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Effect of Black Pepper & Rosemary on Attention, Motivation, Mental Energy & Fatigue
Lindheimer JB, Loy BD, O'Connor PJ
The objective of this experiment was to test whether the consumption of a single, practical amount of black pepper or rosemary impacts feelings of mental energy and fatigue, perceived motivation to perform cognitive tasks, or performance on a cognitive task that required sustained attention.
Forty young adults with below average feelings of energy were given capsules containing either black pepper [2.0 g], rosemary [1.7 g], or a placebo [3.1 g rice flour]. Outcomes were measured before and twice after they orally consumed capsules [after a 1 hour rest period to allow treatments to become bioavailable]. Sustained attention was measured using a 16-min dual task, in which, single-digit numbers were presented every second on a screen and the participant performed both a primary task [detection of three successive, different odd digits] and a secondary task [detection of the number 6]. Feelings of energy and fatigue were measured using the vigor and fatigue subscales of the Profile of Mood States and visual analog scales (VAS).
Analysis of variance showed non-significant condition [spice versus placebo] x time [T1, T2, & T3] effects for motivation, measured with a VAS, and the intensity of energy and fatigue feelings. Unadjusted effect sizes revealed that rosemary induced small, transient reductions in false alarm errors (d = 0.21) and mental fatigue (d = 0.40) at isolated time periods. Time-varying analysis of covariance, controlling for motivation to perform cognitive tasks, showed no significant effects on the primary or secondary task outcomes of correct responses [hits], errors [false alarms, misses], speed of response [reaction time], and signal detection sensitivity.
It was concluded that black pepper and rosemary, consumed in a capsule form, in the doses used and while wearing a nose clip to block olfactory effects, do not induce consistent short-term improvements in sustained attention, motivation to perform cognitive tasks, or feelings of mental energy and fatigue in young adults with low energy.
Lindheimer JB, Loy BD, and O'Connor PJS. The Short-Term Effects of Black Pepper (Piper nigrum) and Rosemary (Rosmarinus officinalis and Eriocalyx) on Sustained Attention and Energy and Fatigue Mood States in Young Adults with Low Energy. J Med Food. 2013 Aug 1. Link to the paper