Protein

What are proteins?

Proteins are organic molecules made up of amino acids – the building blocks of life. These amino acids are joined together by chemical bonds and then folded in different ways to create three-dimensional structures that are important to our body’s functioning.

There are two main categories of amino acids in the body. First, we’ve got essential amino acids – those that the body can’t manufacture, and thus we must consume in our diets. Some amino acids are conditionally essential, which means that our bodies can’t always make as much as we need. Some amino acids are nonessential – those that the body can usually make for itself.

Essential amino acids	Conditionally essential amino acids	Nonessential amino acids
Histidine	Arginine	Alanine
Isoleucine	Cysteine	Asparagine
Leucine	Glutamine	Aspartic acid
Lysine	Tyrosine	Glutamic acid
Methionine		Proline
Phenylalanine		Serine
Threonine
Tryptophan
Valine

Why is it important to get enough protein?

During digestion, the body breaks down the protein we eat into individual amino acids, which contribute to the plasma pool of amino acids. This pool is a storage reserve of amino acids that circulate in the blood.

The amino acid pool in the bloodstream readily trades with the amino acids and proteins in our cells, provides a supply of amino acids as needed, and is continuously replenished.

Since our bodies need proteins and amino acids to produce important molecules in our body – like enzymes, hormones, neurotransmitters, and antibodies – without an adequate protein intake, our bodies can’t function well at all.

Protein helps replace worn out cells, transports various substances throughout the body, and aids in growth and repair.

Consuming protein can also increase levels of the hormone glucagon, and glucagon can help to control body fat. Glucagon is released when blood sugar levels go down.  This causes the liver to break down stored glycogen into glucose for the body.

It can also help to liberate free fatty acids from adipose tissue – another way to get fuel for cells and make that body fat do something useful with itself instead of hanging lazily around your midsection!

How much protein do you need?

The basic recommendation for protein intake is around 0.36 g/lb (or 0.8 g/kg) of body mass if untrained, generally healthy adults. For instance, a 150 lb (68 kg) person would consume around 54 g a day.

For people doing high intensity training, protein needs might go up to about 0.64 - 0.9 g/lb (or 1.4 - 2.0 g/kg) of body mass. For instance 150 lb (68 kg) person would need about 95-135 g of protein per day.

We may need even more protein in our diets for optimal functioning, including good immune function, metabolism, satiety, weight management and performance. In other words, we need a small amount of protein to survive, but we need a lot more to thrive.

The body needs its protein stores to be continually replenished, which means that you should consume moderate amounts of protein at regular intervals.

Consuming more protein may help maintain an optimal body composition (in other words, help you stay leaner and more muscular) and a strong immune system, good athletic performance, and a healthy metabolism. It may promote satiety (make you feel full longer) and consequently help you manage your body weight.

After resistance exercise such as weight training, the body synthesizes proteins for up to 48 hours after training.

Interestingly, during and immediately after resistance exercise, protein breakdown is increased as well. In fact, for a brief period, the rate of breakdown exceeds the rate of building.

The body actually drops into a short-term wasting or catabolic state. However, taking in enough protein during the pre and post-exercise period can offset catabolism.

Can I eat too much protein?

If you overeat protein, this extra protein can be converted into sugar or fat in the body. However, protein isn’t as easily or quickly converted as carbohydrates or fat, because the thermic effect (the amount of energy require to digest, absorb, transport and store protein) is a lot higher than that of carbohydrates and fat.

While 30% of the protein’s energy goes toward digestion, absorption, and assimilation, only 8% of carbohydrate’s energy and 3% of fat’s energy do the same.

The statement that a high protein intake harms the kidneys. This is a myth. In healthy people, normal protein intakes pose little to no health risk. Indeed, even a fairly high protein intake – up to 1.2 g/lb (2.8 g/kg) – does not seem to impair kidney status and renal function in people with healthy kidneys. In particular, plant proteins appear to be especially safe.

Protein Quality: Nutritive Value

The quality of protein depends on the level at which it provides the nutritional amounts of essential amino acids needed for overall body health, maintenance, and growth. Animal proteins, such as eggs, cheese, milk, meat, and fish, are considered high-quality, or complete, proteins because they provide sufficient amounts of the essential amino acids. Plant proteins, such as grain, corn, nuts, vegetables and fruits, are lower-quality, or incomplete, proteins because many plant proteins lack one or more of the essential amino acids, or because they lack a proper balance of amino acids. Incomplete proteins can, however, be combined to provide all the essential amino acids, though combinations of incomplete proteins must be consumed at the same time, or within a short period of time, to obtain the maximum nutritive value from the amino acids. Such combination diets generally yield a high-quality protein meal, providing sufficient amounts and proper balance of the essential amino acids needed by the body to function.

High Protein Foods

Protein Quality chart