Omega-3s Influence Macular Pigment

Investigating the role of omega-3s in macular pigment formation

High dietary intake of lutein and zeaxanthin, or their oral supplementation, is known to increase their accumulation within the macula to form protective macular pigment (there is evidence that this accumulation relies on specific carotenoid binding proteins).

Omega-3 fatty acids and particularly DHA, are abundant in the human retina where they play structural, functional and neuroprotective roles. A number of epidemiological studies have observed decreased AMD risk with higher intake of the omega-3s EPA and DHA.

Since lutein and zeaxanthin are fat soluble, their metabolism is strongly interlinked with lipids. It has been suggested, in fact, that dietary omega-3 intake enhances retinal accumulation of lutein and zeaxanthin.

To better understand the factors influencing macular pigment accumulation, French investigators recently looked at the relationship between MPOD and plasma levels of lutein, zeaxanthin and omega-3s in a homogeneous population of healthy volunteers. The researchers report a significant correlation between MPOD and all of these dietary nutrients.

The results of this study suggest that omega-3 fatty acids may act synergistically with lutein and zeaxanthin in constituting the macular pigment, and could be an added reason for concurrent supplementation of these nutrients. Such supplementation is currently being tested in the ongoing AREDS 2 clinical trial.

Results

MPOD within 6° correlated with plasma levels of lutein and zeaxanthin (r=0.35, p<0.001 and r=0.30, p<0.005, respectively).

MPOD also significantly correlated with total plasma omega-3 polyunsaturated fatty acids (PUFAs) (r=0.22, p<0.05).

Among the different omega-3 PUFAs, docosapentaenoic acid (DPA) had the highest correlation with MPOD (r=0.31, p<0.001), while correlation with EPA was moderate (r=0.21, p<0.05), and did not reach significance for DHA.

Scatter plots depicting the correlations between macular pigment optical density (MPOD) at one degree of eccentricity with (A) lutein and zeaxanthin (L+Z); with (B) total omega-3 long chain polyunsaturated fatty acids (LCPUFAs); with (C) EPA (eicosapentaenoic acid) and with (D) DPA (docosapentaenoic acid)

Comments

In this study, MPOD correlated not only with plasma lutein/zeaxanthin, but also with the omega-3 long chain fatty acids – particularly EPA and DPA. DPA, a metabolic intermediate between EPA and DHA, is the second most abundant long chain omega-3 found within the retina.

While the mechanisms by which the omega-3 may influence MPOD remain to be determined, it is possible that they: 1) modulate the gastro-intestinal uptake of lutein and zeaxanthin; 2) enhance transport of these carotenoids to the eye by lipoproteins; or 3) affect the concentration or utilization of lutein and zeaxanthin in the macular area.

Reference: Delyfer MN, et al. Association of macular pigment density with plasma omega-3 fatty acids: the PRIMAVOSA study. Invest Ophthalmol Vis Sci. Epub ahead of print, Jan 24, 2012.