Behind the headlines

Does cooking at high temperatures increase your risk of heart disease?

deep frying

South Asian people are at greater risk of heart disease, and new research suggests that high-temperature cooking (such as deep frying) could partly be to blame. We look behind the headlines.  

The research reviewed existing studies and specifically looked at people from India, Pakistan, Bangladesh and Sri Lanka, where deep frying is more common, compared to China, where it is less common and they are less susceptible to coronary heart disease (CHD).

Cooking food at high temperatures changes its chemical structure, producing toxic products called NFCs, such as trans-fatty acids (TFAs) and advanced glycation end-products (AGEs).

These are linked to damaging processes in the blood vessels, which may lead to high blood pressure and hardening of the arteries, researchers suggested.

Since South Asian food is diverse, they focused on Indian cuisine, and broke this down into North and South India. Roasting and frying are the main cooking methods in both regions. Although Chinese cuisine includes frying, the food is mainly cooked by braising, steaming, and boiling, which produce less NFCs because of the lower cooking temperatures and lower fat content.

Is the research reliable?

The researchers were unable to use studies that looked directly at ethnic origin and high-heat cooking, as none currently exist. So the researchers had to analyse studies that looked at food intake for South Asian people.

These studies that they looked at relied on people remembering their food intake, and truthfully writing this down, usually based on a three-day record. Some people may have struggled to accurately recall what they ate over the last three days, so this could make the data less reliable. Also, the AGE levels were calculated by using a food database that gives typical figures for these foods, and this may not always be the same level as the food that was actually eaten.

The BHF view

Tracy Parker, Heart Health Dietitian at the British Heart Foundation, said: “We’ve known for a long time that rates of heart disease in South Asian communities are higher than other sectors of the population. But there are likely to be many reasons for this, including differences in traditional diets as well as genetic factors which put people at higher risk of developing coronary heart disease.

“The researchers suggest that cooking food at high temperatures could increase the risk of heart disease by creating toxic products called NFCs, which early studies show could increase heart disease risk. But there is currently no evidence to support that theory.

“South Asian people often have a high saturated fat intake and trans fat intake, partly due to their use of ghee (clarified butter - a saturated fat) and vanaspati ghee (a type of hydrogenated vegetable oil, which is high in trans fats), which both increase cholesterol levels. To reduce the risk of developing heart disease, use healthier unsaturated oils like rapeseed or corn oil, and cut down on fried food.”

To reduce the risk of developing heart disease, use healthier unsaturated oils like rapeseed or corn oil, and cut down on fried food

Media coverage

The research was featured in The Telegraph, The Sun and The Daily Mail.

In each case, the reporting suggested there was a direct cause and effect – eat less fried food/ steam your food and you are at a lower risk of heart disease. The stories suggested that this applied to “you” the reader, but the research only looked at South Asian people. If you’re not a South Asian reader then it’s unclear how much this link will apply to you.

Moreover, even the scientists themselves were keen to highlight that the research showed a link rather than a cause and effect, and that more research is needed.

The Sun’s headline was ‘DEEP FAT KILLER How gorging on FRIES could kill you – and no, it’s not because they make you fat’. However French fries (chips) were only mentioned once in the report, as one example of a food that’s high in AGEs. Other items that were mentioned that are high in AGEs include tea and coffee with boiled full-fat milk that has been heated for prolonged periods (as it is commonly made in India), roasted coffee beans, and reused oil/fat used for deep-frying, but these were not mentioned in the article. Furthermore, the focus of the study is on the more general link between food cooked in high-temperatures and CHD - the study certainly does not directly say that fries will kill you.

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