Ginseng Research Trends
Recurring issues in study design
This page is not a summary of particular papers. It sets out, from the institute's perspective, the issues that come up repeatedly in designing human ginseng studies and having them reviewed.
1. Is it the same material?
The commonest reason ginseng studies disagree is that the material differed. Two preparations both called 'red ginseng' can differ in ginsenoside composition according to the number of steaming cycles, the extraction conditions and the part used. A study that did not quantify its marker compounds is hard to compare with others, and its result is hard to attribute to the material.
To settle at the design stage: quantified marker content for the batch to be used, batch uniformity across the whole study period, and whether the placebo matches in appearance and taste.
2. Individual variation and the gut microbiota
A substantial proportion of ginsenosides are not absorbed as such but are converted first by gut microbiota. That capacity differs between individuals, so the same intake produces markedly different systemic exposure. Reducing that variation is one reason fermented preparations are studied.
In design terms this means variance is large, and a larger variance requires a larger sample to detect the same effect. A sample size calculation that ignores this yields an underpowered study.
3. Effect size and the primary endpoint
Effects of ginseng in humans are generally modest, which makes the choice of a sufficiently sensitive primary endpoint central to the design. Measuring a wide range of markers and selecting the significant ones afterwards creates a multiplicity problem and is criticised in review.
4. Designing the pathway in
A study that measures only the outcome demonstrates that an effect exists but not how it works. Measuring candidate mediators — hormonal, autonomic, lipid — alongside allows the hypothesis to be tested by path analysis.
All three of the director's studies of fermented red ginseng were designed this way, addressing respectively hormones and the autonomic nervous system (Lee & Ji, 2014a), lipids (Lee & Ji, 2014b) and hormonal interaction (Lee et al., 2013).
5. How strongly it may be stated
Wording that goes beyond what was observed causes problems both academically and in regulatory terms. 'Improved' and 'treats' are entirely different statements, and the latter breaches health functional food labelling and advertising review standards.
| Avoid | Use instead |
|---|---|
| Treats X | An improvement in the X marker was observed |
| Cures X | X decreased significantly (p < 0.05) |
| Boosts immunity | A change in the immune-related marker X was observed |
| Has no side effects | The adverse events reported during the study period were X |
References
- Lee, K. J., Lee, S. Y., & Ji, G. E. (2013). Diabetes-ameliorating effects of fermented red ginseng and causal effects on hormonal interactions: Testing the hypothesis by multiple group path analysis. Journal of Medicinal Food, 16(5), 383–395. https://doi.org/10.1089/jmf.2012.2583
- Lee, K. J., & Ji, G. E. (2014a). Free-fatty-acid-regulating effects of fermented red ginseng are mediated by hormones and by the autonomic nervous system. Journal of Ginseng Research, 38(2), 97–105. https://doi.org/10.1016/j.jgr.2013.12.003
- Lee, K. J., & Ji, G. E. (2014b). The effect of fermented red ginseng on depression is mediated by lipids. Nutritional Neuroscience, 17(1), 7–15. https://doi.org/10.1179/1476830513Y.0000000059