Inclusion criteria

Population: studies involving populations of any age.

Type of outcome measures:

1. Consumption patterns (sugar intake);

2. Health outcomes (body weight, dental health, type 2 diabetes and cardiovascular disease risk).

Type of interventions: Any studies investigating the effectiveness of product reformulation measures to reduce the population's sugar consumption and improve health outcome.

Type of studies: Both quantitative and qualitative research designs will be included in the review. Also, commentaries, editorials, reviews or discussion pieces that focused on reformulation will also be included. Studies will not be selected on methodological quality. However, the number of excluded studies (including reasons for exclusion for those excluded following review of the full text) will be recorded at each stage. Searches will be conducted from 1990 onwards. This is because publications about reformulation, particularly salt reformulation, began to appear in the literature in the early 2000, so setting the search from 1990 will guarantee the capture of any publications published pre-2000.

Exclusion criteria

• Non-English language studies and papers

• Studies published outside of stipulated publication dates

• Studies with no relevant outcome measures.

Search strategy

Electronic database will be systematically searched using a combination of terms, tailored to optimise sensitivity, specificity, and the syntax and functionality of each database (draft search in online supplementary file 1). The databases searched will include the Cochrane Library, EMBASE, MEDLINE (Ovid) and Scopus. The bibliographies of those papers that match inclusion criteria will be searched by hand to identify any further, relevant references, which will be subject to the same screening and selection process. The database search results will be supplemented by hand searches.

In addition to the peer-reviewed literature, a number of grey literature searches will be undertaken using the broad search terms ‘sugar’ and ‘food’ or ‘drink’ and ‘reduction’, these searches will include key government and organisation websites as well as general searches in Google. Despite being named ‘grey literature’, they are an important source of information. Indeed, they may provide more useful information in some areas, such as ours.

Screening and data extraction

All papers identified from the initial electronic search process will be imported into an Endnote library and duplicates will be removed. The eligibility criteria will be applied to the results and all identified references screened independently by two reviewers (KMH and FJH) using a two-stage approach. First stage involves reviewing the title and abstract. Second stage will extract and assess the full text versions of the shortlisted papers. GAM will be consulted where any question or ambiguity arise. A standardised data extraction form will be finalised (see online supplementary file 2). The data extraction form will be piloted prior to its use. Data to be extracted will include authors, year of publication, country, study design, participant characteristics, description of the intervention and study findings.

Quality assessment

Quality appraisals will be carried out for each included study using the Joanna Briggs Institute appraisal tools.39 All data will be extracted and quality assured by two reviewers.

Data synthesis and analysis

The PRISMA flow chart38 will be used to document the number of studies identified during the search process and those excluded and included according to the outlined eligibility criteria (figure 1). The data will be initially analysed through a narrative synthesis method. The availability of appropriate data and resources to conduct a meta-analysis will be considered, where feasible.

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Figure 1

Flow diagram of systematic review.

Gaps and limitations

There are a few gaps and limitations that we want to acknowledge in anticipation of the findings of the systematic review. First, the average sugars intake reported in dietary surveys in adults is likely to be an underestimate of how much free sugars are consumed25 because under-reporting is highly prevalent.26–29 Therefore, any studies of associations with health based on self-reported data may potentially underestimate the effect of reformulation but also underestimate the scale of the policy responses necessary to deal with excessive free sugars intake. Second, free sugars exclude other sugars such as lactose and intrinsic sugars in fruit and vegetables. However, there is no current test that distinguishes these types of sugars and neither does the current labelling requirements for ‘total sugars’. One implication of this is that it is difficult to determine the extent of reformulation in dairy products such as yogurts and milkshakes and in products that contain substantial amounts of fruit and vegetables. This can add a layer of complication when estimating effect of reformulation. Also, this can act as a disincentive to manufacturers to attempt sugar reformulation when their efforts at reduction can be confounded by the presence of milk, fruit and vegetables.

Implications

This systematic review aims to summarise the evidence on the effectiveness of product reformulation measures to reduce the sugar content of food and drink on the population's sugar consumption and health. Results of this systematic review will therefore provide new insights into the approaches tested thus far. The systematic review may also identify specific gaps in the evidence, which would inform agenda for future research and policy.

Amendments

If we need to amend this protocol, the date, rationale and a description of each protocol change will be reported.

Ethics and dissemination

Ethics approval will not be required as this is a protocol for a systematic review. This systematic review will be published in a peer-reviewed journal. It will be disseminated electronically and in print.