Awareness, understanding and use of sodium information labelled on pre-packaged food in Beijing:a cross-sectional study

It is well documented that there is a strong relationship between excessive sodium intake and hypertension [1–4]. Sodium differs from salt (sodium chloride). But for the purpose of this paper, we use “sodium” to mean “salt”. The implementation of effective salt reduction strategies has been regarded as one of the most cost-effective measures to prevent cardiovascular diseases [5–7]. Member States of the World Health Organization (WHO) have agreed to a global target of a 30% reduction in population salt intake by 2025 [8]. Salt intake in China is known to be higher than in most other countries [9, 10], two or three times higher than the 5 g daily limit recommended by WHO [11]. Hence, effective salt reduction programs are urgently needed in China.

Pre-packaged processed foods are the major source of salt intake in developed countries and their consumption is rising in many developing countries [10]. Some governments have initiated national approaches to work with the food industry to reduce salt in foods by setting salt reduction targets [12–14]. Meanwhile, labelling the amount of sodium and/or salt on the nutrition information panel (NIP) of pre-packaged foods is also among health initiatives to reduce salt. Many countries have added sodium or salt to the list of required nutrients that must be declared on the NIP [15–19]. Some countries, like the US, now highlight the sodium content of food in larger, bold font in black on the label, to draw consumers’ attention to the sodium content in pre-packaged food. Although pre-packaged food is not the main source of salt intake in China, the sales and consumption of pre-packaged food are increasing very quickly and becoming an important source of salt intake.

The Chinese Government introduced nutrition labelling regulations (General Rules for Nutrition Labelling of Pre-packaged foods - GB 28050–2011) in 2011 and officially implemented the regulation from January 1, 2013 (Fig. 1). These regulations require all pre-packaged food, with some exceptions (some fresh foods, alcohol, etc.) to display the energy content (kJ), as well as the amount of protein (g), total fat (g), carbohydrate (g) and sodium (mg) on the NIP. The nutritional values are displayed per 100 g, or per 100 ml or per serving of the food. The sodium label or labelling, in this study, means the sodium concentration shown in mg per 100 g or per 100 ml or per serving on the NIP, as well as its nutrient reference value (NRV%).

To our knowledge, few studies have evaluated the awareness, understanding and use of current sodium labelling among Chinese consumers. This cross-sectional study tries to answer these questions and explore the factors associated with them. In this paper, we also recommend changes and improvements to the current sodium labelling system.

In urban Beijing, our survey found that most participants had a good basic knowledge of salt and its harmful effects on health. Over two thirds of participants were aware of the recommended daily salt intake in China and the majority of them recognized the harm of a diet high in salt, believing that reducing salt intake is beneficial. However, only half of the urban adults know the relationship between “sodium” and “salt”, very few people (5.5%) understood the meaning of NRV%, less than one-fifth (19.5%) of them were aware of the sodium label, and only 12.6% used (read or checked) the sodium label while purchasing pre-packaged foods. Those with a higher income and higher education levels had an increased awareness of and understanding of sodium labels. Considering that this was conducted in urban Beijing where people have nearly the highest income and education levels in China, the level of the awareness, understanding of health diets and sodium labels might be less elsewhere in the country.

The high awareness (91.3%) of about the harmfulness of excessive salt intake found in this study reflects the success of Government’s “salt” reduction advocacy. The results showed that, participants with hypertension were no more aware of the “sodium” label than those without hypertension. This might be largely due to the low awareness of the relationship between ‘sodium’ and ‘salt’ as well as the low level of awareness of NRV% and sodium.

In our study, only about one-half (52.3%) of the participants reported knowing the relationship between salt and sodium. A similar study conducted in Japan in 2012 concluded that few people (only 13.3%) understood the correlation of 1000 mg sodium in grams of salt (2.50–2.60 g) [18]. This suggests that the current label of showing salt by sodium content may not be effective in informing consumers of the salt content in food. It would therefore be prudent to update the design and content of the NIP to show salt rather than sodium in order to improve awareness and understanding. This is also suggested by the CODEX Guidelines on Nutrition Labelling [21], and some countries such as UK, have mandatorily required to use “salt” rather than “sodium” on the NIP because the term “salt” is more readily comprehensible by consumers than “sodium” [22].

The reported use of the sodium label in our study was significantly lower than a similar study conducted in New York City (50.0% ± 2.2%) [19]. Moreover, in our logistic regression analysis, although we found that educational levels meant a higher awareness of the sodium label and better understanding of the relationship between salt and sodium, it did not transfer to the use of the sodium label when other factors were controlled. This means that although people with relatively high education levels were equipped with some basic knowledge and understanding of the sodium label, this knowledge did not result in them reading the NIP when shopping. This may be partially due to that health is not always the top driver of food choice.

Compared to the traditional NIP on the back of pack, front-of pack (FoP) labelling may be another effective way to convey sodium or salt information to the public. FoP labelling has been adopted by some countries to provide clearer information on nutrition information of food. In June 2013, the UK introduced a voluntary hybrid front-of-pack system that displays traffic-light colors to indicate whether the salt level is ‘low’ (green), ‘medium’ (amber) or ‘high’ (red), to help consumers make ‘at a glance’ healthier choices [23]. FoP labelling has been proven in various studies to be easier to understand and more effective for consumers in helping them to choose healthier foods [17, 18, 24, 25]. In addition, FoP labelling is believed to encourage food manufactures to reformulate their foods. In the 1980s, Finland introduced legislation to require food products containing a high level of salt to carry a high salt warning [15]. As a result, food companies reformulated their products and some high salt products disappeared completely from many shops.

Assisting consumers to choose lower-salt foods should not be limited to nutrition labelling itself. Smartphone applications by various research groups to help the public choose healthier food. For instance, The George Institute for Global Health launched an ‘app’ called FoodSwitch in 2012 in Australia and more recently in China, which aimed to help consumers choose healthier foods. Consumers scan the barcode on the package of the food and the nutritional information is presented in traffic light colour-coded format. In addition, healthier alternatives will be listed underneath the NIP of the scanned food [26]. Furthermore, the ‘app’ also includes a SaltSwitch filter which allows consumers to choose foods lower in salt [27]. A recent study has shown that SaltSwitch helpful consumers choose low-salt foods [26]. Considering the increasing coverage of smartphone (58% of Chinese people have smartphones) an app might be successful in helping people reduce their salt intake.

However, evidence has shown that the implementation of education and awareness-raising interventions alone are unlikely to be adequate in reducing population salt intake to the recommended levels [28]. New methods of health promotion on salt reduction should also be considered, for example, advocacy in schools. A study conducted in Northern China showed that integrating salt reduction into routine education for primary school children to be very successful. [29].

Several limitations existed in our study. Firstly, the survey was conducted in central districts of Beijing, where the level of awareness of sodium labels is higher than average. Secondly, as the study sample was not population-representative the results may not be representative of the whole country. Thirdly, nearly all the questions we designed were single or multiple choice. This may skew results due to a limited choice for answers on the questionnaire.

Our survey showed that the participants had a good understanding of the harmful effects of salt, but the awareness and use of sodium labels was very low in Beijing. Few people understand what NRV% means on food packaging. There may be less awareness of salt and NIPs nationwide. Efforts should be taken to educate the public to understand and use the NIP better and design clearer ways of displaying such information, such as front-of pack (FoP) labelling or health-related smartphone applications to improve health and help people make better food choices.