Abstract
To address hyperlipidemia, flaxseed demonstrates a great impact on experimental and clinical trials. Therefore, the effects of flaxseed on lipid profiles of healthy and dyslipidemic subjects were assayed. The literature search was performed based on English reports of randomized control trials (RCTs) up to April 2021 to seek the effect of flaxseed on lipid profiles of healthy and dyslipidemic subjects. A total of 14 RCTs with 1107 participants were evaluated. Based on results, flaxseed significantly improves the lipid profile in dyslipidemic patients comprising total cholesterol (TC), low-density lipoprotein (LDL-C) and triglyceride (TG) in comparison with the control group. Nevertheless, no significant changes were observed in high-density lipoprotein (HDL-C). Although in healthy individual flaxseed significantly increased HDL-C, LDL-C and TG. Subgroup analysis on healthy subjects showed that flaxseed improved LDL-C on overweight subjects with BMI>25. The evidence suggests that flaxseed significantly improved TC, LDL-C and TG in dyslipidemic subjects and additionally improved the HDL-C on healthy subjects.
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Key Points
There are controversial studies on the lipid-lowering effects of flaxseed with a great variety observed between the type of diseases and the kind of flaxseed. This study minimized the changes and focused on flaxseed and dyslipidemic subjects and healthily and dyslipidemic subjects ere assessed separately. The flaxseed supplements lead to remarkable improvement in lipid profile of dyslipidemic subjects and healthy subjects specifically with BMI > 25. In dyslipidemic subjects of the experimental group, LDL-C (-0.69 mg/dl), TC (-1.41 mg/dl), and TG (-1.47 mg/dl) levels significantly decreased compared to controls. However, the HDL-C was not changed significantly (0.32, P = 0.06). In the healthy, experimental group, a significant reduction in TC (-16.53 mg/dl) and elevation in HDL-C (5.12 mg/dl) and LDL-C (2.41 mg/dl) were observed compared to controls. The effect on TG was insignificant (2.6, P = 0.720). The difference in results of the dyslipidemic and normolipidemic subjects is due to the expression of lipid metabolism-related genes modulated by inflammation mediators associated with dyslipidemia. For human consumption four forms of flaxseed are available: ground flaxseed, whole flaxseed, flaxseed oil, and partially defatted flaxseed meal. The composition of whole flaxseed (22.8 g ALA, 82-2600 mg lignan) and ground flaxseed (23.1 g ALA, 82-2600 mg lignan) are similar while flaxseed oil (57 g ALA) and partially defatted flaxseed meal (6 g ALA, 2500 mg lignan) are different. Based on evidence, whole flaxseed, ground flaxseed and dietary flaxseed had a better effect than flaxseed oil on lipid profile; this is probably due to the lipid lowering effect of lignans, fiber, phytic acid and polyphenols which are absent in flaxseed oil but present in other forms of flaxseed.