Oil in Salads Increases Absorption of Nutrients

An Iowa State University researcher found that oil brings out the full nutritional benefits of vegetables.

Oct. 18, 2017
By Mary West

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Because nutri­ents in food work syn­er­gis­ti­cally, eat­ing a com­bi­na­tion of cer­tain foods is often more ben­e­fi­cial than eat­ing them alone, and such is the case with driz­zling oil over your salad. The oil boosts the absorp­tion of eight micronu­tri­ents, accord­ing to new research pub­lished in the American Journal of Clinical Nutrition.

The best way to explain it would be to say that adding twice the amount of salad dress­ing leads to twice the nutri­ent absorp­tion.- Wendy White, Iowa State University

While soy­bean oil was used in the study, olive oil would be a bet­ter choice because of the numer­ous health ben­e­fits asso­ci­ated with it.

Lead author Wendy White, an asso­ciate pro­fes­sor of food sci­ence and human nutri­tion also found that eat­ing a salad with­out oil reduced the like­li­hood that the nutri­ents in the veg­eta­bles would be absorbed.

The eight nutri­ents involved are needed for good health. They include four carotenoids: alpha-carotene, beta-carotene, lycopene, and lutein. The remain­ing three are vit­a­min K and two forms of vit­a­min E.

The oil also aided in the absorp­tion of vit­a­min A, which is made in the intestines from alpha and beta-carotene. Increased absorp­tion of the nutri­ents pro­duces impor­tant well­ness advan­tages such as vision preser­va­tion and can­cer pre­ven­tion.


Absorption of the nutri­ents cor­re­lated with the amount of oil added to the salad. This means that the more oil used, the bet­ter the nutri­ents were absorbed.

The best way to explain it would be to say that adding twice the amount of salad dress­ing leads to twice the nutri­ent absorp­tion,” White said.

Despite the find­ings, con­sumers shouldn’t drench their greens with dress­ing, White cau­tioned. Instead, she rec­om­mends fol­low­ing the U.S. dietary guide­line of includ­ing two table­spoons of oil per day in the diet.

In the study, 12 col­lege-age women ate sal­ads with dif­fer­ent amounts of soy­bean oil, which is a stan­dard ingre­di­ent in salad dress­ings. Afterwards, the lev­els of nutri­ents in their blood were mea­sured to deter­mine how much was absorbed. The results showed those who con­sumed the most oil, which was a lit­tle over two table­spoons, absorbed the max­i­mum amount of nutri­ents.

For most peo­ple, the oil is going to ben­e­fit nutri­ent absorp­tion,” White said. The aver­age trend, which was sta­tis­ti­cally sig­nif­i­cant, was for increased absorp­tion.”

Although the study clearly showed that driz­zling oil over sal­ads presents an advan­tage, soy­bean oil may not be the best choice. According to Joseph Mercola, noted nat­ural health prac­ti­tioner, olive oil would be far more health­ful. He warns that soy­bean oil con­tains highly processed omega‑6 fatty acids, which pro­mote inflam­ma­tion, the con­di­tion under­ly­ing most chronic dis­ease.

Conversely, olive oil, a fat rich in antiox­i­dants and impor­tant vit­a­mins, has anti-inflam­ma­tory prop­er­ties and may reduce the risk of chronic dis­eases like car­dio­vas­cu­lar dis­or­ders and dia­betes. In addi­tion, since olive oil is also asso­ci­ated with weight loss, even dieters can pour a lib­eral amount over their greens.


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