Whey and Casein Work Hand in Hand for Protein Anabolism, but Scientists Overlook Fat, When They Reassemble Milk

Image 1: Ex-Mr. Universe, Manohar Aich, turns 100 and swears by milk and other whole foods (NYDaily)

Do you know the good old saying that you often only realize what you had, once you have lost it? A recent study by scientists from the Division of Endocrinology at the Mayo Clinic in Rochester (Soop. 2012) is only the latest instance, in which we (in this particularly case not even scientists, but the food industry) disassembled a natural product, namely milk, in order to maximize its benefits (or our revenues?) only to realize now that the the resulting parts - as good as they may be - are not up to what the whole has had in stock for us.

Whey + casein + lactose = almost milk

In order to quantify the quantity and time course of the total body, splachnic (hepatic) and leg protein flux of whey and casein, Mattias Soop, Vandana Nehra, Gregory C. Henderson, Yves Boirie, G. Charles Ford, and K. Sreekumaran Nair conceived a clever experiment. They used differently labeled whey and casein proteins to determine the individual metabolic fate of the two dairy proteins over 7 hours after their ingestion. To this ends, their 18 healthy subjects (6 men, 12 women) who had been consuming a weight-maintaining diet (20% protein, 50% carbohydrate and 30% fat) for three days before the experiment and had reported to the lab the evening before the actual testing procedure took place, ingested one of the following test meals

• 0.625 g/kg LBM whey + casein + 0.9g/kg LBM lactose, or
• 1.85g/kg LBM lactose

In that, it is important to note that the portion sizes were prepared according to the lean not the total body mass of the study participants and that there were two versions of the first test meals ([13C]WP/[15N]Cas and [15N]WP/[13C]Cas) to make sure that the tracer did not influence the protein kinematics.

Figure 1: Mean rates of appearance (left) and disappearance (right) of radiolabeled phenylalanine via the hepatic vein and portal vein, respectively (Soop. 2012)

The results, you see in figure 1, are actually not really surprising, we all know that whey is the faster of the two protein sources and casein takes longer to digest - what is news though is that this is the first time that we can see their individual contribution to the protein flux in different parts of the body upon co-ingestion.

Surprise?! Lactose is not the working ingredient in milk

Similarly unsurprising as the different amino acid kinematics of whey and casein are is probably that lactose alone did not elevate the protein synthesis in the legs of study participants to a similar level as the ~25g of whey + casein test meal (mixed, mitochondrial and sarcoplasmic FSR were elevated to the same roughly the same degree; data not shown).

Figure 2: Insulin, glucagon and glucose increases (peak at ~60min) after ingestion of the test meals (Soop. 2012)

The pronounced insulin response (figure 2), the scientists observed in response to the test meals could yet actually surprise a few of you, I believe. After all, you hear everywhere that the bad, bad carbohydrates are the sinners who will rise your insulin levels and make you fat and sick - now, despite the fact that lactose obviously is a carbohydrate, the insulin spike which followed the ingestion of the test meals was virtually identical. The only difference being that the lactose only test meal also increased the blood sugar levels, while it the sudden increase in insulin in the protein only group involved a significant increase in glucogon, insulins counterpart that is also released by the pancreas in order to increase gluconeogenesis (in this case obviously from amino acids) and keep the blood sugar levels stable.

Scientists put the pieces back together, yet not without making a fat mistake

Image 2: I wonder if those are the physical consequences of drinking skimmed milk - I mean, David looks like he had a hell lot of glucagon going on, right? ... what? You mean David did not even drink milk, just took the money, no - impossible!

Overall, this study therefore confirms two things we should actually have grasped all-along. Firstly, the combination of whey and casein as it is found in milk has worked to nicely for generations of physical culturists, because it is (if you will) "evolutionary" designed to trigger and sustain protein synthesis. And secondly, milk does contain a hell lot of "sugar", to avoid that the protein-induced surge in insulin leads has to be countered by a similarly pronounced secretion of glucagon, to kickstart gluconeogenesis and stabilize the blood sugar levels.

If you will, you could however argue that nature must have a design flaw in its muscle builder #1, after all the amount of carbs appears to be insufficient to fully negate the release of glucagon; yet while the lactose to protein ratio was 1.44 and thus identical to milk, there was one essential component of milk scientists tend to forget missing: fat! And you know what - an increase in free fatty acids as the one that follows the ingestion of the allegedly bat saturated fats blunts the release of glucagon. What? Yeah, nature is actually pretty smart, you are right!