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Recycled cooking oil linked to cancers
Fast food stalls in Kampala. PHOTO/STEPHEN OTAGE
What you need to know:
- Research indicates that repeated heating of cooking oil often leads to its degradation, causing the formation of products that are toxic to consumers.
Makerere University researchers have linked the commonly used recycled cooking oils and deep-fried foods like potato chips and fish in Kampala to an increased risk of cancer and heart disease.
This information is contained in a new study report by Emmanuel Okalany and his colleagues from the Makerere University School of Food Technology, Nutrition and Bioengineering. It was published in March this year in Applied Food Research, an academic journal.
The researchers said they collected samples of recycled cooking oils used to separately deep-fry potato chips (35 samples) and fish (35 samples) from street food vendors in Kampala and then analysed them.
“The majority of recycled oil from street food vendors failed to meet quality standards, posing potential health hazards for consumers and compromising the safety of deep-fried foods,” the researchers wrote in the report.
According to the researchers, repeated heating of cooking oil often leads to its degradation, causing the formation of products that are toxic to consumers. They observed that such dangerous products can include “trans fatty acids, free radicals, and other toxins.”
“These (hazardous products formed) get absorbed by the (deep fried) food and are associated with cardiovascular diseases (such as stroke and heart disease), cancers, obesity, diarrhoea, type 2 diabetes and stomach and intestinal discomfort in humans,” the researchers said available evidence shows.
They also noted that some volatile and sweet-smelling substances formed during frying, when inhaled over time “expose food processors to respiratory tract cancer.”
“Over 94 percent of oils used to deep-fry chips and fish obtained from food vendors surpassed the recommended specification for peroxide value. Their mean peroxide values were about four times higher than the recommendation,” the report reads, further.
Peroxide value is a measure of the extent to which an oil has undergone primary oil degradation due to exposure to high heat in the presence of air.
Deep-fried foods are increasingly becoming popular in Uganda and the world over due to their distinct texture (crispy crust and tender and moist inside), and taste amid the effect of rapid urbanisation, according to the available studies and opinions of experts. To cut the cost of preparing deep-fried foods, researchers noted that the oil used is often recycled, or cooking oil is reused.
“This is concerning because deep-frying is done aerobically at 160–190 degrees Celsius leading to oil degradation and formation of hazardous compounds,” they added.
This report is also coming at a time when the Health Ministry is warning of the rise in cases of the above non-communicable disease, partly because of changing lifestyles and the choice of food to eat.
Information from the World Health Organisation (WHO) shows that “33 percent of total deaths are due to NCDs and for every Ugandan citizen, the probability of dying prematurely from one of the four main NCDs is 22 percent.” The WHO also states that more than 278,000 deaths each year globally can be attributed to the intake of trans-fats which can be found in “fried street and restaurant foods often contain industrially produced trans-fat.”
A 2022 study report by researchers at Uganda Cancer Institute (UCI) and Makerere University, indicated that the burden of cancers in Uganda could increase by as high as 40 percent in 2030 due to changes in risk factors and population growth.
Dr David Miti, a specialist at UCI said they are seeing a rise in “gastro-intestinal malignancies –which is cancer of the esophagus (throat), stomach and colon (intestine), and liver.”
He linked this increase to changing lifestyles. “People eat so much processed foods, a problem which is worsened by rapid urbanisation,” he said, adding that “We are becoming more sedentary where people don’t do [physical] exercises.”
According to 2020 study report by Kumar Ganesan from the University of Hong Kong in China, “Repeatedly heated cooking oils (RCO) produce various by-products, containing polycyclic aromatic hydrocarbons and aldehydes [hazardous substances to human health], well-known to be a carcinogenic [cancer-causing], mutagenic [altering genetic material of a person], and tumorigenic [causing formation of tumours] properties.”
Dr Charles Oyoo Akiya, the commissioner for Non-communicable diseases control at the Health Ministry said they are working with community leadership to increase awareness about healthy lifestyle.
“Our emphasis is on reducing the risk factors for non-communicable diseases. We know them, they are linked to our behaviours and they are preventable and requires a lot of commitment,” he said.
“Most of the non-communicable diseases are linked to the foods we eat. We eat a lot of salt, sugar, bad fats, less vegetables, less fruits and many don’t exercise. All this is expounding the problem,” he added.
According to information WHO, “among other dietary factors, high intake of trans fat [which can be found in fried food) increases the risk of death from any cause by 34 percent, coronary heart disease deaths by 28 percent, and coronary heart disease by 21 percent.”
The WHO explains that “Trans-fat clogs arteries, increasing the risk of heart attacks and deaths,” adding that “Trans-fat has no known health benefits.”
American researchers Taraka Gadiraju and colleagues in a 2015 report titled “Fried Food Consumption and Cardiovascular Health: A Review of Current Evidence” advised people to avoid fried foods.
“In summary, there is strong evidence suggesting an association of fried food consumption with a higher risk of developing chronic disease in adults. The strength of current evidence makes it reasonable to recommend complete avoidance of fried foods or at most infrequent to moderate fried food consumption within the context of an overall healthy dietary pattern (rich in fruits, vegetables, whole grains, low sodium, low red/processed meat, among others),” the researchers wrote.
Although some risk factors such as eating safe and healthy foods can be mitigated, researchers from the School of Food Technology say the government is not doing enough in terms of regulation and awareness creation to ensure foods sold to the public are safe.
“Urgent measures such as public education, awareness campaigns, and stringent laws to regulate the usage of commercial cooking oil are needed to protect consumer health,” the researchers recommended.
“The recycling of cooking oil used for deep-frying is thus discouraged despite the economic challenges. Future research should explore the influence of diverse food matrices, oils, and frying equipment on recycled cooking oil quality, establishing safe recycling frequencies for various food types,” the researchers added.
Use the oil once and discard?
Associate Prof Ivan Muzira Mukisa, the head of the Department of Food Technology and Nutrition at Makerere University, who was also one of the researchers in the study, told this publication it is advisable that in deep frying of foods, cooking oil should only be used once.
“From the study, we noted that just after one frying cycle, the oil starts getting some parameters that make it be considered unsafe,” he said.
“And ideally, you would recommend that you just throw it away. But you know our practices; people keep on reusing and put risks upon yourself,” he added.
According to the new report, cooking oil recycling should at least involve filtration/ decantation and although this does not make the oil completely safe, “it somewhat may make it suitable for reuse in various culinary applications.”
“It also mitigates waste and minimises the environmental footprint associated with used oils. However, some street-food vendors in cities like Kampala, Uganda’s capital ignore this and instead continue to deep-fry several batches of food without basic oil refinement practices,” the researchers noted.
Dr Mukisa says the country has not yet gotten to the point where people are recycling the cooking oil.
“In other countries, some companies put in starch to make it a bit clear, to remove the dark things, but that doesn’t make it safe. We think that after this research, we try to find out if there is anything that can be done to improve these parameters. We haven’t seen that some people are getting the oil and recycling it,” he added.
Government speaks
The Uganda National Bureau of Standards (UNBS), in a statement sent to this publication on Tuesday by their spokesperson, Ms Sylvia Kirabo, warned against recycling cooking oil.
The standards agency asked city authorities and local governments to increase the monitoring of operations of the restaurants and street-food vendors to address these concerns.
“As UNBS, sometimes we get such complaints from the public that some bakeries and probably restaurants or even roadside vendors are reportedly recycling oils that have previously been used by other facilities,” the statement reads.
The agency continued: “This is because it is obtained at a very cheap price. UNBS condemns such vices and calls upon the public health officers in the respective cities, municipalities and towns to curb the vice. As UNBS, we do not regulate restaurants and food vendors, it’s the mandate of the respective local government authorities.”
“UNBS advice to both the consumers and those using recycled oil is: Desist from the use of recycled oil if not originally used by yourself. Recycled oil is contaminated oil and is just unsafe for use. The contaminants are a probable source of several health complications,” UNBS added.
In the same statement, UNBS also appealed to the public to always purchase their products from facilities that have been certified by UNBS. They said there are 76 brands of edible oils and fats currently certified by UNBS.
“This is because the certification process is, at a minimum, an assurance that the entity does some quality assurance in their procurements of the inputs into their processes. UNBS has an open system that allows for the receipt of intelligence, information or complaints. UNBS will go verify the claims and handle the situation according to the guiding Laws and Regulations,” the agency added.
