Probing into protein

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Tuesday, 10 February 2009 17:03

Johanna Shiu, SUPGlobal's sport scientist, looks this month into the importance of protein in sport.

You might need to get a drink (a protein shake?) before you sit down to read this one – it’s quite a biggy, but that’s because sports nutrition just isn’t that simple to sum up briefly... enjoy!!

Protein – what is it?

Protein is essential for all life and makes up about 15% of a human’s bodyweight –most of this being muscle. It is made up of amino acids and is a vital part of organisms that participate in every process within cells. Protein has a wide range of functions, anything from initiating chemical reactions that are necessary for metabolism, to forming the scaffold that gives cells shape.

The word protein is a derivation of the Greek word “protos,” meaning “first,” since protein is the basic material of all living cells.

 

Why do we need to eat protein?

Various tissues in our body are in a constant state of turnover, breaking down and re-forming. Through the process of digestion, humans break down eaten protein into amino acids, which can then be used again as the building blocks for proteins, as needed. So really, our requirement is for amino acids rather than protein, as such.

As mentioned before, proteins are made up of amino acids; humans have a need for a wide range of amino acids. We have the ability to make some of the amino acids within our own body, but there are eight that we have to get through diet. These are termed “essential amino acids” (for those who really want to know , these are isoleucine, leucine, lysine, methionine, phenylaianine, threonine, tryptophan and valine. In addition, arginine and histadine is an essential amino acid for infants).

If we don’t have enough of these amino acids in our diet, then proteins within the body break down, body protein content decreases, and over the long-term, this leads to decreases in endurance/strength and eventually, illness.

 

Protein use during exercise

During lengthy exercise, such as long-distance stand up paddle surfing or just lots of hours in the water, proteins can be broken down to provide around 3% of the amount of energy used. When the carbohydrate stores in the muscle get low or if there weren’t enough carbohydrate stores initially, the contribution from protein can rise to more like 10%.

An extreme example of this can be seen in people who do things like treks to the North Pole; they are able to complete the exercise, but will come back noticeably thinner and with loss of muscle because they simply can’t meet the carbohydrate and overall calorie requirements of the task, so along with using up the fat stores, the body relies on using it’s own protein as energy, and as a result, muscle is broken down.

Fortunately, unless you’re planning to SUP across the Atlantic, this shouldn’t be a problem for you. What will influence how much protein you’ll use is whether you are out doing a distance paddle venture/race, or going out for a full-on session in big waves that requires lots of full throttle activity.

 

How much protein?

Unlike with carbohydrate, you can’t really make the body store more protein in reserve than it wants to and any excess beyond what’s needed to build/repair muscle and meet metabolism needs would either be converted to glucose, metabolised or stored as fat.

There appears to be an increase in protein breakdown during and straight after exercise, while at the same time, the making of protein slows down. The more intense the exercise, the greater your protein breakdown and so the greater the protein needs become. Also, your protein need increases if you are purposely training to gain muscle.
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However, while active people/athletes do appear to need more protein than non-active people, there doesn’t appear to be a valid reason for eating very high protein diets, either to “bulk up” or to improve endurance, not least because it’s just a way of making very expensive urine! At worst, there is some evidence to suggest you can put unnecessary strain on your body, particularly the kidneys, when excess protein is eaten, though this remains a contentious issue.

So, how much is needed? It’s pretty difficult to answer exactly as the amount of protein that gets used can vary considerably.

The average guidelines for “normal” adults is to consume 0.9g of protein per kg body weight per day ie, for a 75kg man (165lbs), this would be 67.5g protein per day. However, quite a lot of previous work has suggested that athletes taking part in intense training need to eat anything up to twice the amount of protein that a sedentary individual does in order to meet the demands. So, given that SUPing is not really about building large amounts of muscle, but is somewhere between high intensity and endurance, it is probably safe to assume you might need somewhere in the region of 1.5-times the average amount of protein. This would be around 1.35g per kg bodyweight per day, so for the 75kg (165lb) man, this would be just over 101g protein per day.

Since each gram of protein contains 4kcal energy, this would mean you’d get about just over 400kcal per day from protein, which would equate to about 15 to 20% of your overall energy intake if you were eating between 2,000 to 2,500kcal per day. This is about the right percentage. It is worth bearing in mind that excess protein will be converted into fat and stored as fat in the body.

It is also worth bearing in mind that different protein sources have different “quality” ie, an excellent source of protein will be almost completely absorbed by the body, so for 100g of the protein source, you may get 75g of protein from it, whereas for a poor source of protein, for 100g of food, you may only get 10g of protein from it (see protein quality information later on).

When to eat the protein?

As noted before, carbohydrate is the necessary first source of energy for exercise, so taking on carbohydrate before and during exercise is wise. It is also generally advised that eating some protein after exercise will help to replenish and repair any protein breakdown or muscle damage resulting from the exercise.

There are also various studies conducted in cyclists to suggest that taking on protein as well as carbohydrate during exercise can increase endurance.

How and why this is the case is not quite clear, it may be simply from additional calories, but may also be about how the protein regulates the release of carbohydrate or helps to spare the muscle carbohydrate stores, effectively making them last longer. The strategy of adding protein to supplements is becoming increasingly popular with athletes, and many companies now offer drinks and snacks containing both carbohydrate and protein to take on during exercise.

To make your own mixed-source sports drink, you could add whey protein (around 1.5 to 2%) to a 6% carbohydrate drink (eg, add 6 to 10g of protein and 30 to 60g of carbohydrates to 32 ounces (approx 900ml) of water.

One warning with this, there has been some work suggesting that adding protein to a sports drink reduces how quickly the drink then leaves your stomach, which would then affect how quickly a) the fluid can enter your system and rehydrate you and b) the carbohydrate and protein energy would be available for your body to use. You will have to be the judge of this yourself as at the moment, the jury is out on this one.

What are good sources of protein

Different foods provide different quality protein; the better the quality, the more of it the body will use. As ever though, it’s not just as simple as that, because by combining some of the less good quality proteins, you can improve the amount of usable protein (eg, combining rice and beans). It’s best not to get too caught up with this thought, instead, concentrate on eating a highly-varied diet. For vegetarians, make sure you include those non-meat protein sources in the “excellent” category as much as possible, as well as eating a wide range of vegetables, dairy produce, nuts, seeds and pulses.

Excellent sources of protein
Eggs
Whey protein
Cottage cheese
Yoghurt
Fish
Seafood
Meat
Tofu
Quinoa
Brown rice
Milk
Cheese

 

Reasonable sources of protein
Chick peas
Soya beans
Baked beans
Wheatgerm
Most nuts and seeds
Most green vegetables
Potatoes

Poor sources of protein
Kidney beans
Lentils

 

 
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