Introduction:
Assessment of the fatty acid status [particularly the highly labile, long-chain omega-3 species eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] of both blood and breast milk is important in epidemiological studies that seek to discover relationships between fatty acid status and health outcomes. Both blood and milk samples are difficult to collect and process in the field, and they are expensive to ship frozen to the laboratory. Hence improved approaches to sample acquisition and transport are needed to expand the research base for these metrics.
Methods:
The purpose of this study was to validate methods to collect, preserve and analyze the fatty acid composition of dried blood spots (DBS) and dried milk spots (DMS). Single drops of blood from 5 volunteers and of milk from 5 lactating women were applied to Whatman 903 cards which had been pretreated with an antioxidant preservative cocktail (OxyStop®). The omega-3 fatty acid content of the milk and the blood samples spanned a 5-fold range. These cards were then kept in the dark at room temperature, 4°C, -20°C, and -80°C for 28 days. Samples were analyzed weekly (in triplicate) and were compared to baseline values and to liquid samples stored under the same conditions. Red blood cells (RBC) from the 5 blood samples were also included in the experiment. Samples were considered stable up until the week that the mean omega-3 fatty acid content had decreased by >10% from baseline. In a separate experiment, the RBC omega-3 index was estimated from the DBS EPA+DHA value using blood samples from 106 healthy subjects.
Results:
Based on the stability criterion, both DBS and DMS samples were stable for 4 weeks under all storage conditions. RBC EPA+DHA (the omega-3 index) was also stable for 4 weeks under all conditions except storage at -20°C at which temperature degradation occurred within 1 week. The correlation between the omega-3 index and DBS EPA+DHA was 0.98 (p<0.0001) indicating that the RBC omega-3 levels can be accurately estimated from whole blood analysis. DHA levels in liquid vs. dried milk were also strongly correlated (r>0.99; p<0.0001).
Conclusion:
Both blood and milk omega-3 fatty acid content can be accurately assessed from samples collected and transported at room temperature on filter paper.
Influence of Omega-3 Fatty Acid Status on the Way Rats Adapt to Chronic Restraint Stress
