Written by: ASN



Time to read 7 min

Whether you hit the gym daily for a strength session, pound the pavement regularly for cardio or do your best to remain active throughout your busy week, there's no denying the benefits of a high-quality protein powder to complement your goals and lifestyle.

Over the years, the evolution of protein powder has been a real game-changer for those serious about their health and fitness. From muscle mass goals and recovery to weight management and wellness, achieving your results with the help of a premium quality protein powder has never been easier thanks to the wide variety of proteins on the market today, two of the most popular types being slow-release protein and fast-release protein.

Fast vs slow release protein powder. Let's dive in.

Why do I need protein powder?

The role of protein is essential for the body's biological processes, from structuring cells and transporting nutrients around the body to energy production, wound healing, tissue repair and building and maintaining muscle mass. It's not just for athletes or those who have serious muscle goals! Simply put, proteins are the building blocks of life and are vital for the quality of your long-term health and muscle protein synthesis, whether you train regularly or not.

Protein Benefits:

  • It's necessary for tissue building and repair

  • It contributes to the growth of muscle mass

  • It contributes to the maintenance of muscle mass

  • It contributes to the maintenance of normal bones
  • It's vital for quality nutrient recovery

What is muscle protein synthesis (MPS)?

The stimulation of muscle protein synthesis is triggered by the ingestion of protein combined with resistance/ strength training. Proteins are broken down into simpler forms known as amino acids when digested. In a nutshell, MPS is the metabolic process that narrates the consolidation of amino acids into bound skeletal muscle proteins. It's the primary instigator behind the adaptive response to exercise and is a naturally occurring process producing protein to repair damaged muscle tissue due to intense exercise. MPS is a vital process for our bodies to build the proteins we need to perform essential functions like counteracting muscle breakdown, building new muscle and creating essential components like hormones and enzymes.

When selecting a suitable protein powder for your goals, you want to know you're choosing one that will maximise MPS in response to your training and optimise your recovery. So getting clear about your body goals is a must when selecting your next protein powder. Let's look at slow-release protein vs fast-release protein so that when you're ready for your next tub, you know which is your best pick based on your goals!

What is slow-release protein?

Slow release protein powder is just that, slow-releasing! Once consumed, slowrelease protein powder takes longer to digest, delivering amino acids to the body over an extended period of time. For example, consuming slow-release protein before bed is a great way to minimise muscle degradation. When you're asleep, your muscles aren't getting amino acids from food to contribute to their maintenance, growth and recovery. So with the help of a slow-release protein, your muscles continue to get the nourishment they need during your downtime for optimal recovery so you can keep working hard towards your goals.

Have you got weight management goals? Slow-release protein is a fantastic option if you're looking for a protein powder to keep you fuller for longer, coming in handy when you're striving toward specific body goals like weight loss or aren't able to prepare and eat regular meals.


Like whey protein, casein is also a milk derivative and is a complete protein source containing all of the essential amino acids (EAAs) required to build and repair muscle. Also known as a 'time release' protein due to its slower absorption rate, Casein is best taken at night before bed to deliver a lower level of amino acids to your muscles over an extended period. It helps reduce muscle breakdown and therefore is known as 'anti-catabolic'. (Res, P et al. 2012)

Studies show that over seven hours, those who consumed casein over whey protein showed a reduced amount of protein burned as fuel, improving their overall net protein balance, which is crucial for the growth and retention of muscle mass. (Phillips, S et al. 2009).

Our recommendation:

Optimum Nutrition Gold Standard 100% Casein

Typically, most opt for a fast-release protein to quickly activate nutrient recovery post-workout. However, when it comes to bedtime, your body goes without food and nutrients for hours, which may have a catabolic effect on all your hard work in the gym. Optimum Nutrition GS 100% Casein is the best slow-release protein due to its premium quality, the first choice for many for slower absorption, and an extended-release of amino acids while you sleep. High in BCAAs, Glutamine, Glutamic Acid and the best slow-release protein, Casein, Optimum Nutrition's GS 100% Casein is an ideal meal replacement, pre-bed shake or guilt-free midnight snack to keep your body nourished for longer while you sleep!

See why this highly-rated casein protein is a must-have for many serious about their goals. Click here for more info!

What is fast-release protein?

A fast-release protein powder intends to act quickly when delivering amino acids, speeding up the recovery process and encouraging muscle protein synthesis. (Miller, P et al. 2014) Fast-release protein is broken down and absorbed quicker by the body, allowing for rapid delivery and a spike of amino acids in the bloodstream. Generally, this process is maximised around 60-90 minutes after consumption.

This type of protein powder is ideal for athletes and those who undertake intense, frequent training, requiring quality protein to boost recovery and support muscle growth and maintenance in between sessions. As whey protein offers a higher leucine content than casein, fast-release whey protein is often the formula of choice for those working towards specific body composition goals like muscle gain, which need optimal time-sensitive recovery.

Whey Protein Isolate (WPI)

Offering the highest, purest content of protein (90-95%) and less lactose than slow-release protein, WPI is a gut-friendly option suitable for those seeking a premium protein formula, minus the tummy ache. WPI also offers a leaner macronutrient profile; however, as the lactose and fats are filtered out, so are many vitamins and minerals found in slow-release protein. WPI is often the protein of choice in addition to a nutritionally balanced diet and strategic training plan for those looking to reduce body fat and increase their overall muscle mass.

Available in various classic and fun flavours, WPI is the go-to protein for many who are as serious about their recovery as they are about their performance.

Our recommendation:

Rule 1 WPI Protein

Formulated with 100% whey protein isolate and hydrolysed whey protein isolate, R1 WPI Protein is a superior option for those chasing serious results. As an ASN team favourite, this tasty game-changing formula offers a nutritious macronutrient profile designed to boost your nutrient recovery and support the maintenance and growth of muscle.

Ideal for a post-workout refuel, this fast-release amino abundant whey protein powder offers instant response and absorption, so you know your hard work hasn’t gone to waste. For more on this low-lactose fast-acting protein powder, click here.

Slow-release vegan protein powder

When it comes to slow-release vegan protein powders, you'll find that most offer a sustained release. This is because slow-release protein is formulated with Casein (dairy) and is generally unsuitable for someone following a plant-based diet.

If you're searching for a slow-release vegan protein before bed, opt for an alternative like White Wolf's creamy high-protein Plant Protein Custard! Free from gluten and dairy and low in carbs with added MCTs, White Wolf's Plant Protein Custard is naturally high in amino acids to nourish your recovery so you can enjoy the sweeter things in life without sacrificing your results.

Slow-release protein vs fast release, which is best?

As you can see, there are multiple benefits to both fast and slow-release protein, but ultimately, it comes down to your desired body goals and macronutrient needs. There's no one size fits all! While both types of protein support nutrient recovery with the time-release delivery of amino acids, the absorption rate may also affect your results depending on your individual body goals, digestion and the state of your nutritional diet and macronutrient needs. Quality is essential when selecting protein powders because, unfortunately, not all are created equal and have the same integrity as front-running brands like Evolve, Optimum Nutrition and Rule 1.

Both fast and slow-release proteins serve various purposes beneficial to the growth and maintenance of muscle mass, tissue building and repair, and supporting your daily macronutrient needs. In fact, many use both types of proteins within their supplement schedule!

Slow Release Protein Fast Release Protein
Slow digesting Fast digesting
Higher in lactose Lower in lactose
Before bed protein Post workout protein
Meal replacement - Keeps you full! Absorbed quickly - Not ideal for a meal!

We recommend chatting to one of our friendly team members in-store or reaching out to our online team for further advice if you're still unsure which protein type is best for your goals!


Res, P et al. 2012, ‘Protein ingestion before sleep improves postexercise overnight recovery’. National Library of Medicine, accessed 7 June 2022,>

Phillips, S et al. 2009, ‘The role of milk- and soy-based protein in support of muscle protein synthesis and muscle protein accretion in young and elderly persons’. National Library of Medicine, accessed 7 June 2022,>

Miller, P et al. 2014, ‘Effects of whey protein and resistance exercise on body composition: a meta-analysis of randomized controlled trials’. National Library of Medicine, accessed 7 June 2022,>