Currently, a war is quietly brewing in the global food market—the war against "trans fatty acids." According to a Reuters report from the UK on July 2, New York City became the first city in the United States to ban the use of trans fatty acids in all restaurants, fast-food chains, bakeries, etc., starting from July 1. This has triggered a strong reaction in the global food market, and food producers in Japan and Southeast Asian countries have been notified by their governments to strictly control the trans fatty acid content in foods exported to the United States. "Another DDT is here."
Trans fatty acid, also known as trans fat or trans unsaturated fatty acid, is an unsaturated artificial vegetable oil. Common artificial creams and butters in daily life belong to this category. Analyzed from a molecular structure, "unsaturated" means that the fatty acid molecules can be hydrogenated (hydrogen atoms added to both ends), becoming saturated fatty acids.
Depending on the position of hydrogen atoms on the carbon chain in their molecular structure, unsaturated fatty acids can be divided into two types. If all hydrogen atoms are on the same side, they are called "cis fatty acids," and the chain is curved, looking like a "U" shape. If the hydrogen atoms are on both sides, they are called "trans fatty acids," looking linear.
Under normal circumstances, unsaturated fatty acid molecules are curved and often liquid; however, trans fatty acid molecules are arranged in a straight line, becoming solid. The process that changes these molecules from curved to straight is "hydrogenation"—a process where unsaturated fatty acids react with hydrogen atoms under the action of a catalyst or with heat and pressure. This can prevent the molecules from oxidizing, turn liquid oil into semi-solid oil suitable for special purposes, and extend the shelf life.
Since German chemist Wilhelm Norman discovered the method of oil hydrogenation in 1902, trans fatty acids have made "great contributions" to global food production. This hydrogenated oil is easy to preserve and the cooked food is delicious, making it widely used in the food industry. However, after 1990, scientists discovered that trans fatty acids are very harmful. Experts from the US Food and Drug Administration (FDA) exclaimed: "Another DDT has appeared!" DDT, known as dichlorodiphenyltrichloroethane in Chinese, is a pesticide that was once widely used. In the first half of the 20th century, it played a significant role in preventing agricultural pests and diseases and reducing the harm of mosquito-borne diseases such as malaria and typhoid. However, scientists found that DDT is difficult to degrade in the environment. DDT in bird bodies causes them to lay soft-shelled eggs that cannot hatch, leading to the near-extinction of some bird species. Research also shows that DDT affects human liver function and can cause cancer. After the 1970s, DDT was gradually banned by various countries. Three Sources of Trans Fat
Similar to DDT, the impact of trans fatty acids is also "benefited" by its widespread use. Common foods such as vegetable oils, candies, chocolates, cakes, breads, pizzas, margarines, and cookies all contain trans fatty acids. Trans fatty acids mainly come from the following three sources:
1. Hydrogenated vegetable oils. When vegetable oils undergo hydrogenation, some unsaturated fatty acids undergo a structural change, transforming from their natural cis structure to a trans structure.
2. Meat and milk of ruminants such as cattle and sheep. The content of trans fatty acids in the body fat of ruminants accounts for 4% to 11% of total fatty acids, and in cow's and goat's milk, it accounts for 3% to 5% of total fatty acids.
3. Trans fatty acids produced by excessively high oil temperatures. When refined oils and cooking oils are at excessively high temperatures, some cis fatty acids will convert to trans fatty acids. Although the increase is not significant, excessively high oil temperatures should be avoided during cooking.
A nutritionist from Harvard University pointed out that "partially hydrogenated vegetable oils" containing trans fatty acids cause 30,000 deaths in the United States each year. Researchers from the Netherlands published an article in the British medical journal "The Lancet," stating that "a 2.4% reduction in trans fatty acid intake can reduce coronary heart disease mortality by 23%."
Consequently, the US Consumer Council recommended in 1993 not to use hydrogenated vegetable oils for frying food. Subsequently, many countries began to issue warnings against trans fatty acids. The Danish government was the first to ban the use of cooking oils containing trans fatty acids in 2003. In 2006, the US government passed legislation requiring the trans fatty acid content to be labeled on food products, a practice that most countries have since followed. Western Fast Food Accused of High Content
Fast-food chains like McDonald's and KFC, which are popular worldwide, meet people's expectations for safety, hygiene, and efficiency, but the safety of these two chains is being questioned. Their flagship products—french fries, potato chips, pies, and other fried products—are generally cooked with vegetable oil, in which trans fatty acids exist. According to a report from Yonhap News Agency this April, among the french fries sold in the top 5 fast-food chains in South Korea, McDonald's had the highest trans fatty acid content.
However, McDonald's insists that all its fried products, including potato chips, contain zero trans fatty acids. The reason is that the fast-food chain uses palm oil with a purity of up to 99.9% in its cooking process, which contains only trace amounts of antioxidants and does not produce trans fatty acids.
However, it has been proven that McDonald's "zero content" claim is not credible. A report released this April by the Korea Food and Drug Administration showed that McDonald's french fries contain an average of 1.6 grams of trans fatty acids per 100 grams, while Burger King (the second-largest restaurant company in the US) and KFC both contain an average of 1.3 grams of trans fatty acids per 100 grams. These trans fatty acids come from the hydrogenated vegetable oil mixed in their cooking oil. Based on this, it can be estimated that the trans fatty acid content of these Western fast-food chains in China is roughly the same as in South Korea. Four Crimes of Trans Fatty Acids
Due to high public attention, Western fast-food chains like McDonald's have relatively strict control over trans fatty acid content. However, trans fatty acids are almost ubiquitous and are found in almost all fried foods, as well as in common foods like biscuits, cream cakes, doughnuts, and salad dressings. Trans fatty acids are currently widely added to foods by food processors. Because adding trans fatty acids to food enhances the texture, making food crispier and more delicious. However, trans fatty acids, which can make food delicious, are extremely harmful. In summary, they have four major crimes. First, They Cause Cardiovascular Diseases
Due to the difference in molecular structure from common cis fatty acids, the properties of trans fatty acids also change. Many people know that unsaturated fatty acids found in safflower oil, corn oil, and cottonseed oil can lower cholesterol levels in human blood, but when they are hydrogenated into trans fatty acids, the effect is the opposite. Trans fatty acids can increase LDL (low-density lipoprotein cholesterol) while decreasing HDL (high-density lipoprotein cholesterol). Scientific research has found that LDL is the culprit causing high blood pressure, arteriosclerosis, and other cardiovascular diseases. Second, They Cause Obesity
Many people have heard that people who often eat potato chips, cream, and fried foods are more prone to obesity, and children often taken by their parents to enjoy Western fast food are more likely to become "chubby." Scientific research has found that this is because trans fatty acids are not easily digested by the human body and are more likely to accumulate in the abdomen, leading to obesity. This effect is more obvious for people who like to eat snacks like french fries, as the trans fatty acids in fried foods contribute significantly to fat accumulation.
Kelly Cavan of the Wake Forest University School of Medicine in the US conducted a 6-year study on the obesity-causing effects of trans fatty acids. He did an animal experiment: for about six months, two groups of monkeys were fed the same amount of trans fatty acids and ordinary unsaturated fatty acids, respectively. After one year, it was found that the first group of monkeys gained 7.2% in weight, while the second group only gained 1.8%. The first group of monkeys had 30% more fat in their bodies than the latter group. Third, They Affect Human Fertility
Trans fatty acids also have adverse effects on infants and young children in their developmental stages and on adolescents in their growth stages. Fetuses can absorb trans fatty acids through the placenta, and newborns can absorb them through breast milk, which affects the absorption of essential fatty acids. Trans fatty acids can also adversely affect the development of the central nervous system in adolescents, inhibiting the synthesis of prostaglandins. Trans fatty acids can also reduce male hormone secretion, have a negative impact on sperm, and interrupt sperm production in the body. Fourth, They Impair Memory
As early as the 1990s, when the harm of trans fatty acids was first recognized, researchers found that people with poor eating habits in their youth and middle age had a higher incidence of Alzheimer's disease ("senile dementia") in old age. According to the latest research from the French National Institute of Health and Medical Research, this is related to the decrease in HDL levels caused by trans fatty acids. HDL, because it can effectively prevent heart disease and other cardiovascular diseases, is known as "good cholesterol." Researchers at the institute found that "good cholesterol" can promote human memory, while trans fatty acids have an inhibitory effect on "good cholesterol."