Conversion of α-linolenic acid in humans is influenced by the absolute amounts of α-linolenic acid and linoleic acid in the diet and not by their ratio1

https://doi.org/10.1093/ajcn/84.1.44Get rights and content
Under an Elsevier user license
open archive

ABSTRACT

Background: Human in vivo data on dietary determinants of α-linolenic acid (ALA; 18:3n−3) metabolism are scarce.

Objective: We examined whether intakes of ALA or linoleic acid (LA; 18:2n−6) or their ratio influences ALA metabolism.

Design: During 4 wk, 29 subjects received a control diet (7% of energy from LA, 0.4% of energy from ALA, ALA-to-LA ratio = 1:19). For the next 6 wk, a control diet, a low-LA diet (3% of energy from LA, 0.4% of energy from ALA, ratio = 1:7), or a high-ALA diet (7% of energy from LA, 1.1% of energy from ALA, ratio = 1:7) was consumed. Ten days before the end of each dietary period, [U-13C]ALA was administered orally for 9 d. ALA oxidation was determined from breath. Conversion was estimated by using compartmental modeling of [13C]- and [12C]n−3 fatty acid concentrations in fasting plasma phospholipids.

Results: Compared with the control group, ALA incorporation into phospholipids increased by 3.6% in the low-LA group (P = 0.012) and decreased by 8.0% in the high-ALA group (P < 0.001). In absolute amounts, it increased by 34.3 mg (P = 0.020) in the low-LA group but hardly changed in the high-ALA group. Nearly all ALA from the plasma phospholipid pool was converted into eicosapentaenoic acid. Conversion of eicosapentaenoic acid into docosapentaenoic acid and docosahexaenoic acid hardly changed in the 3 groups and was <0.1% of dietary ALA. In absolute amounts, it was unchanged in the low-LA group, but increased from 0.7 to 1.9 mg (P = 0.001) in the high-ALA group. ALA oxidation was unchanged by the dietary interventions.

Conclusion: The amounts of ALA and LA in the diet, but not their ratio, determine ALA conversion.

Keywords:

Ratio of α-linolenic to linoleic acid
conversion
oxidation
stable isotopes
humans

Cited by (0)

2

Supported by the Wageningen Centre for Food Sciences (to PLZ, MBK, and RPM), an alliance of major Dutch food industries, Maastricht University, TNO Nutrition and Food Research, and Wageningen University and Research Centre, with financial support by the Dutch government. The model development was partially supported by NIH grant P41 EB-001975, “Resource Facility for Population Kinetics.” The experimental pastries were produced by V.T.I.V.T. Ter Hercke (Herk-de-Stad, Belgium).