Lutein, a carotenoid thought to help prevent age-related macular degeneration and cataracts, may be found in even higher amounts in eggs than in green vegetables such as spinach, which have been considered its major dietary sources, as well as in supplements. Research presented at the annual American Dietetic Association Conference in San Antonio, Texas, in 2003, by Elizabeth Johnson from the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University also showed that natural lutein esters found in eggs are as or even more bioavailable as the forms of the nutrient offered in purified lutein products. Johnson's trial tested serum lutein concentration in 10 healthy men, before and after daily consumption of 6mg lutein obtained from four different sources: eggs from chickens fed marigold petals (which are high in lutein), spinach (one of the best known sources of dietary lutein), lutein ester supplements (purified lutein) and lutein supplements. Differences in serum lutein levels in response to the various types of doses were observed the day after the first dose: the serum lutein response to egg was significantly greater than the supplements but no higher than the response to the spinach. After nine days of daily lutein dosing, the serum lutein response was significantly greater in the egg phase than either of the supplements or the spinach. The bottom line: this study suggests that eating lutein-rich foods may be a more effective means of boosting lutein concentration in the eye than taking supplements.
Another human study, published in the Journal of Nutrition, confirms that lutein is best absorbed from egg yolk-not lutein supplements or even spinach. Egg yolks, although they contain significantly less lutein than spinach, are a much more bioavailable source whose consumption increases lutein concentrations in the blood many-fold higher than spinach.
Although the mechanism by which egg yolk increases lutein bioavailability is not yet known, it is likely due to the fats (cholesterol and choline) found in egg yolk. Lutein, like other carotenoids, is fat-soluble, so cannot be absorbed unless fat is also present. (If this is the case, then to enhance the lutein absorption from spinach and other vegetables rich in this nutrient, we suggest enjoying them with some fat such as extra virgin olive oil). To maximally boost your lutein absorption, you could also combine both eggs and spinach. Whether you prefer your spinach steamed, sautéed or fresh in spinach salad, dress it with a little olive oil and a topping of chopped hard-boiled egg. For a flavorful, quick and easy recipe featuring eggs and spinach, try our Poached Eggs over Spinach and Mushrooms.
Two new studies published in the Journal of Nutrition add further evidence to the theory that a daily egg-whose yolk is a rich source of vision-protective carotenoids, including not only lutein but also zeaxanthin-may reduce the risk of developing age-related macular degeneration (AMD).
The studies, both conducted at the University of Massachusetts, show that, in addition to keeping hunger at bay longer (eggs' satiety index is 50% than that of most breakfast cereals), an egg a day boosts blood levels of both lutein and zeaxanthin, thus reducing the risk of AMD-without increasing cholesterol or triglyceride levels.
In AMD, the macula, the central part of the retina which controls fine vision, deteriorates, greatly limiting eyesight or even resulting in blindness in those afflicted. The leading cause of blindness in people over age 50, AMD afflicts more than 10 million people in the United States, plus an additional 15 to 20 million worldwide.
In the first study, a randomized cross-over trial, Elizabeth Goodrow and her team investigated the effects of eating one egg a day on blood levels of lutein, zeaxanthin, cholesterol and triglycerides in 33 men and women over age 60.
After a no-egg start up week, volunteers ate either an egg or egg substitute daily for 5 weeks, then again ate no eggs for a week before crossing over to the other intervention for a second 5 weeks.
After the 5-week period in which they ate a daily egg, participants' blood levels of lutein and zeaxanthin significantly increased by 26 and 38%, respectively, compared to their levels of these carotenoids after their no-egg week.
And although eggs are well-known for containing cholesterol, participants' blood levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides were not affected by eating an egg a day.
In the second study, researchers led by Adam Wenzel looked at the effect of a 12-week egg intervention on lutein and zeaxanthin levels in both the blood and the retina of the eye (the macular pigment optical density or MOPD) of 24 women ranging in age from 24 to 59.
The women were randomly assigned to eat 6 eggs every week containing either 331 micrograms (Egg1) or 964 micrograms (Egg2) of lutein and zeaxanthin per yolk, or a placebo (a sugar-filled pill).
No changes in cholesterol levels were seen in the women eating eggs, but in those given the placebo (the sugar pill), increases in total cholesterol and triglycerides were recorded.
Unlike the first study, only blood levels of zeaxanthin, but not lutein, increased in both Egg1 and Egg2 groups; however, carotenoid levels in the retina (MPOD) increased in both egg intervention groups, a result that suggests a daily egg offers protection against AMD.
Although egg yolk contains less lutein and zeaxanthin than some other foods-spinach, for example-when supplied by eggs, these carotenoids appear to be especially well absorbed into the retina. "Increasing egg consumption to 6 eggs per week may be an effective method to increase MPOD," wrote lead study author Wenzel.
So, enjoy a quick and easy, vision-sustaining poached or soft boiled egg for breakfast. Take an egg salad sandwich to work or add a hard boiled egg to your luncheon salad. On the weekend, treat yourself to our Healthy Breakfast Frittata or Egg Crepes filled with veggies, one of the delicious egg recipes featured in The World's Healthiest Foods Essential Guide. We suggest choosing organic omega-3-rich eggs if available. Produced by hens fed a diet rich in flaxseed, these eggs are an exceptional source not only of lutein and xeaxanthin, but anti-inflammatory omega-3 essential fatty acids as well.