The importance of DHA intake to support fetal development and maternal health is well established. In this pilot study we applied the natural abundance approach to determine the contribution of 200 mg/day of DHA supplement to the plasma DHA pool in 19 healthy pregnant women on a free diet. Women received DHA, from pregnancy week 20 until delivery, from an algal source (N=13, Algae group) or from fish oil (N=6, Fish group) with slightly different content of 13C. We measured plasma phospholipids DHA 13C:12C ratio (reported as δ13C) prior to supplementation (T0), after 10 (T1) and 90 days (T2) and prior to delivery (T3). The δ13C of DHA in algae and fish supplements were -15.8±0.2 mUr and -25.3±0.2 mUr (p<0.001). DHA δ13C in the Algae group increased from -27.7±1.6 mUr (T0) to -21.9±2.2 mUr (T3) (p<0.001), whereas there were not significant changes in the Fish group (-27.8±0.9 mUr at T0 and -27.3±1.1 mUr at T3, p=0.09). In the Algae group 200 mg/day of DHA contributed to the plasma phospholipid pool by a median value of 53% (31-75% minimum and maximum). This estimation was not possible in the fish group. Our results demonstrate the feasibility of assessing the contribution of DHA from an algal source to the plasma DHA pool in pregnant women by the natural abundance approach. Plasma δ13C DHA did not change when consuming DHA of fish origin, with almost the same δ13C value of that of the pre-supplementation plasma δ13C DHA.
