Can Black Pepper Aroma Change the Body’s Response During Mental Arithmetic?

Black pepper is a pungent spice, but how does the body respond when people smell it while working? In a study of 20 male students, presenting black pepper essential oil during mental arithmetic led to a smaller decrease in one measure of heart rate variability than an unscented condition. The change in skin response was smaller than with ginger, the other aroma used for comparison.

This 2024 study explored whether an aroma perceived as stimulating might nevertheless moderate autonomic responses during a demanding task. It measured cardiac responses, skin responses, and participants’ own feelings separately.

Comparing black pepper, ginger, and an unscented condition in the same people

The participants were 20 healthy male university students aged 20–24. Each experienced three conditions on three separate days: black pepper essential oil, ginger essential oil, and the unscented solvent DPG. The presentation order was arranged to avoid systematic bias.

Each session consisted of 10 minutes of rest, 30 minutes of mental arithmetic, and 15 minutes of recovery. During the task, participants repeatedly added single-digit numbers on a screen as quickly and accurately as possible. Although simple, the task required sustained concentration and created a short-term workload.

During the task, aroma was delivered through a tube beneath the nose for only the first 20 seconds of each minute. A dedicated olfactometer allowed tighter control of delivery timing and airflow than dispersing fragrance throughout a room. The authors nevertheless noted technical limitations in precisely establishing the concentration of the inhaled aroma.

Measuring heart rate, heart rate variability, and electrical skin responses

An electrocardiogram was used to calculate heart rate and heart rate variability, the fluctuations in intervals between heartbeats. Its high-frequency component, HF, was used as an index related to parasympathetic activity at the heart. Sensors attached to the fingers also measured skin conductance level, which reflects how readily the skin conducts electricity as sweating and other factors change.

For the analysis, values were standardized separately for each person and condition, and changes from the initial resting period were compared. Figures in the original paper describing a response as a certain percentage smaller refer to differences in these processed responses. They do not mean that heart rate itself fell by tens of percent, or that overall stress disappeared by that proportion.

In all conditions, heart rate and skin conductance rose during arithmetic, while HF fell. The researchers then examined whether the size of these changes differed between aroma conditions.

A smaller decrease in HF with black pepper, and a similar pattern with ginger

In the black pepper condition, the decrease in HF during arithmetic was 32.9% smaller than in the unscented condition, a significant difference even after accounting for multiple comparisons. With ginger, it was 25.2% smaller than in the unscented condition. For this heart rate variability measure, both aromas showed a change in the same direction.

The rise in heart rate also tended to be smaller with black pepper than in the unscented condition. However, the p-value of 0.048 for this comparison was the value before correction for multiple comparisons, so caution is needed before treating it as a firm difference. With ginger, the increase in heart rate was smaller than in the unscented condition and remained significant after correction.

The rise in skin conductance was 15.5% smaller with black pepper than with ginger, a significant difference. By contrast, the difference between black pepper and the unscented condition was not significant. Importantly, the comparison showing a significant difference was not the same for the cardiac and skin measures.

Feeling less fed up than without aroma, but not an overall change in mood

Participants also rated tension, effort, concentration, fatigue, irritation, boredom, and feeling fed up with the task on scales from 0 to 100. Most items did not differ significantly between aroma conditions, and there was no clear difference in arithmetic performance.

One exception was feeling fed up during the task. The mean was 30.0 with black pepper and 36.7 in the unscented condition; Table 3 reports a difference with an adjusted p-value of 0.049. Although the abstract and some summaries in the original paper describe no differences in subjective ratings, this individual result needs to remain part of the reading.

There were no significant differences among the three conditions in liking the aroma itself, comfort, or how awakening it felt. Nor did any aroma show a clear correlation between liking or comfort and the physiological measures. Simply assuming that a more pleasant aroma produces a smaller bodily response does not fully explain these findings.

People who perceived black pepper as more intense also had higher heart rates, while those who found it more awakening had lower HF. Average differences between conditions may therefore coexist with differences related to individual impressions.

The components and mechanisms remain questions for future research

The black pepper essential oil contained 35.1% β-caryophyllene, 15.0% limonene, 10.3% α-pinene, and 10.2% β-pinene, among other components. However, the study did not compare these components individually, so it cannot establish which molecules were responsible for the responses.

The sample consisted of a small number of young men, and the stressor was limited to 30 minutes of arithmetic. Participants could distinguish the three conditions, making it impossible to fully conceal their awareness of, or expectations about, the aromas. Effects on long-term everyday stress, or effects of eating black pepper in food, require separate investigation.

Summary

With black pepper and ginger aromas, the decrease in HF during arithmetic was smaller than in an unscented condition. The rise in skin conductance with black pepper was smaller than with ginger, but its difference from the unscented condition was not clear. Most subjective ratings did not differ, although participants felt less fed up with black pepper than without aroma.

An aroma’s stimulating impression and the body’s response under workload do not necessarily move in the same direction. Separating the measures and the comparison conditions provided clues to the effects of black pepper aroma.

The research was partly funded by Takasago International Corporation and Nagaoka University of Technology, and the essential oils used were also from Takasago. The paper lists one coauthor as affiliated with the company at the time of the research; the authors declared no competing interests.

References

Dilrukshi EAC, Nishiyama Y, Ito K, Nomura S. Alleviation of acute stress response by black pepper aroma administration. Journal of Physiological Anthropology. 2024;43:3. doi:10.1186/s40101-023-00352-1