Georgina E. Crichton

Dairy consumption and metabolic syndrome: a systematic review of findings and methodological issues

A growing body of observational research suggests that dairy consumption may have a beneficial effect on the metabolic syndrome (MetS). MetS is a clustering of cardiometabolic risk factors within an individual that carries with it an increased risk of developing cardiovascular disease. A systematic search of electronic databases identified cross‐sectional studies (n = 10) and prospective cohort studies (n = 3) that assessed dairy intake in relation to MetS. The quality of the included studies was assessed based on study methodology, measurement and reporting of dietary intake, use of standardized MetS diagnostic criteria and statistical analysis. Dairy intake was inversely associated with incidence or prevalence of MetS in seven out of 13 studies. Three studies found no association between dairy and MetS. Three studies reported mixed relationships between specific dairy foods and MetS. The majority of studies suggested a potential benefit of dairy consumption on the risk of having MetS, but methodological differences, potential biases and other limitations in the studies conducted prevent conclusions to be drawn. Future randomized controlled trials are needed to confirm the effect of dairy consumption on MetS.

Dietary Antioxidants, Cognitive Function and Dementia - A Systematic Review

Antioxidant compounds, contained in fruit, vegetables and tea, have been postulated to have a protective effect against age-related cognitive decline by combating oxidative stress. However, recent research on this subject has been conflicting. The aim of this systematic review was to consider current epidemiological and longitudinal evidence for an association between habitual dietary intake of antioxidants and cognition, with consideration given to both cognitive functioning and risk for dementia and its subtypes, including Alzheimer’s disease and vascular dementia. Searches of electronic databases were undertaken to identify peer-reviewed journal articles that reported on associations between antioxidant intakes (vitamins C, E, flavonoids, carotenoids) and cognitive function or risk for dementia. Eight cross-sectional and 13 longitudinal studies were identified and included in the review. There were mixed findings for the association between antioxidant intake, cognition and risk of dementia and Alzheimer’s disease. Large heterogeneity in study design, differential control of confounders, insufficient measures of cognitive performance, and difficulties associated with dietary assessment may contribute to the inconsistent findings. Overall, findings do not consistently show habitual intakes of dietary antioxidants are associated with better cognitive performance or a reduced risk for dementia. Future intervention trials are warranted to elucidate the effects of a high intake of dietary antioxidants on cognitive functioning, and to explore effects within a whole dietary pattern.

RELATIONS BETWEEN DAIRY FOOD INTAKE AND ARTERIAL STIFFNESS: PULSE WAVE VELOCITY AND PULSE PRESSURE

Modifiable risk factors, such as diet, are becomingly increasingly important in the management of cardiovascular disease, one of the greatest major causes of death and disease burden. Few studies have examined the role of diet as a possible means of reducing arterial stiffness, as measured by pulse wave velocity, an independent predictor of cardiovascular events and all-cause mortality. The aim of this study was to investigate whether dairy food intake is associated with measures of arterial stiffness, including carotid-femoral pulse wave velocity and pulse pressure. A cross-sectional analysis of a subset of the Maine-Syracuse Longitudinal Study sample was performed. A linear decrease in pulse wave velocity was observed across increasing intakes of dairy food consumption (ranging from never/rarely to daily dairy food intake). The negative linear relationship between pulse wave velocity and intake of dairy food was independent of demographic variables, other cardiovascular disease risk factors, and nutrition variables. The pattern of results was very similar for pulse pressure, whereas no association between dairy food intake and lipid levels was found. Further intervention studies are needed to ascertain whether dairy food intake may be an appropriate dietary intervention for the attenuation of age-related arterial stiffening and reduction of cardiovascular disease risk.

Dairy consumption and cardiometabolic health: outcomes of a 12-month crossover trial.

BackgroundA growing body of research suggests that regular consumption of dairy foods may counteract obesity and other components of the metabolic syndrome. However, human intervention trials are lacking. We aimed to determine the cardiometabolic health effects of increasing the consumption of reduced fat dairy foods in adults with habitually low dairy intakes in the absence of energy restriction.MethodsAn intervention trial was undertaken in 61 overweight or obese adults who were randomly assigned to a high dairy diet (HD, 4 serves of reduced fat dairy/day) or a low dairy control diet (LD, ≤1 serve/day) for 6 months then crossed over to the alternate diet for a further 6 months. A range of anthropometric and cardiometabolic parameters including body composition, metabolic rate, blood lipids, blood pressure and arterial compliance were assessed at the end of each diet phase.ResultsTotal energy intake was 1120 kJ/day higher during the HD phase, resulting in slight weight gain during this period. However, there were no significant differences between HD and LD in absolute measures of waist circumference, body weight, fat mass or any other cardiometabolic parameter.ConclusionRecommended intakes of reduced fat dairy products may be incorporated into the diet of overweight adults without adversely affecting markers of cardiometabolic health.Trial RegistrationThe trial was registered with the Australia and New Zealand Clinical Trials Registry (ACTRN12608000538347) on 24th October, 2008.

Metabolic syndrome, cognitive performance, and dementia.

Obesity, hypertension, dyslipidemia, and insulin resistance have been associated with an increased risk of cognitive impairment or dementia. Together, these risk factors cluster as metabolic syndrome (MetS). The first aim of this systematic review was to identify and critically review studies assessing associations between MetS and cognition, with consideration given both to early cognitive changes and the severe endpoint of dementia. The second aim was to identify and discuss limitations in the literature and subsequent difficulties in drawing conclusions from research to date. Nine studies that assessed cognitive performance and ten studies that estimated incidence of dementia in relation to MetS were identified and appraised. Limitations in the literature include the lack of standardized nomenclature for cognitive variables, the use of multiple MetS definitions, and the difficulty in differentiating the adverse effects of multiple risk factors on cognition.

Cardiovascular health and cognitive function: the Maine-Syracuse Longitudinal Study.

Background Smoking, physical inactivity, and poor diet, along with obesity, fasting glucose and blood pressure have been independently associated with poorer cognitive performance. Few studies have related scales representing a combination of these variables to multiple domains of cognitive performance. The aim of this study was to investigate the association between overall cardiovascular health, incorporating seven components, and cognitive function. Methods A cross-sectional analysis employing 972 participants, from the Maine-Syracuse Longitudinal Study was undertaken. Four health behaviors (body mass index, physical activity, diet, smoking) and three health factors (total cholesterol, blood pressure, and fasting plasma glucose) were measured. Each was categorized according to the American Heart Association definitions for ideal cardiovascular health, except diet, for which two food scores were calculated. A Cardiovascular Health Score was determined by summing the number of cardiovascular metrics at ideal levels. Cognitive function was assessed using a thorough neuropsychological test battery. Results Cardiovascular Health Score was positively associated with seven out of eight measures of cognitive function, with adjustment for age, education, and gender. With further adjustment for cardiovascular and psychological variables, these associations remained significant for Visual-Spatial Memory, Working Memory, Scanning and Tracking, Executive Function and the Global Composite score (p<0.05 for all). Ideal levels of a number of health factors and behaviors were positively associated with global cognitive performance. Conclusion Increasing cardiovascular health, indexed by a higher number of metrics at ideal levels, is associated with greater cognitive performance. Smoking, physical activity, and diet are important components of cardiovascular health that impact upon cognition.

Review of Dairy Consumption and Cognitive Performance in Adults: Findings and Methodological Issues

Background: Diet is a modifiable factor that could be targeted as an appropriate intervention to optimise cognitive health and well-being in ageing. Aim: The aim of this systematic review was to consider current evidence for an association between dairy intake and cognitive functioning. Methods: Searches of the electronic databases Medline, Embase, Web of Science, CINAHL, and PsychInfo were undertaken to identify peer-reviewed journal articles that reported on associations between dairy consumption and cognitive outcomes. Results: Three cross-sectional and 5 prospective studies were identified. Poorer cognitive function and an increased risk for vascular dementia were found to be associated with a lower consumption of milk or dairy products. However, the consumption of whole-fat dairy products may be associated with cognitive decline in the elderly. Conclusion: Methodological variability and study limitations do not enable conclusions regarding optimal dairy intake and cognitive performance to be drawn. Randomised controlled trials are needed to confirm the relationship between dairy intake and cognition.

Cross-comparison of diet quality indices for predicting chronic disease risk: findings from the Observation of Cardiovascular Risk Factors in Luxembourg (ORISCAV-LUX) study.

The scientific community has become increasingly interested in the overall quality of diets rather than in single food-based or single nutrient-based approaches to examine diet-disease relationships. Despite the plethora of indices used to measure diet quality, there still exist questions as to which of these can best predict health outcomes. The present study aimed to compare the ability of five diet quality indices, namely the Recommendation Compliance Index (RCI), Diet Quality Index-International (DQI-I), Dietary Approaches to Stop Hypertension (DASH), Mediterranean Diet Score (MDS), and Dietary Inflammatory Index (DII), to detect changes in chronic disease risk biomarkers. Nutritional data from 1352 participants, aged 18-69 years, of the Luxembourg nationwide cross-sectional ORISCAV-LUX (Observation of Cardiovascular Risk Factors in Luxembourg) study, 2007-8, were used to calculate adherence to the diet quality index. General linear modelling was performed to assess trends in biomarkers according to adherence to different dietary patterns, after adjustment for age, sex, education level, smoking status, physical activity and energy intake. Among the five selected diet quality indices, the MDS exhibited the best ability to detect changes in numerous risk markers and was significantly associated with lower levels of LDL-cholesterol, apo B, diastolic blood pressure, renal function indicators (creatinine and uric acid) and liver enzymes (serum γ-glutamyl-transpeptidase and glutamate-pyruvate transaminase). Compared with other dietary patterns, higher adherence to the Mediterranean diet is associated with a favourable cardiometabolic, hepatic and renal risk profile. Diets congruent with current universally accepted guidelines may be insufficient to prevent chronic diseases. Clinicians and public health decision makers should be aware of needs to improve the current dietary guidelines.

Dairy Foods and Dairy Protein Consumption Is Inversely Related to Markers of Adiposity in Obese Men and Women

A number of intervention studies have reported that the prevalence of obesity may be in part inversely related to dairy food consumption while others report no association. We sought to examine relationships between energy, protein and calcium consumption from dairy foods (milk, yoghurt, cheese, dairy spreads, ice-cream) and adiposity including body mass index (BMI), waist (WC) and hip circumference (HC), and direct measures of body composition using dual energy X-ray absorptiometry (% body fat and abdominal fat) in an opportunistic sample of 720 overweight/obese Australian men and women. Mean (SD) age, weight and BMI of the population were 51 ± 10 year, 94 ± 18 kg and 32.4 ± 5.7 kg/m2, respectively. Reduced fat milk was the most commonly consumed dairy product (235 ± 200 g/day), followed by whole milk (63 ± 128 g/day) and yoghurt (53 ± 66 g/day). Overall dairy food consumption (g/day) was inversely associated with BMI, % body fat and WC (all p < 0.05). Dairy protein and dairy calcium (g/day) were both inversely associated with all adiposity measures (all p < 0.05). Yoghurt consumption (g/day) was inversely associated with % body fat, abdominal fat, WC and HC (all p < 0.05), while reduced fat milk consumption was inversely associated with BMI, WC, HC and % body fat (all p < 0.05). Within a sample of obese adults, consumption of dairy products, dairy protein, and calcium was associated with more favourable body composition.

Dairy food intake is positively associated with cardiovascular health: findings from Observation of Cardiovascular Risk Factors in Luxembourg study ☆

Conflicting findings have been reported about dairy food consumption and risk for cardiovascular disease. Furthermore, few studies have examined dairy food intake in relation to cardiovascular health and the incorporation of lifestyle factors such as diet and physical activity. This study examined whether dairy food consumption was associated with cardiovascular health, recently defined by the American Heart Association. Data were analyzed from 1352 participants from the Observation of Cardiovascular Risk Factors in Luxembourg survey. A validated food frequency questionnaire was used to measure intakes of milk, yogurt, cheese, dairy desserts, ice cream, and butter. Seven cardiovascular health metrics were assessed: smoking, body mass index, physical activity, diet, total cholesterol, blood pressure, and fasting plasma glucose. A total cardiovascular health score (CHS) was determined by summing the total number of health metrics at ideal levels. It was hypothesized that greater dairy food consumption (both low fat and whole fat) would be associated with better global cardiovascular health, as indicated by a higher CHS. Total dairy food intake was positively associated with the CHS. Higher intakes of whole fat milk, yogurt, and cheese were associated with better cardiovascular health. Even when controlling for demographic and dietary variables, those who consumed at least 5 servings per week of these dairy products had a significantly higher CHS than those who consumed these products less frequently. Higher total whole fat dairy food intake was also associated with other positive health behaviors, including being a nonsmoker, consuming the suggested dietary intakes of recommended foods, and having a normal body mass index. Increased dairy food consumption was associated with better cardiovascular health.