Abstract
Background: Conclusive data on the effectiveness of dietary interventions in heterozygous familial hypercholesterolemia (HeFH) management are unavailable. Whether this is due to a true lack of effects or biases in intervention designs remains unsettled. We systematically assessed the impact on LDL-C of published dietary randomized controlled trials (RCTs) conducted among individuals with HeFH in relation to their design and risk of bias. Methods: We systematically searched PubMed, Web of Science, and Embase in November 2020 to identify RCTs that assessed the impact of: (1) food-based interventions; (2) dietary counseling interventions; or (3) dietary supplements on LDL-C in individuals with HeFH. We evaluated the risk of bias of each study using the Cochrane Risk of Bias 2 method. Results: A total of 19 RCTs comprising 837 individuals with HeFH were included. Of those, five were food-based interventions, three were dietary counseling interventions and 12 were dietary supplement-based interventions (omega-3, n = 3; phytosterols, n = 7; guar gum, n = 1; policosanol, n = 1). One study qualified both as a food-based intervention and as a dietary supplement intervention due to its factorial design. A significant reduction in LDL-C levels was reported in 10 RCTs, including eight dietary supplement interventions (phytosterols, n = 6, omega-3, n = 1; guar gum, n = 1), one food-based intervention and one dietary counseling intervention. A total of 13 studies were judged to have some methodological biases in a way that substantially lowers confidence in the results. Studies at low risk of biases were more likely to report significant reductions in LDL-C concentrations, compared with studies at risk of bias (chi-square statistic: 5.49; p = 0.02). Conclusion: This systemic review shows that the apparent lack of effectiveness of diet manipulation in modulating plasma levels of LDL-C among individuals with HeFH is likely due to biases in study designs, rather than a true lack of effects. The likelihood of reporting significant reductions in LDL-C was associated with the concurrent risk of bias.
Highlights
heterozygous familial hypercholesterolemia (HeFH); (2) they assessed the impact of a dietary intervention on plasma lipids, including LDL-C; (3) they provided head-to-head post-intervention comparison between the intervention and the control arms for LDL-C concentrations; or (4) they were published in English
We assessed whether the impact on plasma lipids of previously published dietary interventions conducted among individuals with HeFH was associated with study design and quality
Among the 19 unique studies we identified and analyzed, a significant reduction in LDL-C was observed in 10 of these, including eight dietary supplement interventions, one food-based intervention and one dietary counseling intervention
Summary
None of the previous reviews thoroughly assessed the impact on plasma lipids of dietary interventions conducted in HeFH, in line with the intervention design per se [6,7] This element is critical to investigate, as food-based interventions, dietary counseling studies and dietary supplement trials are exposed to specific biases (e.g., food substitution effect [8], adherence to dietary advice [9] or compliance with supplementation protocol [10]) which are likely to have different, yet direct impacts on their effectiveness in modulating plasma lipids [11]. Results: A total of 19 RCTs comprising 837 individuals with HeFH were included
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