Association between Different Types of Tea Consumption and Risk of Gynecologic Cancer: A Meta-Analysis of Cohort Studies.

Plenty of studies have shown that tea has an effect of inhibiting gynecologic tumors. However, there still remained controversy of the association between tea and gynecologic tumors in epidemiological studies. In this study, PubMed, Embase, and Cochrane Database were used to search the literature from 1 January 1960 to 26 December 2022 to investigate the association between tea intake and gynecologic cancer risk. In total, 19 cohort studies with 2,020,980 subjects and 12,155 gynecological tumor cases were retrieved. The pooled relative risk (RR) of gynecologic tumor for tea intake was 1.00 (95% CI: 0.96-1.04). RRs were 0.94 (95% CI: 0.88-1.01) for ovarian cancer, 1.02 (95% CI: 0.97-1.07) for endometrial cancer, and 1.06 (95% CI: 0.91-1.23) for cervical cancer. Subgroup analyses were adopted based on the tea type and geographic location. Interestingly, significant preventive impact of non-herbal tea on ovarian cancer (pooled relative risk: 0.67; 95% CI: 0.55-0.81) was found, especially for black tea (pooled relative risk: 0.64; 95% CI: 0.51-0.80). Dose-response analysis indicated that although it is not statistically significant, a decreasing trend of ovarian cancer risk could be observed when the tea consumption was 1.40 to 3.12 cups/day. In conclusion, our findings suggested that ovarian cancer, but not other gynecologic cancers, could possibly be prevented by drinking non-herbal tea. In addition, the preventive impact of green tea on gynecologic cancer seemed to be relatively weak and needs further cohorts to validate it.

Association between vitamin D/calcium intake and 25-hydroxyvitamin D and risk of ovarian cancer: a dose-response relationship meta-analysis.

BACKGROUND: The association between vitamin D/calcium and risk of ovarian cancer is still a debatable point. The aim of our study was to systematically investigate the association between vitamin D/calcium, and the risk of ovarian cancer and estimate their dose-response association quantitatively. METHODS: PubMed, EMBASE, and Web of Science databases were searched to identify relevant observational studies. Two investigators screened citations and extracted data independently. Data were extracted and the association between vitamin D/calcium and ovarian cancer risk was estimated by calculating pooled relative risks (RRs). Subgroup analyses, publication bias estimation, and dose-response analyses were carried out as well. RESULTS: In total, 21 articles involving 980,008 participants were included in our present study. No significant association was observed between total vitamin D intake and ovarian cancer risk (RR: 1.02; 95% CI, 0.89-1.16, p = 0.81). Further subgroup analysis suggested that neither dietary vitamin D intake (RR: 0.80; 95% CI, 0.62-1.03, p = 0.09) nor supplementary vitamin D intake (RR: 0.98; 95% CI, 0.85-1.13, p = 0.80) was associated with the risk of ovarian cancer. As for calcium, total calcium intake was found to be statistically inversely associated with ovarian cancer risk in case-control studies (RR: 0.73; 95% CI, 0.63-0.86, p < 0.001) but not in cohort studies (RR: 1.05; 95% CI, 0.90-1.24, p = 0.52). Besides, supplementation with calcium plus vitamin D was not effective for the prevention of ovarian cancer (p = 0.98). Of note, dose-response analysis based on cohort studies suggested a potential inverse U-shape relationship between calcium intake (including total calcium and dietary calcium) and ovarian cancer risk, which indicated that low dose of calcium intake might reduce ovarian cancer risk while high dose of calcium intake might not. CONCLUSIONS: Taken together, vitamin D could not decrease the risk of ovarian cancer. The role of calcium intake was not proven for reducing ovarian cancer risk. Besides, no evidence showed combinative use of calcium and vitamin D have additional benefits for ovarian cancer prevention.