Fish consumption and multiple health outcomes: Umbrella review
Graphical abstract
Introduction
Fish, especially fatty fish, contains a variety of essential nutrients such as omega-3 polyunsaturated fatty acids (n-3 PUFAs) (Van Hecke, Goethals, Vossen, & De Smet, 2019), protein (Shomrony, 1978), iodine (Harrison, McFarlane, Harden, & Wayne, 1965), selenium (da Silva, da Costa, Silva, & Dos Santos, 2019), taurine (Torris, Smastuen, & Molin, 2018), and vitamin D (Birgisdottir et al., 2012), which may contribute to multiple health benefits in humans. The long-chain (LC) n-3 PUFAs, consisting of marine-derived eicosapentaenoic acid (EPA; 20:5) (Tichelaar, 1990), docosahexaenoic acid (DHA; 22:6) (Guesnet & Alessandri, 2011), and docosapentaenoic acid (DPA; 22:5) (Kaur, Cameron-Smith, Garg, & Sinclair, 2011), are incorporated into the phospholipids of cellular membranes and have antithrombotic (Knapp, Reilly, Alessandrini, & FitzGerald, 1986), anti-inflammatory (Q. Zhou et al., 2019), antioxidant (Peng et al., 2019), anti-adipogenic (Oliveira et al., 2019; Pahlavani et al., 2019; Zhuang et al., 2019), anticancer (J. Li et al., 2019), antihyperlipidemia (Gui et al., 2019), neuroprotective (M. M. Zhou et al., 2018), and antiarrhythmic effects (Charnock, 1991). Conversely, in some regions (including the Baltic Sea (Svensson et al., 1991)) some fish species also contain contaminants (such as methylmercury, dioxins, and polychlorinated biphenyls [PCBs]), resulting in confusion over the health impact of fish consumption (Mozaffarian & Rimm, 2006). The US FDA has issued advice about safe fish consumption for young children, breastfeeding mothers and pregnant women (Voelker, 2017), which also supports the recommendations of the Dietary Guidelines for Americans (USDHHS, 2015). A science advisory from the AHA recommended to consume nonfried fish, especially species higher in n-3 PUFAs, 1 to 2 servings per week for cardiovascular benefits (Rimm et al., 2018).
Until now, a lot of observational and interventional studies have been conducted in humans to evaluate the risks and the benefits of fish consumption (Mozaffarian & Rimm, 2006). Previously, systematic reviews (SR) and meta-analyses (MA) have become the “gold standard” for judging whether an intervention does more good than harm (Sackett, Rosenberg, Gray, Haynes, & Richardson, 1996). Currently, there is a lot of misleading, unnecessary, and conflicted MA and SR (Ioannidis, 2016). Therefore umbrella review is needed to systematically collect, integrate data and evaluate information on all clinical outcomes and provide a wide view of the evidence landscape (Ioannidis, 2009; Papatheodorou, 2019).
To provide a better overview of potential biases, strength of evidence and validity of fish consumption with diverse health outcomes, we conducted an umbrella review of this issue in humans.
Section snippets
Umbrella review methods
We systematically collected, integrated data and evaluated information from multiple SR and MA on all clinical outcomes and provide a wide view of the evidence landscape (Aromataris et al., 2015; Ioannidis, 2009; Papatheodorou, 2019; Yi et al., 2019).
Literature search
The following databases were searched for entries from the inception through March 2019: Embase, Medline, the Cochrane Database of Systematic Reviews and Web of Science. The following pre-defined search strategy were used: fish AND (systematic
Characteristics of MA
Flowchart of the selection process is presented in Fig. 1. A total of 809 articles were identified after systematic search, after applying the inclusion or exclusion criteria, 89 SR and MA with 55 unique health outcomes were yielded (Fig. 2). Table 1 presents the association between fish intake and mortality and cardiovascular disease. The associations between fish intake and cancer outcomes are shown in Table 2. Table 3 presents the associations between fish intake and metabolic, neurological,
Main findings and interpretation
A total of 89 SR and MA with 55 unique health outcomes were identified. Fish consumption did more benefit than harm for a variety of health outcomes with largest risk reduction at 2 to 4 servings per week. Dose-response analyses revealed that every 20 g/d (approximately one serving/week) increment could decrease by 2%–7% risk of CHD mortality, CVD mortality, all-cause mortality, stroke, myocardial infarction, acute coronary syndrome, heart failure, gastrointestinal cancer, metabolic syndrome,
Conclusions
In sum, fish intake looks generally safe in this umbrella review with largest risk reduction for a range of health outcomes at two to four servings per week, and seems more beneficial than harmful. Caution is warranted for potential allergy or contamination when advising during pregnancy and young children. High-quality prospective studies are needed.
Declaration of competing interest
The authors declare no competing interests.
Acknowledgements
This work was supported by Chinese Medical Board Grant on Evidence-Based Medicine, New York, USA (No. 98-680), National Natural Science Foundation of China (No.30901427).
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