Introduction
Food choice of consumers has a direct link with their health status [
1]. Chronic non-communicable diseases have been considered as an important public health problem during twenty-first century in developing countries such as Iran. Healthy nutrition prevents most of the diseases, including chronic ones [
2]. Food products that have been developed with the purpose of improvement in specific physiological process of the body are known as functional foods (FF). They are found under many food categories. Some of them, fortified with special constituents, enhance physiological functions and also, reduce the risk of diseases [
1,
3]. Accordingly, FF marketed as foods that are capable of improvement of well-being of consumers [
4].
In spite of the importance of FF for physical and mental health, use of FF is not very common. The food choice behavior of consumers depends on many factors like awareness [
5]. Italian consumers reported low knowledge and awareness about FF and accordingly, frequency of FF usage is low [
6]. A total of 78.1% of North American residents were unfamiliar with the term “functional food” [
7]. Several studies indicate that the food choice behavior of consumers not only depends on awareness, but also influenced by demographic factors including gender, age, or education. Furthermore, attitudes and lifestyle factors strongly affect the consumer’s behavior [
8‐
12]. Other significant predictors, including self-efficacy, user’s intention to perform the behavior and subjective norms to consume foods were also reported for the consumer’s choice of FF [
13].
In the food industry, the need for further research into consumer behavior of food choice has been really felt [
13]. Until now, several questionnaires were used to assess the status of consumption of FF and its determinants in different countries [
4‐
6,
8‐
10,
13‐
22], though, these are mainly developed in European and Western countries. It was reported that attitudes and perceptions of consumers highly depends on the resident’s country [
14,
21,
22]. Attitudes of American and Danish consumers were lower than Finnish ones in the evaluation of the effect of culture values on the acceptance of FF [
20]. Limited studies were performed on consumer’s attitudes in Iran toward FF [
23]. No information is available about the status of consumption of FF in Iran. To best of our knowledge, there is no questionnaire in Persian language to be used in Iran for evaluating the consumer’s determinants toward FF. Thus, the aim of the present study was (a) to construct a cultural adopted questionnaire for evaluation of consumer’s attitudes toward functional foods among Iranian’s population and (b) to investigate the attitudes toward vitamin enriched foods (VEF). For this reason, we used the Theory of Planned Behavior (TPB) as a conceptual framework. This theory is one of the most suitable theories for the prediction of healthy behavior. Based on this theory, attitude, subjective norms and perceived control of behavior are determinants of behavioral decision making of people [
24]. These determinants will affect the consumers’ intention to carry out special behavior [
24].
Discussion
In the current study, a reliable and valid questionnaire for assessing the attitudes toward functional foods among Iranian consumers was developed based on the TPB model. As the consumption of FF depends on various factors, a multidimensional questionnaire must be designed. The prepared questionnaire included a wide range of items to test the personal, interpersonal, and social factors relating to functional foods’ perception among consumers. It was exposed to a comprehensive approach of critical analysis to be valid.
In the face validity, two items were excluded from the initial 40 items due to difficulty in comprehension. Among the remained 38 item, 30 of them had a good content validity and subjected to further analysis. According to descriptive statistics, the Cronbach’s alpha of two subscales, including attitudes and subjective norms were satisfactory, but perceived control items was lower than the acceptable range. In order to increase the reliability of the questionnaire, some items [
11] were deleted, but to retain the internal structure of the questionnaire, the authors decided to respect some items. ICC of the subscales was reasonable that shows the good consistency of the items overtime.
According to KMO in EFA analysis, the sample size of the study was adequate. During EFA analysis, the conceptual framework of the study was tried to remain. A total of 16 questions were categorized in three subscales of the proposed model and three items were not properly grouped in theses subscales and excluded.
In order to examine the dimension of the model, several fit indices were used [
34], such as Chi-Square (χ2), GFI, TLI, CFI, PNFI, PCFI, and RMSEA. Cut-off values of model fit indices show acceptable values for the model of TPB for assessing the attitudes toward functional foods among Iranian consumers. Although, GFI was very close to the nominal value of 0.9 [
34]. Some factors including sample size, the number of items, and the degrees of freedom to sample size ratio can be affected GFI and does not indicate poor model fit [
35,
36]. The RMSEA is one of the most popular values of fitness which was in the acceptable range [
34]. Based on the results of CFA analysis, the items showed a good fit for the scale according to the theoretical approach of TPB and properly confirmed by assessed indices.
Furthermore, two subscales of the questionnaire showed adequate reliability. Greater coefficient alphas for the perceived control would be desirable. It may be due to nature of the target group that most of them (71.1%) aren’t the corresponding person of the shopping in the family. Moreover, lower amount of coefficient alphas for the perceived control in comparison with subjective norm or attitudes may be due to low level of awareness of consumer about FF and complex nature of them [
13]. In order to enhance the reliability of the scales, the number of questions should be increased [
23]. It may be produced a more reliable scale, but leads to a longer and less parsimonious model [
37]. Accordingly, a previous study on use of vitamin supplements had a poor reliability on the perceived control items and they assess it with a single self-efficacy item [
13]. They conclude that perceived control is not a significant predictor of consumer’s preference to use health products and might relate to high levels of consumers’ confidence to control their behavior [
13]. Respecting the items, all of them had a strong contribution to the whole questionnaire.
In the current study, about 57.1% of respondents were familiar with the VEF. Previous studies conducted in a number of different countries, reported different level of consumers familiarity with the concept of FF [
7,
16,
23,
38‐
40]. As, 39.4% of high school and university students in Croatia were familiar with the term “functional food” [
38], and 67% of surveyed people in city of Thessaloniki of Greece was unfamiliar with the term FF [
40]. Uruguayan adults had a low familiarity with FF [
16]. 83.6% of university students of Chile had no knowledge of FF [
17]. Hence, people have limited idea regarding the term ‘functional food’.
In the present study, users and nonusers of VEF were similar in both age and sex. Some studies reported similar results [
4,
13,
19,
39], but contradicts the findings of other studies which reported that women consume more functional foods than man and younger people use more FF [
1,
17,
39,
41]. Regarding the role of sex in other studies, it might be relates to the women’s correspondence of shopping in some families and more interested in healthy eating and in health generally. Furthermore, other studies revealed that young people use less functional foods [
1,
4,
17]. Considering the current role of age and FF attitudes among Iranian students, it would seem to be more important to focus on different age groups to clarify the potential influencing factors in FF consumers.
Higher level of parent education was significantly increased the consumption of VEF in the current study. Other studies revealed that educated participants had higher awareness and more willingness to consume FF [
4,
39]. Along the increase of family’s income, the use of VEF was increased. Markovina et al. (2011) also reported that families with higher income are most buyers of FF [
38]. It was also reported in other studies [
17,
39] that the power of pay of family is influenced on the consumed food. Urbanized people consumed the VEF more than rural ones. Participants from urban areas were more aware about FF and more likely to consume FF than rural areas [
39]. Use of FF by urbanized people showed that they were exposed by these foods in the markets, though the FF might be unavailable for rural people. Place of shopping affect the use of VEF. People who purchased from hypermarkets were the most users of VEF. It may be related to the availability of FF in these markets. In the present study, read of food label enhanced the consumption of VEF. Previous studies reported different findings regarding impact of food labels on the consumers’ acceptance of FF. Some of them reported positive effects [
18,
42] and some others released negative ones due to distrust to labels and health claims on the consumption of these products [
43,
44]. It should be noted that reliable information on the food label is a noteworthy point.
In the current study, attitudes and subjective norms were significant determinants of use of VEF. This may reflect that good evaluation of the behavior and social pressure to perform it may increases the likelihood of performing the behavior. Urala and Latheenmaki (2004) reported the positive attitude as one of the strong predictor of use of FF [
9]. The similar results were also reported by other researchers [
17,
41]. Some other studies also revealed the attitudes and subjective norms as strong predictor of nonuser’s willingness to use of vitamin supplements and FF [
13]. Danes or Americans had a less positive attitude towards FF than Finns [
20]. These different attitudes among consumers may be due to diversity of FF in the market or cultural differences among countries [
20]. According to Chen (2011), consumer’s belief in health claims of FF and its safety increased the use of FF [
1]. One of the important factor in relation to test new foods was the recommendation of family or friends [
45].
O’Connor and White (2010) did not report perceived control as determinant of nonuser’s willingness to consume the vitamin supplements or FF [
13]. According to the results of present study, perceived control could not predict the use of VEF. This result may be due to low mean for perceived control measure that reveal the low level of confidence of the consumer to control their behavior as, they are students and had not more options to choose their foods. Also, the study participants were young and they are usually less sensitive on long term health effects of foods than elderly.
One of the main limitations of the current study was the specific age group and university settings, it’s better to perform future studies on different age group especially elderly people or different target group like housewives. It may be lead to stronger confirmation of the current scale. Moreover, TPB is designed for specific behaviors and application of it for dietary behavior may have weakened the prediction especially considering FF that is new for most of people. As the prevention is a major motivation of healthy diet use especially FF, it was proposed to perform future studies on a sample where illness is present.
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