Heterogeneity of Associations between Total and Types of Fish Intake and the Incidence of Type 2 Diabetes: Federated Meta-Analysis of 28 Prospective Studies Including 956,122 Participants.
Nutrients 2021 ; 13: .
Pastorino S, Bishop T, Sharp SJ, Pearce M, Akbaraly T, Barbieri NB, Bes-Rastrollo M, Beulens JWJ, Chen Z, Du H, Duncan BB, Goto A, Härkänen T, Hashemian M, Kromhout D, Järvinen R, Kivimaki M, Knekt P, Lin X, Lund E, Magliano DJ, Malekzadeh R, Martínez-González MÁ, O'Donoghue G, O'Gorman D, Poustchi H, Rylander C, Sawada N, Shaw JE, Schmidt M, Soedamah-Muthu SS, Sun L, Wen W, Wolk A, Shu XO, Zheng W, Wareham NJ, and Forouhi NG
DOI : 10.3390/nu13041223
PubMed ID : 33917229
PMCID : PMC8068031
The association between fish consumption and new-onset type 2 diabetes is inconsistent and differs according to geographical location. We examined the association between the total and types of fish consumption and type 2 diabetes using individual participant data from 28 prospective cohort studies from the Americas (6), Europe (15), the Western Pacific (6), and the Eastern Mediterranean (1) comprising 956,122 participants and 48,084 cases of incident type 2 diabetes. Incidence rate ratios (IRRs) for associations of total fish, shellfish, fatty, lean, fried, freshwater, and saltwater fish intake and type 2 diabetes were derived for each study, adjusting for a consistent set of confounders and combined across studies using random-effects meta-analysis. We stratified all analyses by sex due to observed interaction ( = 0.002) on the association between fish and type 2 diabetes. In women, for each 100 g/week higher intake the IRRs (95% CIs) of type 2 diabetes were 1.02 (1.01-1.03, = 61%) for total fish, 1.04 (1.01-1.07, = 46%) for fatty fish, and 1.02 (1.00-1.04, = 33%) for lean fish. In men, all associations were null. In women, we observed variation by geographical location: IRRs for total fish were 1.03 (1.02-1.04, = 0%) in the Americas and null in other regions. In conclusion, we found evidence of a neutral association between total fish intake and type 2 diabetes in men, but there was a modest positive association among women with heterogeneity across studies, which was partly explained by geographical location and types of fish intake. Future research should investigate the role of cooking methods, accompanying foods and environmental pollutants, but meanwhile, existing dietary regional, national, or international guidelines should continue to guide fish consumption within overall healthy dietary patterns.
Eating fish is generally considered part of a healthy diet. This is based on previous evidence from research that found benefits of consuming fish for heart disease. That is why there are various dietary guidelines that recommend that people should consume fish regularly.
Whether fish consumption also has a role in the prevention of type 2 diabetes is not clear. In previous research it was reported that the relationship between eating fish and developing type 2 diabetes may vary in different parts of the world. So in some places like Asia higher fish intake was related with a lower risk of developing type 2 diabetes, but in other places such as in North America and Europe, the opposite was observed, with higher fish intake related with higher diabetes risk. The reasons for this are unclear.
To understand this better, we undertook research including data from studies in several world regions. The InterConnect project enabled us to analyse data from nearly one million people from 28 studies across the world, among whom 48,000 people developed type 2 diabetes over time.
We analysed data on different types of fish, including shellfish, fatty fish, lean fish and fried fish. Among men, fish consumption had no positive or negative relationship with type 2 diabetes. In contrast, among women, we observed that higher fish consumption was related with a modestly higher risk of developing type 2 diabetes, but only in the Americas. This higher risk was seen for both fatty fish and lean fish. The reasons for the difference in risk for women and men are unknown, but possible explanations could include the role of differences in cooking methods such as frying or not, accompanying foods consumed alongside fish, and potential interactions between fish nutrients and environmental fish contaminants as well as sex differences in hormonal profiles. More research is needed to understand this better. In the meantime, existing dietary guidelines on fish consumption should be followed and fish should be included as part of a healthy diet.
The approach we used in the InterConnect project was to “take the analysis to the data” so that we could efficiently bring together individual person data from multiple countries and have the participation of some studies that have previously collected the data but were not able to analyse and publish their research findings. This is important because this reduces the so-called “publication bias” when some studies are published because of their positive results while others remain unpublished. This approach should enable further important research to understand the link between diet and the risk of type 2 diabetes, a condition that is common and has potentially serious health consequences.
Study : EPIC-InterAct