Cooking Oil Selection Guide

When choosing a healthy cooking oil, the main factors to consider are: aflatoxins, erucic acid, whether it’s genetically modified, unsaturated fatty acids, and cooking temperature. Recently, prompted by the news about industrial oil tanker trucks being used to transport edible oil, we also need to consider the potential risk of mineral oil contamination. Beyond these six health factors, we also need to consider whether the price is reasonable.

1. Aflatoxins

As is well known, aflatoxin is a potent carcinogen with extremely high toxicity, particularly harmful to the liver. Long-term exposure to even trace amounts of aflatoxin can increase the risk of liver cancer. Aspergillus flavus and Aspergillus parasiticus are widespread in soil, plants, and decaying organic matter, and they grow and reproduce more easily in warm, humid environments. Common oilseed crops can become contaminated with aflatoxin during production, harvesting, processing, and storage if humidity and temperature are not properly controlled. Oilseed crops with higher aflatoxin content include peanuts, soybeans, and rapeseed. In traditional oil pressing methods, contamination can come not only from the raw materials themselves but also from unclean oil presses. Although temperatures above 250°C can break down aflatoxins, Chinese kitchens rarely reach this temperature even during high-heat stir-frying.

2. Erucic Acid

Erucic acid is a monounsaturated fatty acid. Rapeseed oil has a relatively high erucic acid content. It is metabolized slowly in the human body, and long-term intake of high levels of erucic acid may have adverse health effects. High erucic acid intake can lead to fat deposits in the heart muscle, affecting cardiac function. Additionally, some animal studies suggest that excessive erucic acid intake may affect growth and development. This is why healthy rapeseed oils nowadays like to advertise low erucic acid content. However, as with any toxin, the dose matters; even at low levels, long-term consumption isn’t scientifically advisable.

3. Genetically Modified or Not

Genetically modified foods have been around for a relatively short time—the world’s first commercialized GM food was only born in the United States in 1994. In just 30 years, GM foods have achieved enormous economic and environmental benefits. For example, genetically modified soybeans have improved pest resistance and herbicide tolerance, increasing yields while reducing pesticide use, with positive effects overall. However, GM technology has existed for such a short time that its long-term safety remains a highly debated topic. Whether to eat them or not is a personal choice. That said, when dining out, we inevitably come into contact with GM foods to some degree. But when it comes to choosing cooking oil for your own home, you can still make that decision yourself—labels clearly indicate whether an oil is made from genetically modified ingredients.

4. Unsaturated Fatty Acids

Unsaturated fatty acids are a class of fatty acid molecules whose carbon chains contain one or more carbon-carbon double bonds (C=C). Unsaturated fatty acids are generally liquid at room temperature and offer many health benefits, including lowering bad cholesterol levels, reducing the risk of cardiovascular disease, helping reduce inflammation in the body (some research suggests that human aging is essentially a process of repeated inflammatory responses), and being beneficial for brain development (children especially should eat them). The opposite of unsaturated fatty acids is saturated fatty acids; the animal fats we commonly consume in large quantities contain very high levels of saturated fatty acids, and it’s advisable to eat less of them.

5. Cooking Temperature

When certain cooking oils are heated to high temperatures, they can produce harmful substances. These include acrylamide, free radicals, and polycyclic aromatic hydrocarbons, which may be harmful to health. Common oils that break down easily at high temperatures: sunflower oil, soybean oil, corn oil, grape seed oil. It’s recommended to lower the cooking temperature when using these oils. Oils that are more stable at high temperatures: peanut oil, rapeseed oil, olive oil, coconut oil.

6. External Contamination of Cooking Oil

Transportation via oil tanker trucks can contaminate cooking oil. So why do some manufacturers source oil externally? It generally comes down to a few scenarios:

• Small brands lack sufficient production capacity. Some small factories can’t meet demand on their own and purchase oil in bulk to bottle under their own brand.
• Large brands with multiple plants transport oil between facilities to balance production capacity.
• Bulk purchasing channels. Companies or oil vendors with large oil requirements purchase in bulk. These scenarios essentially cover all the channels through which we buy cooking oil. Oil manufacturers won’t voluntarily admit to mineral oil contamination, so ordinary consumers have no way to avoid eating contaminated oil. But if you can’t fight it, you can at least avoid it.

7. Price

Here’s a price comparison for 1L of oil, based on JD.com data:

Perilla oil, camellia oil, olive oil > grape seed oil > peanut oil, flaxseed oil, linseed oil, coconut oil > sunflower oil > soybean oil, rapeseed oil, corn oil

Perilla oil, camellia oil, and olive oil are relatively expensive, with 1L generally priced above 80 RMB; Grape seed oil is about 40 RMB per liter; Peanut oil, flaxseed oil, linseed oil, and coconut oil are around 20–30 RMB per liter; Soybean oil, rapeseed oil, corn oil, and sunflower oil are about 8–16 RMB per liter.

Based on these seven factors, let’s use a scientific approach to select cooking oils that are both healthy and relatively safe:

According to data from China Forward Industry Research Institute, the main cooking oil varieties consumed in China are soybean oil, rapeseed oil, palm oil (mainly used in industrial foods and fast food restaurants), peanut oil, and sunflower oil. In 2022, soybean oil consumption accounted for 29.6% of China’s edible vegetable oil consumption; followed by rapeseed oil at 14.5%; and palm oil at 8.8% of total consumption.

The higher the sales volume of an oil, the more manufacturers and sales channels it has, making it more susceptible to transportation contamination—and the oil exposed in this news was precisely soybean oil. So let’s exclude soybean oil and rapeseed oil; and due to aflatoxin, erucic acid, and GMO concerns, we again exclude rapeseed oil and soybean oil; corn oil and peanut oil are also ruled out. Oils priced above 30 RMB per liter are too costly for regular consumption; otherwise grape seed oil and olive oil would be the best choices—heat-resistant, rich in unsaturated fatty acids, and non-GMO. That leaves sunflower oil and flaxseed oil as excellent options; both crops are essentially non-GMO; sunflower oil is rich in unsaturated fatty acids and vitamin E; flaxseed is rich in alpha-linolenic acid, a plant-based Omega-3 fatty acid that helps reduce inflammation, support heart health, and brain function.

The author’s personal favorite used to be sunflower oil. Ukraine is the world’s largest sunflower seed producer; after the Russia-Ukraine war, the most repurchased Ukrainian imported sunflower oil was no longer available. Combined with the recent tanker truck mineral oil contamination incident, perhaps lesser-known cooking oils are the safest bet, such as flaxseed oil.