Frying in olive oil infuses vegetables with extra nutrients

fried eggplant
CC BY 2.0 Jeremy Eades -- A plate of fried eggplant

Say goodbye to insipid boiled veggies; frying can actually improve their nutritional profile, study finds.

Here is a piece of happy news for you on a Tuesday morning. There is no need to compromise flavor for health! A new study out of the University of Granada, Spain, has found that frying vegetables in extra-virgin olive oil (EVOO) can be healthier than boiling.

Since olive oil is used so extensively in Mediterranean cuisine, the researchers decided to take a closer look at what really happens when vegetables are cooked. There is a common assumption that less oil is better when cooking, and that vegetables are healthiest when raw (or closest to a raw state). From the press release:

"It is often thought that when we cook raw vegetables in certain ways and using certain cooking techniques, their antioxidant properties, such as the phenolic compounds, are to some degree lost or destroyed."

The researchers took four popular vegetables -- eggplant, tomato, potato, and pumpkin -- and cooked them three ways. One method was frying in extra-virgin olive oil, another was boiling in water, and a third was boiling in a mixture of water and olive oil.

"The vegetables were also kept in optimum conditions in order to accurately measure their moisture, fat, dry matter, and phenol contents, along with their antioxidant capacity, before and after each cooking method was employed."

What they found was surprising. The fried vegetables had higher level of natural phenols, which are antioxidants that have been linked to the prevention of chronic degenerative diseases such as cancer, diabetes and macular degeneration. The reason for this was that the olive oil essentially transferred its phenols to the vegetables, enriching their nutritional value. The authors wrote:

"The presence of EVOO in cooking increased the phenolics identified in the raw foods as oleuropein, pinoresinol, hydroxytyrosol and tyrosol, and the contents of vegetable phenolics such as chlorogenic acid and rutin."

Boiling, on the other hand, resulted in the transfer of phenols to the water, which meant nutrients are retained if a person drinks the broth along with the cooked vegetables (in the case of a soup), but lost if not. Overall, the number of phenols was not increased by boiling, as it was with frying.

The tradeoff, of course, is calories. Frying in olive oil results in a much more calorically dense food, but for those people opting for a higher-fat, lower-carb diet, this shouldn't be a concern. Olive oil is considered a 'good fat', filled with monounsaturated fatty acids.

The press release describes this as a breakthrough in the field of nutrition and food science, a discovery that will have a significant effect on perceptions of 'healthy' and 'unhealthy' ways of preparing foods. It is certainly one that will please many a home cook and hungry eater.

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