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Researchers at the University of Bari’Aldo Moro in Italy conÂducted a study on layÂing hens to deterÂmine if includÂing extra virÂgin olive oil in their diets would influÂence egg qualÂity and yolk choÂlesÂterol levÂels, findÂing that eggs from hens fed high polypheÂnol EVOO had lower choÂlesÂterol conÂtent and a betÂter fatty acid proÂfile. The study, pubÂlished in the jourÂnal Lipids in Health and Disease, sugÂgests that feedÂing hens a diet rich in polypheÂnol EVOO could lead to the proÂducÂtion of healthÂier eggs that may be benÂeÂfiÂcial for human health.
Eggs are a breakÂfast staÂple for most peoÂple. Although an excelÂlent source of proÂtein, peoÂple with high choÂlesÂterol levÂels, heart disÂease or diaÂbetes often avoid eatÂing eggs because high choÂlesÂterol conÂtent of egg yolk is believed to raise blood choÂlesÂterol levÂels.
So what if eggs could be lower in satÂuÂrated fat and choÂlesÂterol? Several studÂies conÂducted on fat intake of hens have shown that the type of dietary fat influÂences lipid comÂpoÂsiÂtion of egg yolks. In one such study, hens fed soyÂbean oil had egg yolks with a higher conÂtent of omega‑6 polyunÂsatÂuÂrated fatty acids; while those fed linÂseed oil had a higher conÂtent of omega‑3 polyunÂsatÂuÂrated fatty acids.
Based on results of past studÂies and the fact that polypheÂnols in extra virÂgin olive oil proÂvide proÂtecÂtion against heart disÂease, researchers at the University of Bari’Aldo Moro’ in Italy decided to includeÂexÂtra virÂgin olive oil in the diets of layÂing hens to deterÂmine if it would influÂence egg qualÂity.
The study, pubÂlished in the February 2015 issue of the jourÂnal Lipids in Health and Disease, evalÂuÂated the effects of dietary supÂpleÂmenÂtaÂtion of hen feed withÂexÂtra virÂgin olive oil from two difÂferÂent olive culÂtiÂvars with difÂferÂent polypheÂnol conÂtent on egg qualÂity and egg yolk choÂlesÂterol.
In a first of its kind study, researchers divided 150 layÂing hens into three groups and fed them a norÂmal wheat and soyÂbean meal that difÂfered only in the source of oil for 10 weeks.
All feeds conÂtained 2.5 perÂcent of oil as either sunÂflower oil for the conÂtrol or first group;extra virÂgin olive oil with low polypheÂnol conÂtent of 38 mg/kg from the Cima di Bitonto variÂety for the secÂond group; andexÂtra virÂgin olive oil that conÂtained a high conÂtent of polypheÂnols of 254 mg/kg from the Coratina variÂety for the third group of hens.
Egg layÂing rate, egg weight and egg shell qualÂity were simÂiÂlar in hens of all three groups. The amount of polypheÂnols in the feed, howÂever, was found to influÂence egg yolk color score, which was lowÂest in eggs from hens fed sunÂflower oil and highÂest in eggs from hens fedexÂtra virÂgin olive oil with high polypheÂnol conÂtent.
Similarly, hens fed high polypheÂnolexÂtra virÂgin olive oil laid eggs that had lower total yolk choÂlesÂterol levÂels than hens fed low polypheÂnol extra virÂgin olive oil. The total choÂlesÂterol conÂtent of egg yolk decreased by 4.04 perÂcent in hens fed low polypheÂnol EVOO, while it decreased by 6.74 perÂcent in hens fed high polypheÂnolexÂtra virÂgin olive oil when comÂpared to choÂlesÂterol levÂels in egg yolks from the conÂtrol group.
Additionally, eggs from the high polypheÂnolexÂtra virÂgin olive oil group had lower satÂuÂrated fatty acids, higher polyunÂsatÂuÂrated fatty acids and a betÂter satÂuÂrated to unsatÂuÂrated fatty acid ratio than conÂvenÂtional eggs. The atheroÂgenic index also decreased as the conÂtent of polypheÂnol of the diet increased — 0.77 in egg yolks of hens fed the high polypheÂnolexÂtra virÂgin olive oil diet, 0.86 in egg yolk of hens fed low polypheÂnolexÂtra virÂgin olive oil and 1.09 in the conÂtrol group.
Findings of this invesÂtiÂgaÂtion indiÂcate that feedÂing layÂing hens a diet that includes polypheÂnol-rich EVOO could lead to the proÂducÂtion of eggs that have lower choÂlesÂterol conÂtent and a betÂter fatty acid proÂfile as comÂpared to conÂvenÂtional eggs. According to the authors of the study, such healthÂier eggs could be benÂeÂfiÂcial for human health.