Olive oil and nuts among two ethnic groups: an evaluation of their acceptability, a survey and systematic review of previous interventional evidence of their effects on cardiovascular health, and results from an RCT intervention study

Liang, Fan (2021) Olive oil and nuts among two ethnic groups: an evaluation of their acceptability, a survey and systematic review of previous interventional evidence of their effects on cardiovascular health, and results from an RCT intervention study. Doctoral thesis, Northumbria University.

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Abstract

Among the physiological and metabolic changes occurring with ageing, the ageing of heart function is a key determinant of health. The death number from CVDs is expected to reach over 23.6 million by 2030. An estimated 17.9 million people died from CVDs in 2019 in the UK, representing 32% of all global deaths. Evidence suggested that the Mediterranean diet supplemented with extra virgin olive oil (EVOO) (25-50 ml/day) is highly reported as associated with a reduction of CV risk factors. However, the acceptability of the Mediterranean diet and the feasibility of this dietary pattern which includes consumption of olive oil remains unknown among Caucasians and East Asians in Northeast England. An Online Survey with two ethnicities in equal number and similar mean age and BMI that were undertaken for this PhD programme indicating that the acceptability and frequency of olive oil intake among East Asians is higher with a great MD score (8.02±SD1.8) (p<0.001) while Caucasians who consume olive oil were scored higher for MD score (6.51±SD2.2) (p<0.001), scored higher for MD acceptability (10.21±SD2.3) (p=0.017) and reported lower perceived barriers to healthy eating (PBHE) (1.81±SD4.0) (p=0.03) than non-consumers. Olive oil intake is likely to be positively associated with older age, higher MD score, higher MD acceptability and lower PBHE in both ethnicities. Evidence examining the effectiveness of nuts and olive oil, on both traditional and novel CV risk factors, in a comprehensive study in adults with different ethnic background is lacking. Our systematic reviews and meta-analysis of previous relevant literature on nuts that were undertaken for this PhD programme showed that nuts improve TC (MD: -7.54; 95% CI: -10.2 to -4.89; p < 0.00001; I2= 59%, n=66), HDL (MD: 0.89; 95% CI: 0.04 to 1.75; P=0.04; I2= 53%; n=67), LDL (MD: -7.21; 95% CI: -9.38 to -5.04; P< 0.00001; I2= 68%; n=68), TG (MD: -8.83; 95% CI: -13.12 to -4.53; P< 0.0001; I2= 64%; n=65) and FMD (MD: 0.74; 95% CI: 0.09 to 1.39; P=0.03; I2=5%, n=10). The non-Asian group potentially tends to benefit more CV biomarkers with moderate nut consumption than Asian group. Olive oil systematic review reported that olive oil improves biomarker - PAI-1 (MD: -1.02ng/ml, 95% CI: -1.92 to -0.12; p = 0.03, I2 = 0%). Nevertheless, studies on olive oil on different ethnicities were lacking. A 6-week, cross-over, randomised controlled dietary interventional study with 2 weeks interventional duration was undertaken to test the effects of EVOO on cardiovascular health. Overall, this study provided evidence on the benefits of over a 2-week period produced a positive effect on 24-hour SBP including daytime SBP, night-time DBP and MAP and TC, LDL for all participants. For East Asians, olive oil exerts a beneficial effect on 24-hour SBP and daytime SBP, MAP while night-time DBP was improved among Caucasians following EVOO. EVOO intake also has a positive effect on blood lipids - TC and circulating biomarkers - sE-selectin in East Asians while LDL and non-HDL are improved among Caucasians after EVOO intake. The findings reported in the present thesis could be valuable to health professionals to develop more effective interventions and could also help the public to make better informed food choices relating to cardiovascular health.

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