Eating cake = being poisoned? Does it really take 51 days to metabolize a mouthful of trans fatty acids?

Many people are familiar with "trans fatty acids". Some people seem to downplay their attitude towards it and just eat less; but some people are firm in their attitude towards it and do not allow it to be eaten at all.
Recently, the topic #Mom gets mad because her child ate classmate’s birthday cake# has become a hot topic. The mother claimed that the child was “poisoned” after eating the cake and forced the child to drink oil in an attempt to force trans fatty acids out of the body.
The mother in this incident is someone who has a firm attitude towards trans fatty acids and would never allow her children to eat any unhealthy food.

He got angry in the group just because his child ate the cake given by his classmate's mother. It is understandable that he loves his child so much, but his behavior is a bit extreme and will cause great harm to the child's physical and mental health.

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Since the incident was caused by the trans fatty acids in the cake, in this article we will talk about trans fatty acids in detail to see whether it is a "disaster" and how to treat it.

01
What is trans fatty acids?

Fatty acids exist in two forms, one is cis fatty acids and the other is trans fatty acids. In nature, most unsaturated fatty acids are cis fatty acids, such as the unsaturated fatty acids in vegetable oils.

But it has a disadvantage, which is that its structure is unstable and cannot be stored for a long time.

Therefore, scientists used the hydrogenation process to combine the unsaturated double bonds of unsaturated fatty acids with hydrogen to turn them into saturated fats, which make their structure stable. As the degree of saturation increases, oils can change from liquid to solid, enhancing the antioxidant effect of oils.

However, by-products will appear in the hydrogenation process. The spatial structure of some unsaturated fatty acids will change from the original cis to trans, thus trans fatty acids appear.

02
Which foods contain trans fatty acids?

Trans fatty acids are ubiquitous in our daily lives and we come into contact with them almost every day. Its sources mainly include the following three aspects.

1. Processing source

This is the most familiar to everyone, including cakes, small desserts, cocoa butter substitute chocolate, ice cream, shachima, wafers, crispy biscuits, etc. These pre-packaged foods may contain trans fatty acids.

In particular, foods that use shortening, margarine, and jelly during processing have a lower trans fatty acid content in shortening, while margarine and jelly contain a relatively higher content. [2]

2. Ruminants

Some ruminants, such as cattle, sheep, and camels, have microorganisms in their rumen that undergo enzymatic biohydrogenation reactions with unsaturated fatty acids in feed, a process that produces trans fatty acids. [2] Ruminant trans fatty acids are found in animal meat, fat, and dairy products, such as beef, mutton, fresh milk, milk powder, and yogurt that we often eat. The content is highest in mutton and lowest in yogurt. [3]

3. Cooking at high temperatures

The cooking oil used in daily cooking also contains trans fatty acids. High-temperature deodorization is the main reason for the formation of trans fatty acids during the oil refining process.

In addition, frying food produces more trans fatty acids.

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Because during the frying process, some cis fatty acids in oils are converted into trans fatty acids. The higher the frying temperature, the longer the frying time, and the more times the frying is done, the higher the trans fatty acid content will be. [2]

03
Does it take 51 days for the human body to metabolize trans fatty acids?

There is a saying that "trans fatty acids have a half-life of 51 days in the human body."

This mother also mentioned in the group that the claim that it takes 50 days for the human body to metabolize trans fatty acids is really exaggerated. The claim came from a foreign chiropractor. The claim that "trans fatty acids have a half-life of 51 days" was based on his own research and experience, and was not supported by reliable research data. [4]

Therefore, this statement has no scientific basis and does not exist. Trans fatty acids and regular fats are metabolized in the same way in the body, with no significant difference. [5]

04
What harm does it cause?

The reason why trans fatty acids made the mother in this hot event angry is that eating them will cause certain harm to the body, mainly affecting cardiovascular health.

1. Increased risk of death from cardiovascular disease

Trans fatty acids can increase low-density lipoprotein cholesterol ("bad" cholesterol) and lower high-density lipoprotein cholesterol ("good" cholesterol), thereby increasing the risk of death from cardiovascular disease.
Meta-analysis has confirmed that excessive intake of trans fatty acids can lead to a 14% increase in the risk of death from cardiovascular disease. Further analysis of the effect relationship showed that for every 1% increase in energy from trans fats, the risk of death from cardiovascular disease increased by 6%. [6]

2. Promote the body's inflammatory response

Some studies have shown that trans fatty acids can aggravate the body's inflammatory response and promote atherosclerosis by activating inflammation.

3. May Increase Diabetes Risk

A prospective study in the United States that followed 84,941 female nurses for 16 years showed that the intake of trans fatty acids was significantly positively correlated with the incidence of diabetes.
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Two other prospective studies in male health workers and Iowa women showed no significant association between trans fatty acid intake and the risk of diabetes.[7]
The relationship between trans fatty acids and diabetes remains to be further confirmed.
However, not all trans fatty acids are harmful to the body, and two of them are controversial.

4. Ruminant trans fatty acids

Its effects on human vascular health are controversial.

Some studies have shown that it can lower blood lipids and prevent cancer; others have shown that it has a negative impact on cardiovascular health; and still others have shown that it is beneficial to health within a certain range, but excessive amounts are harmful. [3]

5. Trans-dienoic acid

It is a trans fatty acid containing two carbon-carbon double bonds, mainly conjugated linoleic acid, which is a relatively special trans fatty acid.

Some studies have mentioned that it is not only harmless to humans and animals, but also a nutrient that may have the effects of improving human immunity and preventing atherosclerosis. [8]
However, some studies have also mentioned that the intake of conjugated linoleic acid may be positively correlated with the risk of breast cancer. [9] Further research is needed to confirm the effects of conjugated linoleic acid on the human body.

05
Is it necessary to keep it at a distance?

Although trans fatty acids have adverse effects on health, there is no need to be afraid of them. It is almost impossible to completely avoid them in life. After all, even the beef, mutton, milk and cooking oil we eat contain trans fatty acids.

As for trans fatty acids in processed sources, my country has taken a series of measures to control the content; margarine, shortening, cocoa butter substitutes, etc. currently sold on the Chinese market basically no longer use partially hydrogenated fats as raw materials, and the trans fatty acid content of most refined vegetable oils is already very low.
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my country's "General Rules for Nutrition Labeling of Pre-packaged Foods" stipulates that if hydrogenated and/or partially hydrogenated fats are used in the ingredients, the content of trans fatty acids must be marked in the nutrition label.

When the content is ≤0.3%, the content can be labeled as 0, which means that the proportion of hydrogenated oil and/or partially hydrogenated oil in the ingredients is very small, or the vegetable oil is hydrogenated relatively completely and the trans fatty acid content produced is very low.

When we buy pre-packaged foods, we can look at the labels on the packaging and choose products whose trans fatty acid content in the nutrition information table is 0 grams/100 grams.

Nutritional information of a certain brand of biscuits.

WHO recommends that the daily trans fatty acid energy supply ratio of adults should not exceed 1% of the total dietary energy. However, the trans fatty acid intake level and risk assessment results of Chinese residents show that:
The energy provided by trans fatty acids in the diet of Chinese people accounts for only 0.16% of the total dietary energy. For residents of large cities such as Beijing and Guangzhou, it is only 0.34%, which is far below the 1% limit recommended by the WHO and significantly lower than the intake of residents in developed Western countries. Overall, the risk is currently controllable. [10]

In addition, you should also control the intake of cooking oil and pay attention to the cooking method. The daily intake of cooking oil should be controlled at 25-30 grams, and the types of cooking oil should be changed frequently; the cooking method should be less frying, and more steaming, boiling, stewing, and quick stir-frying should be used.

Summarize:

Although trans fatty acids are unpopular, they are not "poison". It's okay to eat a little occasionally, but don't take it to an extreme. If you really feel disgusted, cook more of your own food and use healthy cooking methods to further reduce your intake.

References:
[1] Sun Changhao. Nutrition and Food Hygiene 7th Edition[M]. People's Medical Publishing House. 2017:45
[2] Wang Tianxi. Research on the sources, health risks and control measures of trans fatty acids in food[J]. Market Supervision and Quality Technology Research, 2023, No.7(01):57-61.DOI:10.15902/j.cnki.zljsjdyj.2023.01.003.
[3] Niu Xian, Deng Zeyuan, Li Jing. Survey on trans fatty acid intake of ruminants in my country[J]. China Oils and Fats, 2021, 46(05): 103-108. DOI: 10.19902/j.cnki.zgyz.1003-7969.2021.05.020.
[4] https://sciencebasedmedicine.org/the-trans-fat-51-hour-half-life-myth/?continueFlag=beb34e75b9f54fa714cc212147b7fd74
[5] Emken E. Human studies using isotope labeled fatty acids: answered and unanswered questions. J Oleo Sci. 2013;62(5):245-55. doi: 10.5650/jos.62.245. PMID: 23648399.
[6] Yan Jing, Sun Qinmei, Feng Qin. Harm and mechanism of trans fatty acids on diseases related to dyslipidemia[J]. Medical Review, 2021, 27(11): 2119-2123.
[7] Yang Yuexin, Ge Keyou. Chinese Nutrition Science Encyclopedia 2nd Edition (Volume 1)[M]. People's Medical Publishing House, 2019
[8] Li Shuang, Shao Shiping, Chen Xiuming, et al. Study on the content of trans fatty acids in edible vegetable oils[J]. China Inspection and Testing, 2018, 26(05): 18-20. DOI: 10.16428/j.cnki.cn10-1469/tb.2018.05.006.
[9] Chen Xiaodong, Zhao Jingjing, Xu Baocheng, et al. Meta-analysis of trans fatty acid intake and breast cancer risk[J]. Journal of Chinese Institute of Food Science and Technology, 2023, 23(04): 490-502. DOI: 10.16429/j.1009-7848.2023.04.044.
[10] The results of trans fatty acid intake and risk assessment of Chinese residents were officially released[J]. Chinese Journal of Food Hygiene, 2013, 25(03): 293.

Author: Xue Qingxin, one of the first nutrition instructors of the National Health Commission, China's registered nutritionist Reviewer: Zhang Na, associate researcher, doctoral supervisor, Peking University School of Public Health