Examining the relationship between beverage intake and cardiovascular health Ian Macdonald University of Nottingham UK
Outline Assessment of evidence in relation to health risks of dietary components Cardiovascular health/disease Tea Cocoa Milk Red wine
Assessment of evidence in diet/nutrition studies Types of studies: cross-sectional epidemiology, cohort studies, randomised controlled trials Systematic review with or without meta-analysis Outcome variables: events or risk factors/markers Limitations of studies Cross-sectional epidemiology: associations, no links to causality or time-trends Cohort studies: confounding from other lifestyle factors. For CVD/metabolic outcomes need to control for smoking, alcohol, BMI, gender, physical activity If looking at dietary macronutrients, what changes/differences exist (eg if CHO goes down what goes up)? RCTs often do not achieve a long term magnitude of change which is intended (eg WHI increase fruit & vegetable intake)
Cardiovascular health Tea Peters et al (2001) - tea associated with reduced CVD risk (although 3 studies showed increased risk) Arab et al (2009) - meta-analysis of green and black tea and stroke >3 cups a day reduced stroke risk by 21% (no difference between black or green tea) Wang et al (2011) - meta-analysis of links between tea and coronary artery disease (CAD). 13 on black tea (USA and Europe) 5 on green tea (China and Japan). No significant association was found between black tea consumption and CAD. Green tea associated with reduced risk of CAD (10% decrease for 1 cup/day). (Ethnic / regional confounding?)
Arab et al Stroke reduction
Wang et al, Black tea and CAD
Wang et al, Green tea and CAD Geleijnse et al (1999) - Rotterdam Heart study, clinically diagnosed atherosclerosis and tea intake - Significant negative association. Relative risk was 1 for <125ml/d, 0.54 for 125-250ml/d, 0.31 for >500ml/d
Tea: CV health markers BP no apparent effect of tea on BP. Acute consumption may even increase it (caffeine?) Cholesterol some indication that green tea may reduce total and LDL cholesterol FMD Ras et al (2011) meta-analysis of intervention studies investigating tea and endothelial function. FMD 2.6% greater with 500ml/d of tea compared to placebo.
Taubert et al Tea and BP RCTs
Ras 2011 Tea and FMD RCTs
Tea and CV Health: Longer term RCTs Hartley et al (2013) Systematic Review of RCTs of >3 months, duration. 11 studies -7 looked at the effects of green tea, and 4 at black tea. Green tea reduced total cholesterol, and BP. Black tea reduced LDL cholesterol and BP. Black Tea LDL Black Tea SBP BUT only 2 studies for both black & green tea
Cardiovascular Health Cocoa Analysis of 7 countries/zutphen studies suggested cocoa/chocolate may be associated with reduced CV disease risk Several recent reports of potentially beneficial effects (RCTs) of acute and chronic cocoa flavanol intake, from high flavanol cocoa drinks, on BP and endothelial function
Taubert et al Cocoa and BP RCTs
Flavonoids and type 2 DM Balzer et al, JACC 2008 (Balzer et al, 2008) 963mg 963mg Entry Baseline Dose 963mg 30 days 371mg 75mg 75mg Reduction in LDL, no change in BP at 30 days
Cognitive function, BP and cocoa flavanols in elderly subjects (CoCoA study) Desideri et al 2012 3 group of 30 elderly subjects (71yr) with MCI received low (45mg), medium (520mg) or high (990mg) doses of CF daily for 8 weeks Cognitive function (MMSE, Trails A and B, verbal fluency), BP measured and blood samples taken for insulin, glucose, lipids. Saw cognitive improvements (partly dose related), reduction in BP and Insulin Resistance estimates. Latter was associated statistically with the cognitive changes
Milk and BP Livingstone KM, Lovegrove JA, Cockcroft JR, Elwood PC, Pickering JE Hypertension. 2013 in the highest group of milk consumption systolic blood pressure was 10.4 mm Hg lower (P trend=0.033) than in non-milk consumers after a 22.8-year follow-up
Cardiovascular Health Red wine Vidavalur et al (2006) - systematic review of wine and CVD risk. Wine drinkers had higher HDL and ApoA1 and lower lipoprotein(a) than non-drinkers. Moderate red wine consumption was associated with reduced platelet aggregation, (possibly due to reduced prostanoid synthesis) reduced fibrinogen, and increased fibrinolytic activity. Some of the CVD benefits may be due to red wine increasing NO dependant signalling.
Cardiovascular Health Red wine Chiva-Blanch et al (2013) - evidence relating red wine consumption and CVD. Stated that: Clear that heavy alcohol consumption is associated with increased mortality and morbidity. Moderate alcohol intake, especially drinks high in polyphenols, confer CVD protective effects, both in healthy volunteers and those with high CVD risk. However, most of these effects/associations are weak and not consistent across groups of subjects Overall the evidence for CV Health benefits is not convincing
Conclusions Some reasonable evidence of potential benefits for CV Health in relation to tea intake Whether there are major differences between green and black tea remain to be determined, and the confounding from ethnic/lifestyle differences in relation to tea consumption need to be resolved Whether any effect of tea is due to the flavanoids remains to be confirmed, but if this is the case then other beverage sources of flavanoids (Cocoa, Orange Juice) may also be of interest and the current level of research into effects of cocoa flavanols may generate some important findings