The World Turned Upside Down: The Second Low-Carbohydrate Revolution (8 page)

One of the rarely cited responses to
the
Seven Countries study
was a letter written by researchers at the University of Crete and
published in
the journal
Public Health
Nutrition
[28]
.
The important part of this
letter:

"In the December 2004
issue of your
journal...Geoffrey Cannon referred to ... the fact that Keys and his
colleagues
seemed to have ignored the possibility that Greek Orthodox Christian
fasting
practices could have influenced the dietary habits of male Cretans in
the
1960s....Professor Aravanis confirmed that, in the 1960s,
60% of the study participants
were fasting during
the 40 days of Lent
, and strictly
followed all fasting
periods of the church...periodic
abstention from meat, fish,
dairy products, eggs and
cheese
, as well as abstention from
olive oil consumption on
certain Wednesdays and Fridays...."

"....this was not noted in
the study, and
no attempt was made to
differentiate
between fasters and non-fasters
. In
our view this was a
remarkable and troublesome omission." (my emphasis).

The whole sorry tale has now been
told many times, most
recently and completely by Nina Teicholz whose exposé of the low-fat
fiasco,
"The Big Fat Surprise" [11] "Surprise" was published as this book was
being
finished, at the moment when the loyalists began scrambling to claim
dedication
to freedom and revolutionary ideas.

Returning to the
composition of dietary fats.

Going back to
Figure
3.1
, the composition of different dietary
fats turns out to be
somewhat surprising. It is true that there is a lot of oleic acid, the
major
monounsaturated fatty acid, in olive oil (73 %) and canola oil (58%).
Less well
known is that the highest amount is found in avocado oil. Probably most
surprising, however, is that oleic acid makes up almost half of the
fatty acids
in beef tallow and lard (44% and 47 %). Beef tallow, rendered fat, was
what
McDonald's used to use to fry their French fries in – at the time, they
got
thumbs up from Julia Child – until they were pressured to switch to
vegetable
oil in a movement spearheaded by Michael Jacobson. Michael Jacobson,
the head
of the Committee for Perpetual Responsibility or something similar,
might be
described as humorless, up-tight and puritanical. I have been accused
of
inappropriate behavior in making this characterization but you can
check out
this
interview with
Stephen Colbert
). Of course, when McDonald's did
switch to vegetable
oil the amount of
trans
-fat
went up and that got Jacobson riled up again. In any case, most of the
saturated fat in beef is stearic acid which was considered neutral or
"heart-healthy" but the question is at least ambiguous. And, again,
beef fat is
only half SFA, the other half is mostly oleic acid as in the
Mediterranean

Canola oil, it turns out, is named
for
CAN
adian
O
il,
L
ow
A
cid,
an oil isolated
from rapeseed (rape, from Latin for turnip in this context) which also
contains
euricic acid. This fatty acid is the star of Lorenzo's oil but it not
as
beneficial as in the movie and is generally considered toxic and it is
removed
in making canola oil. My original vision of the
Quebecoise
in their native costumes picking
canola fruit from the canola tree turned out not to be correct. There
is no
canola tree. The rapeseed plant, a member of the
Brassica
family (like broccoli) was
originally processed to remove the euricic acid. The plant has now been
bred to
have low euricic acid and there now really is a plant called canola and
the oil
is one of the major export products from Canada. Processing also
produced
trans
-fatty
acids but
this has been removed from current versions of the product. (Wikipedia
has an
interesting
read about canola oil
).

Back to the quiz... We asked students
about
the "cholesterol"
species that are reported in your lipid profile and that are supposed
to be indicators of risk of cardiovascular disease (CVD). What is called
cholesterol
in this context is actually a supramolecular (more than one type of
molecule)
known as a
lipoprotein
which contains lipid protein). The simplified structure and the
relative sizes
are shown in
Figure 3-5
.

Lipoproteins. "good"
and "bad" cholesterol.

There
were a few
questions not shown here. Most of our students knew that low-fat diets
lower
low density lipoprotein cholesterol (LDL-cholesterol), the so-called
"bad
cholesterol." Considered bad because it is assumed to correlate well
with heart
disease. Not well appreciated is that the correlation is not strong.
Less than
half the people with a first heart attack have high cholesterol and
less than
half have high LDL (although "high" is subject to interpretation). The
skepticism expressed in the Introduction is still appropriate here.

Figure 3-5
. Sizes and
structure of the common lipoproteins.

Cholesterol is not a cause of heart
disease – we don't know what
the cause is – but it is considered a risk marker, something associated
with
incidence of disease. There are, however, better risk markers including
triglycerides and the "good cholesterol" HDL-cholesterol.

9.
     
The
diet component that is most likely to raise triglycerides (fat in the
blood)
is:

_____ Fat

__
X
__
Carbohydrate

_____ Protein

Student Performance on Question 9

The phenomenon of
carbohydrate-induced hypertriglyceridemia
(high blood triglyceride) has been known for at least sixty years. A
major
contributor is the process of
de
novo
fatty acid synthesis, more usually called
de novo
lipogenesis
(DNL), in which fatty acids are made from other components, mainly
carbohydrate. It is significant that the fatty acid that is made in DNL
is
palmitic acid, the sixteen carbon saturated fatty acid. In other words,
carbohydrate in the diet raises saturated fat in the blood. This was
demonstrated most convincingly by experiments at the University of
Connecticut
[29-31] described below in
Chapter 9
.
It turns out that saturated fatty
acid in the blood may be deleterious but this is more dependent on
dietary
carbohydrate than dietary fat. In any case, our students completely
missed the
boat on this.

How much of a risk factor is high
triglycerides? Well, it is
impossible to tell. The American Heart Association (AHA) tends to
downplay the
importance of triglycerides. This is probably related to the need to
avoid
talking about low-carbohydrate diets, and the fact that dietary
carbohydrate restriction
is the most effective method of reducing high triglycerides except
perhaps for
total starvation. On the other hand, increases in triglycerides become
a
tremendous threat to the AHA in the context of sugar, or fructose in
particular. Sugar is carbohydrate and whether an increase in fructose
is more
or less effective than glucose in elevating triglycerides or, what we
really
know from experiments, total carbohydrates, probably depends on how you
do the
study: despite what you read in the media, fructose and glucose are
closely
linked: as much as 60% of added fructose can be turned into glucose, so
you
don't even really know what your adding. In addition, the effect of one
sugar
is tied to how much of the other you have. For example, fructose taken
up by
the liver is a signal to increase the uptake of glucose.

10.
 
In general, what effect does
a low-fat diet have on HDL-C (high density lipoprotein cholesterol,
"good
cholesterol") ?

     
_____ Increase

     
__
X
__
Decrease

     
_____ No change

     
_____ Don't know

Student Performance on Question
10

A low-fat diet reduces cholesterol,
both
"good" and "bad." The
bottom line on the cholesterol problem: the literature studies tend to
show
that a sub-type of LDL particle, the smaller LDL are generally found to
be most
atherogenic (highest risk for CVD). High levels of small-dense LDL are
characterized as "pattern B" and this pattern is most dependent on the
level of
carbohydrate, not the level of fat. This critical observation has had
little
effect on official positions of the AHA or other agencies and
anecdotally, they
don't think LDL size matters but have not said exactly why not. The AHA
has,
however, quietly removed their proscription against total fat in 2000;
you
didn't know that?

LDL particle size is not generally
measured in a standard lipid
profile and your physician is most likely to look at total cholesterol
or
LDL-cholesterol to determine if you are at risk for heart disease. The
recognized surrogate for pattern B is the ratio of triglycerides/HDL.
The
cut-off is 3.5
[32]
. If
your value is below that mark,
there is limited risk for cardiovascular disease.

The question of whether the reduction
in
triglycerides or HDL
that is a consequence of a low-carbohydrate diet has any protective
effect is
much harder to answer. As suggested in the introduction, it is possible
that,
outside of well-defined genetic abnormalities, what you eat may have no
effect
on your risk of heart disease. We will come back to this theme. The
response to
doubt separates science from religion. It is revolutionary to even
consider the
possibility that the diet-heart hypothesis as currently constituted is
not only
wrong but there is no replacement. In religion, you pray for relief
from doubt.
We don't want to do that.