Background: Plasma phospholipid EPA and DHA have been used as biomarkers of intake. Previously, we found dietary alpha-linolenic acid (ALA) intake was positively associated with triglycerides in men. Therefore, we investigated plasma phospholipid fatty acids (FA) composition in healthy South Africans and explored associations between dietary FA intake and plasma FA composition, as well as associations between plasma FAs and blood lipids.
Methods: A cross-sectional analysis within the Prospective Urban Rural Epidemiology (PURE) baseline study of healthy subjects (35-70 years) in South Africa. Dietary data were collected. Blood lipid and plasma total phospholipid FA analyses were performed on a random subsample (n=716).
Results: Mean plasma DHA ranged between 3.45-5.43%. We found a positive correlation between dietary ALA and plasma DHA (men r=0.33, P<0.001; women r=0.30, P<0.001), which was stronger than the association between dietary and plasma DHA (men r=0.21, P<0.001; non-significant in women). Plasma phospholipid DHA was positively associated with triglycerides in men (β=0.410, P<0.001) and women (β=0.379, P<0.001).
Conclusions: Even though previously reported median dietary EPA+DHA intake in this population was below recommendations, mean plasma DHA was relatively high compared to healthy individuals in other studies. The positive correlation between dietary ALA and plasma DHA, together with the association between plasma DHA and triglycerides, is in line with the finding from our previous study, indicating towards an efficient conversion of ALA to DHA. These results suggest that plasma phospholipid FAs shouldn’t be used in isolation as biomarkers for intake in epidemiology without assessing dietary intake.
Funding source: SASA, SANPAD, NRF, PHRI Canada.