Our daily diet is mainly composed of different classes of food, including fats. One of the major types of fatty acids is the glycerol esters which generate triacylglycerols. Food types that are of plant and animal origin contain cis unsaturated fatty acids, which are lipids that carry double hydrogen bonds on the same side of the carbon atom. On the other hand, the trans configuration, have two hydrogen bonds on the opposite sides of the carbon atom. Trans fatty acids (TFA), therefore, are fatty acids that have at least one double hydrogen bonds on opposite sides of the carbon chain.
Simultaneous to the significant increase in the use and consumption of food that contain trans fatty acids, the effects of trans fatty acids on human health has been a major topic of scrutiny in the last twenty years. A number of research investigations have been conducted in order to determine the degree and effect of trans fatty acids on the human body. This paper aims to provide the current scientific information on trans fatty acids in relation to human consumption and health, as well as regulatory guidelines that are now being implemented in the food industry.
II. THE CHEMISTRY AND PRODUCTION OF TRANS FATTY ACIDS The trans fatty acids that are present in our daily dietary supply generally come from two sources, biohydrogenation and industrial hydrogenation. It has been determined that the trans fatty acids that are generated from both types of processes are similar, however, there is a significant variation in the content of trans fatty acids in each process.
Such disparity in the quantitative features of the two sources of trans fatty acids may therefore influence any associated physiological process that trans fatty acids go through in the human body. It is also possible to determine, through the employment of chemical assays, whether a certain trans fatty acid came from an industrial process or from the fat tissues of a ruminant animal. Hence, once the source of the trans fatty acid has been established, it is easy to calculate the content of trans fatty acids in a particular type of food.
BIOHYDROGENATION. The process of generating trans fatty acids through the natural method is known as biohydrogenation, which is the biological transformation of unsaturated fatty acids into trans fatty acids through the action of bacteria in the rumen of ruminant animals such as cattle, sheep, lamb and poultry. In the biohydrogenation process, trans vaccenic acid is created, which comprises approximately 2 to 5% of the trans fatty acid content. Vaccenic acid can be further conjugated into linolenic acid which is another trans fatty acid.
Agricultural scientists have determined that it is possible to regulate the content of trans fatty acids in ruminants by modifying the feeds that are given to the ruminant animals (Lock and Bauman, 2004). Most of the efforts in food production from animal sources over the past two decades have concentrated on increasing the amounts of conjugated linolenic acid because it was earlier postulated that linolenic acid was beneficial to human health. INDUSTRIAL HYDROGENATION. Industrially produced fatty acids are created by partial hydrogenation of edible oils made up of unsaturated fatty acids.
The result of this chemical reaction is a solid fat mixture, composed mostly of monounsaturated trans fatty acids, that is relatively stable for storage at room temperature and is characterized by a unique texture. These monounsaturated trans fatty acids make up at most 60% of the trans fatty acid content of industrial trans fatty acids, of which can then be easily modified to generate other forms such as conjugated trans fatty acids. Industrial hydrogenation was initially designed to facilitate the processing of massive amounts of food by the food companies without destroying the flavor and texture of the food product.
III. TRANS FATTY ACIDS IN DAILY DIETARY INTAKE Current studies in the United States and in Europe have calculated that 4 to 7% of an individual’s daily food consumption is composed of trans fatty acids (Allison et al. , 1999). Trans fatty acids are present in common food types that an individual eats on a daily basis. FAST OR FROZEN FOODS. It has been determined that the oil used in deep-frying food items at fast food restaurants supplies the largest portion of the daily trans fatty acid intake of an individual.
The oil used in these fast food chains is generally industrial frying oil that contains more than 10% of trans fatty acid. The most common items at fast food chains would include French fries, hash browns and donuts (Martin et al. 2007). In addition, frozen food products also contain approximately 4% trans fatty acids. These frozen food items include frozen potatoes and frozen cakes, which are usually thawed out once they are ready for use. PACKAGED SNACKS. It has been determined that packaged snacks such as cakes and confectionary products contained trans fatty acids.
These products generally describe their contents to have “hydrogenated” fat or oil, which simply means that the item contains trans fatty acids. Content analysis of packaged snacks revealed that most of the products contained approximately 7 to 30 grams of industrially generated trans fatty acids in every 100 grams of the food product. Such amount of trans fatty acids is significantly higher than the trans fatty acid content from biohydrogenation products from ruminant animals, resulting in a major increase in the normal consumption of trans fatty acids by an individual on a daily basis.
Another packaged snack that contains high levels of trans fatty acid is microwave popcorn. Approximately 40% of microwave popcorn products is comprised of trans fatty acids (Sundram et al. , 1997). Hence, if a package description on a box of microwave popcorn indicates that one bag of popcorn contains 10 to 30 grams of fat then approximately 12% of trans fatty acid is present in one bag of microwave popcorn. It has been determined that around 30 million bag of microwave popcorn are bought by the public every year. BAKERY PRODUCTS. Margarine is a common ingredient in baked food items.
It has been established that most of the margarine brands used in baking contains 5% trans fatty acids. Hence, bakery products such as cakes, chocolates, soft caramels and cookies that are commercially sold generally contain a significant amount of trans fatty acid. INFANT FORMULAS AND BABY FOOD PRODUCTS. It has been reported that infant formulas and baby food items contain approximately 4% trans fatty acid. The product labels of these items would often describe the constituent as milk fat which typically contains 2 to 5% trans fatty acid. IV.
THE EFFECTS OF TRANS FATTY ACIDS IN THE HUMAN BODY The significant consumption of commercial food products over the past decades has resulted in the concern for trans fatty acid content in specific food items, in relation to its effects of human health. CARDIOVASCULAR SYSTEM. Research studies have shown that the massive consumption of trans fatty acids in daily dietary meals is strongly correlated with an heightened risk for coronary heart disease. The suggested cause of coronary heart disease is the effect of trans fatty acids on the lipoproteins that are present in the blood serum.
It has been determined that the presence of trans fatty acids in the blood influences the increase in the levels of serum low-density lipoproteins, which is a form of cholesterol (de Roos et al. , 2001; Gatto et al. , 2002). In addition, serum high-density lipoproteins, better known as the good cholesterol, is reduced by the presence of trans fatty acids in the bloodstream. Such disparity in the ratio of the two types of cholesterol is unsafe to human health because such physiological setting promotes the onset of coronary heart disease and other cardiovascular diseases (Gatto et al. , 2003).
Hence, trans fatty acids affects the general level of lipids in the blood. It has also been reported that trans fatty acids also result in changes in vascular function (Mozaffarian et al. , 2006). A positive correlation has also been established between the amount of trans fatty acid intake and adipose tissue. The increase in the deposition of adipose tissues, also known as atherosclerosis, often results in the increase in risk for myocardial infarction (Ara et al. , 1995). More importantly, trans fatty acids have been strongly linked to the increase in risk of sudden death that may be due to cardiac reasons.
Individuals that eat food items that contained trans fatty acids were reported to have three times the probability of suffering from sudden death from cardiac causes (Lemaitre et al. , 2002). DIABETES. Trans fatty acids have also influenced the sensitivity of the human body to insulin. Variable results were observed and this may possibly be a result of human variation or the length of consumption of fatty acids among different individuals. Research has also determined that the consumption of food items that contained trans fatty acids was strongly correlated to the increase in the risk for diabetes (Hu et al. , 2001).
Estimates have described that individuals have a 39% greater risk for diabetes if their lifestyle is composed of eating food items that contain trans fatty acids. METABOLISM AND BODY WEIGHT. Studies have shown that the daily intake of food items containing trans fatty acids modifies the physiology of adipocytes, which are cells that comprise the fat tissues of the human body. It has been observed that the genes that code for peroxisome proliferator–activated receptor-? , resistin, and lipoprotein lipase were altered, resulting in a change in the metabolism of fatty acids and sugar in the body (Saravanan et al.
, 2005). The presence of trans fatty acids in daily dietary intake has also been observed to affect of the postprandial activity of tissue plasminogen activator, a compound that is secreted by tissues for proper food digestion. It seems that trans fatty acids have a different effect on individuals that have a higher body-mass index, wherein their intake of food items that contained trans fatty acids resulted in the increase in the amount of interleukins and C-reaction proteins in their bodies.
In addition, those individuals who were classified as overweight and were determined to ingest food items with trans fatty acids were observed to show a higher activity of the tumor necrosis factor (TNF) system. PREGNANCY AND FETAL DEVELOPMENT. Reports have been released that describe associated between the consumption of elevated amounts of food items that contain trans fatty acids and effects on intrauterine development. IMMUNE SYSTEM. Trans fatty acids have also been reported to play a role in the onset of allergic diseases.
In addition, specific inflammatory and immune reactions have been observed to result from the intake of food items that contained conjufated linolenic acid (Nugent et al. , 2005). This reaction is associated with a significant activation of the tumor necrosis factor (TNF) system. CELLULAR FUNCTION. It has been reported that trans fatty acids in the daily dietary intake of individuals have results in the abnormal functioning of the endothelial system, including the activity of intercellular adhesion molecules, which are compounds that are responsible for the proper attachment of cells to their substrates in the body (de Roos et al.
, 2001). In addition, the vascular-cell adhesion molecule and E-selectins were also reported to be produced at abnormally high levels. These reports reflect the decrease in the flow of the blood along the brachial arteries, which in turn results in the vasodilatation of these blood vessels. Trans fatty acids have also been observed to affect the fluidity of the cell membranes, thereby affecting the receptors that are located at the membranes of cells for their proper trafficking of nutrients and ions (Tricon et al. , 2006). The nuclear membrane has also been reported to be affected by trans fatty acids.
This membrane is responsible for regulating gene transcription of specific receptors proteins that are needed for the normal physiological functioning of the cell, organ and system of the human body. V. PRECAUTIONARY MEASURES IN TRANS FATTY ACID INTAKE Given the abovementioned risks of ingestion of food items that contain trans fatty acids to human health, several precautionary measures have been implemented for the control and monitoring of the increase in cases and reports of health disorders. Consumers currently have the option of choosing which food brands to buy for their own personal consumption.
In addition, healthcare providers are aggressively supporting changes in the use of trans fatty acids in the food outlets such as schools and hospitals. The food industry has also required food manufacturers to disclose the amount of trans fatty acids that are incorporated in the food items they are manufacturing in the nutrition labels (Shaw, 2004). This information will provide the consumer knowledge of the contents of what they are buying, so they have the choice of buying or not buying, or even picking another brand that contains less or no trans fatty acids in that particular food item.
However, it should also be noted that not all consumers read the nutrition labels of every food item they purchase. The food industry has also allowed food manufacturers that produce food items that contain less than 500 mg of trans fatty acids per serving to label their products as 0 trans fat in their packaging hence it is also tricky and somewhat deceiving to believe that a food product has absolutely no trans fatty acids. Health aficionados have also educated consumers to be aware of the phrase “partially hydrogenated oils” which are included in the nutrition labels of food products.
Partically hydrogenated oils actually mean trans fatty acids hence the consumer can gauge the amount of trans fatty acids that will be consumed if he buys that food product. The phrase “fully hydrogenated”, on the other hand, means that there are no trans fatty acids in that specific food item. Another issue that still has to be resolved is the eating places such as restaurants and bakeries, because these places do not provide nutrition labels in the dishes they are serving.
It is therefore essential that the consumer is aware of what items may possibly contain trans fatty acids.
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