Date Published: March 07, 2018
Publisher: Oxford University Press
Author(s): David J Mela, Elizabeth M Woolner.
There is consistent public guidance to limit sugars intakes. However, WHO recommendations are for “free” sugars, whereas some other guidance documents and public discussion focus on “added” sugars, and globally most food labeling states “total” sugars. Total sugars comprise all mono- and disaccharides, regardless of source, whereas both added and free sugars exclude the sugars that naturally occur in dairy products and intact fruit and vegetables. Definitions of added and free sugars differ mainly in their respective exclusion or inclusion of sugars in juiced or pureed fruit and vegetables. To date, there has been little evidence-based analysis of the scientific basis for these different sugar classifications or implications of their adoption for consumer communication and nutrition labeling. Evidence of discriminating relations of total compared with added or free sugars with weight gain or energy intake, type 2 diabetes, and dental caries was identified from recent systematic reviews and meta-analyses. The relations were weakest for total sugars and most consistent for dietary sources corresponding to free sugars (including sugars added to and in fruit juices). Consideration of these health outcomes suggests that the emphasis for intake monitoring, public health guidance, and consumer communication should be on free sugars. However, at present, the adoption of free sugars for these purposes would also carry challenges related to implementation, including consumer understanding, consensus on specifications, and current (labeling) regulations.
There is consistent guidance to the public to reduce or limit intakes of sugars, which has been accompanied by public health policies and commercial action (e.g., product reformulations) intended to help achieve this goal. In 2015, for example, major evidence-based risk assessments with quantitative recommendations for sugars intakes were published by 3 major independent authorities: the WHO (1), the Scientific Advisory Committee on Nutrition (SACN) (2) in the United Kingdom, and the Dietary Guidelines Advisory Committee (DGAC) (3) in the United States. The recommendations and their quantitative basis are briefly summarized in Table 1. These indicate a relatively good consensus where the same outcomes were assessed, although the quantitative recommendations have different derivations. Furthermore, although WHO and SACN make their recommendations on “free” sugars, the DGAC recommendation is for “added” sugars. This variation is also apparent in recommendations from other international authorities (4, 5). It is, however, notable that none of these organizations base their recommendations on “total” sugars, although globally that is most commonly used for labeling and informing consumers about the sugar contents of foods and beverages.
Broadly accepted definitions of total, added, and free sugars are given in Table 2 (5–8). The differentiation between added and free sugars is particularly relevant. All added sugars are also free sugars, and both exclude all of the naturally occurring sugars in dairy foods and in intact (fresh, cooked, or dried) fruit and vegetables. The key distinction between added and free sugars is that the latter includes all naturally occurring sugars in nonintact (i.e., juiced or pureed) fruit and vegetables. However, as noted by others (5, 7–9) and considered in further detail below, there still are some inconsistencies and gray areas to be resolved in defining added and free sugars for research, monitoring, and labeling, as well as for public health and policy uses.
The research evidence base for sugars often does not explicitly define or differentiate exposures sufficiently to allow for direct analysis of total compared with added or free sugars. These limitations arise from the way that dietary data are collected and coded, the lack of standardization in the categorization of sugars in foods or beverages (especially fruit-based products), and differences between nutrient databases (5). The literature on sugar-health relations is dominated by research on total sugars (as a nutrient) and on commercially manufactured soft drinks, intakes of which are relatively easily defined and measured and that make a substantial single-category contribution to total, added, and free sugar intakes in many regions.
Taken together, the evidence summarized here underscores the point that, although the molecules are the same, there is an important differentiation in the relations of health risks to sugars delivered by different dietary sources, which supports distinctions between total, added, and free sugars. For energy intake and weight gain, it seems reasonable to conclude that concern should be directed at free (compared with total or just added) sugars. For diabetes, it is clear that total sugars fails to distinguish the exposures associated with adverse risks, although the evidence is mixed as to whether the greater diabetes risk reported for manufactured SSBs (reflecting added sugars) is also shared by pure fruit juices (reflecting free sugars). For dental caries, there is also some evidence favoring an emphasis on free sugars, and no clear justification for limiting this only to added sugars. The evidence does not implicate the naturally occurring sugar (lactose) in dairy products in any of these outcomes, although assignment of any relations to the lactose component specifically would in any case be difficult.
Solely on the basis of relations with health outcomes, free sugars may be seen as the most relevant basis for sugars-related public health action. However, there are important challenges to be addressed in implementing free (compared with total or added) sugars in regulation and public health guidance. These mainly fall under 3 headings, as outlined in the following sections.
Relative to total and added sugars, the term “free sugars” best conveys the nature and sources of dietary sugars that are most consistently related to risks of positive energy balance, and that are also associated with diabetes and dental caries. Free sugars are also the basis for recent international policy recommendations on sugars (1). However, successful implementation of free sugars as a basis for intake assessment, public health guidance, and consumer communication would benefit from a consistent and globally harmonized specification, wider recognition and use of the term in the expert and regulatory communities, and assurance that the concept is understood by consumers.