Q and A

Great protein debate


If you have been in the fitness industry for any amount of time there is no doubt that you have experienced the Great Protein Debate.

The debate about which protein is best is a major topic in research as well.

When we start comparing proteins it is imperative to know how we are defining the word ‘best’. Best for what satiation, weight loss, recovery, muscle protein synthesis, what?

In our world of creating and maintaining muscle mass, one critical issue is muscle protein synthesis. So which is best for that?

A recent 2-part study investigated the effects that food meals containing various amounts of the amino acid leucine had on plasma leucine levels and muscle protein synthesis.

Investigators fed rats either a diet containing whey isolate, wheat gluten, soy isolate or egg white protein. All meals contained the same amount of total protein and calories. They measured plasma amino acid levels at various times noting that peak blood amino acid concentration took place 90 minutes after the meal.

Rats fed whey isolate had the highest plasma leucine levels, followed in order by the egg white group, soy isolate group and lastly the wheat group. Not surprisingly, only the whey isolate and egg white group had plasma leucine levels high enough to stimulate MPS.

In the second part of the study researchers again compared the effects of wheat and whey on plasma leucine levels. This time rats were fed a diet of whey, wheat gluten, or wheat plus leucine. Researchers again measured plasma leucine levels at 30 minutes, 90 minutes and 135 minutes after feeding.

The groups receiving whey, and wheat plus leucine had elevated plasma leucine levels compared to the wheat gluten group. Interestingly, there was no significant difference between the effects on plasma leucine levels or muscle protein synthesis between the whey isolate and whey plus leucine groups.

Previously studies had suggested that increasing plasma leucine alone might not be enough to trigger muscle protein synthesis. In this landmark study researchers showed that adding sufficient leucine to wheat, a protein already shown NOT to trigger muscle protein synthesis, is enough to trigger muscle protein synthesis.

What is sufficient leucine?
Researchers in this study added leucine to wheat, giving it the equivalent of 2-3g of leucine content.

What does this mean for you?

Don’t discount the importance of other amino acids, but optimizing the leucine concentration in your food and liquid meals may spell the difference between muscle gain and stagnation.

Also, for those folks who are unwilling or unable to consume whey isolate protein (which has the highest leucine content) perhaps adding extra leucine to the protein that they are using will increase its effectiveness in the muscle-building department.

So, to settle The Great Protein Debate-which is best for muscle protein synthesis?

Regardless of protein source, increasing the leucine content to match that of whey isolate may promote the maximial activation of muscle protein synthesis.

Read more on this topic here.

Read more on leucine here

Read more on Protein for performance & muscle here

Norton L. Leucine content of dietary proteins is a determinant of postprandial skeletal muscle protein synthesis in adult rats. Nutrition & Metabolism 2012, 9:67 http://www.nutritionandmetabolism.com/content/9/1/67

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