Serum or plasma lutein concentration

Method

Lutein concentration in serum or plasma by high-performance liquid chromatography, fasting state and matrix recorded on the edge. Where a study reports lutein and zeaxanthin as a combined figure that is recorded as such, since the two are separated by most but not all assays.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

17 papers, 14 randomised. This is CIRCULATING SUPPLY, not retinal deposition, and the distinction is the whole reason this node exists: macular pigment optical density names serum lutein as its near-miss and records the correlation as only moderate — roughly r = 0.33 to 0.40 in PMID 27420092, which measured both. A serum rise does not entail a retinal rise. Before this node existed an extractor finding a serum result had nowhere to put it, which is precisely the pressure that produces a near-miss mapping onto the retinal node. Rising is more circulating lutein and carries no health claim on its own.