A comparison of perceptions of nuts between the general public, dietitians, general practitioners, and nurses

Introduction

Nuts have been part of the human diet since paleothic times (Salas-Salvado, Casas-Agustench & Salas-Huetos, 2011), providing rich sources of cis-unsaturated fats, fibre, and a number of phytochemicals (Alasalvar & Bolling, 2015; Brufau, Boatella & Rafecas, 2006; Ros, 2010). Although specific types of nuts differ in their micronutrient content, as a food group they can provide substantial amounts of vitamin E, folate, calcium, copper, magnesium, potassium, and selenium to the diet (O’Neil et al., 2010; O’Neil, Nicklas & Fulgoni, 2015). The regular consumption of nuts is associated with lower total mortality (Grosso et al., 2015; Hshieh et al., 2015). This reduction is largely due to a lower risk of cardiovascular disease (Guasch-Ferre et al., 2017; Kris-Etherton et al., 1999; Nash & Nash, 2008; Ros, 2010; Ros, Tapsell & Sabate, 2010; Sabate, Oda & Ros, 2010). The regular consumption of nuts has also been associated with reductions in certain cancers including colorectal, endometrial, gastric, lung, and pancreatic (Aune et al., 2016; Bao et al., 2013a; Bao et al., 2013b; Fadelu et al., 2018; Hashemian et al., 2017; Lee et al., 2018; Lee et al., 2017; Van den Brandt & Nieuwenhuis, 2018; Wu et al., 2015). Although nut consumption has been negatively associated with the incidence of diabetes (Afshin et al., 2014), these findings are not consistent across studies (Hshieh et al., 2015; Luo et al., 2014; Zhou et al., 2014). A number of epidemiological studies have examined the association between cognitive function and dietary patterns that are characterised by high intakes of nuts, including the Mediterranean and Dietary Approaches to Stop Hypertension (DASH) diets (Katsiardanis et al., 2013; Samieri et al., 2013; Valls-Pedret et al., 2012; Wengreen et al., 2013). On the whole, these studies show better cognitive function among those adherent to these dietary patterns. Several mechanisms appear to be implicated in the protective role of nuts, including antioxidant and anti-inflammatory properties, largely related to their nutrient composition, in particular their cis-unsaturated fat, vitamin, and polyphenol content (Grosso & Estruch, 2016).

Although the cardioprotective effects of nuts have been widely established, the population intake of nuts has been reported as far from optimal in a number of countries (Brown et al., 2014; Jenab et al., 2006; O’Neil et al., 2012; O’Neil, Nicklas & Fulgoni, 2015). For example, in New Zealand (NZ), Europe, and the United States of America (USA) less than 8% of the population on a given day consumed whole nuts (Brown et al., 2014; Jenab et al., 2006; O’Neil et al., 2012; O’Neil, Nicklas & Fulgoni, 2015). In addition, the mean population intake of whole nuts is low at less than 3.5. Given that dietary guidelines recommended daily nut intakes of 30 to 42 (Tey, Brown & Chisholm, 2012; US Food and Drug Administration, 2003), it is apparent that strategies to increase regular nut consumption at the population level are needed.

Two studies have suggested that individuals would increase their nut intake if they were advised to do so by their doctor (Pawlak, Colby & Herring, 2009; Pawlak et al., 2012). Thus, it appears that health professionals may be important facilitators of nut intake. However, despite this willingness to increase nut intake, in both these studies, which included those with or at risk of CVD and/or diabetes (Pawlak et al., 2012), or those on a low income (Pawlak, Colby & Herring, 2009), there was general agreement among participants that eating nuts on most days of the week would not be consistent with the advice of their doctor. Therefore, it is important to gain an understanding on how health professionals perceive nuts, and how this may influence their advice to consume nuts. Comparison with the general public could assess whether there are any disparities regarding perceptions of nuts which may affect recommendations and nut intakes respectively. In addition, gaining information from the general public on the motivators of and deterrents to nut consumption may provide important information for health professionals to use in practice in order to increase regular nut consumption among their patients and clients.

Therefore, this study aimed to examine the beliefs, attitudes and perceptions of nuts among health professionals and a cross-section of the general public in New Zealand. In addition we aimed to determine the conditional motivators of and deterrents to regular nut consumption among the general population.

Materials & Methods

The study methods are described in detail elsewhere (Brown et al., 2017; Yong et al., 2017), and only essential details are presented here.

Results

Discussion

To the best of our knowledge, this is the first study to investigate motivators of, and deterrents to, nut intake among the general population, and to compare the perceptions of nuts between the general public and health professionals. Very few general public respondents reported receiving advice to eat nuts regularly from health professionals.

In general, there was agreement among the groups for the perceptions that nuts are healthy, high in protein and fat, are filling, and some nuts are high in selenium. There was an overall pattern of higher agreement amongst dietitians, followed by GPs and practice nurses, with the lowest level of agreement among the general public. There appeared to be some confusion among groups regarding the effects of nut consumption on diabetes risk and weight gain.

It is concerning that less than 4% of the general public had previously been advised to eat more nuts by a dietitian, GP or practice nurse. This seems especially low given that there was strong agreement among health professionals that nuts are healthy. Also, it appears that the general public would be responsive to such advice, given that over 50% of participants reported that they would eat more nuts if advised to do so by a dietitian or a doctor. These findings are consistent with those of Pawlak et al., who reported strong agreement among their low-income participants that they would eat nuts if advised to do so by their doctor (Pawlak, Colby & Herring, 2009). Also, among a cohort with or at risk of CVD and/or diabetes, 63% of participants claimed they would eat nuts on most days of the week if this was recommended by their doctor (Pawlak et al., 2012). In both these studies, participants did not generally agree that eating nuts on most days of the week was consistent with advice from their doctor. Collectively, the results from the present study and those by Pawlak, Colby & Herring (2009) and Pawlak et al. (2012) suggest that the general public are not receiving advice to eat nuts regularly by health professionals, but many would do so, if they received such advice. Therefore, health professionals are potentially important facilitators of regular nut consumption.

In order to increase population intakes of nuts, it is useful for health professionals to understand what would motivate their patients to eat more nuts, and what might deter them. These barriers and facilitators also provide useful information for designing public health messages aimed at increasing nut intake. The most popular motivators to eat more nuts were largely related to health outcomes e.g.,“would help me feel healthier” and “would help me get more nutrients”. This indicates that people are largely interested in their health. Therefore, highlighting the health benefits of eating nuts on a regular basis is important. This information should be included in promotion material encouraging nut consumption.

The top deterrent to eating more nuts was “if they cost too much”. This is congruent with the second most prevalent motivator, which indicated people would eat more if they were more affordable. Further to this, 34% of health professionals reported that their patients did not eat nuts because they considered them to be too expensive. Nuts range in price in NZ (1US dollar = 1.48NZ dollar) from around NZ$0.21 (peanuts) to NZ$2.37 (pine nuts) per 30 g serve. The less expensive types are peanuts, almonds, and cashew nuts. Peanut butter is also an affordable form at around NZ$0.36 per 30 g serve. Therefore, these types of nuts, especially in forms with no added sugar, salt, and oil, could be promoted as the most affordable, especially to those on a low income. In addition, it is important to put the price of nuts into context with other snacks where they compare favourably to fruit (e.g., one banana NZ$0.70), cereal bars (around NZ$0.50 per bar), and potato crisps (around NZ$1.49 per 40 g packet).

Other deterrents to nut consumption included if they “cause me to eat too much fat”, “cause me to gain weight, and “cause me to eat too many calories”. These latter two were also reasons that around one-fifth of patients gave to health professionals for not eating nuts. It therefore appears that some of the general public are worried about weight gain. Nuts are energy-dense and high in fat. However, epidemiological research suggests that regular nut consumers are leaner than non-nut consumers (Bes-Rastrollo et al., 2007; Bes-Rastrollo et al., 2009; Martinez-Gonzalez & Bes-Rastrollo, 2011; Mozaffarian et al., 2011). Also, intervention studies have shown that the addition of nuts to the regular diet results in no weight gain, or less weight gain than predicted (based on the extra energy from the nuts) (Alper & Mattes, 2002; Flores-Mateo et al., 2013; Hollis & Mattes, 2007; Mattes, Kris-Etherton & Foster, 2008; Tey et al., 2011). Suggested mechanisms for this finding include increased satiety (Brennan et al., 2010; Mattes, 2008; Tan & Mattes, 2013) increased metabolic rate (Alper & Mattes, 2002; Claesson et al., 2009; Coelho et al., 2006), and increased loss of metabolisable energy in the faeces (Ellis et al., 2004; Gebauer et al., 2016; Grundy et al., 2015; Grundy, Lapsley & Ellis, 2016; Novotny, Gebauer & Baer, 2012). Given that the fear of weight gain may be deterring some people from consuming nuts on a regular basis, nut-promoting messages should include information from the wealth of research suggesting that adding nuts to the diet does not result in weight gain, especially when nuts are used to replace other less healthful snacks. In addition, it is likely that there needs to be more education aimed at health professionals in this area, given the majority of these participants seemed unsure about the potential of nuts to cause weight gain. In fact, around 10% of dietitians and around one-fifth of GPs and practice nurses agreed that eating nuts caused weight gain. Thus targeted education on this topic is needed to improve the advice given to patients.

A further barrier to regular nut consumption highlighted by the current research was dentition issues. Over one-quarter of health professionals reported that their patients did not wish to eat nuts because of dental issues. An alternative to eating whole nuts is to incorporate nut butters into the diet. It seems intuitive that nut butters should provide health benefits similar to those seen with whole nuts. However, few studies have investigated whether the benefits of whole nuts can be extrapolated to nut butters. Two recent epidemiological studies (Luu et al., 2015; Van den Brandt & Schouten, 2015) reported significantly lower total mortality with increased nut intake, but not nut butter alone. Conversely, the Nurses’ Health Study (NHS) showed peanut butter consumption was inversely associated with type 2 diabetes in women (Jiang et al., 2002) and in a subset including women with type 2 diabetes, cardiovascular risk was significantly lower among those consuming peanuts and peanut butter at least five times per week (Li et al., 2009). Two interventions found significant improvements in blood lipids after consuming different forms of peanuts or almonds (including butter), with no significant differences between groups (McKiernan et al., 2010; Spiller et al., 2003). While promising, these studies had short intervention periods (28 days) and were possibly underpowered. Longer, adequately-powered studies are required in order to develop firm conclusions. One potentially important difference between nuts and nut butters is the effects on energy balance. As mentioned previously, studies examining body weight (Alper & Mattes, 2002; Fraser et al., 2002; Hollis & Mattes, 2007; Sabate et al., 2005; Tey et al., 2011) indicate eating whole nuts results in less weight gain than predicted, possibly through increased satiety (Mattes, 2008). The effect of nut butters on weight and satiety needs clarification. Also, a recent study reported the measured metabolisable energy of whole almonds (4.42 kcal/g) and almond butter (6.53 kcal/g) differed significantly (Gebauer et al., 2016), and thus may have differing effects on energy intake and body weight regulation (Gebauer et al., 2016; Grundy, Lapsley & Ellis, 2016). Therefore, given there is surprisingly little information on the health benefits of consuming nut butter, it is an important area for future research, so that evidence-based guidelines can be developed.

It is of interest to compare the perceptions of nuts between health professionals and the general public to examine if there are major disparities, which need to be addressed so that there is a consistent understanding of the health benefits of regular nut consumption. For the statements regarding the perceptions of nuts, dietitians were least likely to respond that they “did not know”, while the general public were mostly likely to, with the GPs and practice nurses intermediary. There was a similar pattern when analysing agreement and disagreement for the perceptions. Among the top five perceptions to which participants, especially the general public, were most likely to respond “I don’t know”, were “eating them can increase people’s total blood cholesterol”, “they are high in antioxidants”, “some of them are high in selenium”, “some of them are high in iron”, and “eating them can help lower people’s risk of diabetes”. It is not surprising the latter statement received a high prevalence of “I don’t know” responses as there is conflicting evidence regarding this in the scientific literature. While one meta-analysis reported a small but significant decrease in the incidence of type 2 diabetes, this study has been criticised on the basis of study selection (one study did not examine the independent effects of nuts), and failure to adjust for BMI (Afshin et al., 2014). Conversely, two other meta-analyses have reported no association between nut consumption and the risk of developing type 2 diabetes (Luo et al., 2014; Zhou et al., 2014). There was also confusion regarding the iron content of nuts. Some nuts can be useful sources of iron, but this will be in the form of non-haeme iron, which is less absorbable and can be influenced by other components of the diets. Also, despite the high prevalence of “I don’t know” responses, it is well established that nuts have hypocholesterolaemic properties (Musa-Veloso et al., 2016; Sabate, Oda & Ros, 2010), are rich sources of antioxidants (Bolling et al., 2011), and that some nuts, in particular, Brazil nuts, are high in selenium (Thomson et al., 2008). Interestingly, among those who responded with agreement or disagreement to the perception statements, overall there was greatest agreement that “some of them are high in selenium”. This tends to indicate that the message that Brazil nuts are high in selenium is reaching some people. Given that NZ soils are low in selenium and the risk of inadequate intake of selenium has been estimated at 45% (University of Otago and Ministry of Health, 2011), Brazil nuts offer a useful source of this nutrient.

The strengths of the study include the recruitment of large national samples and the rigorous survey method using a mixed-mode approach using both an online and paper mail version of the questionnaire to improve response rates.

There are also a number of limitations to be considered when interpreting the data. The cross-sectional nature of the study allows for generation of hypotheses for future research, but means that causal inferences cannot be drawn. The surveys were self-administered, and it is possible that some respondents did not correctly interpret all questions. However, careful development and pre-testing of the questionnaires was undertaken to address this. Response rates were 44% for the general population and 53% for the health professionals. Although these are comparable to other mail surveys in Australasia (Lee et al., 2005; Timperio et al., 2000), it is possible responders and non-responders differed. While this may influence means, medians, and percentages; there are no clear reasons why the observed associations would differ between responders and non-responders. The results may not be generalisable to countries with healthcare systems that differ from those seen in NZ. Also, we cannot link the perceptions/beliefs of health professionals with their patients due to the design of the study. Linked data would help to determine whether attitudes can be transmitted between these groups. This would provide useful information on whether an intervention, which positively influences health professionals’ views on nuts could be expected to influence the views of their patients.

Conclusions

It is concerning that so few of the general public report they have received advice from health professionals to consume more nuts, especially given their apparent responsiveness to such advice. Interestingly, both the general public and health professionals consider nuts to be healthy, which may mean that they would be willing to increase intake and advice to increase nuts respectively, if some of the deterrents for eating nuts are addressed. These deterrents included cost, weight gain, and causing one to eat too much fat. We also identified some important motivators to increase nut consumption such as improving health, increasing nutrients in the diet, helping get the right balance of fat, and if they were more affordable. Given that over half of the participants would eat more nuts if advised to by their doctor or dietitian, health professionals should use these potential facilitators to promote regular nut consumption. In addition, these factors should also be addressed in public health messages to encourage regular nut consumption among the public.

Supplemental Information