Creatine Non-Responder? Age+Meat Intake - Determinants of Creatine's Effect on PCr (±200%) + Probably Performance

Vegetarian strength athletes belong to the group of people who will probably benefit most from creatine supplementation. Their young, meat-eating peers, on the other hand, may well turn out to be non-responders, because they see highly individual, but overall only non-significant increases in phosphocreatine.

It has been a while since I published the last creatine article ("Dubious Effects of Creatine on Markers of CNS Adaptation and Heart Health in "Bodybuilders" - Reason to Be Afraid?" | read it); the last time that I addressed the issue of "creatine non-responders", i.e. reasons why people simply don't seem to benefit from creatine supplementation has been published in 2014, already, when I presented the results of a study suggesting that it's not a high dietary creatine intake from meat that makes the difference (learn more).

Needless to say, meat still made it on the list of possible determinants of the individual performance increases in response to creatine supplementation... I mean, it's meat - and we all know how people love to blame it for everything, these days ;-)
Before we get into any further details, though, I have to point out that the soon-to-be-published study by Marina Yazigi Solis and colleagues from the Univerity of Sao Paulo did not actually test the performance effects of creatine. Rather than that the goal of the Brazilian scientists was to fill another gap in the extensive literature about creatine supplementation: the way(s) in which your creatine/phosphorylcreatine (PCr) response to creatine supplementation may be modulated by age, diet, and tissue. Or, as the scientists describe it: "[W]e aimed to determine whether the PCr responses vary as a function of age, diet, and tissue.

In their study, fifteen children, 17 omnivorous and 14 vegetarian adults, and 18 elderly were randomly assigned to consume either placebo and subsequently creatine (0.3 g/kg per day) or creatine and placebo for 7 days in a single-blind fashion.

Figure 1: Illustration of the phosphocreatine “shuttle” system (Guimarães-Ferreira 2014); as you can see PCr is - assuming you have the necessary energy in form of ATP available, automatically restored by creatine kinase - the loss in form of creatinine is, at least in healthy individuals, relatively low and may indeed be compensated for by the relatively small amount of creatine omnivores get from (esp. the red) meats in their diet.

PCr was measured via phosphorus magnetic resonance spectroscopy (31P-MRS) in muscle and brain using a whole body 3.0T MRI scanner (Achieva Intera, Philips, Best, The Netherlands) and a 14 cm diameter 31P surface coil.
As you can see in Figure 2, the creatine supplement increased muscle PCr in children (p<0.0003) and elderly (p<0.001). What it did not do, however, was to produce significant increases in the meat-eating (=omnivorous) study subjects (the statistical significance of the changes were far from being below 0.05 | p=0.3348, a sub-group analysis for the amount and type of meat the subjects consumed was not performed and probably wouldn't have made sense in view of the relatively low number of participants).

Figure 2: Delta changes in PCr in response to creatine supplementation (i.e., creatine subtracted from placebo values) in muscle and brain (Solis 2017); with only 18 elderly subjects, it made no sense to distinguish omnivores vs. vegetarians.

What may be quite surprising is that the elderly subjects had greater PCr increases than children and omnivores (p<0.0001 for both). Less surprising, but also worth mentioning: children experienced greater PCr increases than omnivores (p=0.0022). When the scientists eventually compared vegetarians (p<0.0001) to omnivores, they found that the former were the ones with the most significant increase in PCr content and thus the subjects of whom you would expect that they'd see maximal performance gains, as well.

Table 1: Creatine content of some common foods (Tarnopolsky 2010).

Unrelated to your "gainz", but probably highly health-relevant in view of the effects of creatine on the brain, e.g. its protective effect in traumatic brain injury (Sullivan 2000) and its ability to boost brain performance (Rae 2003 + Rawson 2011), is that the study at hand found no increase in Brain PCr in any group, and delta changes in brain PCr (-0.7 to +3.9%) were significantly less pronounced than the increase in muscle PCr content (+10.3 to +27.6%; p<0.0001 for all comparisons).

For the elderly individuals that seems odd, as previous studies demonstrated measurable beneficial effects on the cognitive performance of elderly subjects (Rawson 2011), for the younger subjects, on the other hand, it was to be expected that the PCr levels and thus the availability of immediate response energy wouldn't increase significantly as Rawson et al. demonstrated in 2008, already, that "creatine supplementation does not improve cognitive function in young adults" (Rawson 2008).
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