Whey or Casein? Which Would be the Better "Staple" Protein Source for Your Trip to Desert Island?

Image 1: They are both sourced from cow's milk, but which is the better part? Whey, the byproduct of cheese production, or casein the cheese protein, itself? A recent study would suggest that it's the "waste product" you would have to chose if you could only have one.
"Whey is the way to go!" I suppose even I have had a headline like that in one or even several of the daily news items, here at the SuppVersity - and rightly, so! With it's high content of branched-chain amino acids (BCAAs) this fast-digesting protein source is certainly the #1 choice for anyone whose goal is to build lean muscle tissue. Whey's slow-digesting brother casein, on the other hand, is often hailed as the "muscle-preservative", the 24h-protein source that will prevent muscle catabolism, when for whatever outrageous reason (like sleep, for example) you cannot ingest your bi-hourly protein shake... well, I guess those of you who have been following the Intermittent Thoughts on Intermittent Fasting will already be "rolling on the floor laughing", but hey! Do we really know whether casein or whey would be the better "staple" protein - I mean, if you sipped it throughout the day?

Casein vs. whey - which one to chose if you cannot have both?

While I would not say that one study could provide a definite answer to this question, the results of a recently published paper by St├ęphane Walrand et al. (Walrand. 2011) provides further evidence that whey, not casein would be your best choice - regardless of the diminished return that comes with sipping it.
Figure 1: Ingredients of the 6 diets the rats in the Walrand study were fed for 5 months; CAS = casein, WHEY = whey (data adapted from Walrand. 2011)
In their long-term (5 months!) feeding study, the scientists supplied 21 week old male Winstar rats (at the beginning of the study the animals were thus "middle-aged") with one out of 6 experimental diets (cf. figure 1). The composition of the diets differed not only in their total energy and protein content (ad libitum = 440kj/day; energy restricted only 60%, i.e. 264kj/day), but also with regard to the protein content and source (casein vs. whey). In that, it is particularly noteworthy is that the "energy restricted" diet was actually a "high protein" diet. After all, the protein content of the latter was identical to the one of the rats that had free access to  (the group that was "only" energy restricted received was matched to the average protein consumption of the ad-libitum fed rats.
Figure 2: Effect of 5 months of the experimental diets on muscle and fat weight of male Wistar rats (data adapted from Walrand. 2011)
Contrary, to what you may have expected, the "protein deficient" protein & energy restricted diet did yet not lead to profound losses of lean muscle tissue (cf. figure 2). On the contrary, the protein & energy restricted group that received whey protein as their exclusive protein source had 5% and 2% greater soleus and tibialis anterior mass than the ones that received the "high protein" energy restricted diet. Before you start questioning the value of "high" protein intakes when dieting, you should yet better take a look at the impact of the "high" protein content of the non-protein-restricted diet had on the diet induced reductions of the abdominal fat mass. I mean -87% reduced abdominal fat in the energy & protein reduced group is impressive, the neigh complete annihilation of the abdominal fat (-93%) in the non-protein restricted group, on the other hand, is mind-boggling.
Figure 3: Effect of 5 months of the experimental diets on muscle and fat weight of male Wistar rats (data adapted from Walrand. 2011)
If we also consider the nitrogen balance and the absolute rates of muscle protein synthesis (cf. figure 3), it also becomes evident why the rats on the protein & energy reduced diets retained slightly more lean mass (+3%), when they were fed whey protein, instead of casein. The rats who received whey as their main protein source simply had a favorable nitrogen balance and increased muscle protein synthesis.
Image 2: Sardines for diabetes prevention!?
Before you now throw away your eggs, your cheese, your beef and whatever else, I want to briefly introduce you to the results of two other recently published studies, which would indicate that rotating in some sardines or sheep meat could produce even more favorable results than living on whey alone. While Madani et al. found that sardine protein ameliorated fructose-induced hyperglycemia, insulin resistance, hyperlipidemia and inflammation (vs. casein) in a 2-months rodent study (Madani. 2011), Feng et al. report that the consumption of sheep meat instead of casein lead to increases in free T3 (thyroid hormone) and statistically significant increases in energy expenditure in Sprague-Dawley rats that were fed otherwise identical diets (Feng. 2011).
Despite these and the results of previous studies, most of which would suggest that if you had to chose just one protein source, whey or casein, whey should be the protein of choice, I hope that I do not have to tell you, as a diligent student of the SuppVersity that imbalances are the root cause of many, if not most modern diseases. So, getting all your protein from whey and nothing but whey should not be something you should even remotely take into consideration. And in case you forgot about that: Milk has both of them and a ton of other vital nutrients ;-)
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