This is the first comprehensive study to evaluate the effects of regular use of ginseng and G. lucidum as a complementary therapy at different time points after cancer diagnosis on breast cancer survivor’s QOL in a large, population-based cohort study. We found no evidence that ginseng use post-diagnosis was associated with improved QOL at the 36-month follow-up. Survivors who used G. lucidum regularly after cancer diagnosis reported a higher score for social well-being, but a lower score for physical well-being, compared with non-users. These differences were more apparent for higher frequency and cumulative number of times of use during the entire follow-up period.
Ginseng has been used to maintain natural energy, increase physical and psychomotor performance, and improve mood and general health 
. There are several types of ginseng, including Asian ginseng (Panax ginseng
) and American ginseng (P. quinquefolius
); the major active constituents are ginsenosides. Over 80% of our study population used American ginseng. In vitro
experiments and in vivo
animal studies have reported that ginsenosides have a variety of beneficial effects, including immunodulatory, anti-stress, anti-fatigue, and anti-carcinogenic effects 
. However, in human studies, findings on the effects of ginseng on health-related QOL are mixed 
. A systematic review by Vogler et al. summarized several randomized clinical trials and found contradictory results for ginseng ability to improve physical performance and immune function 
. Coleman et al. reviewed 9 clinical trials and concluded that improvement in overall health-related QOL cannot be attributed to P. ginseng
, although various facets of QOL had improved 
There is a paucity of data from epidemiological studies regarding the effects of ginseng use on QOL among cancer patients. Our previous studies have shown that ginseng use, particularly current use at the fourth year post-diagnosis, was positively associated with QOL scores, with the strongest effects in the psychological and social well-being domains 
. In the present study, however, we found no significant positive associations between post-diagnosis ginseng use and survivors’ QOL at the 36-month follow-up. There are several potential reasons for this discrepancy. First, the design of previous studies differed from the present study, which is a prospective survival study specifically designed to investigate post-diagnostic lifestyle and CAM use and collected relevant information at multiple, pre-determined time points (6, 18, and 36 months after cancer diagnosis). Our previous study was an ad hoc follow-up of breast cancer patients enrolled in a case-control study, for which exposure data were collected at one time point after cancer diagnosis (approximately 48 months). Second, the prevalence of ginseng use among breast cancer survivors was substantially lower in the current study compared with the previous study, which may have obscured the association between ginseng use and breast cancer survivors’ QOL. In the previous study, 62.8% of women with breast cancer reported post-diagnosis ginseng use, and 30.6% were current users. In the present study, 14.2% of participants were ginseng users at baseline and 10.9% were ginseng users at the 36-month follow-up. In addition, the timing of the QOL assessment also differed between our two studies. In our earlier study, QOL was assessed only once at the fourth year post-diagnosis, while in the present study, QOL was assessed at 6 and 36 months post-diagnosis and the association of QOL at the 36-month survey with ginseng use was adjusted for the baseline QOL score.
was the most popular herbal remedy used by our study participants 
. The prevalence of use among women with breast cancer increased during the decade prior to the current study’s recruitment period from 18.9% among breast cancer cases enrolled in our case-control study (1996–1998) 
to 58.4% (2002–2006) 
. In the present study, 58% of participants reported G. lucidum
use at the 36-month survey. To date, over one hundred species of oxygenated triterpenes have been isolated from G. lucidum
. G. lucidum
has been reported to have many biological activities, such as histamine release-inhibitory action, immunomodulatory activity, antitumor cytokines acting on inhibition of leukemic-cell growth, and differentiation inducing activity 
. In vitro
experiments have shown that G. lucidum
can inhibit proliferation, invasive behavior, and growth of tumor cells, and induce tumor cell apoptosis 
. However, no study has reported on the effects of G. lucidum
use on clinical outcomes and/or QOL among breast cancer survivors. In the present study, we found that G. lucidum
use after breast cancer diagnosis was associated with a higher score for social well-being, but a lower score for physical well-being. As a result, the overall QOL score was not significantly associated with G. lucidum
use. The underlying mechanisms for these associations are unclear. The improvement of social well-being may reflect better financial and social support, while the reduced physical well-being score may suggest that either G. lucidum
use negatively influenced patients’ physical well-being or patients with low physical well-being were more likely to seek G. lucidum
as complementary treatment. Given the popularity of G. lucidum
use among women with breast cancer, more studies should be conducted to clarify its effects on breast cancer survivors’ QOL.
Our study has several strengths. It is the first population-based, longitudinal, prospective study with a large enough sample size to investigate relationships between the use of ginseng and G. lucidum after diagnosis and QOL among breast cancer survivors. Multiple assessments improved the quality of both the exposure and outcome information. Selection bias was largely minimized due to the high response and follow-up rates. The detailed data on socio-demographic, lifestyle, and known clinical prognostic factors that we collected allowed a detailed adjustment for potential confounding factors. However, several limitations of our study should also be noted. First, information about pre-diagnosis use of ginseng and G. lucidum was not available; thus, we were unable to evaluate the influence of pre-diagnosis ginseng and G. lucidum use on QOL. Second, the brand of ginseng and G. lucidum products and specific dosages used may affect their effectiveness, but our study did not collect this information. Third, although sexual functioning is an important component of QOL, we were not able to evaluate its association with ginseng and G. lucidum use, because of the very small number of participants who reported being sexually active, which is likely due to the fact that the subject of “sexual functioning” is considered to be very private in Eastern cultures.
In summary, our study found no evidence that ginseng use after breast cancer diagnosis improved survivors’ QOL during the first three years post-diagnosis. G. lucidum use after cancer diagnosis was associated with better social well-being, but poorer physical well-being. Further studies are needed to investigate the benefits and safety of ginseng and G. lucidum use among longer-term cancer survivors.