meat but eats eggs and dairy products
- A vegan eats not meat, no eggs, and no dair products. They also avoid honey
We’ll look at vegetarianism in more detail later on.
Let’s look at the case of a vegetarian weight 60 kilograms who doesn’t eat eggs, cheese or milk. They will have to be more creative in their dietary choices in order to get enough protein in their diet.
In order to get enough protein in their diet, they will need a menu that looks something like this:
Eat some wholegrain muesli with nuts and seeds. This provides around 14 grams of protein. Add soya milk for another 13 grams of protein.
Slice a half cup of tofu onto mixed greens and eat a wholegrain roll and some soya milk. However, it’s not recommended that people drink a lot of soya milk. This adds up to about 35 grams of protein.
Cook a Thai peanut sauce with rice or wholewheat pasta. Add tofu to the peanut sauce. This adds up to about 24 grams of protein.
As you can see, even those who don’t eat eggs, dairy or mean can get enough protein to constitute a healthy diet.
Clearly meat, dairy and egg sources of protein are superior but are not necessary if the proper blending of proteins in the diet is carried out.
You may find in practice that that vegetarian diets do not seem to suit all clients. A sudden dietary change to a vegetarian diet can be too much for the body to adapt to. So if someone wants to become a vegetarian, it’s best to begin gradually.
Some people find beans and pulses difficult to digest. Cooking methods such as adding fennel or cumin seeds to the pulses whilst cooking may help.
Similarly some vegetarians who start eating meat or fish may suffer digestive problems as their bodies may not be accustomed to breaking down whole proteins. Supplementing digestive enzymes may help. Also eating small portions and chewing thoroughly can help ease this problem.
Different choices of diet can be a sensitive subject. Many clients become vegetarian or vegan to support their ethical beliefs or it may be part of their culture or religion.
As a Nutritional Advisor
You are likely to come across a broad spectrum of people and it is important to respect their values, whilst at the same time providing them with accurate information so that they can make educated choices about their diet.