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Trans-Fatty Acids (Trans fat)

Cis and Trans configurations are terms used in organic chemistry to depict the 3-D arrangement of carbon atoms across a double bond. Trans-fatty acids (TFAs) are unsaturated fatty acids containing at least one double bond in the trans configuration.
Cis and trans isomers often have different physical properties. Generally, trans isomers are more stable than cis isomers
In nature, most unsaturated fatty acids occur as cis – configuration and NOT as trans – configuration.
Only small amounts of natural trans-fatty acids are found in the milk and meat of ruminants.
These small amounts of naturally occurring trans fats are NOT considered harmful
It’s the Industry that produces trans-fat by adding hydrogen to vegetable oils which are naturally high in cis-configuration unsaturated fats.

Why does industry convert Cis-fatty acids (found in vegetable oils) into Trans-fatty acids?
For two main reasons:
1) High cost of preferred cooking fats like butter and ghee (clarified butter)
These fats are preferred by cooks and industry as these have a high smoke point, making it ideal for frying foods. The texture and taste are perceived to be better by the consumers.
Moreover the items cooked in these fats have a longer shelf life as the fats are more stable.

2) Early research found the saturated fats like butter and ghee to have adverse effects on cardiovascular health as compared to vegetable oils like olive oil, soybean oil, sunflower seed oil etc. which have a higher content of unsaturated fatty acids.
However most vegetable (having high unsaturated fatty acids) oils are liquid at room temperature and tend to get oxidized over time. Hence the food cooked in vegetable oil tends to have shorter shelf life.
Hydrogenation of vegetable oils saturates some double bonds and converts others to trans-configuration, which is more stable and results in production of solid and semi-solid fats.
It raises the melting points resulting in a longer shelf life without rancidity.
This makes them comparable to ghee and butter.

Hence hydrogenation of vegetable oils was thought to be a technique for:
• Using the healthier vegetable oils
• Without the drawbacks of their physical properties
• I.e. better texture, solid/semi-solid, higher melting point and low risk of rancidity
• Margarines
• Vanaspati Ghee

Hydrogenation has been used to produce solid fats from liquid oils since the beginning of the 20th century.
Hydrogenation can be partial of full.
Full hydrogenation causes all fatty acids to become saturated fatty acids, hence no trans fats.
• But fully hydrogenated oils result in very hard fats with very high melting points and not preferred for production of food items.
It’s the partial hydrogenation that increases the content of trans-fatty acids in the fat.

Why are Trans-fats Bad?
Research has demonstrated that there is a direct connection of trans-fatty acids with
• Cardiovascular diseases,
• Breast cancer,
• Shortening of pregnancy period,
• Risks of preeclampsia,
• Disorders of nervous system and vision in infants,
• Colon cancer,
• Diabetes,
• Obesity and
• Allergy

Cardiovascular diseases:
Trans-fat increases the level of
• ‘Bad cholesterol’ (low density lipoproteins or LDL),
• Triglycerides and
• Insulin
Trans-fat reduces ‘good cholesterol levels i.e. the high density lipoproteins (HDL).

This results in a higher LDL/HDL ratio, which is not desirable.
In fact, it has been recognized that TFA could be worse than the saturated fatty acids.
Saturated fat and TFA may both raise the LDL (bad cholesterol) but,
TFA reduces HDL (good cholesterol) in addition
• Industrial TFAs (i.e. TFA from partially hydrogenated oils) have been thought to responsible for 30,000–100,000 premature coronary deaths per year in the United States.

Breast cancer: It’s reported that women with elevated serum levels of trans-fatty acid have double the risk of developing breast cancer as compared to women with the lower levels.

Pregnancy: Trans-fatty acids are passed on to the fetus too, resulting in the same levels in the blood of newborn infants as in that of mothers.
The duration of pregnancy appears to be shorter in women with evidence of high TFA intake.
In addition, the risk of preeclampsia (pregnancy induced hypertension) increases with a high intake of trans-fatty acids

Disorders of nervous system and vision in infants:
This is due to the interference with Essential fatty acids (EFAs):
The EFA are essential for development of the nervous system and eyesight in the newborn. Newborns need to obtain the EFA from mother’s milk.
TFA can replace these EFA in the nervous system and eyesight in the newborn and result in abnormal development of these.
• The intake of TFA by the mother is passed on to her milk too.
• Hence the TFA consumption of the breastfed infant correlates to the mother’s TFA intake

Colon Cancer: High intake of TFA increase the risk by 50% especially among the elderly

Diabetes: both saturated fatty acids (SFA) and TFA can increase insulin resistance (decreased insulin sensitivity).
However, TFA effect on insulin resistance is greater as compared to SFA
Moreover, this deleterious effect is not prevented by increasing the intake of healthy fat.
Therefore it seems necessary to reduce the absolute intake of TFA

Obesity: Trans-fat may lead to more weight gain, especially abdominal fat, as compared to that caused by a similar amount of intake of other fats.
Abdominal obesity itself increases insulin resistance which may lead to Diabetes.

Allergy: There is evidence that intake of TFA may be associated with occurrence of asthma, allergic cold and asthmatic eczema; especially in children aged 13–14 years.
Such association has not been observed with the intake of monounsaturated and polyunsaturated fatty acids (MUFA, PUFA)

What is the Safe Limit of Trans-fat in Diet?
There is no safe limit of dietary trans-fat. In fact the recommendation is to aim for an intake of ‘zero’ trans-fat in diet. The World Health Organization (WHO) instructs the governments to completely phase out partially hydrogenated oils use in food items.
In 2018, the WHO advocated for elimination of industrially-produced trans-fat from food by 2023 and released an action package ‘REPLACE’ for the purpose.
In India, FSSAI (Food Safety and Standards Authority of India) has committed to the goal of “Freedom from Trans Fat @75.” It has adopted a two-pronged strategy to achieve this goal
1. For food manufacturers, crucial regulations to reduce/eliminate trans-fat have been notified. Oil industries are encouraged to eliminate trans-fat from their products

2. For consumers, FSSAI has launched a mass media campaign via a 30 – seconds Public Service Announcement called “Heart Attack Rewind”-
The aim of this small video is to create awareness regarding the harmful effects of trans-fat

Is there any other source of dietary TFAs?

How to Limit the Intake of Industrial Trans-Fat?

Some Common Foods Containing Trans Fats:
Trans fats in Indian food

Vandana Dhaka & Neelam Gulia & Kulveer Singh Ahlawat & Bhupender Singh KhatkarTrans fats—sources, health risks and alternative approach - A review.J Food Sci Technol (September–October 2011) 48(5):534–541

Dariush M. (2021). Dietary Fat. In: UpToDate, post, MW, DS, JG (Eds.)UpToDate. Retrieved on 31st January, 2022, from:

Trans Fats: FSSAI website. Retrieved from: on 5th February 2022 at 11:40 AM

Replace Trans Fats –Free by 2023: NIHFW hosted website. Retrieved from: on 5th February 2022 at 12:10 PM

Reading the Ingredient Label: What to Look For; Web MD website. Retrieved from: on 5th February 2022 at 12:21 PM

7 Foods That Still Contain Trans Fats; Healthline website. Retrieved from: on 5th February 2022 at 12:21 PM