Dietary intake by food group of individuals with type 2 diabetes mellitus: A systematic review

Abstract

Aims

To synthesize peer-reviewed literature that investigates the dietary intake by food group of individuals with type 2 diabetes mellitus (T2DM) and compare intakes to national and international dietary guidelines.

Methods

Four electronic databases (MEDLINE, EMBASE, CINAHL and Web of Sciences) were searched for studies that investigated the dietary intake of adults (≥18 years) with T2DM using the five main food groups (fruit, vegetables, dairy, grains and meat/meat alternatives). Food group intake in serves was compared against national guidelines and fruit and vegetable intake in grams was compared against the World Health Organization (WHO) guidelines.

Results

After screening 13,662 publications, 11 studies were included. All reported cross-sectional data. Majority of participants were consuming less than the recommended serves of fruit, vegetables, grains and dairy and were meeting or exceeding the recommended serves for meat/meat alternatives. Two of six studies reported fruit and vegetable recommendations were being met, two reported dairy recommendations were being met and two reported grain recommendations were being met. Of the five studies reporting intake in grams, four met the WHO minimum intake for fruit and vegetables.

Conclusions

Individuals with T2DM do not comply with food group recommendations; particularly for fruit, vegetables, dairy and grains. Longitudinal research is required to better understand how food group intake changes over time after diagnosis.

Introduction

Diabetes is a leading global health emergency estimated to cost US$827 billion per year [1]. In 2015 it was estimated that 415 million adults were living with diabetes worldwide, with 90–95% living with type 2 diabetes mellitus (T2DM) [1], [2]. Most of the burden of T2DM is attributed to macro- and micro-vascular complications, and co-morbidities such as cardiovascular disease; many of which are associated with sub-optimal glycaemic control [3]. Effective glycaemic control can help to prevent or delay such complications and co-morbidities [4]. Strategies to assist individuals to optimize glycaemic control to reduce the individual and economic burden associated with T2DM are urgently required.

Dietary intake is well recognized as influencing glycaemic control [5]. Recommendations to manage T2DM include eating healthy foods to have a high-quality diet [6], [7]. A randomized controlled trial (RCT) conducted in New Zealand that provided healthy foods to a group of individuals (n = 53) with T2DM, saw reductions in HbA1c of 0.4% [8]. A cohort study conducted in the United States (US) showed that individuals (n = 234) with T2DM who followed a healthy diet for 12 months experienced improved HbA1c levels of 0.54% [9]. Clearly, having a healthy diet can improve glycaemic control [8], [9].

A variety of different dietary patterns have been shown to be effective at improving glycaemic control in individuals with T2DM [10], [11]. Assessing dietary intake using dietary patterns based on foods and food groups has become increasingly common in nutritional epidemiology studies [12]. This approach provides a more accurate representation of dietary intake than analysing intake of specific nutrients (e.g. carbohydrate) or dietary constituents (e.g. fibre), that are generally not consumed in isolation [13]. Improvements in diet based on foods and food groups have shown stronger and more consistent associations with reduced risk of adverse health outcomes, compared with improvements of specific nutrients [14]. A systematic review and meta-analysis of 20 RCTs compared the following dietary patterns: low-carbohydrate, high-carbohydrate, Mediterranean, low glycaemic-index, high-protein, vegan and vegetarian, and high-fibre to controls for six months or more in individuals with T2DM [10]. Results showed the low-carbohydrate, Mediterranean, low-glycaemic-index and high-protein diets all led to greater improvements in HbA1c than their respective control diets [10]. While these diets have some differing characteristics, they all encourage consuming unprocessed foods from the five food groups; fruit, vegetables, grains, dairy, and meat/meat alternatives. As a result, management guidelines from several countries recommend that individuals with T2DM adhere to national dietary guidelines expressed in terms of the five food groups [6], [7], [15].

The actual food group intake of individuals with T2DM after diagnosis is currently unclear. Evaluating dietary intake is recognized as an important research activity that can help influence dietary education materials and target nutritional interventions [16]. The purpose of this systematic review was to synthesize and evaluate the peer-reviewed literature that investigates the dietary intake by food group of individuals diagnosed with T2DM and compare intakes to national and international guidelines.