Flaxseed fiber has been studied for its potential to support or reduce high triglyceride levels. The primary basis for its use is scientific evidence, though the strength of the evidence is moderate rather than robust. Several clinical trials and meta-analyses have investigated the effects of flaxseed and its fiber component on lipid profiles, including triglycerides. Flaxseed is rich in soluble fiber, particularly mucilage gums, which can bind bile acids in the gut and reduce cholesterol absorption; this action can also have a favorable effect on triglyceride metabolism. Additionally, flaxseed contains alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid, which has been associated with lipid-lowering effects.

Some studies have shown that flaxseed supplementation can lead to a modest reduction in triglyceride levels, especially in individuals with elevated baseline triglycerides. However, results across studies are not entirely consistent. A 2015 meta-analysis in the journal "Nutrition Reviews" found that flaxseed supplementation produced significant reductions in total and LDL cholesterol but had a more limited effect on triglycerides. Other systematic reviews suggest that flaxseed fiber may be more effective when consumed as part of a whole-food diet rather than as an isolated supplement.

In summary, while there is scientific evidence supporting the use of flaxseed fiber for improving lipid profiles, its specific effect on triglycerides is moderate and not as pronounced as its effect on cholesterol. More high-quality, large-scale clinical trials are needed to confirm these findings.