No evidence of hypoglycemia or hypotension in older adults during 6 months of flax lignan supplementation in a randomized controlled trial: A safety evaluation.

Key Findings:

Flaxseed secoisolariciresinol diglucoside (SDG) is converted to the mammalian lignans, enterodiol (ED) and enterolactone (EL), by bacteria in the human colon. Binding of these lignans to estrogen receptors can exert weak estrogenic or anti-estrogenic effects, and such activity is believed to decrease the risk of hormone-sensitive cancers. BeneFlax, containing 543 mg SDG was studied in this 6 month efficacy intervention trial of BeneFlax for its effects on hypoglycemia or hypotension. No changes in hypoglycemia or hypotension were found. The authors suggested that a dose of 543 mg BeneFlax falls at or below the no observable adverse effect level (NOAEL) for hypoglycemia or hypotension. The effects of flaxseed on lowering blood pressure and blood glucose are most likely due to ALA, fiber, lignans or a combination of all three.  However, with regard to this study, the ultimate aim was to show safety and thus the authors concluded that BeneFlax does not pose a risk of hypoglycemia or hypotension in healthy adults aged 49 to 87 years.

ABSTRACT:

Context: The natural health product, BeneFlax, is a standardized flaxseed [Linum usitatissimum L. (Linaceae)] lignan enriched product with evidence of product quality and known quantity of the bioactive component, lignan. The acceptance of this natural health product for its various health benefits requires greater evidence of its safety in the general population. Objective: We determined whether flaxseed lignan causes clinical hypoglycemia or hypotension in healthy older adults as an important aspect of safety. Materials and methods: Participants aged 49 to 87 years were randomized in a double-blind trial to receive flaxseed lignan (543 mg/day in BeneFlax) or placebo while completing a 6 month walking program. The 94 participants who completed the study were stratified by age (<65 years versus >65 years) and treatment category to determine whether older adults were more susceptible to adverse effects. Results: After 6 months of treatment, average plasma glucose level (5.4 +/- 0.6 mmol/L), systolic blood pressure (127 +/- 14mmHg), and diastolic blood pressure (80+/-9mmHg) were within normal clinical range. Controlling for sex and body mass index covariates resulted in no observed differences between plasma glucose or blood pressure measurements between treatment or age groups . No incidents of hypoglycemia or hypotension were observed during BeneFlax treatment, suggesting that 543mg falls at or below the no observable adverse effect level (NOAEL). Discussion and conclusion: These data suggest the flaxseed lignan product BeneFlax does not pose a risk of hypoglycemia or hypotension in healthy adults aged 49 to 87 years. (Authors abstract)