Fatty Acids (FA)
There are twenty different fatty acids in our tissues. FA
are chains of carbon molecules with the form:-C-C-C-
A single bond -C-C-C- is "saturated". If carbon atoms are joined by two of their available
four bonds -C=C=C- the FA is described as "unsaturated". Double bonds facilitate
molecular re-arrangement and unsaturated fats with -C=C=C- have advantages that
saturated bonds lack. The unique properties of each fatty acid are more important to know than general
biochemical properties of groups of fatty acids. The disadvantage of unsaturated
carbon bonds is that they are easily oxidized, and oxidized FAs tend to be
toxic. If vegetable oils are cooked at high temperature in the frying pan or
deep fryer, oxidation occurs rapidly. This is the argument against fried foods.
Slow fat oxidation underlies rancidity of fat. Most oils are preserved with
antioxidants to prevent rancidity. Careful manufacturers may supply sensitive
oils in hydrogen-packed, black, sealed bottles and instruct you to store bottles
in the fridge.
The general chemical formula of a fatty acid is:
Chain length varies from 1 to 24 carbon atoms and the
carbon atoms are numbered from the COOH (the acid) end. The hydrocarbon chain
may contain single and double bonds. A fatty acid with more than one double bond
is described as a polyunsaturated fatty acid (PUFA).Double bonds occur every 3
carbon atoms. The current naming system uses number coding to show the length of
the carbon chain, the number and position of the double bonds. Fatty acids are
also divided into 4 groups, depending on the number of C atoms up to the first
double bond, started at the other end, the omega end, of the chain. The
omega-number refers to the location of the first unsaturated
-C=C- bond from the omega end of the fatty acid chain.
The omega-3 group starts with alphalinolenic acid (ALA)
found in the leaves and seeds of many plants. Longer chain omega-3 fatty acids
are found in fish and marine animals (EPA and DHA).
The omega-6 group starts with linoleic acid (LA), and
progresses to gamma-linoleic acid (GLA), di-homo-linoleic acid and then to
arachidonic acid. Arachidonic acid (AA) is sometimes considered an essential FA
but may be produced internally by the conversion of linoleic acid.
Oleic acid in olive oil is described as a "mono-unsaturate”
because it has only one -C=C- bond rather than two or more. While not essential,
it may be considered a desirable fatty acid.
The omega 3 series of FA are derived from alphalinolenic
acid (18:3n-3). The major sources are flax seed, soybean, canola, wheat germ,
and walnuts oils. The two most publicized long chain omega 3 FAs are:
eicosapentaenoic acid (EPA) C20:5n-3 and docosahexaenoic acid (DHA) C22:6n-3).
DHA is present in all tissues; 60% of the human brain is comprised of PUFAs,
Linoleic acid (LA), the 18 carbon n-6 essential fatty acid,
is found in canola, safflower, corn, soybean, and cottonseed oils. Meat products
are a source of the n-6 fatty acid, arachidonic acid (AA) (C20:4n-6). GLA is
synthesized from LA via an enzyme, delta-6 desaturase. Oils with higher GLA
content have been derived from the seeds of evening primrose, borage and black
Many articles have been written to recommend fish oil
intake to prevent heart disease. Fish eaters suffer less cardiovascular disease.
Eicosapentenoic acid (EPA) is mostly found in fish, especially salmon, herring,
anchovies, mackerel, salmon, sardines, sea bass, swordfish, and trout. Some
recommendations are to increase fish intake, while others recommend specific
amounts of EPA and DHA as a supplement. Kris-Etherton stated that walnut,
flaxseed, soybean, and canola oil can contribute to meeting ALA recommendations.
A high intake of n-6 fatty acids, however, inhibits the conversion of ALA
to EPA and DHA. Epidemiologic studies in the United States report that 500
mg/day of n-3 fatty acids can decrease CHD risk. The average diet only provides
100 mg EPA and DHA per day. Arterburn concluded that DHA is important to supplement, with or without EPA.
To saturate the plasma, 2 g DHA per day is needed for 1 month; to saturate the tissues, 3 to 6
months; and less than 1 week for DHA supplementation to increase human milk
concentrations. To remain at saturation levels in the plasma, tissues, or human
milk, continued supplementation is necessary.
Dwyer et al identified a subpopulation with increased atherosclerosis. They observed
diet–gene interactions which lead to dietary n–6 polyunsaturated fatty acids
promoting inflammation and marine n–3 fatty acids inhibiting inflammation.
Leukotrienes are inflammatory mediators generated from arachidonic acid by the
enzyme 5-lipoxygenase. They hypothesized that a polymorphism in the
5-lipoxygenase gene promoter could influence atherosclerosis and could interact
with the dietary intake of different fats. They found 6 % of a study cohort had
two variant gene alleles and had increased arterial wall thickness. Increased
dietary arachidonic acid increased the atherogenic effect and increased dietary
intake of n–3 fatty acids reduced the effect.
Another variable of fatty acid structure is that the double
bonds may have one of two forms; cis and trans. Only the cis form functions
normally. Animal fats tend to have some trans fatty acids. A high intake of
trans fat increases the risk of coronary heart disease by increasing LDL
cholesterol and decreasing HDL cholesterol.
The American Heart Association guidelines recommend limiting the intake
of saturated fat to 7% and trans fat to less than 1% of daily energy intake.
The hydrogenation of vegetable oils to make shortening,
lard, and margarine produces trans fatty acids. These solid and semi-solid fats
have largely replaced butter with its high content of saturated fatty acids as a
baking and cooking ingredient. Two of the least desirable foods in a store are
margarine and shortening. Trans fats are abundant in processed, boxed, bottled
and fast foods. A wave of negative publicity has attracted regulators who first
demanded a declaration of trans fat content on the nutritional label of foods
sold in stores and more recently are proposing legislation to ban restaurant
foods with high content of trans fats. The food industry has turned bad publicity into marketing opportunities.
New labels boast of zero trans fats.
The Alpha Nutrition Program can be recommended, along with
Alpha DMX, exercise and relaxation as a rational strategy of
preventing and managing cardiovascular disease. The program is
designed to reduce sodium, cholesterol, total fat, saturated fats,
while increasing calcium, potassium, folic acid, omega 3 fatty acids
and vegetable fiber. These are all desirable measures in the effort
to prevent blood vessel diseases, heart attacks and strokes.
High Blood Pressure According to the Canadian Coalition
for High Blood Pressure Prevention and Control, non-drug strategies
should be the priority for hypertension control. Smoking cessation,
low sodium, low fat diet, weight loss, exercise, reduced alcoholic
beverage consumption, and increased calcium, magnesium and potassium
intake are the important steps to avoid high blood pressure.