Free The World Turned Upside Down: The Second Low-Carbohydrate Revolution by Richard David Feinman Page A

in olive
oil. So it
is a question of whether you think that lard is half full of SFA or
half empty.
Most important, as in the epidemiologic study described in the Introduction ,
there is no risk for cardiovascular disease associated with consuming
saturated
fat. This has now been borne out by large population studies and there
is
simply no correlation – if anything, the studies show that carbohydrate
is a
greater risk than saturated fat but these kinds of correlations are too
weak to
attribute any role at all to either. More on this as we go along.

    Figure 3-3. Single
and double chemical bonds and common fatty acids
    The structure of the different kinds
of
fatty acids are shown in Figure 3-3 .
The
major monounsaturated fatty acid is oleic acid. Everybody thinks that
monounsaturated fats, those with a high content of MUFA like olive oil
are
protective of cardiovascular disease but it is not so clear-cut.
    Few fats have only SFAs. Coconut oil
is the exception but
those are medium chain FA (12-16 carbons). Most naturally occurring
fats have
mixtures of FAs but you can make or isolate from natural sources, a fat
that is
all stearic acid (called tristearin or just stearin). It is not usually
used in
food because it is solid and hard but it is used in manufacturing soap
and
other products.
    Saturated fats (again, those with
fairly large number of
SFAs) tend to be solid while those with more unsaturated fatty acids
tend to
be liquid – generally, the more saturation the higher the melting
point. To
understand why, we need to look deeper into the structure of fatty
acids and
the question brings us to the issue of " trans -fats."
    What are trans-fats? In
fact, what is "trans"?
    When vegetable oils are hydrogenated,
the process by which
some of the unsaturated FAs are turned to saturated, a side-reaction
can occur
that changes the configuration of some of the unsaturated fatty acids
from cis -
to trans -.
    Let me explain what " tran s"
means since the Nutritional Murphy's Law dictates that confusion will
be
introduced wherever possible. The carbon-carbon double bond has rigid
geometry,
that is, unlike the carbon-carbon single bond, there is no rotation
around the
bond. So, if you imagine a chain of carbon atoms as in a hydrocarbon
like
gasoline or the backbone of a fatty acid, if the bonds are all
saturated
(single) bonds then you can think of the molecule as somewhat floppy
because of
free rotation around the bonds. If there is a double bond in this
chain, there
are now two ways to arrange the structure. The two carbons in a double
bond can
have hydrogen atoms on the same side of the bond ( cis -)
or on opposite sides ( trans -). Figure 3-4 shows
the geometry around double bonds.

    Figure 3-4. Orientation around chemical double bonds. The two carbons in a double
bond each
have a hydrogen atom and another atom, a carbon or , the case
of FA, carbon
chain. if these are on the same side of the double bond, they have the cis -configuration.
Otherwise, trans -.
    Almost all naturally occurring fatty
acids are have the cis configuration but it
is important to understand that, by itself, it is just a designation
about the
millions of double bond-containing compounds in the world. Figure 3-4 shows that UFAs
have more structure than SFAs
and this is why saturated fats tend to be solid (easier to pack into a
solid;
by analogy, it is easier to pack T-shirts into a box than to pack model
Eiffel
Towers or heads of Nefertiti).
    MUFAs and the
Mediterranean Diet.
    The Mediterranean Diet is widely
recommended for its health
benefits although the data is pretty weak and it is not obvious that
anybody
knows what the diet is beyond the idea that you have to pour olive oil
on
everything. The idea probably comes from Ancel Keys, generally
considered the
father of lipophobia. Keys originally found a good correlation between
fat
consumption (actually fat availability) in six different countries and
the
incidence of heart disease in those countries