by
Dr. John M. McDonough
www.theweightlossresource.com
Summary
Small amounts of some trans fats occur naturally. They are produced during the digestive process of ruminants, such as cows and sheep. Thus we get some very small amounts of trans fats from their meat and their dairy products. Whether these natural trans fats are harmful or not is debatable.
The real problem is with man-made trans fats. These have been around for about a century or so, but never in the amounts we have today. They are used in many processed foods to enable the manufacturers to extend the shelf life. Thus, you can buy old bakery goods, and they will still taste all right. The problem is that you pay a price with your health.
For those who would like to see what is involved in the trans fats situation from a chemist's perspective, I've tried to walk the reader through the process of hydrogenation and offer a look at the products formed.
In recent years, we have all become aware of the bad fats called trans fats. Trans fats do not occur in nature in any appreciable quantity, although small amounts are generated by bacterial / enzymatic action in ruminants, such as cows and sheep. Man is the culprit who makes the vast majority of them. They are unavoidable by-products in a process called hydrogenation.
What is the difference between fats and oils? In the world of nutrition, they are the same. They belong to a class known as triglycerides. They are composed of fatty acids and glycerol. Sometimes, referring to the state at room temperature, the word "fat" is used for a solid triglyceride and "oil" is used for a liquid triglyceride. Aside from that vague distinction, however, there is no difference. Below, we will discuss saturated and unsaturated fats. Unsaturated fats tend to be lower melting than their saturated counterparts. For example, the fatty acid oleic acid (unsaturated, found in olive oil) melts at about 39° F, while its counterpart, the fatty acid stearic acid (saturated, found in tallow), melts at about 156° F. Unsaturated fats (i.e. triglycerides made from unsaturated fatty acids) tend to be liquids at room temperature, while saturated fats (i.e. triglycerides made from saturated fatty acids) tend to be solid. Unsaturated fats can be partially converted to saturated fats by a process called hydrogenation.
What is hydrogenation? Many years ago, we discovered how to convert liquid fats into solid fats by means of this process called hydrogenation. Here, the liquid fat is put into a strong vessel, heated, and put under high pressure with hydrogen in the presence of a catalyst. The catalyst, usually platinum, palladium or nickel, is necessary because the process would be so slow otherwise that it would, for all practical purposes, never happen. Under these catalytic conditions, however, the liquid fat becomes a solid fat. In this process, unsaturated fats are partially converted into saturated fats. The word partially is what makes all the difference, as we’ll see below!
Hydrogenation was employed by the food industry in an effort to convert liquid fats (unsaturated ones) to solids (saturated fats). There were two main topics that could be addressed by this approach: separation of oils (for example, in peanut butter), and shelf life problems.
As a matter of fact, converting the liquid fats to solid fats did indeed solve both problems. Separation could be halted, and the off-tastes and odors produced over time by oxidation of the unsaturated fats (which is called rancidity) could be avoided, because the saturated fats do not oxidize (turn rancid).
But the price the consumer pays for the benefit of the food industry is a cardiovascular risk, in the form of trans fats, which is why the government required the amount of trans fats to be listed on labels starting in January 2006. More recent studies have suggested that, even with the same caloric intake (including fat calories) in two groups, the group with the higher trans fats intake gained more weight. In addition, this weight tended to gather around the middle, giving the “apple” shape, which has been implicated in giving rise to an increased cardiovascular risk. The bad news about trans fats has been gathering for years, but commercial interests would rather bury the information (as well as their victims) than give up any profits.
For those who want to know the details of hydrogenation, I will identify what the following symbols signify, so as to make the subsequent discussion meaningful.
C represents a carbon atom
H represents a hydrogen atom
or | (i.e. horizontal line or vertical line) represents a
single bond
(that is, saturation)
= represents a double bond (that is, unsaturation)
R represents the rest of the molecule
COOH represents the acid portion of the molecule
→ means “goes to”
Here we will discuss the hydrogenation process in terms of the structures of the fatty acids, which are the major components of the fats involved.
The structure
cis form
is the usual molecular geometry, or shape, of the unsaturated fatty acids. This shape is called cis which means the two H’s are on the same side of the molecule. This is the geometry preferred by nature and the human body.
The process consists of two simultaneous reactions, the primary one is hydrogenation, and the secondary one is called isomerization, which simply means “re-arrangement”.
The hydrogenation process can be represented as follows:
(Primary reaction, hydrogenation)
unsaturated saturated
This is the desired result.
Unfortunately, this is not the whole picture. The problem of trans fats arises because the above reaction (Primary reaction, hydrogenation) is necessarily accompanied by the second reaction (Secondary reaction, isomerization), in which the molecular geometry, or shape, is re-arranged to convert the cis geometry to the trans geometry, like this
(Secondary reaction, isomerization)
cis form trans form
Notice that no hydrogen was taken up in this second reaction,
and the double bond (or unsaturation) remains, but with a different geometry.
Now the two H’s are on the opposite sides of the molecule. Such a re-arrangement
is called an isomerization, and the two shapes are referred to as isomers, which
can be defined loosely as molecules which have the same composition, but with
different arrangements. Trans means “across” when describing
molecular arrangements. Cis means “on the same side”.
Isomers are very common in organic chemistry, the branch to which all foods
belong.
Because total hydrogenation has not been found to be commercially viable, all hydrogenated fats in foods are partially hydrogenated fats, and trans fats are an inescapable result in their presence.
Unfortunately, then, we see that one type of by-product formed in the hydrogenation process is the group called the trans fats. Trans fats are unsaturated fats, but their molecular geometry is what makes them so harmful. These are a very bad form of fats from a cardiovascular point of view.
The production and use of partially hydrogenated oils is a very, very large industry, and an enormous amount of money is at stake. No wonder, then, that our food manufacturers are so reluctant to give them up. Yes, there are alternatives, but economics and inertia (e.g. we have always done it this way!) are formidable obstacles to overcome, without legal implications. In the fast food area, one chain in the US claims that they have been working on the problem for years, but just cannot find a satisfactory solution. That's very strange, because the same chain seems to have succeeded in finding a solution in Europe, where the force of law is employed!
Incidentally, the food industry will probably try to replace the partially hydrogenated oils that they have become so fond of with saturated fats. That way, they don't have to show you any trans fat content, and they hope you won't notice the increase in saturated fat content. Alternatively, they may try to make the claim that they have fully hydrogenated their oils (not realistic), or the amount of trans fats is negligible. Perhaps they will reduce the serving size, in order to get their trans fat content below 0.5 grams, so they can call it zero (a sneaky legal maneuver, made possible by the FDA!). Profits are a powerful motivating force. In the final analysis, you are the only one that can look out for you! Read labels, and read between the lines also. Try to limit your trans fats intake to the lowest practical level. In our American society, it would be almost impossible to eliminate them completely, at least for some time to come. But progress is being made on this front!
The author of this article is Dr. John M. McDonough, who frequently writes on topics involving nutrition, weight loss and fitness. You can find other related information on the website at:
www.theweightlossresource.com