Skip navigation
Link to Back issues listing | Back Issue Listing with content Index | Subject Index

Eggs and eyes

Egg evidence
Comment


Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. In the USA 200,000 new cases are diagnosed each year, and nearly six million Americans have suffered some vision loss from AMD. A rapidly aging and longer living population suggests that the prevalence of AMD is likely to triple over the next 25 years as our populations contain increasing numbers of older people.


Age is the biggest risk factor, but diets low in antioxidants low in substances like lutein and zeaxanthin may also contribute to both low serum and retinal levels of these antioxidants (Bandolier 123). Higher serum levels are associated with lower incidence of AMD, as are diets high in antioxidants. Spinach and other green and yellow vegetables, as well as egg yolk, have high contents of lutein and zeaxanthin. Recently there has been something of an interest in eggs, so Bandolier has done a quick review.


Egg evidence


Table 1 contains information from six comparative studies of egg supplementation to diets. Most of these were randomised, and most examined dietary supplementation with one egg per day, measuring serum or plasma concentrations of lutein and zeaxanthin, as well as plasma cholesterol subfractions.



Table 1: Summary of six trials examining dietary egg and changes to serum lutein and/or zeaxanthin concentrations



Reference Study Results
Handelman et al. American Journal of Clinical Nutrition 1999 70: 247-251 Uncontrolled study of 11 subjects aged 48-78 years, mean LDL cholesterol 4.3 mmol/L
Two diets for 4.5 weeks separated by 2 weeks, with or without supplementation with 1.3 egg yolks daily
Significant increases in plasma lutein and zeaxanthin increased plasma lutein by 28% and 50%, and zeaxanthin by 142% and 114%
Surai et al. European Journal of Clinical Nutrition 2000 54: 298-305. Randomised, double blind, placebo controlled study in 44 healthy adults aged 26 to 59 years, mean total cholesterol 5.4 mmol/L, HDL cholesterol 1.2 mmol/L
Diets were either commercial eggs or "designer" eggs from chickens fed supplemented diet rich in lutein (15x greater lutein content); one egg per day for 8 weeks
No increase in plasma lutein with standard egg, but 100% increase with supplemented egg
No significant change in total cholesterol or HDL cholesterol
Chung et al. Journal of Nutrition 2004 134: 1887-1893. Randomised, open, comparison of four lutein diets in 10 healthy men aged 26 to 75 years, all with total cholesterol below 6.2 mmol/L
Four diets tested, lutein and lutein ester supplement, spinach, and egg yolk, each with 6 mg lutein daily for 10 days
Serum lutein increased with all diets:
lutein 82%
lutein ester 83%
spinach 141%
egg 323%
Goodrow et al. Journal of Nutrition 2006 136: 2519-2542. Randomised, open, comparison of two diets in 33 older individuals, mean age 78 years, mean LDL cholesterol 3.1 mmol/L, total cholesterol 5.1 mmol/L
Diet periods consisted of no eggs and 1 egg daily for 5 weeks
Serum lutein and zeaxanthin increased by 26% and 38% on 1 egg per day compared with no egg
No change in cholesterol in total or subfractions
Wenzel et al. Journal of Nutrition 2006 136: 2568-2573. Open comparison of placebo pill with diets of standard and high lutein eggs for 12 weeks in 24 women aged 24 to 59 years (randomisation not stated). Initial mean LDL cholesterol 2.6 mmol/L, total cholesterol 4.7 mmol/L
Change in lutein:
placebo -10%
ordinary egg +23%
high lutein egg +26%
Change in zeaxanthin
placebo -15%
ordinary egg +30%
high lutein egg +60%
Significant increase in macular pigment optical density with both egg groups
No change in serum triglyceride subfractions
Herron et al. Journal of Nutrition 2006 136: 1161-1165. Randomised comparison of 91 people, mean age 31 years, mean total cholesterol 4.3 mmol/L. Analysis according to genetic subtypes
Comparison of 3 eggs daily versus placebo, for 30 days
In 40 patients in whom they were measured, serum lutein increased by about 30% and zeaxanthin by 20%



Most studies showed that eating about one egg a day increased serum or plasma lutein by about 20-30%. Only one [1] failed to show any increase in plasma lutein with a standard egg, though it showed a large increase with a “designer” egg from chickens fed a supplemented diet, with 15 times more lutein per egg (1.9 mg) than a standard egg.


Two other results are interesting. One of them [2] compared four diets containing the same amount (6 mg) of daily lutein as a lutein supplement, lutein ester supplement, in spinach, or egg. While the study was small, involving only 10 healthy men in the crossover study, it showed a much higher increase in serum lutein for eggs compared with spinach or supplements for the same daily lutein dose (Figure 1).



Figure 1: Change in serum lutein concentrations in 10 healthy men with different sources of dietary lutein






Only one study has examined the effects of dietary eggs on the retina [3]. Individuals with low macular pigment optical density may be at greater risk of retinal disease because more potentially harmful short wavelength light reaches tissue at the back of the retina. Higher macular pigment optical density is considered, therefore, to be protective. In 24 healthy younger women given placebo or one of two egg diets for 12 weeks, the change in macular pigment optical density was greatest in those with low initial levels (Figure 2).



Figure 2: Change in macular pigment optical density in 24 women over 12 weeks according to baseline value






Comment


Before anyone rushes off to stuff themselves with eggs, it needs to be said that these are early days, though many Internet sites would try and convince readers otherwise. There is no evidence that eggs are a miracle for preventing or curing macular degeneration. What we are seeing is a reasonably consistent response for useful surrogate markers (serum concentrations of lutein and zeaxanthin or macular pigment optical density), without any major change in serum cholesterol or its subfractions.


What is interesting is that lutein in eggs seems to be more readily available, and that any protective effects are likely to be greatest in those with the greatest risk, in this case those with the lowest macular pigment optical density. A good diet, which includes all those leafy greens and some eggs, is still the right advice, for macular degeneration and all sorts of other ills [4].


References:

  1. PF Surai et al. Designer egg evaluation in a controlled trial. European Journal of Clinical Nutrition 2000 54: 298-305.
  2. HY Chung et al. Lutein bioavailability is higher from lutein-enriched eggs than from supplements and spinach in men. Journal of Nutrition 2004 134: 1887-1893.
  3. AJ Wenzel et al. A 12-wk egg intervention increases serum zeaxanthin and macular pigment optical density in women. Journal of Nutrition 2006 136: 2568-2573.
  4. JD Ribaya-Mercado, JS Blumberg. Lutein and zeaxanthin and their potential roles in disease prevention. Journal of the American College of Nutrition 2004 23: 567S-587S.

previous or next story