Abstract
Overweight and obesity are highly prevalent worldwide, and are associated with cardiovascular disease (CVD) risk factors including systematic inflammation, dyslipidemia, and hypertension. Alpha-linolenic acid (ALA) is a plant-based essential polyunsaturated fatty acid associated with reduced cardiovascular risks. This systematic review and meta-analysis aimed to investigate the effects of supplementation with ALA compared to the placebo on cardiovascular risk factors in people with obesity or overweight (PROSPERO Registration No. CRD42023429563). This review included studies with adults, using oral supplementation or food or combined interventions containing vegetable sources of ALA. All studies were randomized trials with parallel or crossover design. The Cochrane Collaboration's tool was use for assessing risk of bias. PubMed, Web of Science, Embase, and Cochrane library databases were searched from inception to April, 2023. Nineteen eligible RCTs, including 1,183 participants were included in the meta-analysis. Compared to placebo, dietary ALA supplementation significantly reduced C-reactive protein (CRP) concentration (SMD = -0.38 mg/L, 95% CI: -0.72, -0.04), tumor necrosis factor (TNF)-α concentration (SMD = -0.45 pg/ml, 95% CI: -0.73, -0.17), triglyceride (TG) in serum (SMD = -4.41 mg/dL, 95% CI: -5.99, -2.82), and systolic blood pressure (SBP) (SMD = -0.37 mm Hg, 95% CI: -0.66, -0.08); but led to a significant increase in low-density lipoprotein cholesterol (LDL-C) concentrations (SMD = 1.32 mg/dl, 95% CI: 0.05, 2.59). ALA supplementation had no significant effect on interleukin-6 (IL-6), diastolic blood pressure (DBP), total cholesterol (TC), or high-density lipoprotein cholesterol (HDL-C) (all P ≥ 0.05). Subgroup analysis revealed that ALA supplementation at a dose of 3g/d or higher from flaxseed and flaxseed oil had a more prominent effect on improving CVD risk profiles, particularly where the intervention duration was 12 wk or longer, and where the baseline CVD profile is poor.
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