Many South Africans cook with it daily, often without realising how much of it they consume. It is in our frying pans, processed foods, takeaways and vegetable oil blends.
However, a new scientific study suggests that this familiar kitchen staple may affect the body in ways we don’t expect. This raises questions about the health impact of a popular cooking oil and its role in weight gain.
The findings, although from research on mice, could potentially explain why some people are more prone to storing fat than others when consuming this popular cooking oil.
Popular cooking oil health impact – what the study found
Researchers at the University of California, Riverside, explored how a widely used oil affects the body’s metabolic pathways. In controlled laboratory studies, mice were fed a high-fat diet containing large amounts of soybean oil.
They gained significantly more weight than genetically engineered mice consuming the same diet. This finding led researchers to investigate further, determining the health effects of soybean oil.
The researchers found the difference in weight gain linked to a liver protein called HNF4α. It regulates hundreds of genes related to fat metabolism. The genetically modified mice produced an alternative form of this protein that altered how their bodies processed linoleic acid, the main fatty acid found in the oil.
As a result, they generated far fewer oxylipins, inflammatory molecules created when the body breaks down certain fats. This protected them from weight gain and liver stress.
The study’s authors say this suggests it isn’t simply the oil itself causing metabolic changes, but what the oil turns into inside the body. However, further research in humans would be necessary to draw firm conclusions.
Humans also produce both versions of the HNF4α protein; however, the alternative form typically appears during chronic illness, metabolic strain or fasting.
“This may be the first step towards understanding why some people gain weight more easily than others on a diet high in this type of oil,” said Sonia Deol, a biomedical scientist and co-author of the study published in the Journal of Lipid Research.
Another researcher, Frances Sladek, a UCR professor of cell biology, added:
“It’s not the oil itself, or even linoleic acid. It’s what the fat turns into inside the body.”
What this could mean for South Africans
Soybean oil is more common in South African kitchens than many people realise. Several bottles labelled simply as vegetable oil contain it. Soybean oil is ideal for frying, baking, and takeaways and they often use it in ultra-processed foods, which should already tell us more about the health efect of this oil.
While the findings come from animal studies, experts note that the metabolic pathways involved are highly similar in humans. The concern is more about high, chronic intake, especially in diets rich in processed foods.
“The quantities in which we consume it are triggering pathways our bodies didn’t evolve to handle,” Sladek said.
Should you be worried about consuming soybean oil?
There are often larger debates over whether seed oils, or vegetable oils, which include soybean oil, are beneficial or detrimental to our health.
Some sources argue that replacing saturated fats (like butter or animal fat) with polyunsaturated fats from seed oils tends to reduce “bad” LDL cholesterol and lower cardiovascular risk.
At the opposite end, others suggest seed oils are heavily processed and involve chemical solvents (such as hexane), refining, bleaching, and deodorising, and that these processes strip some nutrients away.
Whether you are for or against it, you can take simple steps to minimise the health impact of this popular cooking oil:
- Rotate between different oils
- Read labels to check whether “vegetable oil” means soybean oil
- Limit deep-fried and ultra-processed foods, which tend to contain high-linoleic seed oils.
Soybean oil as cooking fat probably won’t leave our shelves anytime soon, and may affect our metabolisms. This opens the door to questions about the health impact of popular cooking oils and how modern diets shape long-term health.
