Study: Top salads with eggs to better absorb vegetables' carotenoids

WEST LAFAYETTE, Ind. -- Adding eggs to a salad with a variety of raw vegetables is an effective method to improve the absorption of carotenoids, which are fat-soluble nutrients that help reduce inflammation and oxidative stress, according to research from Purdue University.

"Eating a salad with a variety of colorful vegetables provides several unique types of carotenoids, including beta-carotene, lutein, zeaxanthin and lycopene," said Wayne Campbell, a professor of nutrition science. "The lipid contained in whole eggs enhances the absorption of all these carotenoids."

This research is published online in the American Journal of Clinical Nutrition and is funded by the American Egg Board-Egg Nutrition Center, National Institutes of Health and Purdue Ingestive Behavior Research Center.

"Most people do not eat enough vegetables in their diets, and at the same time, people are consuming salad dressings that have less fat or are fat-free," said Jung Eun Kim, a postdoctoral researcher in Purdue's Department of Nutrition Science. "Our research findings support that people obtained more of the health-promoting carotenoids from raw vegetables when cooked whole eggs were also consumed. Eggs, a nutrient-rich food containing essential amino acids, unsaturated fatty acids and B vitamins, may be used to increase the nutritive value of vegetables, which are under consumed by the majority of people living in the United States."

In the study, 16 participants consumed a raw mixed-vegetable salad with no eggs, a salad with one and a half eggs, and a salad with three eggs at different times. All salads were served with three grams of canola oil. The second salad had 75 grams of scrambled whole eggs and the third 150 grams of scrambled whole eggs. The absorption of carotenoids was 3.8-fold higher when the salad included three eggs compared to no eggs.

The study used scrambled eggs to make sure the participants consumed both the yolk and egg whites.

"While other egg forms were not tested, we believe the results would be comparable as long as the egg yolk is consumed," said Campbell, whose research also has looked at salads with different amounts of soybean oil, canola oil and butter. "The lipids in salad dressings also increase the absorption of carotenoids but it is easy to overuse salad dressings and consume excess calories. Many salad dressings contain about 140-160 calories per serving, about two tablespoons. One large whole egg is about 70 calories and provides 6 grams of protein. People are at a greater risk of putting too many calories on a salad because they don't always know proper portion sizes for salad dressings, but you do know the portion size of an egg."

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Note to Journalists: Journalists interested in a copy of the American Journal of Clinical Nutrition article "Effects of egg consumption on carotenoid absorption from co-consumed, raw vegetables" can contact Amy Patterson Neubert, Purdue News Service, at 765-494-9723, apatterson@purdue.edu

The study also included Susannah L. Gordon, a graduate student in the Department of Nutrition Science, and Mario G. Ferruzzi, a professor of food science and nutrition science.

Campbell, whose research focuses on understanding how dietary protein and exercise influence adult health as people age, recently served as a member of the 2015 Dietary Guidelines for Advisory Committee.

Writer: Amy Patterson Neubert, 765-494-9723, apatterson@purdue.edu

Source: Wayne Campbell, campbellw@purdue.edu

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College of Health and Human Sciences

PHOTO CAPTION:

Research led by Wayne Campbell, a Purdue University professor of nutrition science, found that adding eggs to a salad mixed with a variety of raw vegetables is an effective method to improve nutrient absorption. The research is published in the American Journal of Clinical Nutrition. (Purdue University photo/John Underwood)

A publication-quality photo is available at https://news.uns.purdue.edu/images/2015/campbell-eggs.jpg

ABSTRACT

Effects of Egg Consumption on Carotenoid Absorption from Co-consumed, Raw Vegetables

Jung Eun Kim, Susannah L. Gordon, Mario G. Ferruzzi, Wayne Campbell

Background: Dietary lipids are one of the most effective stimulators of carotenoid absorption, but very limited data exist on the impact of endogenous food sources of lipids to enhance carotenoid absorption. The co-consumption of whole egg with carotenoid-rich foods may increase overall carotenoid absorption via lipid-rich egg yolk.

Objective: We designed this study to assess the effects of egg consumption on carotenoid absorption from a carotenoid-rich, raw mixed-vegetable salad.

Design: Healthy young men (n = 16) consumed the same salad (all served with 3 g canola oil) with no egg (control), 75 g scrambled whole eggs (1.5 eggs) [low egg (LE)], and 150 g scrambled whole eggs (3 eggs) [high egg (HE)] (a randomized crossover design). Control, LE, and HE meals contained 23 mg, 23.4 mg (0.4 mg from eggs), and 23.8 mg (0.8 mg from eggs) total carotenoids and 3 g, 10.5 g (7.5 g from eggs), and 18 g (15 g from eggs) total lipids, respectively. Blood was collected hourly for 10 h, and the triacyl- glycerol-rich lipoprotein (TRL) fraction was isolated. Total and individual carotenoid contents, including lutein, zeaxanthin, a-carotene, b-carotene, and lycopene in TRL were analyzed, and composite areas under the curve (AUCs) were calculated.

Results: The total mean (±SE) carotenoid AUC0-10h in TRL was higher for the HE meal than for LE and control meals [125.7 ± 19.4a compared with 44.8 ± 9.2b compared with 14.9 ± 5.2b nmol/ L * 10 h, respectively (values with superscripts without a common letter differ); P < 0.0001]. The TRL AUC0-10h of lutein and zeaxanthin increased 4-5-fold (P < 0.001), and the TRL AUC0-10h of carotenoid not present in eggs, including α-carotene, β-carotene, and lycopene, increased 3-8-fold (P < 0.01) for the HE meal compared with the control meal.

Conclusion: These findings support that co-consuming cooked whole eggs is an effective way to enhance carotenoid absorption from other carotenoid-rich foods such as a raw mixed-vegetable salad.

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