Monday, 3 December 2012

Nothing as it seems! Net Protein Utilisation

This blog entry is a follow up to the entry titled "Protein", the carbohydrate story will follow this entry.
Protein utilisation in the body relies on a very important fact about protein consumption. I stated in early posts that protein is broken into its most basic form of amino acids before it can be absorbed from the gut wall. It's then shipped to the liver when the amino acids are constructed into self proteins. These self proteins are recognised as being friendly by your immune system and a war is avoided. Proteins are a chain of amino acids linked together in a very specific way. If one or more of the "essential" amino acids are missing then the protein can not be constructed. If one or more of the non essential amino acids are missing our liver can construct these by tampering with what it's got.
So what does all this mean?
If you now understand the importance of protein intake and you are trying to ensure you consume enough (1g per 1kg of body weight or 2g per 1kg of body weight if you exercise regularly) on a daily basis it's time to think again!
Net Protein Utilisation means we can only construct proteins with amino acids which total the smallest amount of essential amino acids consumed per meal.
Picture lots of Lego towers of different heights. Some are 8 blocks high, some 12, some 27, some 19, some 14, some 9etc. The smallest tower is 8 blocks high. You decide you want to build a big tower using all the blocks. But there is a catch! You can only use the first 8 blocks of every tower. The rest you have to discard.
In that analogy the small 8 block tower represents essential amino acid. You can use these blocks to build a nice big tower but you can not use more than 8 blocks from the remaining towers.
Then to make matters worse lets say you have 10 replicas of this 8 block (essential amino acid) tower but you have 20 replicas of all the other towers. Now you can only use the bottom 8 blocks from the 10 replicas of all the towers and you must dicard the other 10 or 50% of these towers. That means a lot of protein gets discarded if you are not careful, very careful.

This is why it is important to try and consume more than one protein source at your big daily meal. Say meat, fish or tofu, with some lentils, protein source veg or rice. The more proteins going in together, the higher the Net Protein Utilisation (NPU) and therefore the easier it is for your liver to build proteins.
So when you read a food label that says this food has 20g of protein per 100g this does not account for the NPU. There is a high chance that a lot of this 20g per 100g is unusable protein and therefore it will be excreted. (Once again explaining that calorie counting is so much a waste of time I often wonder why am I even writing about it?) Unless you combine that food with another protein food source. Protein combining is very effective and it usually brings the NPU up quite significantly.
Another way of increasing NPU is by amino acid supplementation. I have a few friends who are gym buffs (which means they love themselves) most of them supplement with amino acids but in true bodybuilder style, I'm not sure they know why they take these little amino acid packs. Most of these have 2g of protein per tablet. So not a lot of the grand scheme of things but very very valuable for increasing NPU.
I try to eat quite well day to day and don't ever supplement. The only exception being when I am in full training for a maratathon when I add some plant based protein to my daily smoothie.
It will never be the point of this blog to tell you what to eat or how to train. What I will try and do is explain how things work so you can make you own decisions based on how you and your body work!