Foodstuffs to stay away from in 2024

“The problem comes with heating the oil. You get a saucepan, pour in the oil and heat it. That is where the problem comes because there are chemicals that also turn dangerous once the cooking oil is exposed to high degrees of heat,” Mr Ssemujju tells Sunday Monitor.

The revelation will come as a major surprise to many Ugandans who have been conditioned to fry their food stuffs by pouring oil in a saucepan, heating it to smoke point before pouring their onions, tomatoes and other vegetables and spices. This time-honoured approach, according to Mr Ssemujju, is flawed at all levels.

“You do not have to heat the oil. If I for example have my beans, I can simply pour the oil in there and allow it to be boiled there. That one is very safe,” he disclosed.

Prof Archileo Kaaya, from Makerere University’s Department of Food Technology and Human Nutrition, weighs in saying the danger arises out of the degradation of some of the carcinogenic components of the cooking oil.

The National Human Genome Research Institute describes a carcinogen as a substance or organism or agent capable of causing cancer. Some carcinogens work by interacting with a cell’s DNA to produce mutations.

Repeatedly heated cooking oils (RCO) produce various byproducts, containing polycyclic aromatic hydrocarbons (PAHs) and aldehydes, well-known to be carcinogenic, mutagenic, and tumorigenic properties.

“Direct heating of some of these oils means that they undergo oxidative reactions, which produce some chemicals that have the potential to damage body cells including DNA. This action is a potential risk for many diseases including cancer,” Prof Kaaya says.

Mr Ssemujju adds that direct heating of oils also results in the degradation of some heat-sensitive nutrients such as Vitamin C and antioxidants. These nutrients would otherwise help the body to resist the effects of attacks on body cells.

Deep fried foods

In a related development, research findings from Makerere University’s School of Food Technology, Nutrition and Bio-engineering have revealed that deep-fried foods such as fish, chicken, sausages and chips sold on the streets of Kampala are exposing consumers to the risk of cancer and heart diseases and complications. In a peer-reviewed paper titled Knowledge, Attitudes and Practices of Processors of Deep-fried Fish and Potato Chips With Regard to Cooking Oil Quality—A Case of Kampala, researchers state that most of the fried foods sold on the streets are the product of recycled cooking oil.

“Unfortunately, when cooking oil is recycled at high temperatures, it leads to changes in fatty acids from the cis (functional groups on the same side of some plane) to the trans (functional groups on opposing sides) isomer (compounds with the same formula but a different arrangement of atoms),” the paper states, adding that this “is associated with poor health outcomes.” And that “chronic consumption of recycled oil for the duration of 24 weeks is linked to a significant increase in blood pressure.”

These are some of the findings of a cross-sectional research study that was carried out in Kampala Central, Kawempe, Makindye, Nakawa and Rubaga Divisions between January and February 2021.

“These negative health outcomes could be because when oil is recycled, free radicals are generated, and vitamin and antioxidant levels are reduced leading to oxidative stress,” the paper further reveals.

Oxidative stress is an imbalance in one’s body between oxygen-containing molecules and antioxidants or substances used to counteract the deterioration of stored food products. The researchers warned that “the quality of oil will not remain the same once it is used for deep-frying because a higher free fatty acid content is present in such oil.” Yet anecdotal evidence indicates that the cost of living crisis has further popularised recycling of cooking oil.

Risks galore

According to the paper, other illnesses attributed to the same food include cardiovascular diseases and complications such as deposition of fatty material on their inner walls and constriction of the large blood vessels on the surface of the heart.

It is also highly likely to increase the amounts of “bad” cholesterol, a development which increases the risk of heart diseases and strokes. The buildup of cholesterol plaques in the walls of arteries is known to cause obstruction in the flow of blood. That might result in ruptures which might cause acute occlusion of the artery by clots.

Other complications likely to arise from long-term consumption of foods fried using recycled cooking oils are obesity and damage to plasma.

Whereas it is generally agreed that factors including the turnover of cooking oil used, the duration and temperatures at which the frying is done, and the type of foods fried are among the many factors that affect the quality of the cooking oil, most street processors in Kampala were found to keep the oil on fire for hours on end. The processors were also found not to be using the right cooking utensils or handling the food well prior to the frying.

“Many processors keep on fire for prolonged periods, use iron cast pans and do not even bother to dry the food before frying,” the researcher disclosed in their findings, adding that the deep-fried foods ultimately prepared “endanger the health of numerous consumers.”

Why the recycling?

According to the paper, most of the street food processors were aware of the risks associated with the consumption of foods fried using recycled cooking oil, but they seemed to give priority to cutting costs and maximising profits.

“Knowledge of food safety practices does not always cause positive changes in food handling behaviour. About 71 percent were concerned that eating foods fried using recycled cooking oil may cause illness like cancer and food poisoning,” the researchers note, adding, “This discrepancy has been attributed to financial gains being a higher priority than food safety. Despite the relatively good knowledge on the dangers of recycling oils, 78.4 percent of the respondents recycled oil more than thrice daily.”

The paper pointed out that whereas most of the processors were found to be knowledgeable about the quality and characteristics of good cooking oil, and more than a third knew that recycling the cooking oil lowers its quality, the knowledge did not deter them from using the cooking oil until it turns dark.

Whereas 62 percent of the street processors said that they discard the oil once it turns dark, others confessed that they only add new oil to it and the frying continues.

“Half of the respondents believed that it was okay to add fresh oil into recycled cooking oil. More than half did not know the indicators of unsafe recycled cooking oil…More than half of the respondents believed that it was right to add fresh oil to re-used oil. When cooking oil is frequently replenished with new oil, the old one is diluted and is believed to have an extended shelf life,” the paper notes.

It was also found that some of the processors used the same oil to fry different items and many of them never bothered to filter or sieve the oil to remove debris or remains from previous frying sessions.

How it is recycled

It is a given that moisture on food causes violent bubbling during the frying. This leads to rapid development of free taffy acids, which affects the quality of the cooking oil. The researchers, however, established that about 40 percent of the processors do not, for one, dry the chips before frying. They did not know that water affects the quality of the cooking oil.

Nearly a quarter of the respondents were found to be using recycled oil that had been discarded by bigger restaurants and hotels.

“It was very alarming to learn that 21.6 percent of the street processors were using recycled oil discarded by big restaurants and hotels. While they claimed it was cheaper for their business, this type of oil is detrimental to consumers,” the researchers revealed.

Dr Ivan Mukisa, who is attached to Makerere University’s School of Food Technology, Nutrition and Bioengineering, says that he hopes that the findings trigger a response in terms of formulation of policy to improve processors practices and create consumer awareness in the face of the big volumes of harmful degraded products that are on the market.

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