There are numerous types of protein powders on the market catering to all the different dietary preferences that are popular today. However, despite the additional options, whey and casein continue to hold the lead spots for the most popular protein supplements.
But what are the benefits and differences between the two? Let’s dive in.
What is Whey Isolate?
Whey isolate is a protein powder made from whey, the liquid portion found as a byproduct in cheese or yogurt production. This is then processed further to remove most other nutrients outside of protein.
The result is a whey protein powder that contains 90% protein, compared to traditional whey protein concentrate which can have up to a maximum of 80% protein with the other 20% being a mixture of carbs and fat.
What is Casein?
Casein is another protein found in cow’s milk. During cheesemaking, an acid is added to curdle the milk into solid chunks (curds) and liquid (whey). The curds are made up of casein which is then further processed into a powder due to its high protein content.
Both whey protein isolate and casein contain a rich source of high-quality protein from cow’s milk, but they differ in a few key things, including absorption.
Fast Absorbing vs Slow Releasing
One of the biggest differences between whey protein and casein is the rate of digestion. Your body takes much longer to digest and absorb casein than whey.
When you consume a protein, your body needs to break it down into its smallest form which is the individual amino acids that make it. These are then circulated into your bloodstream until they are completely absorbed by your body.
Studies have found that when you consume casein, you can find these amino acids circulating in your bloodstream up to 5 hours later. However, when consuming whey, they may only circulate through your bloodstream for about 90 minutes before they are completely absorbed [1].
But if they come from the same source, cow’s milk, why do they digest differently?
When you consume these proteins, they will be exposed to stomach acid and, as with cheesemaking, you can see that casein curdles into a solid form when acid is added while whey becomes liquid.
The solid form of casein takes a lot longer to digest than a liquid, like whey. This is thought to be why there is such a significant difference between the digestion rate of the two proteins.
Benefits of Fast Absorbing Whey Isolate
Knowing how these two proteins digest differently can help you to better apply them to your benefit.
For example, now that we know whey protein isolate is fast-absorbing, it’s a great option to be used when you need the immediate benefits of a protein powder, such as following an intense weight-lifting session.
Getting these amino acids absorbed quickly can help aid in muscle recovery post-exercise as well as the process of building new muscle tissue.
During a heavy-weight training workout, stress is placed on the muscle tissue, creating tiny tears in the muscle fibers that require protein to repair and grow. Having access to this protein shortly after you complete exercise is ideal as it gets these essential amino acids where they need to be for this process to occur.
Whey protein also contains higher amounts of the branched-chain amino acids, isoleucine, leucine, and valine, which are also believed to play a role in processes such as muscle protein synthesis and improved exercise recovery [2].
This explains why the gold-standard protein supplement for those looking to build muscle is whey protein. But that doesn’t mean casein doesn’t have benefits as a result of its slower absorption.
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Benefits of Slow Releasing Casein?
Because casein takes a long time for your body to digest and absorb, it’s ideal for times of fasting because it slowly releases amino acids into your bloodstream over a long period. An example of a time this may be beneficial is before bed.
Taking casein before bed will provide a steady supply of amino acids to your muscle tissues while you are sleeping which can help aid in muscle recovery and growth.
Casein may also be helpful during other times when you may not be eating for prolonged periods, such as between meals or before a long workout. This can help reduce muscle breakdown [3].
Whey Isolate vs Casein
If you are closely comparing whey protein isolate versus casein, there are some key areas to look at including muscle recovery, weight loss, digestion, and lactose content.
1. Muscle Recovery
When it comes to which is best for muscle recovery, the answer depends on the time you are taking it. Whey protein isolate is better for recovery immediately post-exercise while casein is great for muscle recovery before bed or before prolonged exercise.
2. Weight Loss
Protein is an essential part of any successful weight loss journey. Not only does it aid in muscle growth which helps boost metabolic function, but it also keeps you full for longer which can aid in reducing portion sizes and unnecessary snacking.
Whey protein may help support weight loss by increasing your metabolism. It also has less calories, fat, and carbs than casein.
However, casein can help support weight loss by taking longer to digest and therefore keeping you more satisfied with smaller portions.
3. Digestion
While whey protein isolate digests quickly, consuming too much can cause digestive discomfort such as bloating, cramping, and gas.
Casein takes significantly longer to digest which is typically a benefit but for some, it can have similar side effects of nausea, bloating, and stomach pain.
4. Lactose Content
Whey protein isolate is a better option for those who suffer from lactose intolerance as it has significantly lower lactose content compared to casein.
Both are sourced from cow’s milk and are not suitable for those who have a cow’s milk allergy.
Is Whey or Casein More Inflammatory?
Certain foods can cause inflammation in the body and a lot of people feel dairy products are a big food on this list. However, protein from dairy may not be inflammatory.
In fact, whey protein may be anti-inflammatory. One review study found that taking larger doses of whey protein (20g or more) reduced C-reactive protein (CRP) levels in the blood, which is a key marker for inflammation [4].
Keep in mind that some whey protein supplements may include added ingredients that can promote inflammation so always look for products that contain only whey protein isolate if possible.
Casein however can cause inflammation in some individuals, particularly in those who are lactose intolerant or who have celiac disease or other autoimmune conditions [5].
Outside of those factors, there is no significant data to support that either protein is inflammatory-promoting.
Whey Isolate vs Casein: How to Pick the Right One
When deciding between either protein, always consider your goals and the time you plan to take it. As mentioned earlier, the biggest distinguishing factor between the two is the difference in absorption rate.
Unless you have lactose intolerance or other immune conditions in which casein may be triggering, either protein can be beneficial in various areas including muscle growth, post-exercise recovery, and even weight loss.
Whichever you choose, ensure you are picking a product from a trusted brand that offers third-party testing for quality and purity. Look for products that contain only the protein without added fluff or ingredients that you do not recognize.
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