A new study reveals that sulfur-containing vegetables such as garlic and onions can promote the formation of trans-fatty acids (TFAs) when cooked at high temperatures, raising concerns over everyday cooking practices.
A new study uncovers an alarming discovery: sulfur-containing vegetables can contribute to the formation of detrimental trans-fatty acids (TFAs) during cooking. TFAs, often associated with processed foods, have now been linked to home-cooked meals involving certain vegetables.
Trans-fatty acids are notorious for their role in cardiovascular diseases, accumulating along artery walls, restricting blood flow and raising the risk of heart attacks. According to the World Health Organization (WHO), TFAs are responsible for over 278,000 deaths annually worldwide and recommend limiting TFA consumption to less than 1% of daily energy intake. While prevalent in fried and processed foods like margarine and biscuits, a new concern has emerged around natural cooking processes.
Research led by Junji Obi of Nissui Corporation and Masaki Honda, an associate professor of science and technology at Meijo University, has shed light on how sulfur compounds in vegetables like garlic and onions can accelerate the transformation of unsaturated fatty acids (UFAs) into TFAs when subjected to high temperatures. The study, published in the journal Food Research International, delves into this previously unexplored area.
“We wanted to understand the principal characteristics of UFA isomerization in TAGs [triacylglycerols] promoted by sulfur compounds through a model system using reagent-grade sulfur compounds and triglycerides,” Obi, the first author of the paper, said in a news release. “We were interested in the effects of temperature, reaction time, sulfur compound concentration, the type of sulfur compounds and addition of antioxidants on UFA isomerization.”
Utilizing a dual approach, the researchers first examined the impact of sulfur compounds in a controlled model system, followed by experimenting with common ingredients such as garlic, onion, leek, cabbage, horseradish and broccoli sprouts. They sought to simulate real-world cooking scenarios with vegetable oils like soybean and olive oils.
The findings are noteworthy; sulfur compounds significantly enhance the heat-induced trans-isomerization of UFAs in vegetable oils at cooking temperatures above 140°C. Antioxidants like α-tocopherol were observed to mitigate this effect, particularly against isothiocyanates, yet had minimal impact on polysulfides. This critical insight implies that dishes involving polysulfide-rich vegetables, such as garlic and onions, when cooked at high temperatures, could result in trans-fat formation.
Despite this, the study suggests that under ordinary cooking conditions, the increase in TFA formation remains minimal, affecting the trans-isomer ratio by just a few percentage points.
“Release of TFAs under normal cooking conditions is expected to be minimal. Therefore, excessive caution is unnecessary. However, it is important to understand that cooking with ingredients rich in natural sulfur compounds may increase the risk of TFA intake,” added Honda, the corresponding author.
This breakthrough is a crucial piece of the dietary puzzle, especially for health-conscious individuals who favor home-cooked meals over processed foods. Understanding the nuances of how ingredient properties influence health outcomes can guide safer cooking practices and dietary choices. The study’s insights call for a balanced approach, blending cautious cooking techniques with informed ingredient choices to maintain cardiovascular health.