Will this oil promote cancer metastasis? Can we still eat instant noodles, fried chicken, and puffed foods?

Palm oil is widely used in processed foods, so whether it is healthy or not has attracted much attention. There has always been a saying that "palm oil is high in saturated fat and is bad for health", and there are also reports that "research has found that palm oil can promote cancer metastasis". What exactly is palm oil? Is it really that harmful? Can we still eat palm oil?

01

What is palm oil?

Palm oil is a vegetable oil extracted from the palm fruit of the oil palm tree. It has a long history of use in Africa and Southeast Asia. It is one of the three most widely used vegetable oils in the world, along with soybean oil and rapeseed oil, and has long been ranked first [1]. The consumption of peanut oil, corn oil, sunflower oil, sesame oil, etc., which are familiar to everyone, is far lower than that of palm oil.

Oil palm fruit.

Palm oil is used in food processing, daily chemicals, cosmetics and other fields[2]. Many people may say, "Why do I rarely see palm oil? I hardly use it at home." In fact, this is because you don't pay attention to the product ingredient list. In fact, palm is everywhere around us. Many products around us contain palm oil or palm oil ingredients, such as chocolate, ice cream, instant noodles, and daily toiletries such as shampoo, lotion, sunscreen, lipstick, etc., all contain palm oil or palm oil ingredients[3].

02

What are the advantages of palm oil?

Palm oil is also widely used in food processing because of its unique advantage - a relatively high saturated fat content. Common vegetable oils in our lives are low in saturated fat, so they have a low melting point and are liquid at room temperature. But palm oil is quite special. Its saturated fat content is as high as about 50%, which is not inferior to lard. Secondly, its monounsaturated fatty acid content is also close to 40%, but its polyunsaturated fat content is relatively low, which makes its melting point as high as 35 ° C. It is solid or semi-solid at room temperature, has good stability, is not easy to oxidize and deteriorate, and tastes better.

1) Good taste

From the perspective of molecular structure, the molecular structure of saturated fat is in a long straight line. From the perspective of food processing, when it comes into contact with starch and various celluloses, fatty acids can enter the inner part of the spiral structure of the starch, and finally form a stable spiral structure complex, which makes the viscosity and toughness better. Therefore, palm oil can be solid at room temperature and hidden in food, unlike adding a lot of vegetable oil, which will seep out at room temperature [4]. It gives you a delicate taste without making you feel too greasy.

2) Good thermal stability

Due to its high saturated fat content, palm oil is less likely to undergo violent oxidation reactions at high temperatures[5], making it more suitable for high-temperature cooking such as frying[6] and is most widely used in fried foods[7]. This property also makes it a good substitute for hydrogenated vegetable oil in food processing. Traditional hydrogenated vegetable oil contains a lot of trans fats, and everyone knows that trans fats are bad. Palm oil is popular because it does not contain trans fats and its performance is close to that of hydrogenated oil.

03

Does palm oil promote cancer metastasis?

However, when it comes to palm oil, many people think it is a cheap industrial raw material and a synonym for unhealthy. There are even reports that palm oil can promote cancer metastasis. In fact, this statement exaggerates the harm of palm oil.

The claim that “palm oil promotes cancer metastasis” comes from a study by Spanish scientists[8]. In this study, scientists first briefly added fatty acids to human oral cancer or skin cancer cells when culturing them, and then transplanted these cancer cells into the corresponding tissues of mice fed a standard diet. The results showed that several fatty acids had no effect on the primary tumor, but palmitic acid significantly increased the ability of cancer cells to metastasize to the lungs. Another group of experiments directly fed tumor mice a diet rich in palm oil. Although they only ate it for ten days, the cancer cells transplanted into the mice showed a stronger ability to metastasize. However, this study is only an animal study, which is completely different from human clinical studies. The experimental results are actually very preliminary and very different from our actual diet. There is no need to worry too much.

04

What’s the problem with palm oil?

The real problem with palm oil is the saturated fatty acids it contains. This seems to be a double-edged sword. From the perspective of food processing, it has many advantages, but from a nutritional perspective, it is not good for cardiovascular health. The content of saturated fatty acids in palm oil is basically above 50%, and the saturated fat ratio of commercially used (purified) palm oil can be as high as 80% or more. The current mainstream opinion in the scientific community is that excessive intake of saturated fat increases the risk of cardiovascular disease. For this reason, dietary guidelines and health recommendations from countries around the world remind us to limit the intake of saturated fat. For example, the World Health Organization, the latest U.S. dietary guidelines, and my country's dietary guidelines all recommend that the intake of saturated fatty acids should be less than 10% of total dietary energy.

05

Can we still eat palm oil?

As a kind of oil, palm oil also has its nutritional advantages. It can provide us with fatty acids and energy for human activities. In addition, it contains more tocotrienols, which is a type of vitamin E. It also often contains more carotene, which can be converted into vitamin A in the body. When we consider whether to eat palm oil or not, we cannot ignore the "quantity". In fact, it is not just palm oil. Excessive intake of any oil is not good for health, even olive oil.

The "Dietary Guidelines for Chinese Residents" recommends that we consume 25 to 30 grams of edible oil per day; the energy provided by fat for adults should account for less than 30% of the total energy, that is, the total amount of fat an adult consumes per day should be controlled at 50 to 70 grams; saturated fat should not exceed 10% of the total fat intake, which is about 5 to 7 grams. Under this recommended amount, there is no need to worry about health hazards if you eat palm oil appropriately. However, everyone needs to understand that palm oil is indeed not a healthy oil, and foods that use a lot of palm oil, whether it is potato chips, biscuits, spicy strips, etc., are often high in salt, sugar, and fat, so you should be careful not to eat too much. In general, palm oil itself is harmless, and foods containing palm oil are not "monsters". The key is to pay attention to a reasonable diet, develop healthy eating habits, and try to achieve a balanced diet.

References:

[1] Zhang Yufeng, Wang Hui, Song Fei, Chen Hua, Zhang Jianguo, Lei Xintao. Research progress of palm oil processing technology[J]. Journal of Cereals, Oils and Food Science and Technology, 2018, 26(01): 30-34. DOI: 10.16210/j.cnki.1007-7561.2018.01.006.

[2] Gai Zhengyan, Ma Chuanguo, Lou Lijuan. Latest research progress on palm oil[J]. Grain and Oil Processing, 2010(11):6-9.

[3] Yang Guangyu, Wang Dong. Research progress of palm oil and its application in animal husbandry[J]. Feed Expo, 2010(08):33-36.

[4] Li Peiyan. Effect of oil on the texture of fried French fries and its mechanism[D]. Jiangnan University, 2021.DOI:10.27169/d.cnki.gwqgu.2021.001934.

[5] Ji Yanyu. Study on quality changes and oxidative stability of palm oil during thermal processing[D]. Hainan University, 2017.

[6] Kuang Ting, Ji Yanyu, Yao Mengying, Yun Yonghuan, Zhang Weimin. Thermal oxidative stability of palm oil[J]. Food Industry, 2019, 40(11): 186-191.

[7] Li Xu. Research on the changing law and application of polar substance composition of oils and fats during heating and frying[D]. Jiangnan University, 2021.DOI:10.27169/d.cnki.gwqgu.2021.000063.

[8] Gloria Pascual et al., (2021) Dietary palmitic acid promotes a prometastatic memory via Schwann cells. Nature Doi: 10.1038/s41586-021-04075-0

Author: Ruan Guangfeng, Director of the Science and Technology Department of the Kexin Food and Nutrition Information Exchange Center

Review｜Han Hongwei, Researcher at the National Food Safety Risk Assessment Center

The cover image and the images in this article are from the copyright library