Goran Bjelakovic

Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis

BACKGROUND Oxidative stress can cause cancer. Our aim was to establish whether antioxidant supplements reduce the incidence of gastrointestinal cancer and mortality. METHODS With the Cochrane Collaboration methodology, we reviewed all randomised trials comparing antioxidant supplements with placebo for prevention of gastrointestinal cancers. We searched electronic databases and reference lists (February, 2003). Outcome measures were incidence of gastrointestinal cancers, overall mortality, and adverse effects. Outcomes were analysed with fixed-effect and random-effects model meta-analyses and were reported as relative risk with 95% CIs. FINDINGS We identified 14 randomised trials (n=170,525). Trial quality was generally high. Heterogeneity of results was low to moderate. Neither the fixed-effect (relative risk 0.96, 95% CI 0.88-1.04) nor random-effects meta-analyses (0.90, 0.77-1.05) showed significant effects of supplementation with beta-carotene, vitamins A, C, E, and selenium (alone or in combination) versus placebo on oesophageal, gastric, colorectal, pancreatic, and liver cancer incidences. In seven high-quality trials (n=131727), the fixed-effect model showed that antioxidant significantly increased mortality (1.06, 1.02-1.10), unlike the random-effects meta-analysis (1.06, 0.98-1.15). Low-quality trials showed no significant effect of antioxidant supplementation on mortality. The difference between the mortality estimates in high-quality and low-quality trials was significant (Z=2.10, p=0.04 by test of interaction). beta-carotene and vitamin A (1.29, 1.14-1.45) and beta-carotene and vitamin E (1.10, 1.01-1.20) significantly increased mortality, whereas beta-carotene alone only tended to increase mortality (1.05, 0.99-1.11). In four trials (three with unclear or inadequate methodology), selenium showed significant beneficial effect on the incidence of gastrointestinal cancer. INTERPRETATION We could not find evidence that antioxidant supplements can prevent gastrointestinal cancers; on the contrary, they seem to increase overall mortality. The potential preventive effect of selenium should be studied in adequate randomised trials.

Antioxidant supplements and mortality.

Purpose of reviewOxidative damage to cells and tissues is considered involved in the aging process and in the development of chronic diseases in humans, including cancer and cardiovascular diseases, the leading causes of death in high-income countries. This has stimulated interest in the preventive potential of antioxidant supplements. Today, more than one half of adults in high-income countries ingest antioxidant supplements hoping to improve their health, oppose unhealthy behaviors, and counteract the ravages of aging. Recent findingsOlder observational studies and some randomized clinical trials with high risks of systematic errors (‘bias’) have suggested that antioxidant supplements may improve health and prolong life. A number of randomized clinical trials with adequate methodologies observed neutral or negative results of antioxidant supplements. Recently completed large randomized clinical trials with low risks of bias and systematic reviews of randomized clinical trials taking systematic errors (‘bias’) and risks of random errors (‘play of chance’) into account have shown that antioxidant supplements do not seem to prevent cancer, cardiovascular diseases, or death. Even more, beta-carotene, vitamin A, and vitamin E may increase mortality. Some recent large observational studies now support these findings. According to recent dietary guidelines, there is no evidence to support the use of antioxidant supplements in the primary prevention of chronic diseases or mortality. SummaryAntioxidant supplements do not possess preventive effects and may be harmful with unwanted consequences to our health, especially in well-nourished populations. The optimal source of antioxidants seems to come from our diet, not from antioxidant supplements in pills or tablets.

Systematic review: primary and secondary prevention of gastrointestinal cancers with antioxidant supplements

Background  The evidence on whether antioxidant supplements prevent gastrointestinal cancers is contradictory.

Meta-Regression Analyses, Meta-Analyses, and Trial Sequential Analyses of the Effects of Supplementation with Beta-Carotene, Vitamin A, and Vitamin E Singly or in Different Combinations on All-Cause Mortality: Do We Have Evidence for Lack of Harm?

Background and Aims Evidence shows that antioxidant supplements may increase mortality. Our aims were to assess whether different doses of beta-carotene, vitamin A, and vitamin E affect mortality in primary and secondary prevention randomized clinical trials with low risk of bias. Methods The present study is based on our 2012 Cochrane systematic review analyzing beneficial and harmful effects of antioxidant supplements in adults. Using random-effects meta-analyses, meta-regression analyses, and trial sequential analyses, we examined the association between beta-carotene, vitamin A, and vitamin E, and mortality according to their daily doses and doses below and above the recommended daily allowances (RDA). Results We included 53 randomized trials with low risk of bias (241,883 participants, aged 18 to 103 years, 44.6% women) assessing beta-carotene, vitamin A, and vitamin E. Meta-regression analysis showed that the dose of vitamin A was significantly positively associated with all-cause mortality. Beta-carotene in a dose above 9.6 mg significantly increased mortality (relative risk (RR) 1.06, 95% confidence interval (CI) 1.02 to 1.09, I2 = 13%). Vitamin A in a dose above the RDA (> 800 µg) did not significantly influence mortality (RR 1.08, 95% CI 0.98 to 1.19, I2 = 53%). Vitamin E in a dose above the RDA (> 15 mg) significantly increased mortality (RR 1.03, 95% CI 1.00 to 1.05, I2 = 0%). Doses below the RDAs did not affect mortality, but data were sparse. Conclusions Beta-carotene and vitamin E in doses higher than the RDA seem to significantly increase mortality, whereas we lack information on vitamin A. Dose of vitamin A was significantly associated with increased mortality in meta-regression. We lack information on doses below the RDA. Background All essential compounds to stay healthy cannot be synthesized in our body. Therefore, these compounds must be taken through our diet or obtained in other ways [1]. Oxidative stress has been suggested to cause a variety of diseases [2]. Therefore, it is speculated that antioxidant supplements could have a potential role in preventing diseases and death. Despite the fact that a normal diet in high-income countries may provide sufficient amounts of antioxidants [3,4], more than one third of adults regularly take antioxidant supplements [5,6].

Meta-analysis: antioxidant supplements for primary and secondary prevention of colorectal adenoma

Colorectal cancer may be prevented by reducing the development of adenomatous polyps.

Antioxidant Supplements to Prevent Mortality

CLINICAL QUESTION Are antioxidant supplements associated with higher or lower all-cause mortality? BOTTOM LINE Antioxidant supplements are not associated with lower all-cause mortality. Beta carotene, vitamin E, and higher doses of vitamin A may be associated with higher all-cause mortality.

Meta-analysis: antioxidant supplements for liver diseases - the Cochrane Hepato-Biliary Group.

Aliment Pharmacol Ther 2010; 32: 356–367

The model for the end-stage liver disease and Child-Pugh score in predicting prognosis in patients with liver cirrhosis and esophageal variceal bleeding

BACKGROUND/AIM Esophageal variceal bleeding is one of the most frequent and gravest complications of liver cirrhosis, directly life-threatening. By monitoring certain clinical and laboratory hepatocellular insufficiency parameters (Child-Pugh score), it is possible to determine prognosis in patients who are bleeding and evaluate further therapy. Recently, the Model for the End-Stage Liver Disease (MELD) has been proposed as a tool to predict mortality risk in cirrhotic patients. The aim of the study was to evaluate survival prognosis of cirrhotic patients by the MELD and Child-Pugh scores and to analyze the MELD score prognostic value in patients with both liver cirrhosis and variceal bleeding. METHODS We retrospectively evaluated the survival rate of a group of 100 cirrhotic patients of a median age of 57 years. The Child-Pugh score was calculated and the MELD score was computed according to the original formula for each patient. We also analysed clinical and laboratory hepatocellular insufficiency parameters in order to examine their connection with a 15-month survival. The MELD values were correlated with the Child-Pugh scores. The Students t-test was used for statistical analysis. RESULTS Twenty-two patients died within 15-months followup. Age and gender did not affect survival rate. The Child-Pugh and MELD scores, as well as ascites and encephalopathy significantly differed between the patients who survived and those who died (p < 0.0001). The International Normalized Ratio (INR) values, serum creatinine and bilirubin were significantly higher, and albumin significantly lower in the patients who died (p < 0.0001). The MELD score was significantly higher in the group of patients who died due to esophageal variceal bleeding (p < 0.0001). CONCLUSION In cirrhotic patients the MELD score is an excellent survival predictor at least as well as the Child-Pugh score. Increase in the MELD score is associated with decrease in residual liver function. In the group of patients with liver cirrhosis and esophageal variceal bleeding, the MELD score identifies those with a higher intrahospital mortality risk.

Microalbuminuria in children with vesicoureteral reflux.

Vesicoureteral reflux (VUR) is a common congenital anomaly of the urinary tract that may be inherited. Reflux of infected urine may cause scarring in susceptible kidneys with the potential to compromise renal function. The aim of the study was to evaluate the possible influence of different grades of VUR on glomerular damage using microalbuminuria as a parameter. Children with VUR detected by voiding cystourethrography (VCUG) were investigated. According to the grade of VUR, patients were separated into three groups. The first group included 12 children with VUR grade I–II. The second group consisted of 12 children with grade III of VUR. Patients with VUR grade IV–V (n = 11) were members of the third group. The control group consisted of 17 healthy children. Microalbuminuria was examined in samples of morning urine specimens using a microalbumin/creatinine reagent kit. Serum urea, creatinine levels and creatinine clearance (CCR) were measured as markers of renal function. The mean value of microalbumin excretion in the third group showed a statistically significant increase (p < 0.001) compared to all other groups. CCR in the third group was statistically significantly decreased (p < 0.05) in comparison to the group of healthy children. There were no statistically significant changes of microalbumin excretion and CCR in the first and second group compared to control values. We discussed the presence of microalbuminuria and decrease of CCR in children with high grade of VUR as a possible consequence of retrograde urine flow (intrarenal reflux), glomerulosclerosis, and consecutive hyperfiltration.

Diagnostic Significance of Nitrates and Nitrites and L-Arginine, in Development of Hepatorenal Syndrome in Patients with End Stage Alcoholic Liver Cirrhosis

Hepatorenal syndrome (HRS) represents a complication of the end-stage liver cirrhosis. The aim of the present study was to analyze concentrations of nitrates and nitrites (NO2 + NO3) and L-arginine in patients with liver cirrhosis and HRS as a possible predictive marker for the development of HRS. The research was performed in a group of 28 patients with cirrhosis and HRS, a group of 22 patients suffering from cirrhosis without HRS and a control group comprised of 42 healthy voluntary blood donors. In patients with end-stage alcoholic liver cirrhosis, with HRS, the concentrations of NO2 + NO3 increased and correlated with the degree of cirrhosis progression, compared to patients without HRS and significantly higher compared to the control group. The level of NO2 + NO3 was in a positive correlation with the degree of liver damage de Ritis coefficient (HRS = 0.72; cirrhosis: = 0.55; control = −0.10). Significant positive correlation was found between NO2 + NO3 concentration and inflammatory marker C-reactive protein (HRSC = 0.75; cirrhosis = 0.70, control = −0.25). The correlation between NO2 + NO3 concentration and creatinine concentration in patients with HRS was significantly higher compared to patients without HRS (HRS = 0.82; cirrhosis = 0.32; control = −0.25). By using binary regression analysis, on the basis of clinical criteria of HRS diagnosis, the strongest independent positive predictor for HRS development was NO2 + NO3, associated with 45.02 times higher incidence of HRS, compared to arginine (12.7 times higher incidence), creatinine (13.1 times higher incidence), and AST/ALT ratio (10.55 higher incidence of HRS). Since the determination of NO2 + NO3 represents a reliable and easily applicable method, it may be used as an early predictive marker for HRS development.