Vitamin D administered pre-diagnostically has been shown to reduce mortality. Emerging evidence suggests a role of post-diagnosis vitamin D supplement intake for survival among cancer patients. Thus, we conducted a meta-analysis to evaluate the relationship. PubMed and Embase were searched for relevant observational cohort studies and randomized trials published through April 2022. Summary relative risk (SRR) and 95% confidence interval (CI) were estimated using the DerSimonian–Laird random-effects model. The SRR for post-diagnosis vitamin D supplement use vs. non-use, pooling cohort studies and randomized trials, was 0.87 (95% CI, 0.78–0.98; p = 0.02; I² = 0%) for overall survival, 0.81 (95% CI, 0.62–1.06; p = 0.12; I² = 51%) for progression-free survival, 0.86 (95% CI, 0.72–1.03; p = 0.10; I² = 0%) for cancer-specific survival, and 0.86 (95% CI, 0.64–1.14; p = 0.29; I² = 0%) for relapse. Albeit not significantly heterogeneous by variables tested, a significant inverse association was limited to cohort studies and supplement use during cancer treatment for overall survival, and to studies with ≤3 years of follow-up for progression-free survival. Post-diagnosis vitamin D supplement use was associated with improved overall survival, but not progression-free or cancer-specific survival or relapse. Our findings require confirmation, as randomized trial evidence was insufficient to establish cause-and-effect relationships.

Dairy consumption in adulthood has been demonstrated to influence cancer risk. Although childhood and adolescence represent critical periods of rapid growth, the relationship between milk intake in early life and later cancer risk is unclear. Thus, we examined this relationship by conducting a meta-analysis of the observational studies. PubMed and Embase were searched for relevant articles that were published throughout December 2021. The summary relative risk (RR) and 95% confidence interval (CI) were estimated using the DerSimonian-Laird random-effects model. The summary RR for the highest vs. lowest milk intake was 0.83 (95% CI = 0.69–1.00; p = 0.05; I² = 60%; seven studies) for breast cancer, 0.98 (95% CI = 0.72–1.32; p = 0.88; I² = 51%; four studies) for prostate cancer, and 0.90 (95% CI = 0.42–1.93; p = 0.78; I² = 83%; three studies) for colorectal cancer. No evidence of an association emerged in subgroup analyses of menopausal status, cancer stage, fat content of milk, life stage of milk intake, or study design. Consistent results were observed in the meta-analyses using total dairy intake. In conclusion, milk intake during childhood and adolescence might not be associated with risks of breast, prostate, and colorectal cancer later in life. Given the small number of studies that were included in our meta-analysis, and the high heterogeneity, more studies are warranted for a definitive conclusion.

Background: Dietary and lifestyle factors are well-studied for colorectal cancer (CRC) prevention. However, less evidence exists on their impact on CRC survival. Methods: PubMed and Embase were searched from inception to September 2024. Summary relative risks (RRs) and 95% confidence intervals (CIs) were estimated using the DerSimonian–Laird random effects model. Results: Lower all-cause mortality was observed with unprocessed red meat (summary RR = 0.74, 95% CI = 0.57 to 0.94), whole grains (summary RR = 0.77, 95% CI = 0.66 to 0.90), coffee (summary RR = 0.65, 95% CI = 0.55 to 0.77), milk (summary RR = 0.82, 95% CI = 0.71 to 0.93), low-fat dairy (summary RR = 0.77, 95% CI = 0.64 to 0.94), total calcium (summary RR = 0.76, 95% CI = 0.61 to 0.94), alcohol intake under 45 g/day (J-shaped association), and physical activity (summary RR = 0.55, 95% CI = 0.44 to 0.69). Higher all-cause mortality was observed with refined grains (summary RR = 1.55, 95% CI = 1.03 to 2.33), high-fat dairy (summary RR = 1.34, 95% CI = 1.05 to 1.71), smoking (current: summary RR = 1.49, 95% CI = 1.24 to 1.78; former: summary RR = 1.18, 95% CI = 1.04 to 1.34), and television watching (summary RR = 1.28, 95% CI = 1.06 to 1.55). Risk increased linearly with body mass index greater than 27 kg/m2 but also increased toward lower body mass index. For CRC-specific mortality, most of the results were largely consistent, with calcium supplement showing an inverse association (summary RR = 0.66, 95% CI = 0.47 to 0.94). Conclusions: Factors related to CRC survival share differences as well as similarities with established factors related to CRC prevention. To optimize CRC survival, CRC patients may be recommended to adopt a diet rich in whole grains, coffee, milk, and dietary calcium; to avoid excessive alcohol, refined grains, high-fat dairy, sugar-sweetened beverages, smoking, and sedentary lifestyle; and to engage in regular physical activity while maintaining a healthy weight.

Background: Water consumption is believed to be a key factor in weight management strategies, yet the existing literature on the subject yields inconsistent findings. To systematically assess the scientific evidence regarding the effect of water intake on adiposity, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) among overweight and obese populations. Methods: PubMed and Embase were searched for relevant articles published up to December 2023. The summary weighted mean difference (WMD) and 95% confidence interval (CI) were estimated using the DerSimonian–Laird random-effects model. Results: In this meta-analysis of eight RCTs, interventions to promote water intake or to substitute water for other beverages as compared to the control group resulted in a summary WMD of −0.33 kg (95% CI = −1.75–1.08, I² = 78%) for body weight, −0.23 kg/m² (95% CI = −0.55–0.09, I² = 0%) for body mass index (BMI), and 0.05 cm (95% CI = −1.20–1.30, I² = 40%) for waist circumference (WC). Among RCTs substituting water for artificially sweetened beverages, summary WMD was 1.82 kg (95% CI = 0.97–2.67, I² = 0%) for body weight and 1.23 cm (95% CI = −0.03–2.48, I² = 0%) for WC. Conversely, among RCTs substituting water for sugar-sweetened beverages, summary WMD was −0.81 kg (95% CI = −1.66–0.03, I² = 2%) for body weight and −0.96 cm (95% CI = −2.06–0.13, I² = 0%) for WC. Conclusions: In conclusion, water intake may not significantly impact adiposity among overweight and obese individuals. However, replacing sugar-sweetened beverages with water might offer a modest benefit in inducing weight loss.

Background/Objectives: Accumulating evidence suggests that dietary factors such as nuts may play a role in depressive symptoms. Yet, existing evidence regarding the relationship between nut consumption and depressive symptoms remains inconsistent. To clarify this association, we conducted a meta-analysis. Methods: PubMed and Embase were searched for observational studies on the relationship between nut consumption and depressive symptoms published up to September 2025. Summary relative risks (SRRs) and 95% confidence intervals (CIs) were estimated using the DerSimonian–Laird random effects model. Results: A total of seven observational studies, comprising 70,136 participants, were included. Higher nut consumption was significantly associated with a lower risk of depressive symptoms (SRRs = 0.75, 95% CIs, 0.67–0.85; p < 0.001, I² = 15%, P_{heterogeneity} = 0.31). Compared to <1 time/week of nut consumption, the inverse relationship was significant for ≥3 times/week of nut consumption (SRRs = 0.75, 95% CIs = 0.63–0.89, p = 0.001, I² = 0%, P_{heterogeneity} = 0.93), but not for 1 to <3 times/week of nut consumption (SRRs = 0.93, 95% CIs = 0.69–1.24, p = 0.62, I² = 52%, P_{heterogeneity} = 0.10). Conclusions: Our meta-analysis of observational studies found that higher nut consumption was associated with a reduced risk of depressive symptoms, particularly when intake reached at least three servings per week. Further research, especially randomized controlled trials, is needed to understand the underlying mechanisms.