How to prepare garlic and onions should be avoided because they can be harmful

In a recent study published in the journal Food Research International , Japanese scientists discovered that frying garlic and onions at high temperatures with vegetable oil can create trans fatty acids (TFA). This type of fat is not good for cardiovascular health, according to the health news site Medical Xpress (USA).

Garlic and onions should not be cooked at temperatures above 140 degrees Celsius.

Trans fatty acids are a type of fat that can build up along artery walls, restricting blood flow and significantly increasing the risk of heart attack. They are often found in processed foods. However, they can also form during food processing.

A common example is polyunsaturated fatty acids (UFA), which are considered healthy fats and are found in olive oil, canola oil, chia seeds, flax seeds, avocados, almonds, walnuts, and fatty fish such as salmon, tuna, herring, and mackerel. However, if cooked at too high a temperature, these beneficial fats will be converted into harmful fats called trans fatty acids.

In the study, scientists wanted to test whether sulfur-containing compounds such as isothiocyanates and polysulfides in garlic, onions, cabbage, broccoli, and horseradish affect the unsaturated fatty acids in soybean and olive oils.

The team of scientists discovered that when cooking at high temperatures, especially above 140 degrees Celsius, sulfur compounds in garlic and onions will strongly promote the process of trans isomerization. This is the process of transforming polyunsaturated fatty acids (UFA), a beneficial type of fat found in soybean oil and olive oil, into harmful trans fatty acids. Meanwhile, when processed at moderate temperatures, only a small amount of trans fatty acids are created.

Therefore, to ensure health, experts recommend that people can use vegetable oil when processing garlic and onions but should not heat it above 140 degrees Celsius. If processing at high temperatures is required, replace it with avocado oil or coconut oil. The trans isomerization process of these oils is less than that of soybean or olive oil, thereby creating less trans fatty acids, according to Medical Xpress .