Eating eggs can increase macular pigment
Thursday, November 19, 2009
Consumption of 2 and 4 egg yolks per day for 5 weeks increases macular pigment concentrations in older adults with low macular pigment taking cholesterol-lowering statins, according to a new study.
Lutein and zeaxanthin may reduce the risk of dry age-related macular degeneration because of their photo-oxidative role as macular pigment. Continuous exposure to blue light (430 nm) may contribute to oxidative reactions within the retina and the breakdown of retinal pigment epithelial cells beneath the macula. Lutein, zeaxanthin, and meso-zeaxanthin - a lutein isomer - accumulate in the macula and are collectively referred to as macular pigment (MP). With an absorption maximum of 460 nm, MP acts as an efficient high-energy blue-light filter that protects the underlying retinal cells. In addition, because lutein and zeaxanthin are potent antioxidants, they are also reported to protect the retina from oxidative stress.
Egg consumption significant increases serum lutein and zeaxanthin concentrations. Increased serum lutein and zeaxanthin leads to increase MP optical density (MPOD) in healthy adults. Lutein and zeaxanthin from natural sources, such as spinach, eggs, and corn, especially eggs, appear to be equally or more bioavailable than from supplements.
Methods and Results
Subjects consumed foods containing 2 followed by 4 egg yolks/d for 5 wk each with a 4-wk egg-free period at baseline and between the 2 interventions.
Changes in MPOD (n = 37) with egg yolk consumption were inversely associated (P < 0.05) with baseline MPOD. Subjects with low-baseline MPOD (defined as MPOD 0.5 at 0.25°, 0.4 at 0.5°, and 0.35 at 1°) showed increases of 50% (P < 0.05) with 4 egg yolks at the 3 retinal eccentricities. MPOD increased by 31% (P = 0.059) at 0.5° with 2 egg yolks. Serum lutein increased by only 16% and 24% (P < 0.05) compared with increases of 36% and 82% (P < 0.001) in serum zeaxanthin (n = 52) after consumption of 2 and 4 egg yolks, respectively. Serum HDL cholesterol increased by 5% (P < 0.05) after consumption of 2 and 4 egg yolks. Serum LDL cholesterol did not change with either egg yolk treatment.
Discussion and Conclusions
The magnitudes of the increases in serum zeaxanthin with 2 and 4 egg yolks/d for 5 wk of 36% and 82%, respectively, were remarkably greater than those observed for serum lutein, which were 16% and 24% respectively. The lower-than-expected serum lutein responses compared with zeaxanthin may have been due to several reasons, including that baseline lutein concentrations were 4.5 times those of serum zeaxanthin, which may be important because baseline concentrations of carotenoids predict their responses to dietary interventions.
The MPOD response was observed with egg yolk interventions only when subjects were divided into subgroups. Subjects with a low-baseline MPOD responded to the 5-wk interventions of 2 and 4 egg yolks/d with significant increases in MPOD (Figure 1). The nonresponsiveness of subjects with high baseline MPOD may indicate saturation of retinal cells in the macula, resulting in a slower uptake of additional lutein and zeaxanthin.
A decrease in MPOD was observed after the 4-wk washout phase in the low-baseline MPOD subgroups (Figure 2). This is a valuable finding because previous reports suggest that MPOD stays high for a long time after supplementation.
It is an interesting finding that 2 egg yolks/d significantly raised serum HDL cholesterol without affecting serum LDL cholesterol in this statin-using population. A significant increase in serum LDL cholesterol from baseline was not observed in the current study, even with 4 egg yolks/d, probably because of the action of statins, although it is important to note that the intervention period in the current study lasted only 5 wk.
To summarize, consumption of 2 and 4 egg yolks/d for 5 wk improved MPOD at a retinal eccentricity of 0.5 degree, whereas consumption of 4 egg yolks/d improved MPOD at retinal eccentricities of 0.25° and 1° in an older population with low MPOD who were taking statins. Also, consumption of 2 and 4 egg yolks/d for 5 wk caused tremendous increases in serum zeaxanthin compared with serum lutein. The other beneficial effect of consuming 2 and 4 egg yolks/d in a population taking statins was the significant increase in serum HDL cholesterol but no change in serum LDL cholesterol compared with baseline.
The researchers are presently evaluating the effect of consuming 12 eggs/wk for 1 y on the progression of dry AMD in a population with early- to mid-stage dry AMD. Another important finding was the addition of high baseline MPOD as an exclusion criterion for short-term lutein or zeaxanthin intervention studies.
WHAT IT MEANS TO YOU: Eggs are not as bad for you as you may think. Many people are concerned about cholesterol, and egg yolks do contain a large amount of cholesterol. But, as illustrated in this study, heavy egg consumption leads to only HDL ("good") cholesterol going up. Other studies have confirmed this observation. So, eating eggs may actually be good for you - especially if you have low macular pigment.
Source:
Am J Clin Nutr. 2009 Nov;90(5):1272-9
http://www.ncbi.nlm.nih.gov/pubmed/19759170
Lutein and zeaxanthin may reduce the risk of dry age-related macular degeneration because of their photo-oxidative role as macular pigment. Continuous exposure to blue light (430 nm) may contribute to oxidative reactions within the retina and the breakdown of retinal pigment epithelial cells beneath the macula. Lutein, zeaxanthin, and meso-zeaxanthin - a lutein isomer - accumulate in the macula and are collectively referred to as macular pigment (MP). With an absorption maximum of 460 nm, MP acts as an efficient high-energy blue-light filter that protects the underlying retinal cells. In addition, because lutein and zeaxanthin are potent antioxidants, they are also reported to protect the retina from oxidative stress.
Egg consumption significant increases serum lutein and zeaxanthin concentrations. Increased serum lutein and zeaxanthin leads to increase MP optical density (MPOD) in healthy adults. Lutein and zeaxanthin from natural sources, such as spinach, eggs, and corn, especially eggs, appear to be equally or more bioavailable than from supplements.
Methods and Results
Subjects consumed foods containing 2 followed by 4 egg yolks/d for 5 wk each with a 4-wk egg-free period at baseline and between the 2 interventions.
Changes in MPOD (n = 37) with egg yolk consumption were inversely associated (P < 0.05) with baseline MPOD. Subjects with low-baseline MPOD (defined as MPOD 0.5 at 0.25°, 0.4 at 0.5°, and 0.35 at 1°) showed increases of 50% (P < 0.05) with 4 egg yolks at the 3 retinal eccentricities. MPOD increased by 31% (P = 0.059) at 0.5° with 2 egg yolks. Serum lutein increased by only 16% and 24% (P < 0.05) compared with increases of 36% and 82% (P < 0.001) in serum zeaxanthin (n = 52) after consumption of 2 and 4 egg yolks, respectively. Serum HDL cholesterol increased by 5% (P < 0.05) after consumption of 2 and 4 egg yolks. Serum LDL cholesterol did not change with either egg yolk treatment.
Discussion and Conclusions
The magnitudes of the increases in serum zeaxanthin with 2 and 4 egg yolks/d for 5 wk of 36% and 82%, respectively, were remarkably greater than those observed for serum lutein, which were 16% and 24% respectively. The lower-than-expected serum lutein responses compared with zeaxanthin may have been due to several reasons, including that baseline lutein concentrations were 4.5 times those of serum zeaxanthin, which may be important because baseline concentrations of carotenoids predict their responses to dietary interventions.The MPOD response was observed with egg yolk interventions only when subjects were divided into subgroups. Subjects with a low-baseline MPOD responded to the 5-wk interventions of 2 and 4 egg yolks/d with significant increases in MPOD (Figure 1). The nonresponsiveness of subjects with high baseline MPOD may indicate saturation of retinal cells in the macula, resulting in a slower uptake of additional lutein and zeaxanthin.
A decrease in MPOD was observed after the 4-wk washout phase in the low-baseline MPOD subgroups (Figure 2). This is a valuable finding because previous reports suggest that MPOD stays high for a long time after supplementation.
It is an interesting finding that 2 egg yolks/d significantly raised serum HDL cholesterol without affecting serum LDL cholesterol in this statin-using population. A significant increase in serum LDL cholesterol from baseline was not observed in the current study, even with 4 egg yolks/d, probably because of the action of statins, although it is important to note that the intervention period in the current study lasted only 5 wk.To summarize, consumption of 2 and 4 egg yolks/d for 5 wk improved MPOD at a retinal eccentricity of 0.5 degree, whereas consumption of 4 egg yolks/d improved MPOD at retinal eccentricities of 0.25° and 1° in an older population with low MPOD who were taking statins. Also, consumption of 2 and 4 egg yolks/d for 5 wk caused tremendous increases in serum zeaxanthin compared with serum lutein. The other beneficial effect of consuming 2 and 4 egg yolks/d in a population taking statins was the significant increase in serum HDL cholesterol but no change in serum LDL cholesterol compared with baseline.
The researchers are presently evaluating the effect of consuming 12 eggs/wk for 1 y on the progression of dry AMD in a population with early- to mid-stage dry AMD. Another important finding was the addition of high baseline MPOD as an exclusion criterion for short-term lutein or zeaxanthin intervention studies.
WHAT IT MEANS TO YOU: Eggs are not as bad for you as you may think. Many people are concerned about cholesterol, and egg yolks do contain a large amount of cholesterol. But, as illustrated in this study, heavy egg consumption leads to only HDL ("good") cholesterol going up. Other studies have confirmed this observation. So, eating eggs may actually be good for you - especially if you have low macular pigment.
Source:
Am J Clin Nutr. 2009 Nov;90(5):1272-9
http://www.ncbi.nlm.nih.gov/pubmed/19759170