Estimating the RBC omega‐3 index and breast milk DHA from dried samples collected on filter paper

Abstract

Assessment of the omega‐3 fatty acid status of both human blood and breast milk is important in studies that examine the relationships between these fatty acid levels and health outcomes. Both blood and milk samples are difficult to collect and process in the field, hence improved approaches to sample acquisition are needed to expand the research base for these metrics. We have therefore developed methods to collect, preserve, transport and analyze the fatty acid composition of dried blood spots (DBS) and dried milk spots (DMS). For both sample types, a single drop of blood/milk were applied to Whatman 903 cards which had been pretreated with an antioxidant preservative cocktail (OxyStop®). Frozen human milk samples (n=5) were thawed and analyzed immediately or spotted on cards and placed in a drawer at room temperature for 5 days. The DHA content of the liquid vs. dried milk samples were analyzed in triplicate. Mean DHA levels were 0.19% and 0.20%, respectively, with an r2 = 0.99 (p<0.01). RBC EPA+DHA (the omega‐3 index) was estimated from DBSs vs. direct RBC analysis in 106 healthy subjects. The correlation was r2 = 0.92 (p<0.0001). Thus both RBC and milk omega‐3 content can be accurately assessed from samples collected and transported on filter paper. These studies were funded with internal support.