Cooking For Engineers article

[Guest guest]

http://www.cookingforengineers.com/article.php?id=40

 

Monday, June 28, 2004

 

Kitchen Notes: Saturated Fats, Cholesterol, and Heart Disease

 

So, last Wednesday I made a Coconut Creme Pie and brought it into work.

No surprise, it was completely consumed with other coworkers on the

waiting list for slices that were disappointed. What was surprising was

a couple of the consumers commented on how bad the pie must be for their

bodies. I assured them that I used no additives and kept the ingredients

as fresh as possible. I admit that there were some trans fats in this

particular pie because I was unable to get graham crackers without

partially hydrogenated oils. It turned out that they were concerned

mainly about the coconut. One of my coworkers who was watching his

cholesterol levels said, " It's high in cholesterol! " I assured him that

as a plant product, it was impossible for coconut to have cholesterol.

Then he said, " Well, it's high in saturated fat then. "

 

Ah, saturated fat. The most maligned and misunderstood " bad " food in the

last thirty years. During the last year, I've been trying to figure out

why everyone thinks saturated fat is evil and I have been unable to

discover any evidence that there is evidence that saturated fats are bad

for you. In fact, quite the opposite. I'll take this space and discuss

briefly (although it might seem long to you) saturated fats,

polyunsaturated fats, cholesterol, and the misconceptions we've been

brought up with. I'll touch briefly on trans fatty acids too, but that

topic is so nasty that it really deserves it's own article along with

the possible manipulation of the American diet by food oil companies.

Okay, back to saturated fat.

 

Something that doesn't help is that saturated fat is specifically called

out on nutrition labels on food products as well as a Daily Value

Percentage. This makes it seem that we need to limit the intake of

saturated fat but not monounsaturated or polyunsaturated. This implies

that saturated fats are worse than the other two fats and that is not

the case.

 

A little background first:

Fats are comprised of fatty acids which are long chains of carbon atoms

with hydrogen atoms hanging off them:

H H H H H H H H H H H

COOH-C-C-C-C-C-C-C-C-C-C-C-H

H H H H H H H H H H H

 

(lauric acid)

(This molecule can be written as CH3(CH2)10COOH.) If all the carbons

between the carboxyl (COOH) group and the methyl (CH3) group have two

hydrogen atoms attached to them then the fatty acid is considered to be

saturated. A saturated fatty acid is more or less straight (in reality

the carbons zigzag a bit, but the overall chain is straight). This

causes the fatty acid to have a high melting point. The longer the

chain, the straighter the chain, the higher the melting point. That

means most saturated fats are solid. In addition, the carbon single bond

is quite strong resulting in a molecularly stable fatty acid.

 

Unsaturated fats refer to fats containing fatty acids that do not have

as many hydrogens attached as is possible. Instead of bonding to

hydrogen, one or more carbon atoms form a double bond with the next carbon:

H H H H H H H H H H H H H H H

COOH-C-C-C-C-C-C-C-C=C-C-C-C-C-C-C-C-C-H

H H H H H H H H H H H H H H H H H

 

(oleic acid)

This is a monounsaturated fatty acid because it has only one carbon

double bond. This particular fatty acid (oleic acid) has a double bond

in the ninth position from the methyl (CH3) group making it an omega-9

fatty acid. The majority of olive oil's monounsaturated fat is comprised

of oleic acid. The double bond causes a bend in the chain (away from the

missing hydrogens) so that the chain is no longer straight. This lowers

the melting point and causes unsaturated fats (like olive oil) to be

liquid at room temperature. Also every double bond in a fatty acid

" weakens " the structure.

When a fatty acid has more than one carbon double bond, then it is

considered polyunsaturated:

H H H H H H H H H H H

COOH-C-C-C-C-C-C-C-C=C-C-C=C-C-C=C-C-C-H

H H H H H H H H H H H H H H H H H

 

(alpha-linolenic)

This particular fatty acid (alpha-linolenic acid) has the first double

bond in the third position from the methyl (CH3) group making it an

omega-3 fatty acid. This fatty acid is found most commonly in flaxseed

oil and salmon. Because of the three double bonds, this fatty acid is

fragile and very sensitive to light and heat. Also, because of the three

double bonds, this fatty acid curves back on itself and has a very low

melting point.

 

When exposed to free radicals (molecules with unpaired electrons that

are highly reactive), polyunsaturated fatty acids can undergo a process

called lipid peroxidation which results in the polyunsaturated fatty

acid to release additional free radicals. Lipid peroxidation has been

directly linked to artherosclerosis (the constriction of the arteries

due to build up of a plaque composed of fats, cholesterol, and other

substances) and coronary heart disease (artherosclerosis of the coronary

arteries that lead to the heart). Free radicals have little or no effect

on the more stable monounsaturated and saturated fats.

 

It is commonly believed that the build up in the arteries is

predominantly saturated fat and cholesterol. This is an inaccurate or

incomplete statement. The plaque in the arteries varies from subject to

subject, but it has been demonstrated that 3/4 of the fatty acids

present in arterial plaque is unsaturated. [1] Also, cholesterol's role

in the body is ignored when discussing artherosclerosis. The plaque

formed in the arteries does contain substantial amounts of cholesterol,

but probably because cholesterol is used as a healing agent. The damaged

interior artery walls are patched up with cholesterol and then

additional plaque builds up and more cholesterol is used to patch up the

walls. The cholesterol is most likely not a cause of the plaque build

up, but instead a body reaction to the plaque. The fact that no

cholesterol is found sticking to the interior vein walls (where

cholesterol concentration is the same as in the arteries) as you would

expect if you were to believe the predominantly advertised theory that

cholesterol causes circulatory disease. [2]

 

This brings us to the common belief that saturated fat increases the

blood LDL cholesterol levels which in turn cause artherosclerosis. Low

Density Lipoproteins (LDL) carry cholesterol from the liver to the

tissues while High Density Lipoproteins (HDL) carry cholesterol in the

blood back to the liver to be broken down. The buzz words " good "

cholesterol and " bad " cholesterol have been used to label HDL and LDL,

respectively. The belief that saturated fat lowers HDL in the blood is

backed by several scientific studies, but there are also a number of

studies that show that saturated fat intake can result in an increase in

HDL as well. [3]Currently, there is no conclusive proof that saturated

fat intake can be correlated to change in HDL/LDL ratio in the bloodstream.

 

An even more interesting fact is that the claim that LDL and HDL levels

play an important part in heart disease and that there is a fight

between " good " and " bad " cholesterol is short on supporting evidence

(but long on media support). There seems to be as much scientific data

that populations with high incidents of coronary heart disease tend to

have higher levels of HDL (so-called good cholesterol). In addition, low

levels of HDL do not correlate to an increased risk for coronary heart

disease. Most interesting of all, is a study of people who have

genetically caused reduced levels HDL do not have a higher risk of

coronary heart disease. [4] Studies across several countries with

similar HDL-LDL levels resulted in very different incident rates of

heart disease. If the theory that HDL-LDL leads to heart disease is to

be true, then a more consistent death rate from the disease would have

been evident in these countries. It has also been shown that cholesterol

level in the blood stream has no correlation with heart disease. In

fact, over 80% of people who suffer heart attacks, do not have elevated

cholesterol levels. [5] In addition, only 30-40% of people with

artherosclerosis have elevated cholesterol levels. [6] It seems that

cholesterol is neither a good indicator nor a risk factor for heart

disease. (Note: A very small percentage of people have a genetic illness

called hypercholesterolemia which interferes with their ability to

matabolize cholesterol. People with this genetic condition do have to

watch blood cholesterol levels.) [7]

 

So, what is the next most likely candidate for leading to heart disease?

Lipoprotein (a) or Lp(a) has been pointed to as a coronary heart disease

risk factor. [8] Although research is incomplete, early findings have

been strongly suggesting that Lp(a) contributes to and promotes

atherosclerosis. Evidence currently points to trans fatty acids as a

major increaser of Lp(a) levels. What's ironic is that saturated fats

have been linked to lowering Lp(a) levels! [9]

 

So, what are trans fatty acids? In polyunsaturated fatty acids, the

chains naturally are found to all bend in the same direction. In

chemistry this is referred to as cis. If the bends alternate, then this

is referred to as trans.

H H H H H H H H H H H H H

COOH-C-C-C-C-C-C-C-C=C-C-C=C-C-C=C-C-C-H

H H H H H H H H H H H H H H H

 

(trans-9,12,15-octadecatrienoic acid)

Trans fatty acids are created through partial hydrogenation of fats

(natural or chemical). In nature this occurs rarely and results in very

small amounts of trans fatty acids. In our supermarkets, this is a

common place fatty acid. It was discovered that if you partially

hydrogenated a fatty acid, about half of the fats would have bends going

the other way (not in the same direction: cis), thus straightening out

the chain. This causes the fatty acid to have a higher melting point,

allowing the public to enjoy solid fats without the saturated fat (which

was thought to be bad at the time). Margarine replaced butter,

shortening replaced palm oil and lard, and partially hydrogenated

soybean oil replaced coconut oil. During the last ten years, a great

deal of research has been performed on trans fatty acids and the

conclusions are not good. Trans fats (fats made of trans fatty acids)

promote artherosclerosis and other cardiovascular dieases and increase

the risk factor for cancer. In addition, trans fats have been found to

replace necessary saturated fats in fat cells resulting in an unusable

substance taking the place where a fuel and nutrient source should have

been. This leads to the body increasing capacity of fat cells in order

to maintain fuel and nutrient storage levels. Trans fats are also

unstable and may lead to promotion of free radicals in the human body

(for the same reasons that polyunsaturated fats do). It should be noted

that fully hydrogenated fats are the same as saturated fats and do not

exist in cis or trans formations (as there is no bend).

 

So, now we have discussed how saturated fats do not cause directly or

indirectly heart disease, cholesterol is not an indicator or risk factor

of heart disease, polyunsaturated fats should be reduced in the diet,

and trans fats are to be avoided completely. (Pretty much the opposite

of what the media and food oil producing companies tell us.) But, I

haven't discussed any benefits of saturated fats.

 

Before I get into that, I want to mention that although a reduced

polyunsaturated fat intake is recommended, there are two families of

essential fatty acids that we should intake: omega-3 and omega-6. These

are polyunsaturated fatty acids where the double bond is three or six

carbons from the methyl group. About 1-2% of the calories you intake in

a day should be omega-3 and about 2-3% should be omega-6. Too much

omega-6, however, can limit your body's ability to use omega-3 fatty

acids. Omega-3 fatty acids can be found in fish, flaxseed, walnut, and

unprocessed soybean oil (the processing that removes color and oil from

soybean oil pretty much destroys all the linolenic acid in it).

 

In a past article, I've mentioned that I cook predominantly with olive

oils and butter. Here's why: olive oil is high in monounsaturated fat.

In fact it is less than 10% polyunsaturated. Butter is less than 4%

polyunsaturated and contains a large amount of heathful substances.

These include naturally occuring vitamins (A, D, E, and K), small

amounts of linoleic (omega-6) and linolenic (omega-3) acids, butyric

acid (demonstrated anti-tumerigenic properties and a major fuel source

for intestines), lauric acid (anti-microbial and anti-viral),

glycosphingolipids (protects against intestinal infections), conjugated

linoleic acid (strong anti-cancer properties and helps prevent weight

gain; found only in butter and milk from grass-fed cows), lecithin

(assists in metabolising cholesterol and fat components), selenium (aids

vitamin E as an antioxidant; butter is one of the richest selenium food

sources available), and cholesterol. It might seem weird to list

cholesterol as a benefit, but cholesterol is a precursor to vitamin D

and many hormones as well as an antioxidant and the body's primary

repair substance. Consuming cholesterol also contributes to intestinal

wall health. Ingesting cholesterol on a regular basis has been shown to

not increase blood cholesterol levels because the body reduces its

natural production and increases cholesterol metabolism to compensate.

 

It should also be noted that the small amount of ingested cholesterol

can hardly be noticed in the large amounts of cholesterol flowing in

your blood stream. For example, if you are capable of intake half of the

cholesterol you consume daily (let's say 150 milligrams of 300

milligrams consumed) and you compare that to the amount of cholesterol

in the blood (150 mg/dL), then you'll find that of the 7500 mg of

cholesterol in your blood (150 mg/dL * 10 dL/L * 5 L/human) you've added

only another 150 milligrams (assuming your body is even capable of

intaking 50% of the cholesterol you've ingested). A healthy body can

easily throttle back cholesterol production and increase metabolism to

absorb the additional cholesterol intake.[3]

 

1. Felton CV, et al; Dietary Polyunsaturated Fatty Acids and Composition

of Human Aortic Plaques. Lancet, 1994.

 

2. Cranton EM and Frackelton J; Free Radical Pathology in Age-Associated

Diseases. Journal of Holistic Medicine, 1984.

 

3. Enig M; Know Your Fats: The Complete Primer for Understanding the

Nutrition of Fats, Oils and Cholesterol; Bethesda Press, 2000.

 

4. Smith R and Pinckney E; Diet, Blood Cholesterol, and Coronary Heart

Disease: A Critical Review of the Literature. Vector Enterprises, 1991.

 

5. Rowland D; The Nutritional Bypass. Heath Naturally Publications, 1995.

 

6. Reiser R; The Three Weak Links in the Diet-Heart Disease Connection.

Nutrition Today, 1979.

 

7. Byrnes S; Diet and Heart Disease: It Is Not What You Think. Whitman

Publications, 2001.

 

8. Garrison J and Somer E; The Nutrition Desk Reference; Keats

Publishing, 1995.

 

9. Enig M; Fat Facts; Price-Pottenger Nutrition Foundation Journal,

Winter 1998.