|Muscle toning with bicarbonate? Without weight gain? For some women probably a dream come true ;-)|
So what's the surprise?
In their 12-week rodent study that was devised to elucidate whether the addition of a neutralizing amount of potassium bicarbonate (KHCO3) to purified diet designed to match the standard acid forming Western way of eating would ameliorate the urinary nitrogen loss and affect the muscle fiber size and number, as well as the levels of circulating and muscle-specific IGF-1 in thirty-six vitamin D sufficient or deficient, 20-month-old, Fischer rats, Lisa Ceglia and her colleagues did not only observe (relative changes in brackets are expressed for vitamin D sufficient / insufficient animals)...
- higher urinary pH (33% / 34%, after only 6 weeks),
- lower urinary nitrogen losses (-28% / -42%) and
- increased circulating 25OHD levels (3% and 15%);
learn more) fiber dominant. What is surprising though is the fact that the researchers did not observe corresponding increases in muscle weights (p > 0.05).
Unfortunately, the scientists don't address the "growth vs. weight" discrepancy in the discussion of the results, so that we are left to come up with our own hypotheses to explain why this may have been the case. We know that it cannot be the mere result of decreased food intakes or total body weight - both were virtually identical in all groups (just a note: the muscle weight per total body weight did not differ either). Moreover, the scientists explicitly state that "the lower UNi/Cr could be considered an indicator of reduced muscle proteolysis" - so that common sense would dictate an increase in muscle size and mass as it was in fact observed in previous human studies from the same laboratory:
"In a 6-week study in 19 healthy adults (average age 62 years), KHCO3 supplementation attenuated a protein-induced rise in UNi/Cr excretion by over 50 % compared to placebo (Ceglia. 2009). A larger study in 162 adults (average age 62 years) given a lower bicarbonate supplement dose or no bicarbonate, also demonstrated a 6 % decline in UNi/Cr excretion (Dawson-Hughes. 2009)." (Ceglia. 2013)In fact, the provision of the bicarbonate supplement in the latter of the two studies did also increase the lower extremity power of the healthy older women who participated in the study by 13%; an observation that speaks in favor of the practical relevance of bicarbonate supplements - at least in the context of a normal / low vegetable and correspondingly low dietary alkali intake and that irrespective of the presence / absence of increases in skeletal muscle mass.
So what's the general mechanism here?
What about the muscle fiber specificity? The scientists speculate that the difference may simply be mediated by the "size difference of type II fiber subtypes (IIa, IIb, IIx) in rat EDL muscle and an inadequate [study] duration to detect a significant fiber size effect." This alone would, warrant a "larger and longer-term" at the end of which it may be possible to "fully characterize effects of this dietaryIf we simply discard the (as of now inexplicable) absence of increases in muscle weight and focus on the increases in muscle cross-sectional area it would in fact appear as if the alkali-induced improvements in nitrogen retention are the primary cause for the "muscle building" effects, the New Yorker researchers observed.
intervention on muscle morphology." (Ceglia. 2013)
intervention on muscle morphology." (Ceglia. 2013)
The latter appears all the more likely, in view of the fact that neither the provision of vitamin D nor the addition of bicarbonate (or a combination of both) resulted in significant reductions in the catabolic signaling molecules E3 ubiquitin ligases, MURF1 and MAFbx. Still, if we don't assume that the rodents expended much more energy and simply burned off the extra protein it must have gone somewhere, so that the most likely explanation for the inconsistencies would actually be the time-point at which the signaling molecules were measured. After all, a pre- vs. post comparison doesn't tell us what happened during the 12-week supplementation period. Neither do we know whether the acid-base balance does not target a completely different set of anabolic molecules than exercise or protein nutrition so that the scientists may simply have missed measuring the "correct" markers of anabolism / catabolism to be able to fully explain their observations.
Bottom line: There is still much to be learned about the effects and detailed mechanisms of alkali supplementation. So much, in fact, that the addition of large boluses of potassium bicarbonate to a whole foods diet that includes large amounts of net alkalizing vegetables and fruits (funny how difficult it was to write that this way around and not "fruits and vegetables" ;-) as a means to increase your gains appears to be unwarranted or at least unnecessary at the moment.
|Latent acidoses can set you up to become obese (learn more)|
- Calcium, Magnesium, Potassium & Co in Food, Water & Supps - Getting Enough is Easy, Knowing How Much Is Not! (read more)
- SuppVersity Science Round-Up on Sodium, Potassium, Alkalinity & Co (listen now)
- Science Round-Up Seconds: The Macro-Mineral Alphabet & the Potential Health Hazards of Diet-Induced Latent Acidosis (read more)
- Previous SuppVersity posts on sodium bicarbonate (browse all)
- Bailey JL, Zheng B, Hu Z, Price SR, Mitch WE. Chronic kidney disease causes defects in signaling through the insulin receptor substrate/phosphatidylinositol 3-kinase/Akt pathway: implications for muscle atrophy. J Am Soc Nephrol. 2006 May;17(5):1388-94. Epub 2006 Apr 12.
- Ceglia L, Harris SS, Abrams SA, Rasmussen HM, Dallal GE, Dawson-Hughes B. Potassium bicarbonate attenuates the urinary nitrogen excretion that accompanies an increase in dietary protein and may promote calcium absorption. J Clin Endocrinol Metab. 2009 Feb;94(2):645-53.
- Ceglia L, Rivas DA, Pojednic RM, Price LL, Harris SS, Smith D, Fielding RA, Dawson-Hughes B. Effects of alkali supplementation and vitamin D insufficiency on rat skeletal muscle. Endocrine. 2013 May 11.
- Dawson-Hughes B, Castaneda-Sceppa C, Harris SS, Palermo NJ, Cloutier G, Ceglia L, Dallal GE. Impact of supplementation with bicarbonate on lower-extremity muscle performance in older men and women. Osteoporos Int. 2010 Jul;21(7):1171-9.