An egg a day may help you keep your eyesight

About 5% of people 65 or older suffer from Age-related Macular Degeneration (AMD), a disease which affects the part of the eye responsible for the sharpest central vision. One type of AMD has been associated with reduced blood levels of two antioxidants, carotenoids known as lutein and zeaxanthin. Chicken yolks provide a source of these carotenoids that is even more readily absorbed by the human body than lutein supplements or spinach, yet there is some concern that intake of additional chicken eggs might raise one's serum cholesterol levels. In a study partially funded by the American Egg Board and the Massachusetts Lions Eye Research Fund, scientists at the University of Massachusetts Lowell sought to shed some light on the subject (J Nutr 2006;136:2519-2524).

They recruited 33 men and women, aged 60-96 (average age: 79), who were not taking cholesterol-lowering medications. In what is known as a randomized, cross-over study, the 33 subjects were randomly allocated to one of two groups. Then each group followed the same four-phase protocol:

Phase 1: A 4-week "baseline" period in which the subjects minimized their intake of foods that contained lutein or zeaxanthin and also avoided eating eggs or high egg-content foods.
Phase 2: A 5-week "intervention" period, during which one group ate no eggs or egg substitute whatsoever (the no-egg group), and the other group ate 1 egg per day in addition to their normal diet (the egg group).
Phase 3: A 4-week "washout" period, similar to Phase 1. Both groups avoided foods containing lutein or zeaxanthin as well as eggs.
Phase 4: A 5-week "intervention" period similar to Phase 2, except that the two groups switched: the no-egg group ate 1 egg per day, and the egg group refrained from eating eggs.

The subjects' blood was drawn at two points during each phase and was tested for cholesterol levels as well as levels of lutein and zeaxanthin. As one might expect, consuming an additional single egg per day increased the subjects' lutein and zeaxanthin levels - by 26% and 38%, respectively. However, total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides were not affected.

The researchers note that other studies utilized carotenoid-enriched eggs as opposed to off-the-shelf eggs, as in this study. Other studies of eggs and carotenoids seemed to indicate that additional eggs led to higher cholesterol levels, but these other studies had either a very different gender makeup of subjects (far more males than in this study), a much smaller sample of participants, or required that subjects consume 3 or more eggs per day. Further, those in this study were much older than the subjects in the other studies, a factor more relevant to the condition being studied (AMD).

What this means for you:

Food for thought. We know that eggs are not as bad for you as they've been made out to be with regards to cholesterol, and this study appears to bear that out. While it's not a green light to have a three-egg omelet every morning, it's certainly a good idea for those of a certain age to look at the amount of anti-oxidants you're getting each day. One egg a day is an easy way to help keep your eyes healthy as you get older.

First posted: October 4, 2006