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Meta-Analysis
. 2021 Oct:72:103633.
doi: 10.1016/j.ebiom.2021.103633. Epub 2021 Oct 14.

Dietary factors and risk of islet autoimmunity and type 1 diabetes: a systematic review and meta-analysis

Anna-Maria Lampousi  1 , Sofia Carlsson  2 , Josefin E Löfvenborg  2
Affiliations
Meta-Analysis

Dietary factors and risk of islet autoimmunity and type 1 diabetes: a systematic review and meta-analysis

Anna-Maria Lampousi et al. EBioMedicine. 2021 Oct.

Abstract

Background: Numerous dietary components have been linked to the development of islet autoimmunity (IA) and type 1 diabetes (T1D); however, no associations are firmly established. This systematic review and meta-analysis aimed to synthesize current knowledge on diet and incidence of IA and T1D.

Methods: Literature search was performed in Medline, Embase, and Cochrane Library, from inception until October 2020. Eligible studies had IA or T1D as outcome; any dietary exposure; case-control, cohort, or randomized controlled trial design; and hazard, risk, or odds ratios as measures of association. Summary relative risks (RR) and 95% confidence intervals (CI) were estimated with random-effects models. Certainty of evidence was assessed with GRADE. PROSPERO registration number: CRD42020212505.

Findings: Among 5935 identified records, 96 were eligible, and pooled estimates could be produced for 26 dietary factors. Evidence with moderate/high certainty indicated lower risk of T1D in relation to longer (≥6-12 vs <6-12 months, RR: 0⋅39, CI: 0⋅26-0⋅58, I2=43%) and exclusive (≥2-3 vs <2-3 months, RR: 0⋅68, CI: 0⋅58-0⋅80, I2=0%) breastfeeding, later introduction to gluten (3-6 vs <3-5 months, RR: 0⋅36, CI: 0⋅17-0⋅75, I2=0%), cow's milk (≥2-3 vs <2-3 months, RR: 0⋅69, CI: 0⋅59-0⋅81, I2=0%), and fruit (4-6 vs <4-5 months, RR: 0⋅47, CI: 0⋅25-0⋅86, I2=0%). Higher childhood intake of cow's milk was associated with increased risk of both IA (per 2-3 portions/day, RR: 1⋅25, CI: 1⋅06-1⋅47, I2=0%) and T1D (≥2-3 vs <2-3 glasses/day, RR: 1⋅81, CI: 1⋅12-2⋅91, I2=31%). For the remaining dietary factors investigated, there was no association, or the evidence was of low certainty.

Interpretation: This study suggests that breastfeeding and late introduction of gluten, fruit, and cow's milk may reduce the risk of T1D, whereas high childhood cow's milk intake may increase it.

Funding: Swedish Research Council, Swedish Research Council for Health, Working Life and Welfare (FORTE), Novo Nordisk Foundation, and Swedish Diabetes Foundation.

Keywords: Diet; Islet autoimmunity; Meta-analysis; Type 1 diabetes.

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Conflict of interest statement

Declaration of competing interest The authors declare no competing interests.

Figures

Fig 1:
Fig. 1
Flow diagram of study selection
Fig 2:
Fig. 2
Summary relative risks and 95% confidence intervals of type 1 diabetes in relation to diet
Fig 3:
Fig. 3
Summary relative risks and 95% confidence intervals of islet autoimmunity in relation to diet
Fig 4:
Fig. 4
Certainty of evidence of the associations between dietary factors at different developmental stages and incidence of type 1 diabetes, based on the GRADE tool.
See this image and copyright information in PMC

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