Effects of Repeated Use of Vegetable Oil on the Brain
Most of the oil used to fry chicken and french fries, or all kinds of skewers, is vegetable oil for repeated frying. Soybean oil, corn oil, sunflower oil, peanut oil, and other vegetable oils are rich in omega-6, and the situation is very different when they are reused.
In the food processing field, vegetable oils are often reused for deep-frying many times to reduce costs, a practice that poses many potential risks.
Repeated frying causes oxidative degradation of vegetable oils, which in turn releases free radicals. The oxidative reactions triggered by these free radicals not only lead to the rancidity of fats and oils but also generate oxidative stress in biological systems, posing a threat to human health.
It will interfere with the normal synthesis, release, and metabolism of neurotransmitters, and disrupt the balance of the brain’s internal environment. Just like an originally harmonious and orderly ecosystem, a sudden intrusion of destructive elements will be thrown into chaos, which in turn will damage brain health.
Repeated Use of Vegetable Oil Harms the Brain
This is a study from Abakaliki, Nigeria that examined the effect of repeated use of vegetable oil by fast food vendors on brain neurotransmitters in normal albino rats.
The researchers selected 35 healthy albino rats, which were randomly divided into five groups labeled A, B, C, D, and E, with seven rats in each group.
Among them, Groups A and B are control groups, and Groups C, D, and E are experimental groups.
Group A (normal control group): received normal feed and water.
Group B: received 5 mL/kg body weight of fresh vegetable oil (FVO) orally.
Group C: received 5 mL/kg bw of reused vegetable oil (RVO) orally.
Group D: 2.5 mL/kg body weight of RVO by mouth.
Group E: 1.5 mL/kg bw of RVO orally.
Before starting the experiment, rats were given 7 days to acclimatize to the conditions. The treatment period lasted 42 days, and body weights were recorded every 7 days. The researchers took brain samples from the rats and analyzed levels of key indicators such as serotonin, dopamine, norepinephrine, acetylcholinesterase (AChE), and epinephrine.
→ Repeatedly used oils harm brain neurotransmitters and trigger depression
The experiment’s results showed that rats consuming reused vegetable oil (RVO) had significantly lower levels of norepinephrine, dopamine, and 5-hydroxytryptamine (serotonin) in their brains than rats consuming fresh vegetable oil and a normal diet.
Decreased levels of norepinephrine may cause a depressive mood and can cause a loss of enthusiasm for life;
A decrease in dopamine can dry up sources of pleasure and affect motor coordination;
A decrease in serotonin may lead to sleep disorders, anxiety, and other problems.
Meanwhile, adrenaline levels and acetylcholinesterase (AChE) activity increase. Elevated adrenaline can be a constant source of stress, which may lead to cardiovascular problems in the long run. Acetylcholinesterase (AChE) is the enzyme responsible for facilitating the breakdown of acetylcholine (ACh) and the production of acetic acid and choline.
Its increased activity accelerates the breakdown of acetylcholine, interferes with the normal transmission of acetylcholine, and disrupts signaling in the nervous system, which in turn affects cognitive functions, such as the ability to learn and remember.
→ Repeatedly used oils that make you fat
Rats consuming both reused vegetable oil (RVO) and fresh vegetable oil (FVO) showed a significant increase in body weight, and the weight gain showed a time-dependent pattern.
This suggests that both fresh and reused vegetable oils have an effect on the metabolism of the rats, causing them to gradually become “mellow”.
The weight gain indicates that the fat in the vegetable oil accumulates in the body tissues, and what may seem to be a mere change in numbers hides behind it complex health problems, such as an increased risk of chronic diseases such as diabetes and high blood pressure due to obesity.
→ Re-used oil, oxidized, damages the body
At high temperatures (160-190°C), oils and fats are repeatedly heated and undergo oxidative reactions, which result in changes like increased foam formation, increased viscosity, deeper color, and lower smoke point.
Oil undergoes polymerization, hydrolysis, and oxidation when heated. During frying, a variety of oxidized substances are formed, such as aldehydes and hydroperoxides. As a result of heating, the vitamin E content of the oil decreases and loses its favorable properties.
The lower smoke point means that the oil breaks down at lower temperatures, producing smoke and harmful substances, including saturated and unsaturated aldehydes and ketones (a harry smell), polycyclic aromatic hydrocarbons (PAHs), etc., which pose a potential risk to human health.
Foam increase is the occurrence of a hydrolysis reaction, was fried food at high temperatures releases water, prompting the hydrolysis of fats and oils, fatty acids, so that the oil quickly rancid and rancid.
Repeated heating causes the geometric configuration of the fatty acid molecule to change from the cis (cis) isomer to the trans (trans) isomer, and trans fatty acids are associated with an increased risk of cardiovascular disease.
Since elevated concentrations of non-heme iron in the brain promote the production of free radicals, the brain is susceptible to oxidative stress, leading to an increased chronic inflammatory response, which in turn increases the risk of neurodegenerative diseases.
Finally, it was concluded that repeated use of vegetable oil affects neurotransmitter levels in the brains of normal rats, posing a risk to the central nervous system and increasing the likelihood of Alzheimer’s disease and Parkinson’s disease.
What are the dangers of repeatedly heating vegetable oil?
→ Elevated blood pressure
This rat study investigated the effects of repeated heating of palm oil on blood pressure, plasma nitrites, and vascular reactivity. It showed that fresh palm oil increased plasma nitrites by 28%, while heating palm oil 5 times (5HPO) and 10 times (10HPO) reduced them by 25% and 33%, respectively.
Rats fed with repeatedly heated palm oil showed reduced relaxation to acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (SNP, vasodilator) and greater contraction to phenylephrine. In other words, ingestion of repeatedly heated palm oil resulted in elevated blood pressure and impaired vasodilation in rats.
→ Increased risk of cardiovascular disease
Lipid oxidation occurs when vegetable oils are repeatedly heated, leading to the formation of harmful reactive compounds that increase the risk of cardiovascular disease. Long-term consumption of repeatedly heated oils increases blood pressure and total cholesterol, causes vascular inflammation, and predisposes to atherosclerosis. For every 2% increase in TFA intake (as opposed to carbohydrate intake), the risk of coronary heart disease approximately doubles.
This study put 36 male white rabbits on a low cholesterol (0.25%) diet containing 5% unoxidized corn oil (control) and 5% oxidized corn oil (oxidized lipid diet) for 12-14 weeks. In both groups, most of the serum cholesterol was in β-very low-density lipoprotein (β-VLDL).
The β-VLDL of the control rabbits contained 3.86 +/- 0.57 conjugated dienes per micromole of cholesterol, whereas the β-VLDL of the rabbits consuming the oxidized lipid diet contained 9.07 +/- 2.14 nmol of conjugated dienes. Among other things, intake of a diet rich in oxidized lipids resulted in a 100% increase in aortic fatty streak lesions, an important risk factor for atherosclerosis.
→ Repeated use of soybean oil, vascular blockage
Another study examined the deleterious effects of repeated heating of soybean oil on atherosclerosis using ovariectomized rats (representing estrogen-deficient states). 24 ovariectomized female rats were divided equally into 4 groups, with the control group fed a 2% cholesterol diet containing no oil at all, and the 3 treatment groups receiving a 2% cholesterol diet with fresh, 1-heated, and 5-heated (repeated) soybean oil.
Compared to ovariectomized rats fed fresh oil, rats with repeatedly heated oil had significantly higher levels of lipid peroxidation low-density lipoprotein (LDL), and higher levels of homocysteine, also suggesting that repeatedly heated oil promotes the development of atherosclerosis.
How to Reduce the Risks of Vegetable Oil?
First of all, you should reduce the frequency of eating fried foods. Don’t eat all kinds of fried foods such as fried chicken and French fries and skewers outside. It is recommended that if you want to eat deep-fried to fry yourself at home, do not use oils with high Omega-6 content, use lard, coconut oil, or olive oil with a high ignition point east is fine.
For food that needs to be deep-fried, try to finish the frying in one go, avoiding frying in batches resulting in repeated heating of the oil. Use an oil thermometer to monitor the temperature of the oil during the frying process to avoid high temperatures that may cause the oil to decompose and oxidize. After deep-frying the food, if the oil has turned visibly dark or has an odor, it should be replaced with new oil and not reused.