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Nutrition Reviews May 2024Seaweed is a promising source of anti-obesity agents, including polysaccharides, proteins, polyphenols, carotenoids, and n-3 long-chain polyunsaturated fatty acids. The...
CONTEXT
Seaweed is a promising source of anti-obesity agents, including polysaccharides, proteins, polyphenols, carotenoids, and n-3 long-chain polyunsaturated fatty acids. The anti-obesity effects of such compounds may be due to several mechanisms, including inhibition of lipid absorption and metabolism, effect on satiety, and inhibition of adipocyte differentiation.
OBJECTIVE
The aim of this study was to assess the evidence from human randomized controlled trials for the effects of seaweed on body-weight status as well as lipid and nonlipid parameters in adults with overweight and obesity.
DATA SOURCES
Four databases-Medline, Scopus, Web of Science, and Cochrane Library-were searched from December 2022 to June 2023 using the following key words: Seaweed OR fucoxanthin OR alginates OR fucoidans OR phlorotannin's OR macroalgae OR marine algae AND obesity OR overweight OR BMI OR body mass index.
DATA EXTRACTION
Eleven interventional studies (10 parallel and 1 crossover) were extracted.
DATA ANALYSIS
Meta-analysis showed a significant effect, favoring the intervention group for BMI (body mass index) (standardized mean difference [SMD]: -0.40; 95% CI: -0.65 to -0.16 kg/m2; P = 0.0013) and percentage of fat mass (SMD: -1.48; 95% CI: -2.66% to -0.30%, P = 0.0138). The results were seen when refined or extracted brown seaweed (BMI) or only refined brown seaweed (% fat mass) were administered to participants for at least 8 weeks. Moreover, a significant overall effect of seaweed supplementation on total cholesterol (SMD: -7.72; 95% CI: -12.49 to -2.95 mg/dL; P = 0.0015) and low-density-lipoprotein cholesterol (SMD: -7.33; 95% CI: -11.64 to -3.02 mg/dL; P < 0.001) was noted. Any significant effects of seaweed on glucose metabolism were not shown.
CONCLUSION
Edible seaweed supplementation shows potential for managing obesity and disorders of the blood lipid profile when administered to participants for at least 8 weeks.
SYSTEMATIC REVIEW REGISTRATION
PROSPERO registration no. CRD42022378484 (www.crd.york.ac.uk/PROSPERO).
PubMed: 38749056
DOI: 10.1093/nutrit/nuae042 -
Frontiers in Endocrinology 2024To evaluate the quality of evidence, potential biases, and validity of all available studies on dietary intervention and diabetic nephropathy (DN). (Meta-Analysis)
Meta-Analysis
OBJECTIVE
To evaluate the quality of evidence, potential biases, and validity of all available studies on dietary intervention and diabetic nephropathy (DN).
METHODS
We conducted an umbrella review of existing meta-analyses of randomized controlled trials (RCTs) that focused on the effects of dietary intervention on DN incidence. The literature was searched via PubMed, Embase, Web of Science, and the Cochrane Database of Systematic Reviews. According to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE), evidence of each outcome was evaluated and graded as "high", "moderate", "low" or "very low" quality to draw conclusions. Additionally, we classified evidence of outcomes into 4 categories.
RESULTS
We identified 36 meta-analyses of RCTs and 55 clinical outcomes of DN from 395 unique articles. Moderate-quality evidence suggested that probiotic supplementation could significantly improve blood urea nitrogen (BUN), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels in DN patients. Low-quality evidence indicated that probiotic supplementation significantly improved the serum creatinine concentration, urinary albumin-creatinine ratio (UACR), fasting blood glucose (FBG), HbA1c and high-density lipoprotein cholesterol (HDL-C) in DN patients. In addition, low-quality evidence suggested that a salt restriction diet could significantly improve the creatinine clearance rate (CrCl) in patients with DN. Low-quality evidence suggested that vitamin D supplementation could significantly improve the UACR in patients with DN. In addition, low-quality evidence has indicated that soy isoflavone supplementation could significantly improve BUN, FBG, total cholesterol (TC), triglyceride (TG) and LDL-C levels in patients with DN. Furthermore, low-quality evidence suggested that coenzyme Q10 supplementation could significantly improve HbA1c, TC and HDL-C in patients with DN, and dietary polyphenols also significantly improved HbA1c in patients with DN. Finally, low-quality evidence suggested that supplementation with antioxidant vitamins could significantly improve the serum creatinine concentration, systolic blood pressure, and HbA1c level in patients with DN. Given the small sample size, all significantly associated outcomes were evaluated as class IV evidence.
CONCLUSION
Moderate to low amounts of evidence suggest that supplementation with probiotics, vitamin D, soy isoflavones, coenzyme Q10, dietary polyphenols, antioxidant vitamins, or salt-restricted diets may significantly improve clinical outcomes in patients with DN.
SYSTEMATIC REVIEW REGISTRATION
https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024512670.
Topics: Humans; Diabetic Nephropathies; Dietary Supplements; Meta-Analysis as Topic; Probiotics; Randomized Controlled Trials as Topic; Systematic Reviews as Topic
PubMed: 38742202
DOI: 10.3389/fendo.2024.1385872 -
The Cochrane Database of Systematic... May 2024According to global prevalence analysis studies, acute upper respiratory tract infections (URTIs) are the most common acute infectious disease in children, especially in... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
According to global prevalence analysis studies, acute upper respiratory tract infections (URTIs) are the most common acute infectious disease in children, especially in preschool children. Acute URTIs lead to an economic burden on families and society. Vitamin A refers to the fat-soluble compound all-trans-retinol and also represents retinol and its active metabolites. Vitamin A interacts with both the innate immune system and the adaptive immune system and improves the host's defences against infections. Correlation studies show that serum retinol deficiency was associated with a higher risk of respiratory tract infections. Therefore, vitamin A supplementation may be important in preventing acute URTIs.
OBJECTIVES
To assess the effectiveness and safety of vitamin A supplements for preventing acute upper respiratory tract infections in children up to seven years of age.
SEARCH METHODS
We searched CENTRAL, MEDLINE, Embase, the Chinese Biomedical Literature Database, and two trial registration platforms to 8 June 2023. We also checked the reference lists of all primary studies and reviewed relevant systematic reviews and trials for additional references. We imposed no language or publication restrictions.
SELECTION CRITERIA
We included randomised controlled trials (RCTs), which evaluated the role of vitamin A supplementation in the prevention of acute URTIs in children up to seven years of age.
DATA COLLECTION AND ANALYSIS
We used the standard methodological procedures expected by Cochrane.
MAIN RESULTS
We included six studies (27,351 participants). Four studies were RCTs and two were cluster-RCTs. The included studies were all conducted in lower-middle-income countries (two in India, two in South Africa, one in Ecuador, and one in Haiti). Three studies included healthy children who had no vitamin A deficiency, one study included children born to HIV-infected women, one study included low-birthweight neonates, and one study included children in areas with a high local prevalence of malnutrition and xerophthalmia. In two studies, vitamin E was a co-treatment administered in addition to vitamin A. We judged the included studies to be at either a high or unclear risk of bias for random sequence generation, incomplete outcome data, and blinding. Primary outcomes Six studies reported the incidence of acute URTIs during the study period. Five studies reported the number of acute URTIs over a period of time, but there was population heterogeneity and the results were presented in different forms, therefore only three studies were meta-analysed. We are uncertain of the effect of vitamin A supplementation on the number of acute URTIs over two weeks (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.92 to 1.09; I = 44%; 3 studies, 22,668 participants; low-certainty evidence). Two studies reported the proportion of participants with an acute URTI. We are uncertain of the effect of vitamin A supplementation on the proportion of participants with an acute URTI (2 studies, 15,535 participants; low-certainty evidence). Only one study (116 participants) reported adverse events. No infant in either the placebo or vitamin A group was found to have feeding difficulties (failure to feed or vomiting), a bulging fontanelle, or neurological signs before or after vitamin A administration (very low-certainty evidence). Secondary outcomes Two studies (296 participants) reported the severity of subjective symptoms, presented by the mean duration of acute URTI. Vitamin A may have little to no effect on the mean duration of acute URTI (very low-certainty evidence).
AUTHORS' CONCLUSIONS
The evidence for the use of vitamin A supplementation to prevent acute URTI is uncertain, because population, dose and duration of interventions, and outcomes vary between studies. From generally very low- to low-certainty evidence, we found that there may be no benefit in the use of vitamin A supplementation to prevent acute URTI in children up to seven years of age. More RCTs are needed to strengthen the current evidence. Future research should report over longer time frames using validated tools and consistent reporting, and ensure adequate power calculations, to allow for easier synthesis of data. Finally, it is important to assess vitamin A supplementation for preschool children with vitamin A deficiency.
Topics: Humans; Vitamin A; Respiratory Tract Infections; Child, Preschool; Randomized Controlled Trials as Topic; Infant; Acute Disease; Dietary Supplements; Child; Vitamins; Vitamin A Deficiency; Administration, Oral; Bias
PubMed: 38738639
DOI: 10.1002/14651858.CD015306.pub2 -
Photodiagnosis and Photodynamic Therapy Jun 2024Protoporphyrin IX (PPIX) is the final precursor of heme, forming heme when iron is inserted. Individuals with erythropoietic protoporphyrias (EPP) have accumulation of... (Review)
Review
BACKGROUND
Protoporphyrin IX (PPIX) is the final precursor of heme, forming heme when iron is inserted. Individuals with erythropoietic protoporphyrias (EPP) have accumulation of PPIX, causing photosensitivity and increased liver disease risk. Many also have iron deficiency and anemia. We investigated outcomes of oral iron supplements in individuals with EPP.
METHODS
A systematic review identified literature on oral iron supplements in EPP patients. Subsequently, we administered iron supplements to EPP patients with iron deficiency. The primary outcome was impact on PPIX level. Secondary outcomes were adverse events and relative differences in hemoglobin and iron parameters.
RESULTS
The systematic review found 13 case reports and one uncontrolled clinical trial with uncertain results. From our department 10 patients with EPP and iron deficiency took daily dosages of 330 mg of ferrous fumarate for two months. Five of our patients had anemia at baseline. After 2 months of supplementation seven patients had increased PPIX level compared to baseline, two had decrease, one remained unchanged. The administration of iron led to a rise in ferritin, and in four of the anemic patients also to an improvement in blood hemoglobin. A small transiently elevation in plasma alanine transaminase concentration was observed during supplementation.
CONCLUSIONS
Overall, iron supplementation in EPP patients replenished iron stores and elevated erythrocyte PPIX and plasma alanine transaminase. For anemic patients, there was some degree of normalization of the hemoglobin level. If iron therapy is needed for EPP patients, monitoring of photosensitivity, PPIX, hemoglobin, and plasma liver enzymes is advisable.
Topics: Humans; Protoporphyria, Erythropoietic; Protoporphyrins; Dietary Supplements; Male; Female; Adult; Iron; Anemia, Iron-Deficiency; Middle Aged; Treatment Outcome
PubMed: 38734198
DOI: 10.1016/j.pdpdt.2024.104211 -
Critical Reviews in Food Science and... May 2024Poor oral health can impact an individual's ability to eat and has been associated with an increased risk of non-communicable diseases. While the benefits of nitrate... (Review)
Review
Poor oral health can impact an individual's ability to eat and has been associated with an increased risk of non-communicable diseases. While the benefits of nitrate consumption on oral health were first proposed more than 20 years ago, no systematic review has been published examining effects of dietary nitrate on oral health. This systematic review investigated the effects of dietary nitrate on markers of oral health in randomized controlled trials (RCTs). Five databases (PubMed, The Cochrane Library, CINAHL, MEDLINE, and SPORTDiscus) were searched from inception until March 2023. Nine articles reporting data on 284 participants were included. Dietary nitrate was provided beetroot juice in most studies. The duration of the interventions ranged from one day to six weeks. Dietary nitrate supplementation increased the relative abundance of several individual bacterial genera including and . Dietary nitrate supplementation increased salivary pH and decreased salivary acidification following consumption of a sugar-sweetened beverage. Furthermore, dietary nitrate supplementation resulted in a decrease in the gingival inflammation index. The results of this systematic review suggest that dietary nitrate could represent a potential nutritional strategy to positively modify oral health by impacting the oral microbiome, altering salivary pH, and minimizing gingival inflammation.
PubMed: 38733290
DOI: 10.1080/10408398.2024.2351168 -
Nutrients Apr 2024This review aims to evaluate the efficacy of any vitamin administration(s) in preventing and managing COVID-19 and/or long-COVID. Databases were searched up to May 2023... (Meta-Analysis)
Meta-Analysis Review
The Efficacy of Multivitamin, Vitamin A, Vitamin B, Vitamin C, and Vitamin D Supplements in the Prevention and Management of COVID-19 and Long-COVID: An Updated Systematic Review and Meta-Analysis of Randomized Clinical Trials.
This review aims to evaluate the efficacy of any vitamin administration(s) in preventing and managing COVID-19 and/or long-COVID. Databases were searched up to May 2023 to identify randomized clinical trials comparing data on the effects of vitamin supplementation(s) versus placebo or standard of care on the two conditions of interest. Inverse-variance random-effects meta-analyses were conducted to estimate pooled risk ratios (RRs) and 95% confidence intervals (CIs) for all-cause mortality between supplemented and non-supplemented individuals. Overall, 37 articles were included: two regarded COVID-19 and long-COVID prevention and 35 records the COVID-19 management. The effects of vitamin D in preventing COVID-19 and long-COVID were contrasting. Similarly, no conclusion could be drawn on the efficacy of multivitamins, vitamin A, and vitamin B in COVID-19 management. A few positive findings were reported in some vitamin C trials but results were inconsistent in most outcomes, excluding all-cause mortality (RR = 0.84; 95% CI: 0.72-0.97). Vitamin D results were mixed in most aspects, including mortality, in which benefits were observed in regular administrations only (RR = 0.67; 95% CI: 0.49-0.91). Despite some benefits, results were mostly contradictory. Variety in recruitment and treatment protocols might explain this heterogeneity. Better-designed studies are needed to clarify these vitamins' potential effects against SARS-CoV-2.
Topics: Humans; Dietary Supplements; COVID-19; Vitamins; Vitamin D; Randomized Controlled Trials as Topic; Ascorbic Acid; SARS-CoV-2; Vitamin A; COVID-19 Drug Treatment; Vitamin B Complex
PubMed: 38732592
DOI: 10.3390/nu16091345 -
International Journal of Molecular... Apr 2024Correct nutrition and diet are directly correlated with mental health, functions of the immune system, and gut microbiota composition. Diets with a high content of some...
Correct nutrition and diet are directly correlated with mental health, functions of the immune system, and gut microbiota composition. Diets with a high content of some nutrients, such as fibers, phytochemicals, and short-chain fatty acids (omega-3 fatty acids), seem to have an anti-inflammatory and protective action on the nervous system. Among nutraceuticals, supplementation of probiotics and omega-3 fatty acids plays a role in improving symptoms of several mental disorders. In this review, we collect data on the efficacy of nutraceuticals in patients with schizophrenia, autism spectrum disorders, major depression, bipolar disorder, and personality disorders. This narrative review aims to provide an overview of recent evidence obtained on this topic, pointing out the direction for future research.
Topics: Humans; Dietary Supplements; Fatty Acids, Omega-3; Gastrointestinal Microbiome; Mental Disorders; Probiotics
PubMed: 38732043
DOI: 10.3390/ijms25094824 -
Medicine May 2024Folic acid is the synthetic form of vitamin B9, found in supplements and fortified foods, while folate occurs naturally in foods. Folic acid and its derivatives are...
Folic acid is the synthetic form of vitamin B9, found in supplements and fortified foods, while folate occurs naturally in foods. Folic acid and its derivatives are extremely important in the synthesis of nucleic acids (DNA and ribose nucleic acid [RNA]) and different proteins. It acts as a coenzyme for the transfer of 1 carbon in the biosynthesis of purine, pyrimidine, and amino acids. Folic acid is critically important in rapidly proliferating tissues, including fetus and trophoblastic tissue to prevent neural tube defect (NTD). The main objective of this review is to identify the role of folic acid to prevent NTD among pregnancy mothers. Electronic databases including Web of Science, Google Scholar, MEDLINE, Scopus, and Cochrane library used to systematically search without limitation of publication date and status. In pregnancy, the first trimester is a significant time for neural tube closure. Decreased blood folic acid levels inhibit DNA replication, repair, RNA synthesis, histone and DNA methylation, methionine production, and homocysteine remethylation reactions that cause NTDs in pregnancy. Therefore, folic acid supplementation is critically important for childbearing mothers before conception and in the first trimester pregnancy. As a result, women are recommended to take 400 microgram FA/day from preconception until the end of the first trimester to prevent NTD-affected pregnancies. This allows the developing neural tissue to acquire critical mass and provides the preferred rostrocaudal orientation so that these divisions contribute to the elongation of the developing neural tube in embryos.
Topics: Female; Humans; Pregnancy; Dietary Supplements; Folic Acid; Neural Tube Defects; Vitamin B Complex
PubMed: 38728462
DOI: 10.1097/MD.0000000000038154 -
The Cochrane Database of Systematic... May 2024Obesity is a major health problem worldwide as it can lead to high blood pressure, heart disease, stroke, diabetes, and insulin resistance. The prevalence of overweight... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Obesity is a major health problem worldwide as it can lead to high blood pressure, heart disease, stroke, diabetes, and insulin resistance. The prevalence of overweight and obesity is increasing worldwide across different age groups. There is evidence of an inverse relationship between calcium intake and body weight. The clinical relevance of a small reduction in body weight has been questioned. However, at a population level, a small effect could mitigate the observed global trends.
OBJECTIVES
To assess the effects of calcium supplementation on weight loss in individuals living with overweight or obesity.
SEARCH METHODS
We searched CENTRAL, MEDLINE, Embase, LILACS (Latin American and Caribbean Health Science Information database), and two clinical trials registries. The date of the last search of all databases (except Embase) was 10 May 2023. No language restrictions were applied.
SELECTION CRITERIA
We included randomised controlled trials evaluating the effect of calcium in participants with overweight or obesity of any age or gender. We excluded studies in participants with absorption problems. We included studies of any dose with a minimum duration of two months. We included the following comparisons: calcium supplementation versus placebo, calcium-fortified food or beverage versus placebo, or calcium-fortified food or beverage versus non-calcium-fortified food or beverage. We excluded studies that evaluated the effect of calcium and vitamin D or mixed minerals compared to placebo.
DATA COLLECTION AND ANALYSIS
We used standard methodological procedures expected by Cochrane. Our primary outcomes were body weight, health-related quality of life, and adverse events. Our secondary outcomes were anthropometric measures other than body weight, all-cause mortality, and morbidity.
MAIN RESULTS
We found 18 studies that evaluated the effect of calcium compared to placebo or control, with a total of 1873 randomised participants (950 participants in the calcium supplementation groups and 923 in the control groups). All included studies gave oral calcium supplementation as the intervention. We did not find any studies evaluating calcium-fortified foods. We excluded 38 studies, identified four ongoing studies, and listed one study as 'awaiting classification'. Sixteen studies compared calcium supplementation to placebo; two studies compared different doses of calcium supplementation. Doses ranged from very low (0.162 g of calcium/day) to high (1.5 g of calcium/day). Most studies were performed in the USA and Iran, lasted less than six months, and included only women. Low-certainty evidence suggests that calcium supplementation compared to placebo or control may result in little to no difference in body weight (mean difference (MD) -0.15 kg, 95% confidence interval (CI) -0.55 to 0.24; P = 0.45, I = 46%; 17 studies, 1317 participants; low-certainty evidence). We downgraded the certainty of the evidence by two levels for risk of bias and heterogeneity. None of the included studies reported health-related quality of life, all-cause mortality, or morbidity/complications as outcomes. Only five studies assessed or reported adverse events. Low-certainty evidence suggests a low frequency of adverse events, with no clear difference between intervention and control groups. Moderate-certainty evidence shows that calcium supplementation compared to placebo or control probably results in a small reduction in body mass index (BMI) (MD -0.18 kg/m,95% CI -0.22 to -0.13; P < 0.001, I = 0%; 9 studies, 731 participants) and waist circumference (MD -0.51 cm, 95% CI -0.72 to -0.29; P < 0.001, I = 0%; 6 studies, 273 participants). Low-certainty evidence suggests that calcium supplementation compared to placebo or control may result in a small reduction in body fat mass (MD -0.34 kg, 95% CI -0.73 to 0.05; P < 0.001, I = 97%; 12 studies, 812 participants).
AUTHORS' CONCLUSIONS
Calcium supplementation for eight weeks to 24 months may result in little to no difference in body weight in people with overweight or obesity. The current evidence is of low certainty, due to concerns regarding risk of bias and statistical heterogeneity. We found that the degree of heterogeneity might be partly explained by calcium dosage, the presence or absence of a co-intervention, and whether an intention-to-treat analysis was pursued. While our analyses suggest that calcium supplementation may result in a small reduction in BMI, waist circumference, and fat mass, this evidence is of low to moderate certainty. Future studies could investigate the effect of calcium supplementation on lean body mass to explore if there is a change in body composition.
Topics: Humans; Randomized Controlled Trials as Topic; Overweight; Obesity; Dietary Supplements; Weight Loss; Calcium, Dietary; Male; Female; Adult; Quality of Life; Bias; Food, Fortified; Middle Aged; Calcium
PubMed: 38721870
DOI: 10.1002/14651858.CD012268.pub2 -
The Cochrane Database of Systematic... May 2024The common cold is an acute, self-limiting viral respiratory illness. Symptoms include nasal congestion and mucus discharge, sneezing, sore throat, cough, and general...
BACKGROUND
The common cold is an acute, self-limiting viral respiratory illness. Symptoms include nasal congestion and mucus discharge, sneezing, sore throat, cough, and general malaise. Given the frequency of colds, they are a public health burden and a significant cause of lost work productivity and school absenteeism. There are no established interventions to prevent colds or shorten their duration. However, zinc supplements are commonly recommended and taken for this purpose.
OBJECTIVES
To assess the effectiveness and safety of zinc for the prevention and treatment of the common cold.
SEARCH METHODS
We searched CENTRAL, MEDLINE, Embase, CINAHL, and LILACS to 22 May 2023, and searched Web of Science Core Collection and two trials registries to 14 June 2023. We also used reference checking, citation searching, and contact with study authors to identify additional studies.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) in children or adults that tested any form of zinc against placebo to prevent or treat the common cold or upper respiratory infection (URTI). We excluded zinc interventions in which zinc was combined with other minerals, vitamins, or herbs (e.g. a multivitamin, or mineral supplement containing zinc).
DATA COLLECTION AND ANALYSIS
We used the Cochrane risk of bias tool to assess risks of bias, and GRADE to assess the certainty of the evidence. We independently extracted data. When necessary, we contacted study authors for additional information. We assessed zinc (type and route) with placebo in the prevention and treatment of the common cold. Primary outcomes included the proportion of participants developing colds (for analyses of prevention trials only), duration of cold (measured in days from start to resolution of the cold), adverse events potentially due to zinc supplements (e.g. unpleasant taste, loss of smell, vomiting, stomach cramps, and diarrhoea), and adverse events considered to be potential complications of the common cold (e.g. respiratory bacterial infections).
MAIN RESULTS
We included 34 studies (15 prevention, 19 treatment) involving 8526 participants. Twenty-two studies were conducted on adults and 12 studies were conducted on children. Most trials were conducted in the USA (n = 18), followed by India, Indonesia, Iran, and Turkey (two studies each), and Australia, Burkina Faso, Colombia, Denmark, Finland, Tanzania, Thailand, and the UK (one study each). The 15 prevention studies identified the condition as either common cold (n = 8) or URTI (n = 7). However, almost all therapeutic studies (17/19) focused on the common cold. Most studies (17/34) evaluated the effectiveness of zinc administered as lozenges (3 prevention; 14 treatment) in acetate, gluconate, and orotate forms; gluconate lozenges were the most common (9/17). Zinc gluconate was given at doses between 45 and 276 mg/day for between 4.5 and 21 days. Five (5/17) lozenge studies gave acetate lozenges and two (2/17) gave both acetate and gluconate lozenges. One (1/17) lozenge study administered intranasal (gluconate) and lozenge (orotate) zinc in tandem for cold treatment. Of the 17/34 studies that did not use lozenges, 1/17 gave capsules, 3/17 administered dissolved powders, 5/17 gave tablets, 4/17 used syrups, and 4/17 used intranasal administration. Most studies were at unclear or high risk of bias in at least one domain. There may be little or no reduction in the risk of developing a cold with zinc compared to placebo (risk ratio (RR) 0.93, 95% CI 0.85 to 1.01; I = 20%; 9 studies, 1449 participants; low-certainty evidence). There may be little or no reduction in the mean number of colds that occur over five to 18 months of follow-up (mean difference (MD) -0.90, 95% CI -1.93 to 0.12; I = 96%; 2 studies, 1284 participants; low-certainty evidence). When colds occur, there is probably little or no difference in the duration of colds in days (MD -0.63, 95% CI -1.29 to 0.04; I² = 77%; 3 studies, 740 participants; moderate-certainty evidence), and there may be little or no difference in global symptom severity (standardised mean difference (SMD) 0.04, 95% CI -0.35 to 0.43; I² = 0%; 2 studies, 101 participants; low-certainty evidence). When zinc is used for cold treatment, there may be a reduction in the mean duration of the cold in days (MD -2.37, 95% CI -4.21 to -0.53; I² = 97%; 8 studies, 972 participants; low-certainty evidence), although it is uncertain whether there is a reduction in the risk of having an ongoing cold at the end of follow-up (RR 0.52, 95% CI 0.21 to 1.27; I² = 65%; 5 studies, 357 participants; very low-certainty evidence), or global symptom severity (SMD -0.03, 95% CI -0.56 to 0.50; I² = 78%; 2 studies, 261 participants; very low-certainty evidence), and there may be little or no difference in the risk of a change in global symptom severity (RR 1.02, 95% CI 0.85 to 1.23; 1 study, 114 participants; low-certainty evidence). Thirty-one studies reported non-serious adverse events (2422 participants). It is uncertain whether there is a difference in the risk of adverse events with zinc used for cold prevention (RR 1.11, 95% CI 0.84 to 1.47; I = 0%; 7 studies, 1517 participants; very low-certainty evidence) or an increase in the risk of serious adverse events (RR 1.67, 95% CI 0.78 to 3.57; I = 0%; 3 studies, 1563 participants; low-certainty evidence). There is probably an increase in the risk of non-serious adverse events when zinc is used for cold treatment (RR 1.34, 95% CI 1.15 to 1.55; I = 44%; 2084 participants, 16 studies; moderate-certainty evidence); no treatment study provided information on serious adverse events. No study provided clear information about adverse events considered to be potential complications of the common cold.
AUTHORS' CONCLUSIONS
The findings suggest that zinc supplementation may have little or no effect on the prevention of colds but may reduce the duration of ongoing colds, with an increase in non-serious adverse events. Overall, there was wide variation in interventions (including concomitant therapy) and outcomes across the studies, as well as incomplete reporting of several domains, which should be considered when making conclusions about the efficacy of zinc for the common cold.
Topics: Adult; Child; Humans; Bias; Common Cold; Dietary Supplements; Gluconates; Randomized Controlled Trials as Topic; Respiratory Tract Infections; Zinc
PubMed: 38719213
DOI: 10.1002/14651858.CD014914.pub2