The impact of healthy nutrition education based on traffic light labels on food selection, preference, and consumption in patients with acute coronary syndrome: a randomized clinical trial

Acute coronary syndrome (ACS) is the most common heart disease and the most significant cause of death and disability-adjusted life years (DALYs) worldwide [1]. ACS is a group of clinical symptoms corresponding to acute myocardial ischemia and has a significant clinical and financial impact. Clinical variants of ACS include unstable angina and acute myocardial infarction (AMI) with or without ST-segment elevation [2]. Globally coronary artery diseases cause approximately 7 million yearly deaths [3]. Coronary artery diseases are also the first cause of death in people over 35 years of age in Iran and cause 39.3% of all deaths in the country [4].

These patients are discharged from the hospital after treatment, but due to the chronic nature of the disease, people who survive the first ischemic attack are at greater risk for cardiovascular events in the future [5]; ACS patients are 20% more at risk than people without coronary artery disease during the five years after an ischemic attack [6, 7]. The most important behavioral risk factors for cardiovascular diseases are inactivity, an unhealthy diet, and smoking. By changing these risk factors, many cases of cardiovascular diseases can be prevented [8]. Secondary prevention guidelines encourage these patients to consume heart-protecting foods (fruits, vegetables, olive oil, and whole grains) and avoid consuming heart-damaging foods such as sweet drinks, processed meats, and foods containing trans fatty acids. It is also encouraged to limit the amount of sodium consumption.

Despite the availability of these guiding principles, previous studies have reported poor patient adherence to this advice, as patients, especially in low-income countries, tend to maintain their pre-heart attack diet [9].

The extraordinary increase in food-related diseases is due to poor eating habits [10]. Unfortunately, even consumers who are motivated to choose healthy foods sometimes fail to accurately assess the healthiness of food due to barriers to understanding nutrition information and utilizing it [11].

Nutritional information is provided through nutritional education [12]. Nutritional education programs can increase nutritional knowledge and improve nutritional behaviors and therefore help prevent many chronic diseases such as cancer, diabetes and cardiovascular diseases [13]. The findings of Pem et al.‘s study showed that a nutrition education program is a promising strategy for nutritional behaviors. Participants who received nutrition education had fundamental changes in their behavior, knowledge, and attitude towards healthier eating, the amount of fruit consumption increased while the consumption of snacks rich in sugar and fat decreased. However, the consumption of vegetables, energy intake, body mass index and physical activity level did not change after training [14]. In Mohammadi et al.‘s study, the educational method was effective in improving the level of nutritional awareness, weight loss motivation, and people’s performance, but people’s attitudes towards the correct consumption of food did not change [15].

The traffic light label (TLL) is a type of front-of-package food labeling (FOPL) proposed by the British Food Standards Agency in 2006. The TLL is an effective tool for conveying complex nutritional information that, by being placed on the front of food packaging, can potentially contribute to reducing the consumption of products with high levels of fat, salt, and sugar. A feature of this label is that it categorizes according to color, with “little” recognized by green, “medium” by yellow, and “high” by red. The amount of energy is also shown in white [10]. In Iran, since 2014, the Food and Drug Organization has required TLL with five factors (energy, fat, salt, sugar, and trans fat) on all packaged food products, except for some exceptions. The energy is shown in kilocalories; the other factors are in grams per 100 g or 100 ml of the food. By providing nutritional information on the front of food packaging, TLL helps people choose food according to their physical conditions and personal needs and thus reduces the burden of chronic diseases [16]. This label can be understood without having nutritional literacy, so it has the potential to be used by the majority of people in society [17]. In addition, the need to disclose nutritional information can encourage food manufacturers to improve the nutritional profile of their products [18].

Previous evidence has shown that food labeling in a cafeteria in Boston, as well as in a sports recreation venue in Canada and a restaurant in Taiwan, increased the purchase of healthier products and decreased the purchase of unhealthy products [19‐21]. In contrast, a study in England and Australia reported no change in the sale of healthier products after introducing the TLL label [22, 23]. Despite the limited studies investigating the effect of TLL on the selection and consumption of food items in healthy populations, no study was found that used TLL to educate patients with a history of hospitalization. Therefore, we hypothesized that introducing TLL to ACS patients would improve their food choices, preferences, and consumption, enabling them to prevent chronic diseases. This study was conducted to determine the effectiveness of using TLL in patient education on food selection, preference, and consumption in ACS patients.

This study found that the intervention group, who received routine patient education by hospital staff and TLL label training by the research team, scored higher than the control group, who received only routine patient education by hospital staff. This result means the intervention group chose, preferred, and consumed healthier food than the control group. These findings suggest that teaching the use of TLL can enhance the effectiveness of patient education and help reduce the burden of ACS in the long run.

The findings from this study are consistent with previous studies that reported positive effects of TLL on food purchasing and consumption behaviors [19, 20, 24]. However, they contrast with some studies that found no relationship between TLL and sales of healthier products [22, 23]. These discrepancies may be due to differences in the settings, populations, and methods of the studies.

To understand the complex nutritional information on food labels by the participants of the intervention group, even the participants who had a low level of education, we taught them to use the TLL label to prefer, choose and consume healthier food with only a few colors. Therefore, teaching the use of TLL can enhance the effectiveness of patient education and help reduce the burden of ACS in the long run.

For instance, Sonnenberg et al. conducted a study in an American hospital in 2010. They labeled foods sold in a cafeteria. A customer survey was carried out during a 2-week baseline period and a 7-week intervention period, with purchases monitored throughout. The study found that traffic light food labeling increased consumer awareness of food and beverage healthiness at the point of purchase. More consumers reported looking at nutrition information during the labeling intervention than the baseline period, and those who noticed the labels bought a higher proportion of healthy items.

Similarly, Olstad et al. used traffic light labels to improve food choices in a recreational and sports venue in Canada. They monitored product sales one week before and one week after food product labeling. The traffic light icons (green, yellow, and red) were placed on the menu screen or directly on the product shelf, and explanatory sheets were placed in the study environment. The study concluded that nutrition guidance labels effectively increased the sale of healthy foods and reduced the sale of unhealthy foods.

In Iran, Esfandiari et al. conducted a study to investigate the effectiveness of education on awareness, attitude, and performance based on the color indicator of appropriate food products. Students’ knowledge, attitude, and performance about the nutritional color indicator were measured using a questionnaire. Training was conducted face-to-face using an educational pamphlet. The questionnaire was filled out again by the participants 3–6 months after the training. The results show improvements in knowledge, attitude, and performance scores compared to before the training.

In contrast, Sacks et al.‘s study in the United Kingdom examined consumer food purchasing changes after TLL labeling to evaluate the label’s impact on the “healthiness” of purchased foods. The sales of two groups of products (prepared foods and sandwiches) were divided according to their healthiness. Comparisons were made before and four weeks after TLL labeling. The results show that the sales of prepared foods increased immediately after introducing the traffic light label. However, the sale of sandwiches did not change significantly after the introduction of labels. There was no association between changes in product sales and product healthiness [22].

A study conducted by Sacks and colleagues in Australia analyzed the changes in online food purchases over a period of 10 weeks, following the implementation of the Traffic Light Nutrition Information (TLNI) system. Four colored traffic light symbols indicated the amount of fat, saturated fat, sugar, and sodium. These were displayed for 53 products in the intervention store alongside the product list. No nutritional information was provided in the comparison shop. No association was seen between the sales changes in the two stores and the health value of the products [23].

This study had some limitations. First, it only assessed the short-term effect of patient education using TLL, so the long-term impact remains unknown. Second, it did not measure the effect of patient education using TLL on nutritional variables such as anthropometric, biochemical, clinical, and dietary indicators. Therefore, future studies should examine these endpoints and follow up with ACS patients for extended periods to evaluate the sustainability and impact of TLL label training on their health outcomes. The study also faced a limitation due to not completing the post-test, leading to the loss to follow-up of many participants. To mitigate this, we compared the demographic characteristics of participants who completed the post-test and those who didn’t. The analysis shows no significant differences in age, gender, or education level between these groups, suggesting that the attrition is unlikely to have introduced a significant bias in our results.

The present study was a randomized controlled trial (RCT) aimed at assessing the efficacy of traffic light labeling (TLL) training on food selection, preference, and consumption among individuals who recently experienced acute coronary syndrome (ACS). The findings indicate that combining TLL training with standard hospital patient education yields superior results compared to the latter alone. Although the study was restricted to ACS patients, it is recommended that future research extend this to healthy individuals with cardiovascular risk factors, as well as those with a history of ACS who have been discharged for a significant period. The results underscore the importance of incorporating TLL education into nutritional guidance for ACS patients and suggest integrating TLL training into hospital education programs. Moreover, placing TLL educational posters in hospital cafeterias and near vending machines may foster healthier dietary habits among patients and staff. The study further proposes extending TLL training to other environments such as schools, workplaces, and supermarkets to promote healthier eating habits in the wider public. It is important to note, however, that this recommendation is only applicable to countries that use TLL on their products, and other countries may require different types of education. Additionally, this educational strategy should be considered as a single component of a patient’s education plan for healthy nutrition.