NUTRITION FACTS ABOUT FATS



Fats are traditionally classified as Lipids.  Free fatty acids (FFAs) are the building blocks of fats that provide energy for the body.  They are either used by cells and muscles as fuel for energy or stored as neutral triglycerides (TG) in fat cells of the adipose tissue for later use.  The normal kinds of fat in the regular diet usually consist of saturated, monounsaturated, polyunsaturated, and trans fatty acids.  While saturated fatty acids (SFAs) with 12 to 18 carbon atoms such as Lauric (C-12), Myristic (C-14), Palmitic (C-16), and Stearic (C-18) acid are normally solid and physically stable at room temperature, the unsaturated fatty acids (UFAs) including both monounsaturated, and polyunsaturated are mostly liquid at room temperature.  On the other hand, Trans fatty acids (TFAs) are usually semi solid at room temperature.  

Bad Fats

Triglycerides in the blood are either derived from dietary sources or made in the body by the liver.  Following mobilization from adipose tissue, FFAs are converted into triglycerides in the liver and then released into the bloodstream for circulation to various sites.  There is enough evidence to suggest that high triglyceride level can be a strong marker for heart attacks.  Excessive carbohydrates intake by the body can raise blood triglyceride levels. 

Saturated fats are used in the liver to synthesis cholesterol for the body.  For example, food derived exogenous saturated free fatty acids such as lauric, myristic, and palmitic acid are normally converted to cholesterol by the liver.  As a matter of fact, saturated fat raises blood cholesterol more than dietary cholesterol does.  In contrast with these saturated free fatty acids, stearic acid is normally stored in the form of fat as fuel for energy, and seldom converted to cholesterol.  On the down side, Stearic Acid is not only high in calories, but it also activates Clotting Factor XII.  Animal Fats and Tropical Oils are all high in saturated fatty acids.  It stands to reason that since vegetarian diets are low in saturated fat and cholesterol free, the vegetarians have a lower risk of heart disease.  

Cholesterol is not a true fat, but a fat-like substance, sometimes referred to as "lipid".  It is found in human and animal tissues and not in plant tissues.  Under normal conditions, cholesterol is essential for good health.  Although it is needed by the body to build cell membranes, manufacture steroid hormones, and make bile acids, it is believed that high blood cholesterol levels can be a risk factor for coronary heart disease and stroke.  Cholesterol in the bloodstream is transported to the cells and tissues throughout the body and back to the Liver by means of two lipoprotein transporters, one known as low-density lipoprotein (LDL), and the other as high-density lipoprotein (HDL).  The LDL is referred to as "bad" transporter because it deposits free cholesterol (FC) in artery walls, leading to fatty deposit buildup and plaque formation.  Conversely, the HDL is referred to as "good" transporter because it protects against cholesterol-laden plaque buildup in arterial walls by returning excess cholesterol to the liver for recycling and fecal excretion.  

Generally speaking, both high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) pose as risk factors for coronary heart disease (CAD); and more often than not, their blood levels are inversely related.  For example, a low TG level usually goes hand in hand with a corresponding high HDL "good" cholesterol level.  Substituting carbohydrates for fats can raise triglyceride levels and lower HDL blood cholesterol levels.  

Trans Fatty Acids are by-products of the hydrogenation process whereby vegetable oils high in unsaturated fatty acids are partially hydrogenated to increase their shelf life by transforming them from liquid to solid state at room temperature, at the expense of saturating some of the unsaturated fatty acids.  Since they are produced in cooking oils during the frying process, fried foods are a major source of trans-fat in the diet.  Research has shown that trans-fats inhibit the enzyme needed for the conversion of essential fatty acids into Prostaglandins in the body.  

Diets rich in saturated fat, trans-fat, and dietary cholesterol raise both total blood cholesterol and LDL (bad) blood cholesterol.  Ironically, saturated fat tends to raise blood cholesterol levels more than the dietary cholesterol in foods does.  On the flip side, trans-fat is even worse than saturated fat since it unequivocally lowers HDL (good) blood cholesterol levels.  

Good Fats

While saturated fats and trans-fats are considered as bad fats, both monounsaturated fatty acids (MUFAs} and polyunsaturated fatty acids (PUFAs) are considered as good fats.  In the body, saturated stearic acid (C-18) is converted to oleic acid (C-18), a heart-healthy monounsaturated fatty acid with one unsaturated carbon-to-carbon double bond.  This monounsaturated fatty acid (Oleic Acid) is sometimes referred to as Omega-9 fatty acid.  Monounsaturated fats are considerably resistant to free radical-induced peroxidation.  Good sources of monounsaturated fats are canola and olive oils, almonds, and sesame seeds. 

Essential Fatty Acids

Essential fatty acids (EFAs) are those that the body needs but cannot synthesize.  For instance, PUFAs such as linoleic acid (LA) and alpha linolenic acid (LNA) are classified as EFAs on the basis that although they are necessary for the biological cell-membrane structure and the production of hormone-like prostaglandins, they are not synthesized by the body but supplied from outside dietary sources including nutritious foods and/or dietary supplements. 

Typical examples of EFAs include polyunsaturated LA-based Omega-6 and LNA-based Omega-3 fatty acids.  As precursors to Prostaglandins (PGs), both Omega-6 and Omega-3 fatty acids obtained from dietary sources are utilized by the body cells to synthesize PGs by the action of enzymes.  Since body cannot synthesize these Omega type polyunsaturated fatty acids on its own, they are considered EFAs.  

While the Omega-6 fat is made up of 18-carbon long polyunsaturated LA with 2 unsaturated carbon-to-carbon double bonds, the Omega-3 fat is made up of 18-carbon long polyunsaturated LNA with 3 unsaturated carbon-to-carbon double bonds.  The first double bond occurs at the third carbon in the case of Omega-3 and at the sixth carbon in the case of omega-6.  

Omega-6 fatty acids are found in edible vegetable sources including corn, cottonseed, sesame, soybean, and sunflower oils.  It is interesting to note that Omega-3 polyunsaturated fatty acids occur naturally in three different forms.  The one derived from plant sources is 18-carbon LNA with 3 double bonds, and the other two found in cold-water, fatty fish are 20-carbon long eicosapentaenoic acid (EPA) with 5 double bonds, and 22-carbon long docosahexaenoic acid (DHA) with 6 double bonds.  

Omega-3 Fatty Acids

Flaxseed is the richest plant source of LNA-based polyunsaturated Omega-3 fatty acids.  Likewise, cold-water fish is rich in EPA and DHA that account for the animal-derived source of Omega-3 fatty acids.  As a precursor to elongated eicosapentanoic and docosahexaenoic acids, LNA is converted first to EPA and then to DHA in the human body.  Only about 10% of LNA is converted to EPA and DHA.  In summary, the body gets its supply of dietary Omega-3 fats from exogenous food sources like herring, sardine, mackerel, lake trout, tuna, and salmon fish, canola oil, flaxseed and flaxseed oil, pumpkinseeds, and walnuts.  The Flaxseed Oil and Canola Oil contain about 50% and 10% of LNA-based Omega-3 fatty acids, respectively.  The animal versions of Omega-3 fatty acids in commercial Fish Oils comprise about 30% of EPA and DHA.  

The Omega-3 fatty acids EPA and DHA play a key role in the prevention of cardiovascular disease (CVD).  As a matter of fact, DHA promotes the brain, retina, and heart health throughout the life span.  Inasmuch as DHA is essential for the development and function of the brain and nervous system, fish is literally considered as "Brain Food".  Recent studies have shown that concentrated fish oil supplements improve learning and cognitive development.  Omega-3 fatty acids have the unique ability to not only serve as building blocks for cell membrane integrity, but also to stimulate thermogenesis by burning stored body fat to produce extra body heat.  Scientists believe that diets rich in the beneficial long-chain Omega-3 fatty acids EPA and DHA may help:

• reduce Inflammation
• thin blood
• enhance Immune system
• lower triglycerides
• lower total cholesterol
• raise HDL (good) cholesterol
• lower blood pressure
• lower the risk for macular degeneration,
• lower the risk of manic depression in bipolar disorders
• control obesity

In contrast to Omega-6 polyunsaturated fatty acid that lowers both the LDL (bad) cholesterol and HDL (good) cholesterol levels, monounsaturated and Omega-3 polyunsaturated fatty acids are the only two that lower LDL (bad) cholesterol without affecting HDL (good) blood cholesterol levels.  

Prostaglandins

By classical definition, Prostaglandins (PGs) are described as a subset of the Eicosanoids Family of biologically active lipids derived from the 20-carbon long-chain polyunsaturated EFAs.  They are short-lived, hormone-like substances formed enzymatically in the cells of virtually all tissues and organs.  There are two prostaglandin pathways, one that begins with Omega-6 fatty acid and the other that begins with Omega-3 fatty acid.  In order to fully comprehend mechanisms involved in the biosynthesis of PGs in the human body, a brief overview of the pertinent concepts is presented hereunder.  

• The Omega-6 pathway begins with the 18-carbon, double-unsaturated LA.  This EFA is desaturated once by the action of a desaturating enzyme, delta-6-desaturase (D6D), resulting in an 18-carbon, triple-unsaturated fatty acid called gamma-linolenic acid (GLA).  Incidentally, GLA differs from the 18-carbon triple-unsaturated LNA in that the unsaturated carbon double bonds are in different places along the carbon chain.  An elongase enzyme then adds 2 more carbon atoms to the GLA chain, resulting in the formation of a 20-carbon, triple-unsaturated fatty acid called dihomo-gamma-linolenic acid (DGLA).  Eventually, this DGLA gets desaturated once to form a 20-carbon, quadruple-unsaturated fatty acid named Arachidonic Acid (AA).  
• Likewise, the Omega-3 pathway begins with the 18-carbon, triple-unsaturated LNA.  This EFA is desaturated twice and elongated once to produce EPA, a 20-carbon long fatty acid with Five double bonds.  EPA is then further elongated and desaturated to produce DHA, a 22-carbon long fatty acid with Six double bonds, as the end product of the Omega-3 pathway.  
• The body uses both types of Omega fats to synthesize various Prostaglandins. Both pathways entail elongation of 18-carbon long fatty acids with 3 double bonds by the enlongase enzyme as well as desaturation by the delta-6-desaturase enzyme (D6D), resulting in the formation of  20-carbon to 22-carbon long fatty acids with 4, 5, and 6 double bonds.  However, desaturation is the rate-limiting step in the production of PGs from these EFAs.  Since both pathways draw on one common D6D resource, overabundance of Omega-6 fatty acids will deplete the D6D reserve to the point where Omega-3 fatty acids will be deprived of their fair share of the reserve.  
• On the basis of functionality, the whole gamut of PGs is conveniently grouped together under three well defined series, PG1, PG2, and PG3, each of which has specific biological effects.  It is common knowledge that while PG1 and PG3 are anti-inflammatory and reduce pain, the PG2 are pro–inflammatory since their effects are opposite to those of PG1 and PG3.  For this reason, the Series 1 & 3 PGs are referred to as 'good' prostaglandins and the Series 2 PGs as ‘bad’ prostaglandins.  On the Omega-6 pathway front, the Series 1 prostaglandins are produced from the 20-carbon, triple-unsaturated fatty acid DGLA found in the liver and other organ meats.  The Series 2 Prostaglandins are produced from the 20-carbon, quadruple-unsaturated fatty acid AA found in butter, animal fats, and eggs.  On the Omega-3 pathway front, the Series 3 Prostaglandins are produced from the 20-carbon, quintuple-unsaturated fatty acid EPA found in dietary Fish Oils including cod liver oil.  
• Prostaglandins are formed in cellular membranes by the action of a myriad of enzymes on EFAs.  The first step in the PGs synthesis cascade via AA route is the release of AA from the cell membrane Phospholipids by the action of the enzyme Phospholipse A2 (PLA2).  An isoenzyme system called cyclo-oxygenase (COX) then catalyzes the conversion of the substrate AA to Prostaglandin PGG2.  Subsequently, this PGG2 is reduced by peroxidase to form the unstable intermediate prostaglandin PGH2, which in turn gets spontaneously converted to relatively more stable Prostaglandins (PGD2, PGE2, and PGF2), Prostacyclin (PGI2), and Thrombaxane (TXA2). 
• Both Prostacyclins and Thromboxanes are synthesized directly from Prostaglandins derived from the Omega-6 type AA.  PGI2 is produced from PGH2 by the action of the enzyme Prostacyclin Synthase, whereas TXA2 is produced from PGH2 by the action of enzyme Thromboxane A Synthase.  PGI2 is a potent vasodilator and an inhibitor of platelet aggregation.  In contrast, TXA2 is a vasoconstrictor, and promotes platelet aggregation.  A correct balance between the two is essential to good cardiovascular health. 
• COX enzyme exists in two distinct forms, COX-1 which is “constitutive” in nature, and COX-2 which is “inducible” in nature.  COX-1 is found in nearly every cell and is used for basic housekeeping functions, and COX-2 is found in specialized cells, where it is synthesized on demand to assist with the process of inflammation.  COX-1 produces PGE1 and TAX2 that play a good-housekeeping role in the Stomach, Kidney, and Platelets.  In contrast, the induction of COX-2 by pro-inflammatory mediators such as Cytokines results in the biosynthesis of both PGE2 and PGI2 responsible for promoting inflammation, pain, and swelling.  
• When the body converts GLA-based Omega-6 fatty acid to DGLA, the COX-1 converts DGLA to ant-inflammatory Series 1 prostaglandins, PGE1.  When the body converts DGLA-based omega-6 fatty acid to AA, the COX-2 converts AA to pro-inflammatory Series 2 prostaglandins, PGE2 and. PGI2.  On the other hand, when the body converts LNA-based Omega-3 fatty acid to EPA and DHA, they in turn produce anti-inflammatory Series 3 prostaglandins, PGE3 that effectively block the production of COX-2 enzyme.  In addition EPA produces PGI3 which reduces platelet aggregation and relaxes blood vessels.  
• In summary, here is the break-down of the salient features of PGs.   

1. LA is an Omega-6 fatty acid and LNA is an Omega-3 fatty acid
2. Other Omega-6 fatty acids manufactured in the body using LA as a starting point include GLA, DGLA, and AA
3. Other elongated Omega-3 fatty acids manufactured in the body using LNA as a starting point include EPA and DHA
4. DGLA, AA, EPA, and DHA are all precursors of Prostaglandins
5. Series 1 & 2 PGs are made from Omega-6 fatty acids, and Series 3 PGs from Omega-3 fatty acids
6. Series 1 PGs reduce inflammation and blood clotting
7. Series 2 PGs promote inflammation and blood clotting
8. Series 3 PGs protect against inflammation and blood clotting
9. Prostacyclin PGI2 is derived from the Omega-6 type AA
10. Prostacyclin PGI3 is derived from the Omega-3 type EPA.

EFAs	TYPES	SERIES
Dihomo-Gamma-Linolenic Acid (DGLA)	C20-B3-L6	Series 1
Arachidonic Acid (AA)	C20-B4-L6	Series 2
EicosaPentaenoic Acid (EPA)	C20-B5-L3	Series 3
Note: C = carbon atoms, B = double bonds, L = location of the first double bond

 

Eicosanoids Family
Prostanoids Class	Leukotrienes Class	Lipoxins Class
Subclasses ·      Prostaglandins (PGE) ·      Thromboxanes (TXA) ·      Prostacyclins (PGI)	Leukotrienes (LT) are fatty acid mediators of Allergic Rhinitis, Asthma, and Atopic Dermatitis	Lipoxins (LX) are anti-inflammatory fatty acids that oppose the effects of Leukotrienes

 

Prostanoids	Series 1	Series 2	Series 3
PGE	PGE 1	PGE 2	PGE 3
TXA	TXA 1	TXA 2	TXA 3
PGI	PGI 1	PGI 2	PGI 3

Cyclooxygenase (COX) Pathway
Prostaglandin	Thromboxane	Prostacyclin
PGE	TXA	PGI
Pro-Inflammatory	Blood Clotting	Blood Thinning
COX-2	COX-1	COX-2

COX	PROSTANOIDS	FUNCTIONS
1	Prostaglandin (PGE1)	·        Stimulate Mucus Secretion ·        Stimulate Bicarbonate Secretion ·        Suppress Excessive Gastric Acid Secretion ·        Cytotec (misoprostol) / PGE1 analog
1	Prostaglandin (PGE1)	·        Increase Na, K, and H2O Excretion ·        Increase GFR ·        Increase Creatinine Clearance (CrCl) ·        Lower Blood Pressure / Decrease Edema
1	Thromboxane (TXA2)	·        Stimulate Platelet Aggregation (blood clotting) ·        Vasoconstrictor
2	Prostacyclin  (PGI2)	·        Inhibit Platelet Aggregation (blood thinning) ·        Vasodilator ·        Limits Excessive Platelet Aggregation ·        PGI2 / TXA2 Ratio (Hemostasis) ·        Cyclo-Prostin during kidney dialysis
2	Prostaglandin (PGE2)	·        Causes Inflammation ·        Pain ·        For Kidney functions
PGE1 for Erectile Dysfunction		·        Alprostadil powder for injection
PGF2 for Glaucoma		·        Decrease IOP / Latanoprost (Xalatan) Eye Drops
PGE2 for Labor		·        For Uterine Contraction ·        Dinoprostone (Prostin-E2 / Cervidil)
PGI2 analog		·        Inhaled iloprost for pulmonary arterial hypertension (PAH)
Prostaglandin Antagonists		·        NSAIDs (inhibit cyclooxygenase) ·        Corticosteroids (inhibit phospholipase A2) ·        COX-2 selective inhibitors ·        EPA is COX-2 Inhibitor ·        EPA produces Prostacyclin (PGI3)

Omega-3 Versus Omega-6 fats

Research has shown that diets too high in Omega-6 fats can create an imbalance in the Omega-6 and Omega-3 fat levels in the body, raising undue risks for inflammatory and cardiovascular diseases.  Traditionally, the normal Omega-6 to Omega-3 ratio in the typical American diet could vary anywhere from 10/1 to 20/1, whereas the most ideal ratio should in practical terms be no greater than 2/1.  With the consumption of diet rich in Omega-3 fats, EPA gets incorporated into cell membranes at the expense of AA, resulting in less of AA being available for synthesis of pro-inflammatory prostaglandins.  

However, contrary to the popular belief that too much Omega-6 fat in the diet may not be conducive to health, not all Omega-6 fats are as bad as we think they are.  For instance, GLA, a member of the Omega-6 family found in botanicals like black currant, borage, and evening primrose oils, has anti-inflammatory and weight loss properties and is beneficial in the treatment of eczema, rheumatoid arthritis, diabetic neuropathy, and PMS and perimenopausal discomforts.  Nevertheless, excess amount of LA-based Omega-6 fat in the diet can use up the D6D enzyme necessary for the much needed production of prostaglandins via Omega-3 pathway. 

Phospholipids

Phospholipids, also called Phosphatides, belong to a class of lipids found in all living cell membranes.  The cell membrane phospholipids are more or less like triglycerides that have only two hydroxyl groups of the glycerin molecule esterified with fatty acids, with the third hydroxyl group esterified with Phosphoric acid, one hydroxyl group of which is further esterified with a nitrogenous base such as Choline or Ethanolamine.  The very presence or absence of some fatty acids such as Stearic, Oleic, Linoleic, Linolenic, and Arachidonic acid in the diet will determine the type of Phospholipids present in the cell membrane.  Basically, there are two kinds of Phospholipids:

• those that have a Sphingosine Backbone
• those that have a Glycerol Backbone

Sphingosine, an 18-carbon amino alcohol with an unsaturated hydrocarbon chain, constitutes the backbone of Sphingomyelin, the only phospholipid not derived from glycerol.  Sphingomyelin consists of sphingosine bonded to one fatty acid and one polar head group. The fatty acid is attached to the second carbon of sphingosine via an amide linkage. 

Phospholipids that contain the Glycerol Backbone are called Phosphoglycerides.  The most abundant types of naturally occurring Phosphoglycerides are:

• Phosphatidylcholine (known as Lecithin)
• Phosphatidylethanolamine (known as Cephalin)
• Phosphatidylserine
• Phosphatidylinositol

By virtue of their polar nature, phospholipids possess surface-active properties that specifically account for the structural integrity and permeability of biological cell-membranes.  In brief, amphipathic molecules of the phospholipids tend to aggregate in water, forming liposome-based bilayer membrane with hydrophobic tails lined up against each other and hydrophilic heads on both sides extending out into the water.  The resulting bilayer matrix of most biological membranes is predominantly made up of Lecithin and Cephalin Phosphatides.  

Lecithin, commonly used as a synonym for pure Phosphatidylcholine, is the most widely distributed Phospholipid found in nature.  It is an integral part of all animal and plant cell membranes.  The highest amount of Lecithin is found in the brain, heart, liver, and kidney.  Commercial Soybean lecithin consists of a group of phospholipids including phosphatidylcholine (25%), phosphatidylethanolamine (20%), phosphatidylinisitol (15%), and phosphatidic acid (10%).  Dietary supplements of Lecithin are touted for:

1. lowering cholesterol
2. reducing the incidence of gallstones
3. improving memory function

Lecithin is a key component of bile.  Low levels of Lecithin may precipitate the formation of cholesterol gallstones.  There is no evidence, however, that lecithin supplements or foods containing it will dissolve gallstones in humans.  As a chemical entity, Lecithin contains about 10% by weight of Choline, an essential component of the neurotransmitter acetylcholine.  As a lipotropic agent (fat burner), Choline improves Fat metabolism in the Liver, rendering cholesterol more soluble and less vulnerable to precipitation in the form of gallstones.  The best dietary source of Choline is Soybean Lecithin.