Slayer's Den

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The Double-Duty Protein​

This protein boosts metabolic rate and muscle protein synthesis.​

Casein has several monikers. For example, it's been called the "bodybuilder's protein." Casein is time-released and slow digesting, leading to a constant release of amino acids into the bloodstream, which prolongs protein synthesis over several hours, unlike whey.

It's also been called the "dieter's protein" for its dual ability to prevent muscle breakdown (catabolism) during cutting phases and keep you full even longer than other protein sources.

So, casein is good stuff, especially the micellar form), which ramps up all of regular casein's benefits. Researchers know this about casein, so they decided to do a study where it was the only source of protein. The catch? Some subjects consumed a low-casein diet and some consumed a high-casein diet. Here's a quick summary.

The Study​

Researchers recruited 12 men and 12 women for the study. All lived in a metabolic respiration chamber for 36 hours that measured their total energy expenditure.

Half the subjects' diets looked like this:

• Protein: 10%, all from casein
• Fat: 35%
• Carbs: 55%

The other subjects' diets looked like this:

• Protein: 25%, all from casein
• Fat: 20%
• Carbs: 55%

So, they consumed about the same number of calories and carbs, but the high-casein group (25%) consumed less fat to make room for extra protein. Both groups got their casein from a special custard made for research purposes.

After some time, the two groups swapped places and did the diet again. Lots of blood, urine, and body composition tests were taken, along with measures of appetite. All subjects remained sedentary since they were sequestered in the little respiration chambers (think: tiny New York apartment).


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What Happened?​

1. Total energy expenditure (TEE) increased 2.6% more per day in the high-casein group. That means they burned more calories than the low-casein group.
2. The high-casein group also burned more calories during sleep (SMR or sleeping metabolic rate).
3. The high-casein diet resulted in a positive protein balance and a negative fat balance compared to the low-casein diet.
4. Hunger was 41% more suppressed with the high-casein diet and satiety (fullness) increased 33% more.
5. Although the carb content of both diets was the same (55%), plasma glucose concentrations were lower with the high-casein diet, probably because of slower gastric emptying. The same was reflected in the insulin responses.

What Can We Learn?​

Based on a 2000-calorie diet, the high-casein group had 125 grams of casein per day, while the low-casein group had 50 grams. So, in many ways, this study tells us that more protein is better than less protein. Duh. But it also highlights the powers of casein and tells us that a good portion of our daily protein should come from casein, at least if we're interested in getting/staying lean or building muscle.

Dietary sources of casein include milk, cottage cheese and most cheeses, and Greek yogurt which is strained to remove the whey, making it higher in casein content.

Supplementally, most cheap protein powders contain little to no casein. Whey is less expensive and has its benefits, but elicits a significant insulin response. Other products use calcium caseinate, which is absorbed by the body even faster than whey and causes a rapid rise in insulin. Likewise, it doesn't provide sustained levels of amino acids. Calcium caseinate is basically "fake" casein. You'll find it often in RTDs. So be aware of that.

What you want is a supplement containing micellar casein. Micellar casein is composed of soap-bubble-like molecules (micelles) that form a bolus in the stomach when consumed. That makes them digest really slowly. Plus, micellar casein is powerfully anti-catabolic, more so than standard casein.