By analysing fatty acids from red blood cells we get information on an individual’s long-term dietary omega-3 intake whereas omega-3 in plasma will give information on very recent intake. The convenience of the blood spot test is that it doesn’t require a phlebotomist but it does mean that the sample will contain both red blood cells and plasma (whole blood would be spun and the plasma removed). Whilst there is a strong correlation between fatty acid levels found within whole blood (containing both plasma and red blood cells as found in the blood spot) and isolated red blood cells we ask that people do not consume fish/fish oils for 48 hours before sampling as this could cause a fatty acid spike in the plasma and therefore reduce the accuracy of the results. The best way to do the test is to avoid omega-3 over a weekend and then take the sample first thing Monday morning before breakfast. We ask this because eating other sources of fat (milk in tea, or butter, for example) can also influence the results by diluting the amount of omega-3 in the plasma. Taking your sample before eating or drinking will therefore ensure that any fatty acids in the plasma will effectively be ‘washed out’, whilst those in the red blood cells will remain, giving us an accurate picture of a person’s omega-3 status.
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