Trans-Fats: Out of the Frying Pan and Into the Fire
There is a lot of buzz these days about trans-fats. Most of us
are aware that they present a health risk. Some researchers have
even hypothesized that the pervasive nature of trans-fats is to
be blamed for the heart disease epidemic of the 1990's. That is
to suggest that much of our current problem with heart disease
can, at least in part, be traced back to the fact that
trans-fats are almost everywhere in our foods. It would also
seem to suggest that reducing trans-fat intake might reduce the
incidence of heat disease.
This article does not deal per se with how to avoid trans-fats
in your diet. That, indeed, is a worthy topic but must be
reserved for another time. Our present concern is one that is a
bit more basic in nature. It is this: What is the source of
trans-fats and why do we find them in so many of our foods? To
theorize that trans-fats may bear some responsibility for the
escalation of heart disease in the 1990's is to propose that
trans-fats were not so prevalent before that time. It further
suggests that the change is due to something we have done to
ourselves.
Around the middle of the previous century we became increasingly
aware that saturated fat consumption poses a risk to heart
health. Conventional wisdom today agrees with that earlier
assessment. It was further believed, as it is today, that mono-
and polyunsaturated fats are much better for us. For the most
part they do not promote atherosclerosis (hardening of the
arteries). In addition many unsaturated fats actually reverse
the damage caused by their saturated counterparts.
So why not simply have a whole culture switch to using
polyunsaturated oils instead of what we were used to using? The
question almost answers itself. It is the same as asking, "Why
don't people stop smoking?" Nobody believes it is a healthy
practice. But as long as we have choices to make we will make
bad ones. And as long as there is money to be made products will
be sold.
Perhaps it is more helpful for us to look at the particular
dilemmas facing the scientists of the 1950's. They knew, as we
do, that people should eat less saturated fats and more
unsaturated fats. However folks were very accustomed to lard and
butter, just to mention two common products. Not only do these
products have a particular taste, they are also in semi-solid
form at room temperature. Unsaturated oils are usually in liquid
form at room temperature. So the first problem facing scientists
was how to convert unsaturated fats into substances that taste
and act like the semi-solid products the populous already
appreciated.
But there was a second obstacle. Unsaturated fats tend to spoil
more quickly producing a rancid odor and taste. Therefore they
cannot be stored for long periods of time. Limited shelf-life
can be a hindrance for food producers and marketers. Any product
that could be widely sold must be able to stand the test of time
in relation to the whole food manufacturing cycle.
Fortunately a solution was found that could simultaneously
overcome both obstructions. That solution? Hydrogenation.
All of us are somewhat familiar with the term. We see a variant
of it almost every time we read the label from one of the
products in the pantry. It has become commonplace. Neatly tucked
away between the various unpronounceable ingredients we find the
words 'partially hydrogenated'. This two word combination will
be coupled with some oil that we might recognize as good for us.
The list of partially hydrogenated oils is impressive and
misleading. When we read the labels we should place an emphasis
in our minds on the first part of the phrase. Instead of reading
the label like this: 'partially hydrogenated soybean
oil', we should read it thus: 'partially hydrogenated
soybean oil'. The end of the phrase is somewhat insignificant.
The beginning of the phrase means everything.
Hydrogenation is simply a process whereby an unsaturated oil
(fat) is saturated with hydrogen. Fats are composed of carbon
(C), hydrogen (H) and oxygen (O) atoms along a carbon chain or
skeleton. At one end of the chain there is a carboxyl group
consisting of bonds between one carbon atom, one hydrogen and
two oxygens, or (COOH). Simply put, fats are composed of a chain
of carbon atoms. A carbon atom has four bonds. Typically two of
the bonds are connected to other carbon atoms in the chain. The
other two bonds will be connected to hydrogen. A saturated fat
has all of its (free) bonds tied up with hydrogen. In an
unsaturated fat some of the carbon bonds are not connected to
hydrogen. Instead the carbon atoms form double bonds with each
other. The problem with these double bonds, from a manufacturing
point of view, is that they make the fat liquid at room
temperature and reduce shelf life.
The solution, however, is rather simple. By heating the fat in
the presence of hydrogen some of the double carbon bonds are
broken and they form an attachment with a new hydrogen partner.
It all sounds so romantic. Of course you can see where this is
going. Now the fat is approaching saturation again. Not to
worry, however. The process is usually stopped prior to the
saturation point. The fat is then said to be 'partially
hydrogenated'. Technically it remains unsaturated. It seems as
if we can have our cake and eat it too. Now we can have
unsaturated fats that act and taste like saturated fats. The
consumer has the best of both worlds. The seller has a product
which is inexpensive to make, has a long shelf-life and has mass
appeal. Who said utopia is not possible?
As is true with most relationships breaking up to form new
attachments usually causes a backlash. The carbon atoms that
share a double bond are each also bound to one hydrogen atom.
The hydrogen atoms are both on the same side of the molecule
chain. This configuration is known as a 'Cis' bond and occurs
naturally in unsaturated fats. The hydrogenation process weakens
these 'Cis' bonds. As mentioned earlier they are not all broken.
However their weakening causes some of the hydrogen atoms to
move to the other side of the carbon chain. The hydrogen atoms
are now across (or trans) from each other. The 'Cis' bond has
now become a 'Trans' bond. Essentially the molecular shape of
the chain is altered. We now have the birth (to keep the
relationship metaphor going) of a new fat named for its altered
'Trans' bonds. We know them as trans-fats or trans-fatty acids.
Though the hydrogen process is difficult to picture its end
result is clear to all of us. Hydrogenation creates trans-fats.
If a high percentage of our manufactured foods contain partially
hydrogenated products, they of course contain trans-fats. And
anyone who has been paying attention lately knows that
trans-fats are bad for us, very bad for us.
There is one more bit of bad news. As noted above, hydrogenation
involves exposing unsaturated oils to high heat. Frying with oil
does the same thing. Granted only a small number of 'Cis' bonds
are converted to 'Trans' bonds during the process of frying. It
might be argued that we should avoid any exposure to trans-fats.
However there is a bigger picture here. I always appreciate
those fast food restaurants that make an attempt to produce
healthier foods. One way they do this is to use healthy oils in
their frying process. But I wonder how many times they use those
healthy oils. If a small number of 'Cis' bonds are converted to
'Trans' bonds during the first frying phase, how many 'Trans'
bonds exist before the oil is changed? It is like playing
trans-fat Russian roulette. "May I have my French fries fried in
a new batch of oil, please?" It puts a new twist on special
orders.
For more information on trans-fats and hydrogenation please use
the links below.
Hydrogenation
Trans-fa
ts