Diet Deoptimization with Rice Protein: Less Weight Gain, Lower Cholesterol and Fatty Acid Synthesis - So What?

Image 1: Rice protein power - I'd bet a pouch of casein protein that this Chinese "body builder" must have eaten plenty of rice protein. I mean, check out how ripped he is! Update: Garymar informed me that this is a Japanese comedian called Yoshiaki Yamane - sorry, my mistake ;-)

The "real" supplement news have been pretty slow as of late - there have not been any, to be precise. Unless you are interested in yet another study on an exotic African or Asian root or herb and its "antioxidative activity" in the petri-dish, you would probably have been as bored as I was by the latest articles in respective journals. And if Stephen Watt had not asked my opinion on a study my colleagues over at ergo-log had in the news, as of late, I would probably have ignored a "rodents on rice protein" study from the Department of Food Science at the School of Food Science and Engineering of the Harbin Institute of Technology in Harbin, China (Yang. 2012) - the headline ergo-log headline "Fat percentage too high? Add rice protein to your shake", did however look too intriguing not to take another look at a study, the abstract of which I did not really suggest that rice protein would actually help you burn body fat.

Rice for lactose intolerant vegetarians and poor Chinese farmers ...

What the scientists from the Middle Kingdom had done, was to feed three groups of 7-week (adolescent*) male Wistar rats on diets containing either

• 22.9% casein - could the one in your cheap protein blend, after all it was from China ;-),
• 23.2% rice protein A - extracted from Oryza sativa L. cv. Longijng by alkaline / acid extraction, or
• 23.2% rice protein E - extracted by sigma aldrich via heat stable starch degradation

The total experiment lasted two weeks and aside from the protein faction, the composition of the chow, to which the rodents had ad-libitum (=whenever they wanted) access was identical.

Figure 1: Blood amino acid concentrations in rodents fed casein or rice protein (the figures in % represent the relative level of the given amino acid in the RP-A group compared to the casein group, e.g. RP-A rats had 92% of the amount of Alanine, the casein rats had in blood; left; data adapted from Yang. 2012) and absolute and relative amounts of amino acids in casein and rice protein (open pars indicate relative amount of the given amino acid in rice compared to casein, eg. 172% more alanine in rice than in casein protein; data adapted from Morita. 1997)

The latter, i.e. the being identical, cannot be said of either of the amino acid structure of the casein and rice protein (figure 1, right), nor the amino acid contents and ratios in the plasma of the lab animals (cf. figure 1, left), though.

... yet not necessarily for aspiring physical culturists!

The muscle head and fitness fanatic that you probably are, you will certainly already have realized that the level of BCAAs in the blood of the animals on the rice protein diets was 26% and 29% (RP-A and RP-E, respectively) lower than that of the rodents receiving the casein chow. An observation which was to be expected in view of the -27% lower BCAA concentration in rice compared to the casein protein (Morita. 1997; figure 1, right). Astonishingly, this does not hold true for all other amino acids, for glycine, for example, the amino acid content in the source was 2x higher, the serum levels were yet only 15% higher than in the casein group (note: the casein chow was enriched with cysteine, in this particular case a comparison of source vs. serum levels would thus be futile).

Figure 2: Fecal analysis (left) and changes in body weight, as well as absolute body fat percentage and food intake  (right) of adolescent male Wistar rats (data calculated based on Yang. 2012.

If you also take into account that a 7-week old male rat has just become fertile (at about the 6th week of its life), think of yourself, your brother or son at the age of 16y, of what you / he ate and how much weight he gained and then take another, closer look at the data in figure 2 I would say that the question whether switching from casein to rice protein would actually help you lose fat appears more than warranted. After all, we are looking at weight (not fat!) gain in a period of growth (the body fat levels of the rodents, were 2.1%, 1.9% and 1.8%, respectively, cf. figure 2, right). If the latter were totally absent, you would call that "failure to thrive" - a term that would not strictly apply in the situation at hand, though.

In view of the huge fecal loss of dietary fat (+60% over casein) and dietary protein (+145% in the RP-A and +217% in the RP-E group), the 5% lower fat free mass in the rodents on the rice protein diets and the reduced ALT and AST levels, which are not necessarily indicative of "improved liver function", but rather of a reduced hepatic protein turnover, it seems as if "Rice protein reduces body weight gain, energy availability and storage in adolescent rodents due to its lower digestibility" would have been a more appropriate title for the study than "Rice protein improves adiposity, body weight and reduces lipids level in rats through modification of triglyceride metabolism" - and alas, a very similar study, yet without the data on the "body weight gain", has already been published by the same research group in 2011 (Yang. 2011).

Diet-deoptimization a novel weight loss strategy?

Image 2: I guess the Chinese have heard how the Americans got rid of their corn and soy and do now try to pull off a similar "it's good for your health"-stunt with rice protein as the US did with their "healthy" vegetable oils and soy proteins.

Personally, I would yet suggest to call the study "diet-deoptimization by the provision of less palatable, less digestible chow to rodents", but I guess in that case the results would never have made it to ergo-log and subsequently to the SuppVersity. It was thus pretty clever to disguise what could simply be a natural (side) effects of a reduced energy intake (-5%) and reduced energy absorption (-60% from fat and -145% or -217% from protein), i.e. a reduction in fatty acid synthesis and an increase in breakdown (you may remember that even rodents need fat, right?), as evidence that (I quote from the conclusion) "rice protein can modify triglyceride metabolism, leading to an improvement of body weight and adiposity" - wouldn't you agree?

In the end, the protein and fat wasting effects of the rice protein diets could even explain the advertised "beneficial" impact on the lipid profile with VLDL/HDL ratios of 0.19 and 0.16 vs. 0.24 in the RP-A and RP-E groups vs. the casein group. Whether similar effects could be observed in a human trial and whether these "improvement" (from one end of the normal range to another) would decrease the risk of heart disease, is yet questionable. Moreover, the reduction (or replacement; not necessarily the complete elimination) of the whopping ~60% carbohydrate content (488g cornstarch and 100g succrose per kg of chow) in the diet and/or the replacement of the pro-inflammatory soy-bean oil with e.g. olive oil would probably elicit way more beneficial effects on the triglyceride and blood glucose level in humans than a switch from casein to indigestible and in rodent-terms obviously non-palatable rice protein.