Effects of different forms of hazelnuts on blood lipids and α-tocopherol concentrations in mildly hypercholesterolemic individuals

European Journal of Clinical Nutrition (2011) 65, 117–124 & 2011 Macmillan Publishers Limited All rights reserved 0954-3007/11 www.nature.com/ejcn ORIGINAL ARTICLE Effects of different forms of hazelnuts on blood lipids and a-tocopherol concentrations in mildly hypercholesterolemic individuals SL Tey1, RC Brown1, AW Chisholm1, CM Delahunty2, AR Gray3 and SM Williams3 1 Department of Human Nutrition, University of Otago, Dunedin, New Zealand; 2CSIRO Division of Food and Nutritional Sciences, North Ryde, New South Wales, Australia and 3Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand Background/Objectives: Diets high in nuts reduce cholesterol, probably due to their favorable lipid profile and other bioactive substances. However, the physical form of the nut may be important as the cell wall of intact nuts may limit the hypocholesterolemic effect of nuts by reducing lipid bioavailability. Therefore, we investigated the effects on blood lipids of incorporating three different forms of hazelnuts (ground, sliced and whole) into the usual diet. Subjects/Methods: In a randomized crossover study with three phases, 48 mildly hypercholesterolemic participants were asked to consume 30 g of ground, sliced or whole hazelnuts for 4 weeks. Body weight, plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triacylglycerol (TAG), apolipoprotein (apo) A1, apo B100 and a-tocopherol were measured at baseline and at the end of each dietary phase. Results: There were no significant differences in any outcome variable between the different forms of nuts (all PX0.159). However, compared with baseline, mean values at the end of each hazelnut intervention were significantly higher for HDL-C (P ¼ 0.023) and a-tocopherol (P ¼ 0.005), and significantly lower for TC (Po0.001), LDL-C (Po0.001), TC:HDL-C ratio (Po0.001), apo B100 (P ¼ 0.002) and apo B100:apo A1 ratio (Po0.001), with no significant difference in body weight (P ¼ 0.813). Conclusions: The ingestion of three different forms of hazelnuts equally improved the lipoprotein profile and a-tocopherol concentrations in mildly hypercholesterolemic individuals. Hazelnuts can therefore be incorporated into the usual diet as a means of reducing cardiovascular disease risk. European Journal of Clinical Nutrition (2011) 65, 117–124; doi:10.1038/ejcn.2010.200; published online 29 September 2010 Keywords: hazelnuts; form; bioaccessibility; lipids; a-tocopherol; cardiovascular disease Introduction The beneficial effects of regular nut consumption are well documented. Both epidemiological studies (Fraser et al., 1992; Kushi et al., 1996; Albert et al., 2002; Hu and Willett, 2002) and clinical trials (Kris-Etherton et al., 1999a; Rajaram et al., 2001; Sabate et al., 2003; Gebauer et al., 2008; Griel et al., 2008; Banel and Hu, 2009; Phung et al., 2009; Torabian et al., 2010) have consistently shown that nuts can have Correspondence: Dr RC Brown, Department of Human Nutrition, University of Otago, PO Box 56, Dunedin 9054, New Zealand. E-mail: Received 12 April 2010; revised 20 July 2010; accepted 20 August 2010; published online 29 September 2010 an important role in the management of plasma lipids, and reduce CVD morbidity and mortality. The American Heart Association recommends the consumption of nuts as a means of replacing saturated fat with unsaturated fats (Krauss et al., 2000). Similarly, the World Health Organization and National Heart Foundation of New Zealand recommend the consumption of 30 g of nuts as part of a cardio-protective diet (American Institute for Cancer Research and World Cancer Research Fund, 1997; New Zealand Guidelines Group, 2003). The cis-unsaturated lipid content of nuts, as well as the presence of dietary fiber, plant protein, phytosterols, antioxidants, vitamins, minerals and other bioactive substances, is thought to be largely responsible for their cardioprotective properties (Kris-Etherton et al., 1999b; Segura Effects of hazelnut form on blood lipids SL Tey et al 118 et al., 2006; King et al., 2008; Sathe et al., 2009). However, recent research has questioned the proportion of nutrients that are readily released from nuts and are thus available for metabolism (Ellis et al., 2004; Berry et al., 2008; Mandalari et al., 2008; Traoret et al., 2008; Cassady et al., 2009). This term has been coined ‘bioaccessibility’. It has been suggested that the cell wall of intact nuts may limit the release of lipids and other nutrients available for digestion (Ellis et al., 2004). Evidence of this concept is derived from in vitro digestion experiments in which lipid, protein and vitamin E from finely ground almonds were found to be more digestible than those from whole almonds (Mandalari et al., 2008). Further, short-term human trials report that whole nut consumption increases fecal fat losses, suggesting that some of the fat passes through the gastrointestinal tract undigested (Ellis et al., 2004; Hollis and Mattes, 2007; Traoret et al., 2008). This could potentially diminish the cholesterollowering properties of whole nuts. The release of these nutrients could theoretically be increased by breaking down the cell walls mechanically through slicing or grinding. To date no studies have examined the cholesterol-lowering properties of different forms of nuts, which potentially differ in nutrient bioaccessibility. Although numerous clinical studies and reviews have consistently shown the hypocholesterolemic effects of several nuts, such as almonds (Sabate et al., 2003; Phung et al., 2009), macadamia nuts (Griel et al., 2008), peanuts (Kris-Etherton et al., 1999a), pecans (Rajaram et al., 2001), pistachio nuts (Gebauer et al., 2008) and walnuts (Banel and Hu, 2009; Torabian et al., 2010), few studies have investigated hazelnuts. To date, only three short-term intervention trials have assessed the effects of hazelnut supplementation on blood lipids (Alphan et al., 1997; Durak et al., 1999; Mercanligil et al., 2007). However, the sample size used in all three studies was relatively small and one of the studies was a poorly designed, non-randomized trial using a convenience sample (Durak et al., 1999). Whether the simple inclusion of hazelnuts into the usual diet can produce similar cholesterol-lowering effects to other tree nuts requires further investigation. Therefore, the primary aim of this study was to compare the effects of consuming three different forms of hazelnuts (whole, sliced and ground) on blood cholesterol and a-tocopherol concentrations. Second, we assessed the effects of consuming hazelnuts for 4 weeks on these outcome variables. food allergies, familial hyperlipidemia, a chronic disease, or were taking cholesterol-lowering medication or medication known to affect blood lipid concentrations. The study protocol was approved by the Human Ethics Committee of the University of Otago, New Zealand. All participants ga (...truncated)