Factors that Influence the Perceived Healthiness of Food—Review

The interest of consumers is the consumption of healthy food, whereas the interest of food manufacturers is that consumers recognize the produced “healthier” food items on the shelves, so they can satisfy their demands. This way, identifying the factors that influence the perceived healthiness of food products is a mutual interest. What causes consumers to consider one product more beneficial to health than another? In recent years, numerous studies have been published on the topic of the influence of several health-related factors on consumer perception. This analysis collected and categorized the research results related to this question. This review collects 59 articles with the help of the search engines Science Direct, Wiley Online Library, MDPI and Emerald Insight between 1 January 2014 and 31 March 2019. Our paper yielded six separate categories that influence consumers in their perception of the healthiness of food items: the communicated information—like FoP labels and health claims, the product category, the shape and colour of the product packaging, the ingredients of the product, the organic origin of the product, and the taste and other sensory features of the product.


Introduction
Which food can be considered beneficial to health? Science and consumers answer this question differently. According to certain sources, there is no precise definition of what can be considered healthy food, or else existing definitions are not yet appropriate [1][2][3]. The understanding of the category of "healthy food" differs even among experts; moreover, some treat the words "healthy" and "nutritious" as synonyms [4,5]. What can be considered healthy for whom depends on gender, age, metabolism, obesity, diseases or sensitivities. A nutritious food product generally considered definitely beneficial to health with several positive effects in case of certain diseases can be harmful for consumers suffering from other diseases [6].
Let us illustrate the effort to define healthy food with two examples. In their article, Zaheer and Bach [7] (p. 1) applied the following definition: "Per the United States Food & Drug Administration (FDA), Healthy foods are defined as those that are "low in fat, low in saturated fat, contain at least 10% of daily value for vitamins A, C, calcium, iron, protein fiber" and are limited in amount of sodium and cholesterol (USFDA)." Rodman and his colleagues [5] (p. 83) employed the following definition for their research: "Foods that provide essential nutrients and energy to sustain growth, health and life while satiating hunger; usually fresh or minimally processed foods, naturally dense in nutrients, that when eaten in moderation and in combination with other foods, sustain growth, repair and maintain vital processes, promote longevity, reduce disease, and strengthen and maintain the body and its functions. Healthy foods do not contain ingredients that contribute to disease or impede recovery when consumed at normal levels. (University of Washington Center for Public Health Nutrition (UWCPHN) 2013 [8])".
Dieticians argue that there is no such thing as healthy or unhealthy food; instead, there is only appropriate or inappropriate diet (e.g., [1]). However, since consumers consider certain foods healthy, while others unhealthy, it is important for us to know how they make this distinction. Mai and Hoffman [9] (p. 8) use the term perceived healthiness, which, based on Howlett et al. [10], they define as "Perceived healthiness is a consumer's expectation of a product's influence on his or her state of health". The importance of "perceived healthiness" is also supported by the research findings on health claims by Steinhauser and colleagues [11] that the higher the level of perceived healthiness of a product is, the more likely it is that the product will be purchased. All this becomes a factor that also increases the willingness to pay and purchase if it takes into account what influences the credibility of the health benefits of a product [12].
The effects of food on health is a widely researched topic, which gets attention from various aspects, thus our knowledge-base related to its consumer perception is also expanding. In their review, Niebylski and colleagues [13] examined the effects of taxation, subsidies and easy access on the consumption of products considered healthy. According to the results of Provencher and Jacob's review [14] specifically on perceived healthiness, cognitive factors-among them, brand and type of product-have an effect on the perceived healthiness of food, but such features do not influence the choice and intake of food. The reviews of Alba and Williams [15], and Krishna [16] highlight the topic that continues to be researched ever since, namely that the perceived healthiness of food has an effect also on the assessment of the taste of food (e.g., [17,18]). However, research attests that the perception of the healthiness of food is not influenced by one factor only, but by a combination of factors [19,20], so we can state that this topic is highly complex and important both for consumers and companies.
The aim of our literature review is to assemble earlier research and survey the factors that influence consumers in their perception of the healthiness of food.

Research Methodology
In an attempt to access the articles related to the perceived healthiness of food, we employed several search engines-Science Direct, MDPI, Emerald Insight, Wiley Online Library-in our literature analysis. In recent years, numerous review-type articles touching on the topic of healthiness have been published (e.g., [12][13][14][15][16][17][18]21,22]), but they only fleetingly mention the issue. The present literature review, however, specifically approaches the topic from the consumers' point of view and so examines the factors which, according to research literature, influence consumer perception of the healthiness of food.
Between 2012 and 2016, several review articles touched on the topic of perceived healthiness of food [13,15,16,21,22] or chose it as their main topic [14]. However, it has remained a widely researched area ever since, so we focused on the time period that followed. Articles published between 1 January 2014 and 31 March 2019 were selected using the following terms: "perceived healthiness of food" II.
"evaluating food product healthfulness" OR "evaluation of food healthiness" We looked for the terms in the title, the abstract or among the key words; naturally, because of the way they work, there were slight differences when using the different search engines.
In the I. case, on the ScienceDirect surface we looked for the exact term "perceived healthiness" in quotation marks in the "title, abstract or keywords" fields, while "food" appeared in the "terms" field. On the MDPI page, a very similar method was used, "perceived healthiness"-again in quotation marks-was searched for in the abstract, while "food" was searched for in "all fields". Between the two terms specified in quotation marks, we used the AND relationship to make sure that the search results include both terms. On the Emerald Insight surface, we looked for the complete terms in the abstract and the title, while with Wiley Online Library, in the abstract only, without quotation marks.
In the II. case, on the ScienceDirect search field first "evaluating healthiness", then "evaluation of healthiness" in quotation marks was in the "title, abstract or keywords" field, while "food" was in the terms field. Very similarly to this and point I, on MDPI, the previously mentioned terms were searched for in the abstract, while the term "foods" was searched for in all fields. Just like in the first case, we ran the search with the AND relationship between the search terms. With Wiley and Emerald Insight, we collected the articles in a similar way, looking for the terms in the abstract only and in the title and the abstract, respectively. The search results and the filtering of hits are illustrated in Figure 1.
Nutrients 2020, 12, x FOR PEER REVIEW 3 of 20 In the II. case, on the ScienceDirect search field first "evaluating healthiness", then "evaluation of healthiness" in quotation marks was in the "title, abstract or keywords" field, while "food" was in the terms field. Very similarly to this and point I, on MDPI, the previously mentioned terms were searched for in the abstract, while the term "foods" was searched for in all fields. Just like in the first case, we ran the search with the AND relationship between the search terms. With Wiley and Emerald Insight, we collected the articles in a similar way, looking for the terms in the abstract only and in the title and the abstract, respectively. The search results and the filtering of hits are illustrated in Figure  1.  In our analysis, we specifically focused on the products of the food industry, so we did not include research on restaurants, catering establishments, and those on various casseroles, boiled and fried foods served on plates. Moreover, articles on children's dietary habits and on healthy food provision were also not included. The accessed full-length articles were evaluated by two authors (B.P. and Á.T.). Any contested issues were resolved by three authors (B.P., Á.T. and Z.L.).

Results
The main question of our research is what influences consumers in their perception of the positive effects of a given product on health, which, for the sake of simplification, we will refer to as the healthiness of the product. We provide a comprehensive display of the main results of the articles on the topic in Table 1, then we analyse them, reviewing the points of agreement and opposition. • Although a bio label influences perceived healthiness, it does not increase the consumption of such products among "health externals" Vila-López and Küster-Boluda [32] 2018 Spain Experimental sessions 300 • Younger consumers are more influenced by aesthetic/commercial signs (colours) than by "technical cues" (healthy messages) To make processed meat products healthier, participants would decrease the sodiumand fat content rather than add health-preserving ingredients "the organic halo effect on hedonic evaluation and purchase intention was totally mediated by increases in sensory ratings and perceived healthiness, providing a process explanation for this effect" • indicating the organic origin of the product significantly increased its perceived healthiness  The taste and other sensory features of the product [41,44,52,70,79].
The perceived healthiness of a food product is influenced by numerous factors. For bigger clarity, the main points of the research results are summarized in Figure 2. • happier people are more variety seeking in the case of healthful products or products they are not familiar with, while sadder people are more open to variety in the case of hedonic or familiar products • The type of the product "(hedonic vs. Healthful products)" influences the relationship between variety seeking and the mood of the consumer The taste and other sensory features of the product [41,44,52,70,79].
The perceived healthiness of a food product is influenced by numerous factors. For bigger clarity, the main points of the research results are summarized in Figure 2.

The Effect of the Communicated Information on the Perceived Healthiness of a Product
When companies provide consumers with information related to nutritional value or to health effects in some way on the product packaging, it has a positive effect on perceived healthiness [26,[34][35][36]47]. At the same time, care must be taken that consumers comprehend this information correctly, so that they do not evoke undesired associations [62], and consumer scepticism related to health claims must also be taken into account [74], as in this case information may even have a negative effect on assessing healthiness.

The Effect of the Communicated Information on the Perceived Healthiness of a Product
When companies provide consumers with information related to nutritional value or to health effects in some way on the product packaging, it has a positive effect on perceived healthiness [26,[34][35][36]47]. At the same time, care must be taken that consumers comprehend this information correctly, so that they do not evoke undesired associations [62], and consumer scepticism related to health claims must also be taken into account [74], as in this case information may even have a negative effect on assessing healthiness.
All this also entails how much of the messages communicated through the product a consumer will comprehend and thus how healthy they will perceive the product. This is supported by the previous knowledge of the consumer, which influences perceived healthiness to a great extent [27,69,78]. Moreover, perceived healthiness of a product is further improved by adding a picture of the product to the communicated information [36] and is also affected by FoP labels and health claims [26,34,38,53].
Although several studies show that FoP labels help consumers choose healthier foods [26,34], due to the diversity of FoP labels, it cannot be clearly stated that their use always helps greatly in increasing the perceived healthiness of the product [53].
The health motivation of the consumer also influences the assessment of the product; Machín et al. [26] maintain that it plays a pivotal role in the way front of package information is used. In contrast, according to the results of Rebouças et al. [47], consumer interest in healthy nutrition does not influence the acceptance and perceived healthiness and nutritional value of the product they examined ("cashew nut beverage").

The Influence of the Shape and Colour of the Product Packaging
Research results confirm that the shape and colour of the product packaging influence the perceived healthiness of the product, but from certain aspects the results contradict each other. Whereas Marques et al. [23] maintain that a product is perceived to be healthier in a rounded packaging, other researchers [28,61] claim that consumers perceive a product healthier in angular shaped packaging. A further result related to the shape of the packaging is that packaging resembling a slim human figure is perceived healthier [25].
The influence of the colour of the packaging has also been examined by several researchers. According to the results of Marques et al.'s research [23], buttered products were perceived healthier in a red and yellow coloured packaging. The effect of the colour red is mentioned by several other studies. Wąsowicz et al. [66], along with yellow, green and blue, mention the colour red as a colour referring to health. At the same time, Reutner et al. [71] assert that the colour red can have a significant effect on the refusal of unhealthy foods. Certain colours and hues, however, can imply that the product is less healthy: research participants considered dark glass [45] and colours hinting at artificiality ("heather", "pink", "celadon") [66] to be referring to unhealthy or less healthy products.
Contrasts resulting from the perception of colour can be attributed to the variety of products and their different packaging investigated in the studies; so it is possible that in the case of a buttered product, the red & yellow colour combination found by Marques et al. [23] was perceived healthier, while it can be different for other products. Therefore, when discussing the effect of colour, it is important to acknowledge the influence of product category. Differences between countries are also important; so for example, in Denmark, paler, whereas in the United States, balanced colour tones are more standard on healthy products [28]. Moreover, the effect of colour can differ according to the age of the consumer: for example, with young people, colours have a stronger effect than health messages [32].

The Effect of the Ingredients of a Product on its Perceived Healthiness
Results related to ingredients show that consumers mostly pay attention to the ingredients that nutrition experts emphasize in relation to healthy nutrition. The majority of the research studies we have examined address sodium-and fat content as well as omega-3 content. According to the results of Lazzarini et al.'s [59] research, the fat content of a product is an indicator of perceived healthiness for consumers.
Whether it is Bolognese sauce, frankfurter sausages, or other processed meat products, consumers prefer a reduced sodium-and fat content, so that is how a company can make consumers perceive these products healthier [24,29,39]. Moreover, while there are consumers who rely on the fatand fibre content of the product for its perceived healthiness [64], others ignore the protein-, sodium-, and saturated fat content when making decisions [76].
The other ingredient featuring in numerous studies was omega-3.
In several cases, consumers would choose to change an ingredient other than the fatty acid [24], or they did not consider the product suitable for the addition of omega-3 [29]; at the same time, they prefer if omega-3 fatty acid is added to the product rather than if nothing is added [40].

The Effect of Product Category on Perceived Healthiness
Perceived healthiness is also influenced by the product or product category [75,78]; in fact, in Orquin's [78] research, product category emerged as one of the two main factors based on which consumers perceived the healthiness of a product. In the studies, products assigned to different categories according to different criteria were compared. Fenko et al. [61] compared consumer perception of cereal-and buttered cookies, of which consumers perceived cereal cookies healthier. Vasiljevic et al. [70] compared muesli bars and chocolate, and their results show that, regardless of label, consumers perceived chocolate tastier and muesli bars healthier. According to Maehle et al.'s [75] surprising result, consumers are less concerned about the healthiness of the product if they consume it for the nutritional value (utilitarian products), than in the case of products consumed for pleasure (hedonic products).

The Effect of Organic Origin on Perceived Healthiness
Results of numerous studies have confirmed a positive effect of organic origin on the perceived healthiness of a product [42,45,48,51,68]. In addition, organic origin also facilitates the understanding of the communication of "healthy food" [5]. Health-conscious consumers also tend to show openness towards bio foods and generally ignore the health-related messages of functional foods [46].

The Effect of the Sensory Features of the Product on Perceived Healthiness
The sensory features of the product also play a role in its perceived healthiness. The taste and other sensory features of the product may dominate over the perception of healthiness [41,52,79], and if the sensory features of the product do not satisfy the consumer, then communicating the nutritional value is not enough to make the product accepted [44].

Discussion
The aim of our literature analysis was to explore the factors that influence the perceived healthiness of food products. Numerous studies set out to discover what influences the perceived healthiness of individual products in the time period we focused on. In the present article, we only considered research results related to foods.
Based on the research results, we identified six categories that influence perceived healthiness of a product: the effect of the communicated information, product category, the shape and colour of the product packaging, the ingredients of the product, the organic origin of the product and the taste and other sensory features of the product.
The effect of the communicated information clearly influences perceived healthiness; at the same time, previous knowledge clearly affects how this information influences perception. Product category is a main factor in the perceived healthiness of a product. In recent years, a diverse range of product categories has been tested, which makes generalizations difficult.
The most numerous contradictory research results were related to the shape and colour of the product packaging, which calls for further investigation. Research results are ambiguous concerning whether angular or rounded packaging is more suitable to communicate healthiness. One of the most researched colours is the colour red. Nevertheless, results related to the colour red do not point in the same direction.
Research results related to the ingredients of the product confirm that reducing the sodium-, sugarand fat content increases consumer acceptance of the improved product in terms of health; at the same time, research does not give a definite answer regarding consumer perception of the possible enriching ingredients.
The organic origin of the product positively influences perceived healthiness. Health halo effect emerged in several studies in connection with bio products.
Basically, the taste and other sensory features of the product dominate over perception of healthiness. A common result of the examined studies showed that the unsuitability of sensory features cannot be balanced out by favourable perceived healthiness.
Our collected results and their juxtaposition can help with the proper planning of product development and marketing communication, and they also raise further research questions related to the inconsistent results. Our conclusions can serve as a baseline from several aspects when devising packaging of a new product. They can help with the proper design of the packaging, both in terms of shape and the used colours, and with choosing the right FoP labels. The choice of the labels used on the packaging requires special care. The type of health claim communicated by the company has to be considered carefully, provided that the use of a health claim is effective in the first place. At the same time, it is also important to consider that communicating the different ingredients may be an effective method to reach its goal.
Within the categories, we have found several conflicting results, as well as unanswered research questions, which call for further research. The most important aim of further research may be to gauge the effect of the discovered aspects relative to each other, even comparing all the aspects.
Further research may also aim at clarifying the emerged controversial results, as the research results are not uniform for example in connection with the shape of packaging and colours that evoke a healthy feeling, keeping in mind that these factors may change according to product category. Apart from clarifying discrepancies, further research may take on the task of testing specific features on different food products. Treating the constructed system as a complex entity, it is worth examining whether a different colour and shape of packaging is justified to communicate the health benefits of each food.

Limitations
In the course of our literature analysis, we encountered several barriers that have to be taken into account when evaluating the results. There has not been a review article on the topic since 2016, even though several new studies have been published since then. As we reviewed only the 2014-2019 time period, we can only report the results of the most modern research. The surfaces used for data collection are also important to mention: during the research, we had no access to the surfaces covering the whole literature, therefore we chose the above described search surfaces, where we could access the full-length articles. Our options were limited by the year-to-year changes in the agreement between the Hungarian Electronic Information Service National Programme (EISZ) and Elsevier [81].

Conflicts of Interest:
The authors declare no conflict of interest.