Predicting intentions to consume functional foods and

Appetite 43 (2004) 55–64 www.elsevier.com/locate/appet

Research Report

Predicting intentions to consume functional foods and supplements to offset memory loss using an adaptation of protection motivation theory D.N. Coxa,*, A. Kosterb, C.G. Russella a

Commonwealth Scientific Industrial Research Organisation (CSIRO) Health Sciences and Nutrition, P.O. Box 10041, Adelaide, SA 5000, Australia b Division of Human Nutrition and Epidemiology, University of Wageningen, Wageningen, The Netherlands Received 6 October 2003; revised 12 December 2003; accepted 16 February 2004

Abstract The widespread use of dietary supplements and so-called ‘functional foods’ is thought to be partially motivated by self-control of health. However, whilst consumers want foods associated with well-being or disease prevention, they are unlikely to be willing to compromise on taste or technology. This presents a dilemma for promoters of functional foods. Middle-aged consumers’ intentions to consume functional foods or supplements that may improve memory were tested within an adaptation of Protection Motivation theory (PMT). Participants evaluated text descriptions of four products described as: having an unpleasant bitter taste (Natural-FF); having ‘additives’ to reduce bitterness (Sweetened-FF); being genetically modified to enhance function (GM-FF) and Supplements. Participants were recruited as being of high and low perceived vulnerability to memory failure. In total, 290 middle-aged consumers (aged 40 – 60 years) participated in the study. Motivations to consume the GM-FF were the lowest. There were gender differences between intention to consume the supplements, Natural-FF and Sweetened-FF and product differences within genders. Women were less favourable than men in their attitudes towards genetic modification in general. Regression analyses indicated that PM predictors of intention to consume functional foods or supplements explained 59 – 63% of the variance ðR2 Þ: Overall, perceived ‘efficacy’ (of the behaviour) and self-efficacy were the most important predictors of intentions to consume. q 2004 Elsevier Ltd. All rights reserved. Keywords: Attitudes; Neutraceuticals; Health; Functional foods; Supplements; Memory; Protection motivation theory; Consumers

Introduction Health behaviour research suggests that there are significant individual differences in perceptions of capacity to influence or control one’s own health. These differences impact upon participation in health-promoting behaviours, including those related to the consumption of food and other substances. A review of those studies utilising psychosocial models including the Theory of Reasoned Action (Fishbein & Ajzen, 1975) and Theory of Planned Behaviour (Ajzen, 1985); Health Belief Model (Strecher & Rosenstock, 1997), Transtheoretical (or Stages of Change) model (Prochaska & DiClemente, 1984); Social Cognitive Theory, (Bandura, 1986) to predict consumption of dietary fat, fruits and vegetables, indicated that these models typically explain a low to moderate amount of variance (, 30%) in intentions * Corresponding author. E-mail address: [email protected] (D.N. Cox). 0195-6663/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2004.02.003

to behave or behaviour (Baranowski, Cullen, & Baranowski, 1999). Baranowski and colleagues suggested that future research should examine (theoretical) models that are better predictors. Protection Motivation theory (PMT) is an alternative theory (Maddux & Rogers, 1983) which has been successfully applied to many health promotion activities and enhancing healthy lifestyle behaviours (for recent reviews see, Boer & Seydel, 1999; Floyd, Prentice-Dunn, & Rogers, 2000). Only a few studies have applied the PMT model to eating behaviours or protection by dietary means (Plotnikoff & Higginbotham, 1995; Plotnikoff & Higginbotham, 1998; Smith Klohn & Rogers, 1991; Wurtele, 1988). PMT has not been applied to perceptions of healthenhancing foods or supplements. The theory lends itself to this type of investigation as it attempts to specify the precise characteristics of a health message or behaviour that influence compliance and the processes at work (Maddux

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D.N. Cox et al. / Appetite 43 (2004) 55–64

& Rogers, 1983). These message characteristics include four categories of information surrounding perceptions: the severity of the health threat, one’s vulnerability to this threat, how efficacious the proposed behaviour is at averting the threat and how efficacious one is at carrying out this advocated behaviour (in this case, consuming functional foods or supplements). Two cognitive processes are activated that subsume the severity, vulnerability, selfefficacy, and response-efficacy elements when one encounters a health threat from the environment: the threat appraisal process and the coping appraisal process (Maddux & Rogers). PMT may be a particularly valuable approach because of the inclusion of the ‘threat appraisal process’ (only part of the ‘coping appraisal process’ is included in, for example, the Theory of Planned Behaviour). We chose to test the efficacy of PMT as tool to understand consumers’ reactions to dietary supplements and ‘functional’ foods (Kwak & Jukes, 2001) to offset cognitive functional limitations. Maintenance of memory is recognized as important for health and quality of life (Calvaresi & Bryan, 2003; Pope, Sowers, Welch, & Albrecht, 2001; Roberfroid, 2000; Salthouse, 1991) however, whilst there is preliminary evidence to suggest that some nutrients could influence cognitive performance (Calvaresi & Bryan, 2001; Milo Ohr, 2003) and, supplements have been produced, no functional food products yet exist even though there is potential demand. A recent study (Cardello & Schutz, 2003) found that there was highest potential demand for a ‘neutraceutical’ that improved ‘thinking’. Yet currently there is little understanding of what may influence consumers’ acceptance of foods or supplements to improve cognitive performance, should such products become widely available. The increasing use of dietary supplements in general is one example supporting the notion of an aspiration towards better health through preventative measures, which Greger (2001) has suggested is a result of consumers wishing to take charge of their own health; a likely reflection of an increase in internal locus of control (Cardello, 1995; Norman & Bennett, 1999; Wallston, Wallston, & Develles, 1978). With the concept of nutrition changing in recent times from simply meeting metabolic requirements to promoting a state of well being, better health and reduction of disease risk (Roberfroid, 2000), it is possible that consumers may also be motivated to use functional foods to protect and enhance their health. However, it is unclear which factors motivate consumers to choose functional foods, particularly in comparison to supplements. Our first research question was: would consumers beliefs concerning self-efficacy and response efficacy differ for functional foods in comparison to supplements? A recent study of Finnish consumers found that the taste of model ‘functional’ drinks could not be compromised for putative functional benefit (Tuorila, Cardello, & Lesher, 2001). This suggests that consumers want foods that are associated with maintenance of well

being or the prevention of a disease, but are not willing to compromise on taste, convenience or value (Augustin, 2001). However, a dilemma for promoters of plant-based functional foods exists, in that recently it has been recognized that active (functional) constituents in many plant foods are particularly bitter, acrid or astringent (Drewnowski & Gomez-Carneros, 2000) and that bitterness can be the principal cause of food rejection Drewnowski (1997). In the current study we sought to determine what characteristics of a product-message would impact on the motivations to purchase functional foods to prevent short term memory loss. That is, we aimed, within an adaptation of PMT, to model how consumers would react to different products described (in text scenarios) in terms of their taste and technological modification of offtastes (bitterness), function and convenience. For example, it is theoretically possible that functional composition could be maintained and off-tastes negated through genetic modification. Genetically, modified foods are generally believed to be ‘unnatural’ and unpopular across a wide range of products and cultures. Sparks, Shepherd, and Frewer (1994) reported that British consumers’ attitudes towards the use of gene technology in food production was significantly determined by perceived benefits, perceived risks, perceived needs, perceived improvements in the quality of life and ethical considerations. Bredahl, Grunert, and Frewer (1998) suggest that attitude towards genetic engineering is related to a weighing up of the perceived risks and benefits. Poor acceptance of GM foods may be due to the fact that most modifications have only benefited the producers (for example, disease and herbicide resistance or shelf-life) and not the consumer directly (Magnusson & Hursti, 2002). It is unclear how consumers would react to a GM food, which was said to have a direct consumer benefit of improved sensory characteristics such as taste (reduction of bitterness) or have enhanced function. Our second research question was: would GM be acceptable if associated with direct consumer benefits? Technological modification via the inclusion of additives such as sweeteners can be used to overcome bitter taste. Whilst artificial sweeteners may be perceived unfavourably, particularly in terms of health and naturalness (Raats & Shepherd, 1996), consumers require palatability in functional foods. Therefore, our third research question was: would functional foods sweetened to offset bitterness and providing direct consumer benefits be acceptable to potential consumers? Widespread use of supplements (Greger, 2001) suggests that motivations for supplement use (as opposed to foods) may be embedded in their convenience (Augustin, 2001). Our fourth research question was would supplements be the preferred vehicle for nutrients to improve memory in particularly terms of self-efficacy and response efficacy?


Pilot study Prior to the main study a pilot study was undertaken to assess the model and the key variables. Results have been reported briefly elsewhere (Cox, Koster, & Russell, 2003). The methodology of the pilot study was the same as for the main study except where specified. Four products were examined: Naturally Bitter-FF, Sweetened-FF, Supplement products GM functional foods modified to reduce bitterness. The 94 women (aged 40 –60 years) who participated were classified a priori as high vulnerability to memory loss (N ¼ 57; HV group) and low vulnerability (N ¼ 37; LV group). Whilst the explained variances ðR2 Þ of the models were generally very high, ranging from 58 to 79%, when significant predictors were found, the findings of the pilot study revealed little discrimination between the Naturally Bitter-FF, Sweetened-FF and Supplement products and most importantly a lack of acceptance of the GM functional foods. As a consequence, in the main study the GM-FF text descriptors were modified to suggest a consumer benefit of enhanced function instead of improved taste. In the main study, we hypothesised that consumers would react differentially to the four product ranges, which were said to be either (1) naturally bitter, (2) genetically modified to enhance the function, (3) artificially sweetened to offset bitterness, or (4) supplements as convenient nonfood products with the same functional benefits.

Methods Participants and design Recruitment Participants aged 40 – 60 years who had previously completed a questionnaire on symptoms experienced during midlife as well as a willingness to be re-contacted, were posted a questionnaire. A postal questionnaire was used to improve response rates, which were modest in the laboratory-based pilot study. Initially these participants were recruited by random selection from the 40- to 60-yearold age band of the South Australian Electoral Rolls (voting is compulsory and approximately 98% of potentially eligible voters are registered) (Calvaresi & Bryan, 2003). As part of this original questionnaire, participants had completed the Memory Functioning Questionnaire (MFQ) (Gilewski, Zelinski, & Schaie, 1990). The MFQ measures self-reported perceived memory loss. Prior to the mail-out, the sample was divided into tertiles based on the MFQ scores. Men and women in the first (n ¼ 209; scores 3– 28) and third tertile (n ¼ 209; scores 40 –78) were contacted as potential members of a perceived high vulnerability group (HV group) or a perceived low vulnerability group (LV group), respectively, for participation in the current study. Each participant was mailed a questionnaire with a replypaid envelope and a letter explaining the nature and purpose

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of the study. Approximately two weeks after the initial posting, non-respondents were posted a reminder letter. Participants completed the questionnaire in the first quarter of 2003. Included with the questionnaire was a description of the aim of the study: to assess the attitudes towards functional foods and supplements. Also included was an introductory paragraph, which defined functional foods as foods which ‘provide additional health benefits over and above normal nutritional values’. Participants were informed that the memory loss referred to in the study concerned short-term memory loss only and that the foods described did not yet exist. Questionnaire. The three functional food ranges and the supplements were provided in the form of short text descriptions. Each explanation was based on the text: ‘A range of functional foods [supplements] is being developed that contains vitamins and natural plant extracts that may improve memory in a group of people in your age group. For any possible effect it is likely you would need to consume foods from the [specified] functional food [supplement] range everyday. The foods [supplements] will be found in supermarkets.’ For the three functional food ranges: natural (NATURAL-FF); sweetened (SWEETENED-FF) and genetically modified (GM-FF) additional text was included which provided more information on the taste or function of the specific products. The NATURAL-FF range included the text ‘the active constituents taste slightly bitter’. The SWEETENED-FF range contained the additional text ‘an artificial sweetener will be added to reduce the bitterness of the active constituents’. For the GM-FF range, the additional accompanying text was ‘the intention of the genetic modification is to double the effectiveness of the active constituents compared to other ‘natural’ products’. Each functional food range was described as being ‘common everyday foods’. No additional text was included with the supplements. The text descriptions of the functional foods and supplements were presented in eight randomised orders so as to minimise any order of presentation effects. Measures. Variables forming the PMT were measured with anchored seven-point scales (unless indicated otherwise below*, see Table 1). Additional questions, included supplement use (open responses). General attitude to genetically modified food was measured by one item: ‘My attitude towards genetically modified (GM) foods is generally’ (seven-point anchored scale, extremely unfavourable – extremely favourable). Responses to these variables are reported to assist with interpretation of the PMT model. Statistical analysis. Cronbach’s alphas were calculated for the composite variables within the PMT model.

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Table 1 Components of PMT model and respective questions The severity of the health threat (two items) Having memory loss would significantly alter my lifestyle Completely disagree/completely agree Memory loss is a severe condition Vulnerability to the threat of memory loss (seven items) People in my age group are vulnerable to memory loss Completely disagree/completely agree Compared to the average person in my age group, my risk of developing Extremely low/extremely high memory loss is I believe that my chances of getting, or already having, some form of memory loss is… Being vulnerable to memory loss isa Extremely unimportant/extremely important Yes/no/don’t know/I do not have a spouse or partner My spouse/partner has a high risk of memory loss*b Someone important to me (other than my spouse/ partner) has developed Yes/no/don’t know memory loss*b My family has a history of memory loss*b Efficacy of the proposed protective behaviour (consumption of functional foods/supplement) at averting the threat (four items) In my opinion, memory loss is inevitable as one gets older and there is Completely disagree/completely agree little one can do about itc In my opinion, a diet that includes functional food range. Naturally bitter/GM/Sweetened/supplement could counteract memory loss Consumption from functional food range Naturally bitter/GM/Sweetened/supplement may be an effective measure to prevent memory loss, for me Please indicate how confident you would be in consuming the necessary Extremely unconfident/extremely confident amount of active ingredients from these foods (supplements) Self efficacy at carrying out the advocated protective behaviour (consumption of functional foods/supplement) (1 item) In your opinion how, how confident are you that you could consume from Extremely unconfident/extremely confident functional food range. Naturally bitter/GM/Sweetened/supplement at the recommended frequency The intention items were divided into primary and supplementary categories. The primary intentions were measured with two items (responses were multiplied giving a range of possible score 221 to 121) For me, protecting my memory through choosing from functional food Extremely unimportant/extremely important range Naturally bitter/GM/Sweetened/supplement is Extremely unlikely/extremely likely If it were available in the supermarkets at a reasonable cost, what is your intention to consume functional food range Naturally bitter/GM/Sweetened/supplement Supplementing the dependent variable ‘intention’ was an additional (secondary dependent variable) question Please indicate how interested you would be in obtaining more Not interested at all/extremely interested information about the functional food range Naturally bitter/GM/Sweetened/supplement a b c

Later analysis determined this item to be a separate independent variable (‘general vulnerability’). These three items were also treated as separate independent variables (‘important others vulnerability’). Analysis determined this item to be a separate independent variable (‘inevitability’).

Chi square ðxÞ; ANOVA and correlation analyses were undertaken on these composite variables. Univariate regression analyses were performed with ‘intention to consume’ variables as the dependent variables and the independent variables were the main variables in the PMT model: severity, vulnerability, product-efficacy and selfefficacy. Intention to consume (each of the four products) was the primary dependent variable and was measured as a composite of agreement multiplied by importance (2 21 to þ 21). A separate regression was run on a second dependent variable: ‘interest in obtaining more information’ on each of the four products. The model was initially run with all PMT variables for males and females separately. However, no gender differences could be detected and so the model was run for the sample as a whole. The multiple regression analyses and the descriptive and testing for mean or

category differences undertaken using SPSS v.11.0 (SPSS, Inc., Chicago, 2001). A value of p , 0:01 was selected as a level of statistical significance.

Results From the 418 participants contacted, 30 questionnaires were returned undeliverable and 290 completed questionnaires were returned, resulting in a response rate of 75%. The 290 participants aged 40– 60 years who returned completed questionnaires consisted of 93 males (32%) and 197 females (68%). One hundred and forty six participants responded from the a priori high vulnerability (HV) group (response rate of 76%) and 144 (response rate of 75%) in the a priori low (LV) vulnerability group (ns).

D.N. Cox et al. / Appetite 43 (2004) 55–64 Table 2 Primary dependent variable: males’ and females’ (gender £ product interaction Chi square ¼ 15.54, p ¼ 0:0014) intentions to consume the functional foods and supplements (agreement £ importance (possible scores range from 221 to þ 21)); p , 0:01

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Table 3 Secondary dependent variable: males’ and females’ (gender £ product interaction Chi square ¼ 16.65, p ¼ 0:0008) interest in obtaining more information on the functional foods and supplements p , 0:01 Mean (SEM)

Mean (SEM) Females ðn ¼ 197Þ Natural functional foods (NATURAL-FF) Supplement Sweetened functional foods (SWEETENED-FF) GM functional foods (GM-FF)

a

9.6 (0.68) 9.6a (0.65) 4.5b (0.63) 2.4c (0.56)

Males ðn ¼ 93Þ a

9.2 (0.82) 7.3b (0.83) 5.6b (0.80) 4.1c (0.73)

Natural functional foods (NATURAL-FF) Supplement Sweetened functional foods (SWEETENED-FF) GM functional foods (GM-FF)

Females ðn ¼ 197Þ

Males ðn ¼ 93Þ

5.5a (0.13) 5.6a (0.12) 4.4b (0.16)

5.5a (0.19) 5.3a (0.20) 4.9a,b (0.21)

3.7c (0.17)

4.5b (0.24)

a–c Values not sharing a common subscript letter were significantly different p , 0:01:

a–c Values not sharing a common subscript letter were significantly different p , 0:01 possible scores (1, lowest; 7, highest).

Scores

(SEM) scores for attitudes to GM foods in general, were, for females and males respectively, 2.67 (0.10) and 3.43 (0.16), t ¼ 24:08; p , 0:001: Unfavourable (low scoring) attitudes to GM generally were moderately correlated with GM-FF intentions to consume and wanting more information (for female respondents: intention r ¼ 0:39; more information r ¼ 0:49; and for male respondents intention r ¼ 0:43; more information r ¼ 0:43; all p , 0:01).

Mean scores from the vulnerability measures in the questionnaire (three items, a ¼ 0:71) confirmed that the HV and LV groups did differ in their perceived vulnerability to memory loss. The mean (SEM) for the HV group was 4.81 (0.10) and for the LV group 3.85 (0.11), p , 0:0001). There were no other significant differences between the LV and HV groups for the main PMT variables. There were gender differences in scores for the dependent variables. Generally for intentions to consume (Table 2), NATURAL-FF were the highest scoring functional foods. However, females were equally favourable towards consuming supplements. SWEETENED-FF were generally viewed unfavourably; particularly by females. For males and females, intentions to consume GM-FF were the lowest (especially for females) suggesting that GM was unacceptable even if the technology provided a consumer benefit of enhanced function. Almost half of the respondents reported taking supplements (48%) and significantly more women (56%) reported current usage of supplements in comparison to men (31%; x ¼ 37:3; p , 0:001). However, gender differences ðp ¼ 0:025Þ in intention to consume the supplements did not meet the significance level chosen ðp , 0:01Þ suggesting that supplement preference in the study was only weakly related to current supplement usage. The scores for ‘wanting to know more information about each product’ (Table 3) were generally consistent with the pattern of scores for intentions to consume such products (Table 2). Male and female respondents were equally curious about obtaining information about NATURAL-FF and supplements. Men did not discriminate between the products greatly, in contrast to women who were significantly less interested in GM-FF. For both genders, mean scores fell below the mid-way point on the scale suggesting generally unfavourable attitudes towards these GM foods. However, scores for attitudes towards the GM-FF (Table 3) differed by gender, with females being more negative in their attitudes. Mean

Predictors Whilst there was generally high internal consistency within the main PMT composite independent variables, some items were treated separately due to low Cronbach’s alphas ðaÞ; indicative of poor internal consistency. Specifically, Vulnerability (three items, a ¼ 0:71) remained as one variable. However, ‘Being vulnerable to memory loss’ (labelled ‘importance of vulnerability’) was treated as a separate variable. Also the categorical vulnerability variables (‘my age group’s’, ‘someone important to me’; and ‘spouse/partner’s’ vulnerability) were treated as a separate independent variable (labelled ‘important others vulnerability’). The variable ‘Severity’ (two items, a ¼ 0:63) was retained as one variable. For the product specific variable ‘Efficacy’ (three items each product), the alpha values were, respectively, for SWEETENED-FF, supplements, NATURAL-FF and GM-FF 0.86, 0.86, 0.88, 0.87). The moderate Cronbach’s alpha for the severity items was attributable to only two items within this variable. Within the efficacy variable, the fourth item (described in Section 2): ‘memory loss is inevitable as one gets older and there is little one can do about it’ was removed and entered into the regression model separately (labelled ‘inevitable’) as its inclusion reduced the internal consistency below acceptable levels. Of the independent (predictor) variables, there were few differences in the composite mean scores according to gender. For the GM-FF only efficacy and self-efficacy were significantly different between males and females. For these functional foods, the mean (SEM) scores for efficacy according to gender, were 3.52 (0.12) and 4.11 (0.15),

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Table 4 Predictors of variance (standardised betas, b; p , 0:01) from the multiple regression for the primary dependent variable: intention to consume each of the functional food (FF) and supplement products Independent variables

Self efficacy Efficacy Severity Importance of vulnerability General vulnerability Important others vulnerability Inevitable

Supplements (R2 ¼ 0:60)

Sweetened FF (R2 ¼ 0:63)

GM FF (R2 ¼ 0:63)

Natural FF (R2 ¼ 0:59)

b

p

b

p

b

p

b

p

0.60 0.16 0.13 0.04 0.08 0.01 0.05

0.00 0.03 0.00 0.37 0.07 0.80 0.22

0.31 0.39 0.15 0.12 0.10 20.01 20.02

0.00 0.00 0.00 0.00 0.03 0.74 0.71

0.27 0.42 0.16 0.12 0.05 0.02 0.01

0.00 0.00 0.00 0.01 0.29 0.59 0.77

0.42 0.35 0.13 0.05 0.05 20.05 0.03

0.00 0.00 0.00 0.27 0.27 0.23 0.43

t ¼ 22:884; p ¼ 0:004 for females and males respectively. For GM-FF self-efficacy mean score (SEM) for the females was 3.2 (0.14) and for males 4.2 (0.20), t ¼ 23:79; p , 0:001: Importantly, however, when the regression slopes for all variables were compared by gender, no significant differences were found and consequently the sample was analysed as a whole. Table 4 shows the results of the multivariate regression analysis for the primary dependent variable: intention to consume. The percentage variance explained (R2 ; the squared multiple correlation of the model) by the main PMT independent variables was generally high (, 60%). Several significant predictors were found and are expressed as standardised b values (that is, for every standardised one unit of change in the independent variable, the dependent variable changes by the value expressed by the b value; Table 4). For the most preferred products (NATURAL-FF and supplements) the perception of the efficacy of the behaviour (response efficacy) was the most important predictor, followed by the respondent’s self-efficacy (confidence to consume). The perceived severity of memory loss and the importance of vulnerability were significant, but less important predictors. For the least preferred products (SWEETENED-FF and GM-FF), self-efficacy was the most important of the significant predictors. Belief in the efficacy of the behaviour was also important for the GM-FF. To a lesser extent,

perceived severity of memory loss was also a significant predictor. Table 5 shows the results of the multivariate regression analysis for the secondary dependent variable: interest in obtaining more information. The percentage variance explained ðR2 Þ by the main PMT independent variables was also generally high (ranging from 57 to 69%) and several significant predictors were found. For the most preferred products (NATURAL-FF and supplements) the perception of the efficacy of taking action was the most important predictor followed by the respondent’s selfefficacy (confidence to consume). The perceived severity of memory loss and importance of vulnerability were significant, but less important predictors. For the least preferred products (SWEETENED-FF and GM-FF), again, self-efficacy was the most important significant predictor. Belief in the efficacy of the behaviour was also important for the GM-FF and, to a lesser extent perceived severity of memory loss was also a significant predictor.

Discussion One of the primary objectives of the present research was to find a theory suitable for predicting intention to consume functional foods and supplements. The adaptation of PMT

Table 5 Predictors of variance (standardised betas, b; p , 0:01) from the multiple regressions for secondary dependent variable: wish for more information on the functional food (FF) and supplement products Independent variables

Self efficacy Efficacy General vulnerability Importance of vulnerability Severity Important others vulnerability Inevitable

Supplements (R2 ¼ 0:57)

Sweetened FF (R2 ¼ 0:62)

Natural FF (R2 ¼ 0:62)

GM FF (R2 ¼ 0:69)

b

p

b

p

b

p

b

p

0.43 0.36 0.12 0.01 0.03 20.01 0.01

0.00 0.00 0.01 0.76 0.41 0.88 0.86

0.54 0.19 0.08 0.07 0.01 0.04 20.04

0.00 0.02 0.09 0.14 0.88 0.38 0.33

0.34 0.42 20.06 0.16 20.02 0.00 20.01

0.00 0.00 0.15 0.00 0.64 0.95 0.71

0.58 0.22 0.09 0.04 0.07 0.05 0.03

0.00 0.00 0.02 0.36 0.04 0.16 0.45


presented here found that generally, there was high internal consistency ðaÞ within the model’s constructs. The model was also successful in explaining a high percentage (59 – 69%) of the variation of intentions to consume functional foods and supplements. Our study adds to a small body literature that has applied the PMT model to eating behaviours or protection by dietary means (Plotnikoff & Higginbotham, 1995; Plotnikoff & Higginbotham, 1998; Smith Klohn & Rogers, 1991; Wurtele, 1988). Given that other models which have previously been used in this context are generally only poor to moderate predictors of eating intentions or behaviours (Baranowski et al., 1999) our findings suggest that there may be value in using a model analogous to the one presented here to study a range of other protective dietary choices such as fruit and vegetable consumption and other dietary protection against chronic diseases. For example, the Theory of Planned Behaviour includes only part of the coping appraisal process, i.e. ‘perceived control’ however it does not assess the efficacy of the behaviour or product as included in PMT. Similarly other theories (in Baranowski et al., 1999 review) do not directly measure threat appraisal. Both cognitive processes were found to be important predictors and are discussed below. The results of the PMT analysis indicated gender differences in intentions to consume the functional foods and supplements, as well as differences between products. Intention to consume was lowest when the product had been genetically modified to improve efficacy, particularly for women. Women had clear preferences for natural (bitter) functional foods or supplements whilst men gave the same rank order but preferred the natural foods over supplements and other products. Our data is supported by a growing literature that women, regardless of culture, have particularly negative attitudes towards GM (Scully, 2003; Subrahmanyan & Cheng, 2000). Intentions to consume the GM product were lower most likely because of the genetic modification intentions were positively correlated with the general (negative) attitude towards genetically modified foods. It has been suggested that poor acceptance of GM foods may be due to the fact that most modifications have only benefited the producers (for example, disease and herbicide resistance, shelf-life) and not the consumer (Magnusson & Hursti, 2002). Previous research on consumer perception of the application of genetic modification in food production has shown similar results (Grunert et al., 2001; Miles & Frewer, 2001). Genetically modified foods are generally believed to be ‘unnatural’ and unpopular across a wide range of products and cultures. We presented a functional food in which the genetic modification was alleged to benefit the consumer by enhancing function (and removal of bitterness in the pilot study). However, these benefits did not offset the overall unacceptability of the GM functional foods. This is in contrast to recent Swedish data (Magnusson

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& Hursti) which found improvement in willingness to purchase GM foods when the GM benefited the consumer directly as improvements in healthiness, or indirectly as environmental benefits. Consistent with our pilot study, that study found no increase in willingness to consume GM foods when taste improvements were offered. Similarly, in the main study, an increase in the efficacy (health benefit) had no effect upon acceptance of GM-FF. Our study was limited in that we only crudely varied the potential efficacy of the products, stating that GM could double the functional capacity of a food to improve memory, and clearly other products were also described as being effective in improving memory. Further studies examining simpler contrasts between consumer benefits of GM products compared to nonGM products would be useful. We created a sweetened functional foods range, hypothesising that added sweeteners would also be perceived as unnatural and unpopular. Indeed, these products seemed to be unacceptable, with this product range scoring below the naturally bitter functional foods and supplements (but above GM products). These results are in accordance with beliefs that consumers’ acceptance of functional foods depends heavily on the perceived naturalness of the product in relation to other product attributes (von Alvensleben, 2001). In our study, respondents found the hypothesised unpalatability of bitter natural foods preferable to potentially more palatable products that had added sweeteners. The common pairing of bitter coffee with the pharmacological effects of caffeine (Zellner, 1991) may have led respondents to interpret our text stimuli in a similar way. However, the acute pharmacological effects of caffeine are less likely with other ‘functional’ products, particularly the example chosen in our study. It has been hypothesised that certain vitamins, minerals and fatty acids have the potential to improve aspects of cognitive function, including memory (Bryan et al., 2001), however the effects are likely to be subtle and dependent upon long-term ingestion. PMT predictors Two cognitive processes were measured by the PMT model with regard to the health threat of memory loss: the coping appraisal process and the threat appraisal process (Maddux & Rogers, 1983). Coping appraisal process Efficacy is located within the coping appraisal process in PMT (Maddux & Rogers, 1983). The perceived efficacy of the behaviour seemed to be the main predictor for the intention to consume the natural functional foods and supplements. This finding is generally congruous with previous research using the PMT (Plotnikoff & Higginbotham, 1995). The efficacy construct most predictive was product specific, suggesting that consumers will demand

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proof of efficacy. General efficacy, as expressed as the ‘inevitability of memory loss’ (fatalism), would not appear to be a problem nor was it predictive in the current study, suggesting that these consumers perceived that the threat of memory loss could potentially be amenable to dietary intervention. The importance of efficacy as a predictor is interesting when the extensive use of supplements by this population segment (48%) is considered. There is evidence for the efficacy of some supplements (e.g. Omega three fatty acids, folate, vitamins B6 and B12) for certain functions but also a lack of evidence for the health benefits of others (e.g. antioxidants) (Davidson & Geohas, 2003). However, in Australia, as in the USA there is minimal regulation and proof of efficacy is not required (Davidson & Geohas; Nesheim, 1999). It is plausible that ambivalent attitudes (Sparks et al., 2001) exist simultaneously for supplements and functional foods and this warrants further research. Functional foods, as food, are subject to different and stricter regulations than supplements. Currently, health claims are proscribed in Australia and Europe but allowed in the USA when substantiated by evidence. It has been observed that in Europe, absence of health claims has hindered the market for functional foods. Conversely, when US health claims were deregulated in 1985 –1995, this particularly encouraged the growth of functional foods in the USA (Bech-Larsen & Grunert, 2003). Subsequently, due to deceptive marketing practices, health claims have been subject to greater regulation in the USA. Indeed there have been calls for even tighter regulation of health claims regarding functional foods (Clydesdale, 1997; Lucchina, 2003) and our findings that consumers’ intention to consume is largely driven by the efficacy of the product lend weight to these calls. Certain evidence-based health claims are likely to be permitted in Australia in the near future (Australia New Zealand Food Authority, 2001). Our study suggests that evidence for the efficacy of these products will indeed be important. This is supported by other research that has observed that because consumers lack nutritional knowledge with which to make judgements they must rely on others to give ‘credence’ to health claims attributed to products (Grunert, 1997). Credibility was not varied in our study and our laboratory (as a governmentfunded agency) is known to have credibility amongst Australian consumers (Cormick, personal communication). Variations in trust and credibility are likely to vary by institution (credible source) and by consumer characteristics (psycho-demographics) in the general area of communicating the benefits of nutraceuticals (Frewer et al., 2001). In a recent US study potential consumers of nutraceuticals, expressed greater trust towards government sources (Surgeon General) than the media or manufacturer (Cardello & Schutz, 2003). Self-efficacy was also an important predictor of intentions to consume, particularly for less preferred products (SWEETENED-FF and GM-FF). This is consistent with

other recent PMT studies on a range of protective behaviours (Boer & Seydel, 1999; Maddux & Rogers, 1983; Plotnikoff & Higginbotham, 1998; Wurtele, 1988) and results from other social psychological models, for example, the Theory of Planned Behaviour with respect to health protection by dietary means (e.g. Cox et al., 1996). Believing in one’s ability to perform the behaviour appears to be a prerequisite for intending to adopt that behaviour. In our study both additives (sweeteners) and GM were disliked technologies and the ability to consume such products was low. Threat appraisal process We deliberately sampled respondents who had reported variation in perceived vulnerability to memory loss (high and low scoring respondents to a previous study). Vulnerability is a component of the threat appraisal process within PMT, and the previously reported perceived vulnerability was confirmed by our own data. It is also noteworthy that the construct ‘vulnerability’ was not cohesive as one item in our study and that separate items were used as predictors suggesting that vulnerability is multidimensional. Vulnerability tended to be a minor, though significant, predictor of variation in intention to consume (or want more information). It was a significant predictor only for the preferred products (NATURAL-FF and Supplements). This suggests that perceived vulnerability will not drive consumers towards putative remedial products that have disliked ingredients, or are produced by technologies that are unpopular. This would appear to be a judgement of relative risks and benefits on the part of the participant, and the technology may represent a barrier that subsumes the perceived vulnerability. The literature has been inconsistent in his respect, finding some support from PMT measures of cardiac patients (Plotnikoff & Higginbotham, 1995; Plotnikoff & Higginbotham, 1998) whose vulnerability did not overcome barriers to exercise behaviour. Conversely, in those same studies an association was found between perceived vulnerability and adoption of a low-fat diet, perhaps perceived to be an easier behaviour to adopt. A strength of this application of PMT was that the explained variances ðR2 Þ of our models were generally very high (59 – 69%). Because the model looks promising in this regard, future research could extend upon these findings and look at more specific products or product groups that had ‘function’ and/or produce ‘actual’ products for consumption. The high explained variances accounted for in our study are particularly high for a PMT study (Floyd et al., 2000) suggesting that PMT is not necessarily the optimum model for the study of all health behaviours however only further studies will reveal if PMT is particularly appropriate for understanding functional food preferences. The functional foods and supplement in the present study were fictional and only text descriptions were given of the four products. A disadvantage of the method was that


the information available to participants about each product range was both abstract and limited. In a recent study, attitudes to concrete examples of functional foods were much more positive than attitudes to the concept of functional foods (Poulsen, 1999). However, ethical considerations restricted a study incorporating consumption of a ‘functional food’ when that food does not yet exist (even though we offered to debrief volunteers post-experiment). Using abstract stimuli in our postal study resulted in a high response rate and therefore more representative sample. In contrast laboratory studies that facilitate ingestion of stimuli may only attract a certain type of volunteer thus creating response bias. Such considerations should be taken into account when designing future studies. We particularly chose a novel functional food so as to avoid preconceived attitudes and because of a strategic interest in the area of diet and cognition however further studies on ‘actual’ products that allow for the measurement of affective responses are required. We acknowledge that the abstract presentation of the stimuli may have influenced the preferences for natural functional foods as no sensory responses were possible. Consumers may say they want natural products but in practice may choose products that suit their sensory preferences (as well as convenience, cost, etc.). Such trade-offs in product choice require further investigations. We presented the four products in eight different orders to participants and found no systematic order effect upon the variables measured. A future refinement of the product text scenarios could be an adoption of conjoint study designs (Bech-Larsen & Grunert, 2003) presenting various combinations of attributes and levels.

Conclusion PMT proved to be a useful means of identifying variance in the intention to consume functional foods to improve memory amongst middle-aged men and women. The answers to our four research questions were: (1) there was no clear distinction between supplements and functional foods in general but rather for preferred products (NATURAL-FF and supplements) ‘efficacy’ was the most important predictor and for the less preferred products (SWEETENED-FF and GM-FF) ‘self-efficacy’ was the most important predictor. Regression analyses indicated that predictors of intention to consume functional foods or supplements were dependent upon preference. (2) Intentions to consume naturally bitter functional foods and supplements were similar for females but not for males. (3) Sweetened functional foods to offset bitterness were not acceptable, however, no actual tasting was undertaken which limits this finding. (4) Improving the efficacy of functional foods by genetic modification was not acceptable.

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Acknowledgements The study was supported by CSIRO Health Sciences and Nutrition Consumer Sciences strategic funding. We thank Eva Calvaresi for use of the Midlife sample and unpublished data on perceived memory loss and Phillip Leppard for statistical help. Annemarie Koster undertook the pilot study as a student intern at CSIRO in partial fulfilment of a degree in Nutrition and Health (Wageningen University, The Netherlands).

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