How long does protein last in your system and in your cupboard?

Protein is a vital part of your diet and that’s especially true for people leading an active lifestyle.

Whether you’re an endurance athlete taking part in triathlons or spending 10 hours a week lifting weights in the gym, protein is key to recovery and repairing muscles.

Many nutrition specialists, including Matt Durkin, who works at SCI-MX as the New Product Development Manager and is the expert behind the information in this article, recommend between 1.4-2g of protein per kilo of bodyweight.

That means if you weigh 70kg, for example, you’ll be looking at a protein intake of between 98-140g per day.

And given the importance of consuming enough protein, you may want to supplement your intake with powders, drinks or bars.

For example, SCI-MX’s Clear Whey Protein Isolate powder delivers 21g of protein per serving when mixed with water in a refreshing package for summer. Or there’s the brand’s Ultra Whey Protein, which packs in 35g of protein and 9.7g of branch chain amino acids.

But exactly how long does protein stay in your system? And does protein powder expire?

Well, let’s hand over to Matt to share his expert analysis…

How long does protein stay in your system?

It totally varies depending on what the protein is actually used for. A small percentage of the protein you ingest will actually be burnt for fuel, so it’ll be used immediately.

Then some will be used to build muscle tissue, which could last years. And some might be used, for example, for red blood cells, which last three months.

Looking at it from a perspective of how long does it last in relation to muscle protein synthesis, so growth and repair of your body, it used to be thought that if you had 20g of protein and over 3g of leucine, which is an amino acid, you’d maximise muscle protein synthesis.

The thinking was that you’d want to have at least three or four feedings spaced throughout the day to get the consistent protein synthesis as the hours ticked by.

But some recent research has actually shown that it’s more of a dose response. It’s shown that some people can gain a lot of muscle just from one big meal a day.

One of the takeaways from the study is that we shouldn’t really be too concerned with when we’re taking the protein so much, but instead focus on the total daily amount of protein we consume.

For example, this study demonstrated that after a 100g intake of protein (which is a lot), the participants were still using that to build muscle over 12 hours later.

On the flipside, if you consume 20g of protein, it might only be used for muscle protein synthesis for four hours, and then you’ll need more protein.

How long does a protein shake take to digest?

Whey protein is good in that it’s broken down quite rapidly, whereas proteins like casein takes longer.

That’s why people often take casein before bed, as it delivers a slow release of protein. The thinking is that it’s releasing amino acids while you sleep and obviously during that time you’re not having any other meals

If you’re wanting protein that will be rapidly absorbed then hydrolysed whey would be the fastest option for you, but we’re getting into the minutiae detail here.

To the average person or even to most athletes, it’s not that significant whether one protein is rapidly absorbed or the other is slightly slower, as long as you’re hitting your overall protein intake goals.

What happens to protein once you’ve ingested it?

Once you’ve consumed protein your body will digest it and absorb it. Then you’ll use the amino acids for turning on muscle protein synthesis.

I’ve already mentioned the amino acid called leucine, which is the key driver of what’s called mTOR, which is your muscle protein synthesis pathway. You need leucine to turn that pathway on, and then the amino acids are collectively like the building blocks on the conveyor belt.

Once it’s been switched on, that process of repairing and rebuilding muscle tissue begins as the different amino acids go and do their jobs.

For clarity, we don’t actually eat amino acids. We consume foods or drinks that contain protein and they’re broken down into their amino acids.

Does protein powder expire?

Wondering how long protein lasts in the cupboard once opened? Well, when we produce whey protein at SCI-MX, we put two years from the date of production as the best before date.

That being said, it’s a ‘best before’ date, which means it’s probably still okay after that date. Because it’s a dry product, it doesn’t have moisture in it and it’s the moisture that accelerates the growth of bacteria, but if consumed after the best before date, it’s likely that the quality of the product will have decreased.

So as long as you’re sealing the tub or sealing the pouch properly, and you store it in a cool, dry place, as recommended on the packaging, the two years is fine.

But what if you go back to some protein that’s been open for a few years? Well, if moisture got into it there’s potentially all sorts of bacteria, yeast and moulds growing there.

So there you have it. Now you know how long protein stays in your system, how much to consume, what happens to it when you’ve ingested it and how long your protein supplements will last.

And if you’re looking for a way to increase your intake, SCI-MX has a range of protein powders to suit varying tastes and requirements.