Abstract
Cardiovascular disease (CVD) is the leading cause of death in New Zealand. As part of a cardio-protective diet, New Zealand dietary guidelines recommend the regular consumption of up to 30 grams (g) of nuts per day, as a means of reducing the risk of CVD. Both epidemiological and clinical studies have demonstrated an inverse relationship between nut consumption and several CVD risk factors, in different populations. Most clinical trials have investigated the effects of consuming raw nuts on health outcomes. However, roasted and salted nuts have been reported to be more palatable than raw nuts. To provide health benefits, nuts need to be consumed regularly and in sufficient quantity. Dry roasting and lightly salting nuts may improve their acceptability and result in intakes congruent with recommendations. However, it is important to determine whether roasting and salting nuts negate the health benefits observed with the consumption of raw nuts. The aim of this study was to investigate the effect of regularly consuming 30 g of raw or dry roasted lightly salted hazelnuts, on cardiovascular risk factors and acceptability, among a group of European and Māori adults in Dunedin, New Zealand.
This was a randomised crossover study involving 73 participants (59 European, 14 Māori). Participants were assigned in random order to consume 30 g of raw or dry roasted lightly salted hazelnuts daily for 28 days, separated by a 14-day washout period. Cardiovascular risk factors were measured at the beginning and at the end of each treatment period. “Desire to consume” and “overall liking” for both forms of hazelnuts were assessed daily during the exposure period using a 150 millimetre (mm) visual analogue scale (VAS). “Overall liking” was also assessed during a pre- and post-exposure tasting session.
Fasting plasma total and low-density-lipoprotein (LDL)-cholesterol, apolipoprotein, glucose, and alpha (α)-tocopherol concentrations, body composition and blood pressure did not differ between forms of hazelnuts. High-density-lipoprotein (HDL)-cholesterol and triglyceride (TAG) concentrations were significantly lower following the consumption of dry roasted lightly salted hazelnuts when compared to the raw hazelnuts. This finding was unexpected and after examining factors that influence these two variables, such as diet, no apparent explanation for these results was found. Compared with baseline, consuming both forms of hazelnuts significantly improved LDL- and HDL-cholesterol, apolipoprotein A1, α-tocopherol concentrations, systolic and diastolic blood pressure, without significantly changing body composition. “Desire to consume” and “overall liking” ratings did not differ between forms of hazelnuts and remained high throughout the exposure period. In addition, “overall liking” rating did not change from pre- to post-exposure tasting sessions. Interestingly, Māori rated the dry roasted lightly salted hazelnuts as more acceptable, when compared to the raw hazelnuts. However, the absolute mean difference in “overall liking” between the two forms of hazelnuts is small. Collectively with the small sample of Māori participants (n=14), this difference does not appear to be clinically meaningful. There were no significant interactions between treatments and ethnic groups for any of the clinical outcomes.
In conclusion, there were no significant between-group differences in any of the outcome measurements, except for TAG and HDL-cholesterol concentrations, which were significantly lower after consumption of the dry roasted lightly salted hazelnuts, compared with raw hazelnuts. Factors which influence these variables were further investigated with no explanation being determined. Consuming both forms of hazelnuts equally improved plasma lipoproteins and α-tocopherol concentrations and blood pressure in a way that would be expected to reduce the risk of CVD. The acceptability results suggest that the Heart Foundation recommendation is appropriate and sustainable, for both raw and dry roasted lightly salted nuts, as a means of reducing the risk of CVD. The ethnicity interaction results should be interpreted with caution due to the small number of Māori participants in this study. Further work with a larger Māori cohort, is required to determine these outcomes.