Casein is a complete protein (meaning it contains all the essential amino acids the human body needs) found in most dairy products, accounting for 80% of milk protein. It is responsible for many of the unique properties of milk, such as its thick consistency and ability to form curds.
Casein, present in some nutritional supplements, is quite popular among bodybuilders for aiding exercise recovery and muscle building. It is also a prevalent ingredient in dairy-based baby formulas.
One of the primary advantages of casein protein is that it is high in calcium and amino acids, which promote bone health and muscle growth and repair. It provides muscles with all the amino acids required for exercise recovery and strength building.
Because it takes up to seven hours to digest, casein helps regulate hunger cravings (thus contributing to weight loss), unlike soy protein and whey protein, which are absorbed into the system faster. Dairy foods high in casein are also good sources of calcium, and research indicates they may help prevent osteoporosis.
Although more human studies are needed, preliminary evidence suggests that casein may enhance elements of health like decreasing triglycerides and aiding in weight loss. Furthermore, casein-rich foods typically contain a high concentration of bioactive peptides, which could help lower blood pressure like certain medications.  
Casein, a protein derived from milk, is unsuitable for individuals with lactose intolerance or milk allergies. People should consult their healthcare provider for testing to detect their specific allergic protein.
It is important to note that high protein intake from casein or other supplements can be risky for some individuals, especially those with impaired kidney function, as it can put more stress on already-weakened kidneys. 
Casein protein can be ingested before, during, and after workouts, as well as before bed, to support muscle recovery and growth. One to two scoops (20 to 40 grams) is enough. The Recommended Daily Allowance (RDA) for protein to prevent a deficiency is 0.36 grams per pound (0.8 grams per kg) of body weight.
For those who exercise often, doubling or tripling the RDA, which equates to 0.72 to 1.08 grams per pound (1.6 to 2.4 grams per kg), may be preferable to optimally support muscle growth and recovery. 
The fast-acting nature of whey protein makes it an easy choice before or after a workout. On the other hand, the slower-acting quality of casein is the best option for days when you do not exercise or before bed.
Other aspects to consider:
Whey protein is the best pick for you if your fitness regimen includes daily strength training with a few days off and you don't have late-night cravings.
If your workouts are often less demanding and you skip meals more frequently, opt for casein. Or, incorporate both into your routine by taking casein protein before bed and whey protein after a workout.
It essentially boils down to personal preference since whey and casein are abundant sources of the amino acids your body needs for protein synthesis and muscle building. Despite their distinctions, both are beneficial for developing your muscles.
Remember that the most crucial factor for muscle growth or gain is to consume more protein than your muscles consume, whether it comes from whey, casein, or another protein source. Whatever your fitness goals are, your results will be determined more by your training and dietary habits than by the protein supplements you use.
You can buy protein blends since they typically have a combination of casein and whey, delivering you the benefits of each. Always add the liquid (water or milk) first and then the scoop of protein. This order prevents the protein from sticking to the bottom of your container. If possible, mix your protein powder and liquid with a blender bottle instead of a spoon.
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