Is Higher α-Linolenic Acid Content Preferable? Assessing Digestive Fate of Flaxseed Oil in In Vitro Digestion Models of Infants, Adults and the Elderly

α-Linolenic acid (ALA) is an essential omega-3 polyunsaturated fatty acid, yet how dietary ALA enrichment interacts with population-specific gastrointestinal physiology to dictate bioaccessibility and lipid peroxidation remains insufficiently understood. This study systematically evaluated the in vitro digestive behaviors and oxidation risks of flaxseed oils containing 52% and 68% ALA using simulated models representative of distinct population groups (infants, adults, and the elderly). Digestive efficiency peaked in the adult model, achieving ALA bioaccessibility of 49.2% (52% ALA oil) and 46.5% (68% ALA oil), significantly outperforming those observed in infants (23.1% and 19.5%) and the elderly (39.4% and 37.3%). Crucially, malondialdehyde (MDA) accumulation directly correlated with digestive lipolysis efficiency across population groups, reaching its maximum in adults (5.00 nmol/mL for 52% ALA oil; 7.54 nmol/mL for 68% ALA oil), followed by the elderly (3.06 nmol/mL and 4.02 nmol/mL), and remaining lowest in infants (0.92 nmol/mL and 1.49 nmol/mL). Within each population cohort, although the 68% ALA oil yielded a higher absolute ALA release amount, its relative bioaccessibility was slightly lower while generating elevated MDA levels. These findings demonstrate that increasing ALA concentration imposes a critical trade-off between lipolytic efficiency and oxidative safety across different population groups, providing a solid scientific rationale for designing population-tailored flaxseed oil products optimized for both nutrient delivery and safety.