NEW YORK, BRONX (ORDO News) — The falafel experiment provided compelling evidence that overused frying oil impairs testicular function by increasing oxidative stress—cell damage caused by oxidation.
Egyptian scientists from Al-Azhar University conducted an experiment with fried falafel and assessed the effect of palm oleic oil used for frying on the tests of laboratory rats. The results were published in the journal Toxicology Reports.
Deep frying is a popular cooking method around the world that involves immersing food in boiling oil. It immediately forms a crust and penetrates into the food as it cools. In Middle Eastern countries, including Egypt, they like to deep-fry falafel – this is the most common street food, which is dried fava beans, chopped and mixed with leeks, parsley, onions, garlic and salt. Street vendors usually fry balls of this mixture in refined palm oleic oil.
Exposure to oxygen, ingress of water, reuse of oil, violation of temperature and cooking time all leading to hydrolysis, polymerization, oxidation of oil and lipids, as well as degradation of its physicochemical and antioxidant properties, followed by oxidative stress and the release of free radicals. Consuming frying oil, which has been used repeatedly, is carcinogenic and leads to negative health consequences, such as hypertension, atherosclerosis, cardiovascular diseases, liver and kidney dysfunction.
“In the new study, we focused on the effects of repeatedly deep-fried refined palm olein used in falafel on rat testes. As far as we know, this has not been discussed in any previous scientific work,” the scientists noted.
Fresh refined palm oleic oil was purchased from a market in the Egyptian city of Assiut. Four kilograms of this oil were added to a wok and heated to 180 degrees Celsius. Every day, about five kilograms of falafel were fried in it four times.
The experiment itself involved 21 mature male Wistar rats. Seven animals were kept in cages and had unlimited access to fresh water and special food. They were divided into three groups – seven rodents in each.
The first, control, group was administered distilled water through a gastric tube for 28 days, the second was given fresh palm oleic oil (at the rate of one milliliter per 100 grams of body weight), the third was given the same oil in which falafel was repeatedly fried. After four weeks, the subjects fasted for 12 hours, after which they were killed.
The scientists then drew blood to analyze testosterone levels, and the left testicle of each rat was removed, divided into two parts, weighed and tested – including lipid peroxidation and antioxidant enzymes (superoxide dismutase and glutathione peroxidase). The authors of the work also determined the number of sperm and their motility.
During the experiment, not a single animal died, and scientists did not observe side effects such as a sharp change in body weight. The weight of the testes in rats from all groups was the same.
However, in rodents that received repeatedly used frying oil, a strong increase in the level of malondialdehyde was found in the testes compared to the other two groups (this aldehyde occurs in the body during the degradation of polyunsaturated fats by reactive oxygen species and acts as a marker of both fat peroxidation and oxidative stress) and a decrease in the level of the main cellular antioxidant glutathione, which protects against toxic free radicals and determines the redox characteristics of the intracellular environment. In addition, these rats showed a decrease in the activity of other components of antioxidant defense, such as superoxide dismutase.
In subjects who were injected with reused oil, the concentration and motility of sperm decreased sharply, and the number of abnormal gametes, on the contrary, increased significantly. According to scientists, this was influenced by oxidative stress.
Finally, histological examination of the testes of rats fed repeated use of frying oil showed that their tubules degenerated to varying degrees.
“They were widely separated and irregular, with interruption of the basement membrane, disorganization and vacuolization of the spermatogonial cells. The tubular lumen was wide, no sperm were detected, and the number of interstitial Leydig cells appeared to be decreased. These results are likely due to oxidative stress and low testosterone levels,” the researchers added.
Testosterone is essential for normal sperm development: it plays an important role in spermatogenesis and serves as the main hormone for spermatogonia differentiation and spermatid production. Therefore, a decrease in the level of this androgen will lead to male infertility.
Scientists have warned that further research is needed to assess the quality of oil used in street food. In addition, strict monitoring of street vendors by health authorities and educating people about the consequences of consuming repeatedly heated oils are crucial.
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News agencies contributed to this report, edited and published by ORDO News editors.
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