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Coffee Consumption and Risk of Hypertension in Adults: Systematic Review and Meta-Analysis.
Haghighatdoost, F, Hajihashemi, P, de Sousa Romeiro, AM, Mohammadifard, N, Sarrafzadegan, N, de Oliveira, C, Silveira, EA
Nutrients. 2023;15(13)
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High blood pressure (hypertension) is the main risk factor for cardiovascular diseases. Over the past decades the number of people experiencing high blood pressure has steadily increased, making it a serious concern for public health. Many dietary factors influence the development of high blood pressure, either increasing of decreasing the risk. Coffee is a widely consumed beverage. The caffeine in coffee can stimulate stress hormones like adrenaline. Adrenaline increases blood pressure, inflammation and decreases sensitivity to insulin, which are all regarded as risk factors for cardiovascular diseases. At the same time coffee contains many blood pressure lowering nutrients and compounds. Whether coffee contributes or diminishes the risks of developing high blood pressure has remained controversial. Hence, this systematic review and meta-analysis aimed to summarise the current evidence on coffee and hypertension risk. The analysis included 25 observational studies published between 2002 and 2023. The results concluded that coffee consumption was associated with a small reduction in risk for high blood pressure development. An inverse association was found, suggesting that as coffee consumption rose, high blood pressure risk falls. However, upon closer examination this inverse relationship was only found in the USA, but not in Europe and Asia. The authors suggested that geographics, genetics, gender, coffee preparation methods, and differences in lifestyle habits (smoking, salt consumption etc.) may contribute to the discrepancies between outcomes and make it harder to compare studies to form a uniform consensus. Hence, they urged for a cautious interpretation of the findings. In the absence of clear, consistent evidence, coffee consumption and cardiovascular risk may need to be assessed on an individual basis in clinical practice.
Abstract
OBJECTIVES The association between coffee intake and hypertension (HTN) risk is controversial. Therefore, this systematic review and meta-analysis aimed at summarizing the current evidence on the association of coffee with hypertension risk in observational studies. METHODS PubMed/Medline and Web of Science were searched for observational studies up to February 2023. Observational studies which assessed the risk of HTN in the highest category of coffee consumption in comparison with the lowest intake were included in the current meta-analysis (registration number: CRD42022371494). The pooled effect of coffee on HTN was evaluated using a random-effects model. RESULTS Twenty-five studies i.e., thirteen cross-sectional studies and twelve cohorts were identified to be eligible. Combining 13 extracted effect sizes from cohort studies showed that higher coffee consumption was associated with 7% reduction in the risk of HTN (95% CI: 0.88, 0.97; I2: 22.3%), whereas combining 16 effect sizes from cross-sectional studies illustrated a greater reduction in HTN risk (RR = 0.79, 95% CI: 0.72, 0.87; I2 = 63.2%). These results varied by studies characteristics, such as the region of study, participants' sex, study quality, and sample size. CONCLUSIONS An inverse association was found between coffee consumption and hypertension risk in both cross-sectional and cohort studies. However, this association was dependent on studies characteristics. Further studies considering such factors are required to confirm the results of this study.
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The Effects of Black Tea Consumption on Intestinal Microflora-A Randomized Single-Blind Parallel-Group, Placebo-Controlled Study.
Tomioka, R, Tanaka, Y, Suzuki, M, Ebihara, S
Journal of nutritional science and vitaminology. 2023;69(5):326-339
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Tea from the leaves of the tea plant (Camelia sinensis) is consumed around the world. Tea has many health benefits, and in part, this is due to its rich content in compounds classed as polyphenols. Through the fermentation process, black tea is particularly high in polyphenols. Previous studies around respiratory infections indicated that regular consumption of black tea appeared to improve immune defence mechanisms that protect mucous membranes, called mucosal immunity. As this mucosal immunity is closely influenced by gut bacteria, the authors speculated whether the previously seen impact of improved mucosal immunity is related to the ability of black tea to also modulate bacteria in the gut. A previously run randomised single-blinded, placebo-controlled trial with 72 Japanese participants who consumed three cups of black tea (2g) or a placebo of barley tea for 12 weeks provided the data for this study. Data gathered included gut flora analysis, short-chain fatty acids (SCFAs) levels - fats that play a role in maintaining gut health, and saliva IgA (SIgA) concentrations - which are antibodies made in the lymph tissue of the gut. The results showed that black tea consumption led to a significant increase in the abundance of Prevotella bacteria, which mediate SCFA production and are involved in normalising immune function. Furthermore, tea increased butyrate-producing bacteria. Butyrate is associated with improved barrier function of the gut walls but also helps to manage pathogens and immune responses. Black tea consumption also increased salivary SIgA concentration - a type of antibody on the mucous membranes that prevents pathogens from entering the body -, and a decrease in stool acetic acid concentration, which may be due to the increase in butyrate-producing bacteria which use acetic acid to make butyrate. Notably, participants with low salivary SIgA levels at the start had a more pronounced positive change in total bacteria, after consuming black tea compared to the placebo group. The authors concluded that regular consumption of black tea may help to improve mucosal immunity by increasing the abundance of beneficial bacteria in the gut.
Abstract
We previously reported that black tea consumption for 12 wk reduced the risk of acute upper respiratory tract inflammation, and improved secretory capacity in individuals with low salivary SIgA levels (Tanaka Y et al. 2021. Jpn Pharmacol Ther 49: 273-288). These results suggested that habitual black tea consumption improves mucosal immunity. Therefore, in this study we evaluated the effect of black tea intake on gut microbiota, which is known to be involved in mucosal immunity, by analyzing the bacterial flora and the short-chain fatty acids (SCFAs) concentration of feces collected during the above clinical study. The clinical design was a randomized, single-blind, parallel-group, placebo-controlled study with 72 healthy Japanese adult males and females, who consumed three cups of black tea (Black Tea Polymerized Polyphenols 76.2 mg per day) or placebo per day for 12 wk. In all subjects intake of black tea significantly increased abundance of Prevotella and decreased fecal acetic acid concentration. Particularly in the subjects with low salivary SIgA levels, the change over time of total bacteria, Prevotella, and butyrate-producing bacteria, which are involved in normalizing immune function, were higher in the black tea group than in the placebo group. In subjects with low abundance of Flavonifractor plautii a butyrate-producing bacteria, black tea consumption significantly increased salivary SIgA concentration and the absolute number of Flavonifractor plautii. In conclusion, our results suggest that improvement of mucosal immunity via an increase in butyrate-producing bacteria in the gut may partly contribute to the suppressive effect of black tea consumption on acute upper respiratory tract inflammation observed in our previous report.
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The Dose-Response Associations of Sugar-Sweetened Beverage Intake with the Risk of Stroke, Depression, Cancer, and Cause-Specific Mortality: A Systematic Review and Meta-Analysis of Prospective Studies.
Wang, Y, Zhao, R, Wang, B, Zhao, C, Zhu, B, Tian, X
Nutrients. 2022;14(4)
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The consumption of sugar-sweetened beverages is high in today's society, which may lead to weight gain, inflammation, and a number of obesity-associated diseases. The objective of this systematic review and meta-analysis was to investigate the associations and causal links between the consumption of sugar-sweetened beverages and cancer, stroke, depression, and cause-specific mortality. Consumption of sugar-sweetened beverages significantly increased the risk of cancer, strokes, depression, and cause-specific mortality when compared with the consumption of low or no-sugar-sweetened beverages. As little as a 250ml increment of sugar-sweetened beverages was associated with an increase in risk. Consumption of sugar-sweetened beverages increases the risk of ischemic stroke by 10%, CVD-caused mortality by 13%, and cancer-caused mortality by 6.0% compared to those who consume less or no sugar-sweetened beverages. These findings can be used by healthcare professionals to understand the clinical significance of intervention strategies that reduce the consumption of sugar-sweetened beverages. It is imperative to conduct additional robust studies as there is an insufficient amount of evidence at present to establish a causal connection between the consumption of sugary beverages and the risk of depression, stroke, cancer, and cause-specific mortality.
Abstract
The associations between sugar-sweetened beverage (SSB) consumption and the risk of stroke, depression, cancer, and cause-specific mortality have not been determined, and the quantitative aspects of this link remain unclear. This meta-analysis therefore conducted a systematic review and dose-response analysis to determine their causal links. The database searches were conducted in PubMed, Cochrane library, Embase, Web of Science up to 10 November 2021. The intervention effects were evaluated by relative risk (RR) with 95% confidences (CI). Thirty-two articles met the inclusion criteria. Higher levels of SSB consumption significantly increased the risk of stroke (RR 1.12, 95% CI 1.03-1.23), depression (1.25, 1.11-1.41), cancer (1.10, 1.03-1.17), and all-cause mortality (1.08, 1.05-1.11) compared with none or lower SSB intake. The associations were dose-dependent, with per 250 mL increment of SSB intake daily increasing the risk of stroke, depression, cancer, and all-cause mortality by RR 1.09 (1.03-1.15), 1.08 (1.06-1.10), 1.17 (1.04-1.32), and 1.07 (1.03-1.11), respectively. The link was curved for depression and cancer risk (pnon-linear < 0.05). Subgroup analysis suggested that higher SSB intake increased ischemic stroke by 10%, CVD-caused mortality by 13%, and cancer-caused mortality by 6.0% than none or lower SSB consumption. It is suggested that SSB accounts for a leading risk factor of stroke, depression, cancer, and mortality, and that the risk rises in parallel with the increment of SSB intake (and is affected by participant characteristics).
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Coffee Consumption and Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis of Prospective Studies.
Sartini, M, Bragazzi, NL, Spagnolo, AM, Schinca, E, Ottria, G, Dupont, C, Cristina, ML
Nutrients. 2019;11(3)
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Coffee is the second most widely consumed drink worldwide, after water. It contains many active compounds that affect the health and functioning of the digestive tract. Previous population studies on the relationship between coffee consumption and cancer prevention have had mixed results. The aim of this systematic review and meta-analysis was to provide an up to date summary of the relationship between coffee consumption and the risk of colorectal cancer. The authors looked at 26 prospective studies. When results from the 26 studies were pooled, no significant relationship between coffee consumption and colorectal cancer was found. The researchers then looked at the results by ethnicity and found a protective effect for coffee on colorectal cancer in people from the US. For colon cancer, coffee was protective in men and women combined and in men alone, regardless of ethnicity. When the results were separated according to ethnicity, a significant protective effect was noted in European men and in Asian women. There was no association between coffee consumption and rectal cancer. Decaffeinated coffee demonstrated a protective effect against colorectal cancer in both men and women. The authors concluded that ethnicity could explain the mixed results of previous studies. Further research is needed into the relationship between a person’s genetic make-up and the risk of colorectal cancer associated with coffee.
Abstract
Coffee is a blend of compounds related to gastrointestinal physiology. Given its popularity and the epidemiology of colorectal cancer, the impact of this beverage on public health could be considerable. Our aim was to provide an updated synthesis of the relationship between coffee consumption and the risk of colorectal cancer. We conducted a systematic review and meta-analysis of 26 prospective studies. Regarding colorectal cancer, no significant relationship was detected. Stratifying for ethnicity, a protective effect emerged in US subjects. Concerning colon cancer, coffee proved to exert a protective effect in men and women combined and in men alone. Stratifying for ethnicity, a significant protective effect was noted in European men only and in Asian women only. Concerning rectal cancer, no association was found. Decaffeinated coffee exhibited a protective effect against colorectal cancer in men and women combined. Studies were appraised for their quality by means of the Newcastle-Ottawa Quality Assessment Scale for Cohort studies. Only one study proved to be of low quality. Ethnicity could explain the heterogeneity of the studies. However, little is known about the relationship between the genetic make-up and the risk of colorectal cancer associated with coffee. Further research is warranted.
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Influence of acute consumption of caffeine vs. placebo over Bia-derived measurements of body composition: a randomized, double-blind, crossover design.
Williamson, CM, Nickerson, BS, Bechke, EE, McLester, CN, Kliszczewicz, BM
Journal of the International Society of Sports Nutrition. 2018;15:7
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Bioelectrical analysis (BIA) is a commonly used method to assess body fat percentage and water values, by running a small electrical current through the body. Prior to testing using BIA, it is necessary to avoid exercise, fasting and caffeine consumption for accurate results. Caffeine’s role as a diuretic is well understood, however, its impact on measures of body water values when consumed prior to BIA testing has not been examined. The main aim of this study was to determine if the consumption of caffeine prior to BIA testing influences the cellular fluid balance and body fat percentage. Participants in the trial were measured on three separate occasions. The first visit worked as a control whilst the second and third visit were conducted using a double blind randomised crossover method. The total number of participants included in the trial were 20 physically active males who were habitual coffee drinkers. Participants were given either 200mg of caffeine or 200mg dextrose (control). The BIA measurements were taken at seven different time points after the preliminary measurements, separated by 15-min. The authors concluded that caffeine consumption in habitual users just prior to testing produced no significant changes in the BIA measurements. Therefore, the pre-testing guidelines for caffeine consumption may not be necessary in habitual caffeine consumers.
Abstract
BACKGROUND Bioelectrical impedance analysis (BIA) is often used to estimate total body water (TBW), intracellular body water (ICW), extracellular body water (ECW), and body fat percentage (BF%). A common restriction for BIA analysis is abstinence from caffeine 12-h prior to testing. However, research has yet to determine whether the consumption of caffeine influences BIA testing results. The purpose of this study was to determine if the consumption of caffeine influences BIA-derived BF% and body water values in habitual caffeine users. METHODS Twenty apparently healthy males (26.6 ± 4.1 years) identified as habitual caffeine consumers (≥ one 95 mg serving per day ≥ four days per week) participated in this study. Participants came to the lab on three occasions, the first visit serving as the control (CON) with no supplementation. The remaining two visits were performed in a randomized double-blind, cross-over fashion. Participants consumed 200 mg of dextrose (PLA) or caffeine (CAF) in capsule form. During each visit, seven multi-frequency BIA measurements were conducted before (PRE) and after (15-min, 30-min, 45-min, 60-min, 75-min, 90-min) consumption. RESULTS Repeated measures ANOVA revealed BF% for CAF was lower than the CON and PLA conditions at PRE and 15-min (p < 0.001, p = 0.004), but not statistically significant for the remaining time points (i.e., 30-, 45-, 60-, 75-, and 90-min). However, the effect size (ES) of the BF% differences were trivial. The CON, PLA, and CAF conditions had higher PRE ICW values than their associated post time points (i.e., 15-, 30-, 45-, 60-, 75-, and 90-min). Similar to BF%, ES of the mean differences for ICW were trivial. No other differences were observed. CONCLUSION Caffeine consumption in habitual users produced trivial changes in TBW, ECW, ICW, or BF%. Therefore, the pre-testing guidelines for caffeine consumption may not be necessary in habitual caffeine consumers.
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A spatial gradient of bacterial diversity in the human oral cavity shaped by salivary flow.
Proctor, DM, Fukuyama, JA, Loomer, PM, Armitage, GC, Lee, SA, Davis, NM, Ryder, MI, Holmes, SP, Relman, DA
Nature communications. 2018;9(1):681
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Identifying spatial patterns in the human microbiota is necessary to provide insight into mechanisms that either maintain or disrupt its healthy state. The aim of this study was to identify the type and extent of oral spatial patterns formed by bacterial communities, as well as observe the impact of low salivary flow on the spatial patterns. Dental exams were performed on 31 participants to evaluate the oral health status and follow-up was dependent on group allocation. This study found bacterial communities were distinguishable depending on types of teeth and tissue. Further, bacteria on soft and hard tissues varied across the front and back of the oral cavity in a gradient-manner, implying that salivary flow plays a role in establishing the bacterial community gradient in the oral cavity. Based on these results, the authors recommend spatial patterns and processes be explored in other body parts to better understand health and disease.
Abstract
Spatial and temporal patterns in microbial communities provide insights into the forces that shape them, their functions and roles in health and disease. Here, we used spatial and ecological statistics to analyze the role that saliva plays in structuring bacterial communities of the human mouth using >9000 dental and mucosal samples. We show that regardless of tissue type (teeth, alveolar mucosa, keratinized gingiva, or buccal mucosa), surface-associated bacterial communities vary along an ecological gradient from the front to the back of the mouth, and that on exposed tooth surfaces, the gradient is pronounced on lingual compared to buccal surfaces. Furthermore, our data suggest that this gradient is attenuated in individuals with low salivary flow due to Sjögren's syndrome. Taken together, our findings imply that salivary flow influences the spatial organization of microbial communities and that biogeographical patterns may be useful for understanding host physiological processes and for predicting disease.
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Emollient use alters skin barrier and microbes in infants at risk for developing atopic dermatitis.
Glatz, M, Jo, JH, Kennedy, EA, Polley, EC, Segre, JA, Simpson, EL, Kong, HH
PloS one. 2018;13(2):e0192443
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Atopic dermatitis (AD) is a type of eczema common in babies and young children. Poor function of the skin barrier is thought to lead to changes in the composition of bacteria found on the skin. This small study investigated the effects of daily use of an emollient, Cetaphil Moisturising Cream, on the barrier function and bacterial communities on the skin of infants at risk of developing AD. After 6 months, the emollient group had a lower skin pH than the control group. The group using the emollient had more diverse skin bacterial communities than the control group. The proportion of Streptococcus salivarius was higher in the emollient versus control groups. The authors concluded that lower skin pH and increased skin bacterial diversity after long-term emollient use may reduce inflammation and lower the risk of infants developing AD.
Abstract
BACKGROUND Emollients are a mainstay of treatment in atopic dermatitis (AD), a disease distinguished by skin bacterial dysbiosis. However, changes in skin microbiota when emollients are used as a potential AD preventative measure in infants remain incompletely characterized. RESULTS We compared skin barrier parameters, AD development, and bacterial 16S ribosomal RNA gene sequences of cheek, dorsal and volar forearm samples from 6-month-old infants with a family history of atopy randomized to receive emollients (n = 11) or no emollients (controls, n = 12). The emollient group had a lower skin pH than the control group. The number of bacterial taxa in the emollient group was higher than in the control group at all sites. The Streptococcus salivarius proportion was higher in the emollient versus control groups at all sites. S. salivarius proportion appeared higher in infants without AD compared to infants with AD. A decrease in S. salivarius abundance was further identified in a separate larger population of older children demonstrating an inverse correlation between AD severity at sampling sites and S. salivarius proportions. CONCLUSIONS The decreased skin pH and the increased proportion of S. salivarius after long-term emollient use in infants at risk for developing AD may contribute to the preventative effects of emollients in high-risk infants.
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Effects of fasting and preoperative feeding in children.
Yurtcu, M, Gunel, E, Sahin, TK, Sivrikaya, A
World journal of gastroenterology. 2009;15(39):4919-22
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Preoperative fasting is usually carried out to prevent the risk of vomiting during anaesthesia. The study investigated whether children should have a long period of fasting before surgery. Eight groups of 10 children (aged 1-10 years) with disorders of groin and scrotum were orally fed normal liquid food (NLF) or a high calorie diet (HCD) in 2 divided doses at 6 hour intervals, then fasted for 2, 3, 4 or 5 hours prior to surgery. Four groups had NLF and 4 groups had HCD. All children had their glucose, prealbumin and cortisol levels measured twice, just after the oral feeding and just before surgery. Once anaesthesia was sufficient and stable, gastric liquid was collected and measured. Patients with disease that could delay gastric emptying, had high acid production or were on medication were excluded from the trial. The researchers found that there was no significant difference in blood prealbumin levels in all groups. There was significant increase in blood cortisol in 4 groups when fasted (NLF-2h fasted, HCD-2h fasted, NLF-3h fasted and HCD-5h fasted). Stomach aid residue liquids were at tolerable levels of 1-2ml in all children. Anaesthesia was uneventful, with no coughing, laryngospasm or vomiting reported, and outcomes of surgery and wound healing were not affected. The authors noted that drinking clear liquids up to 2 hours before surgery was unlikely to substantially affect the volume of gastric fluids, and did not appear to increase the risk of vomiting in normal, healthy children. Glucose and insulin infusions appeared to minimise endocrine stress response and normalised post-op insulin sensitivity. Additionally, there may be a psychological benefit for children as irritability appeared to decrease prior to surgery. The study concluded that there was no need for fasting longer than 2 hours prior to inguinoscrotal region surgery.
Abstract
AIM: To investigate whether children should undergo surgery without a long period of fasting after feeding. METHODS Eighty children with inguinoscrotal disorders (aged 1-10 years) were studied prospectively. They were divided into eight groups that each contained 10 children who were fed normal liquid food (NLF) and a high-calorie diet (HCD) 2, 3, 4 and 5 h before surgery, in two doses at 6-h intervals. NLF was given to four groups and HCD to the other four. In all groups, glucose, prealbumin and cortisol levels in the blood were measured twice: just after oral feeding and just before the operation. After the establishment of adequate anesthesia, gastric residue liquid was measured with a syringe. RESULTS Blood glucose levels in all patients fed NLF and HCD were high, except in patients in the HCD-4 group. There was no significant difference in the blood prealbumin levels. There was a significant increase in the blood cortisol levels in the NLF-2 (14.4 +/- 5.7), HCD-2 (13.2 +/- 6.0), NLF-3 (10.9 +/- 6.4), and HCD-5 (6.8 +/- 5.7) groups (P < 0.05). CONCLUSION The stress of surgery may be tolerated by children when they are fed up to 2 h before elective surgery.