Eggs offer potential to improve the nutritive value of a salad, in more than one way.
Egg yolk is among the few commonly consumed foods containing the carotenoid lutein and its stereoisomer zeaxanthin. Spinach and other dark leafy greens may have a higher content per serving, but lutein/zeaxanthin is absorbed and utilized better from egg yolk [Chung, 2004].
Researchers at Purdue University are studying ways to improve carotenoid absorption and tested whether eggs improved absorption of carotenoids, like lutein/zeaxanthin, from raw mixed-vegetable salad. They reported findings at the Experimental Biology 2015 meeting of nutrition scientists.
Drs. Jung Eun Kim, Wayne Campbell and colleagues, fed sixteen healthy college-age men raw vegetable salad or the same salad with either 10.5 or 18 g scrambled eggs (i.e., 7.5 g or 15 g egg, which is equivalent to about 1 ½ or 3 eggs, respectively). All salads contained the same amount of tomatoes, shredded carrots, baby spinach, romaine lettuce, and Chinese wolfberry.
To determine carotenoid absorption, carotenoid levels were measured in the men’s blood over a 10 hour period after eating salads with or without eggs.
Carotenoid levels in blood were 3-9 fold higher for various carotenoids when the men ate salad with 3 eggs compared to plain salad. And it was more than just lutein/zeaxanthin that increased. Carotenoids in the salad also include beta-carotene, alpha-carotene, and lycopene. And all of these carotenoids were absorbed better with the high egg salad.
These findings are consistent with other research by this group showing that adding certain oils to mixed raw vegetables enhances carotenoid absorption.
This means that eggs provided benefits in two ways: as a direct source of lutein/zeaxanthin and by improving the carotenoid value of raw vegetables.
Research related to lutein/zeaxanthin and eggs is cited at the ENC website.
Views expressed by the author may not be those of the Egg Nutrition Center.
Barbara Lyle, Ph.D. is President of B Lyle, Inc. a nutrition consulting and innovation firm, and guest blogger for the Egg Nutrition Center.