Brain glucose extraction is not fixed and may compensate for changes in cerebral blood flow—Commentary article on “Brain glucose extraction is fixed at 10% despite twofold variability in resting cerebral blood flow in healthy humans”

Duffy et al.¹ in their recent JCBFM article concludes that "<i>glucose extraction is fixed at 10% despite twofold variability in resting cerebral blood flow in healthy humans.</i>" However, in this commentary we raise some important issues, since the title and conclusion are somewhat misleading and do not represent principal physiology. We address the risk for spurious correlation when the cerebral metabolic rate for glucose (<i>CMRglc</i>) is plotted against cerebral blood flow (CBF) as CBF is integrated in the calculation of <i>CMRglc</i>. Furthermore, we draw attention to studies where glucose extraction readily increased when CBF is acutely lowered.