Dietary supplements and risk of cause-specific death, cardiovascular disease, and cancer: a protocol for a systematic review and network meta-analysis of primary prevention trials.

BACKGROUND: In the Western world, dietary supplements are commonly used to prevent chronic diseases, mainly cardiovascular disease and cancer. However, there is inconsistent evidence on which dietary supplements actually lower risk of chronic disease, and some may even increase risk. We aim to evaluate the comparative safety and/or effectiveness of dietary supplements for the prevention of mortality (all-cause, cardiovascular, and cancer) and cardiovascular and cancer incidence in primary prevention trials. METHODS/DESIGN: We will search PubMed, EMBASE, Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, the Cochrane Central Register of Controlled Trials, clinical trials.gov, and the World Health Organization International Trial Registry Platform. Randomized controlled trials will be included if they meet the following criteria: (1) minimum intervention period of 12 months; (2) primary prevention of chronic disease (is concerned with preventing the onset of diseases and conditions); (3) minimum mean age ≥18 years (maximum mean age 70 years); (4) intervention(s) include vitamins (beta-carotene, vitamin A, B vitamins, Vitamin C, Vitamin D, Vitamin E, and multivitamin supplements); fatty acids (omega-3 fatty acids, omega-6 fatty acids, monounsaturated fat); minerals (magnesium, calcium, selenium, potassium, iron, zinc, copper, iodine; multiminerals); supplements containing combinations of both vitamins and minerals; protein (amino acids); fiber; prebiotics; probiotics; synbiotics; (5) supplements are orally administered as liquids, pills, capsules, tablets, drops, ampoules, or powder; (6) report results on all-cause mortality (primary outcome) and/or mortality from cardiovascular disease or cancer, cardiovascular and/or cancer incidence (secondary outcomes). Pooled effects across studies will be calculated using Bayesian random effects network meta-analysis. Sensitivity analysis will be performed for trials lasting ≥5 years, trials with low risk of bias, trials in elderly people (≥65 years), ethnicity, geographical region, and trials in men and women. The results of the corresponding fixed effects models will also be compared in sensitivity analyses. DISCUSSION: This is a presentation of the study protocol only. Results and conclusions are pending completion of this study. Our systematic review will be of great value to consumers of supplements, healthcare providers, and policy-makers, regarding the use of dietary supplements. PROSPERO: CRD42014014801 .

Association between water consumption and body weight outcomes in children and adolescents: a systematic review.

OBJECTIVE: Water is recommended to replace sugar-containing beverages for prevention of childhood obesity. Because this recommendation is not evidence-based yet, the existing evidence on the association between water consumption and body weight outcomes was summarized. METHODS: In a systematic review, studies were retrieved from four electronic databases (MEDLINE, EMBASE, CINAHL, Cochrane) and further search methods. Studies including children aged 2-19 years on the association between water consumption and any body weight-related outcome were eligible. RESULTS: Out of 3,023 retrieved records, 13 studies were included: four longitudinal and nine cross-sectional studies. One cross-sectional analysis in one longitudinal study was additionally included, resulting in ten cross-sectional analyses. One non-randomized controlled study and two observational longitudinal studies showed that increased water consumption reduced the risk of overweight or body mass index. Another observational longitudinal study did not indicate this association. Six cross-sectional analyses found a direct association between water consumption and at least one body weight outcome. Four cross-sectional analyses did not show any association. CONCLUSIONS: On the cross-sectional level, higher water consumption seems to be associated with higher weight status. In contrast, longitudinal studies suggest a weight-reducing effect of water consumption, but evidence for a causal association is still low.