Lipids

As you read this lecture, you should consider how this information affects you personally and how the person whose diet you tracked compares to this information...

    The lipids, commonly known as fats & oils, are your secondary source of energy, but also provide the precursors of several important hormones and are key ingredients in cell membranes.

§ 1. classes of lipids

There are three classes of lipids that are important to Nutrition:
  triglycerides consist of three fatty acids attached to a glycerol ‘backbone’
  phospholipids which are triglycerides with two fatty acids and one phosphorylated fatty acid
  sterols consist of interconnected carbon ring compounds with differing side chains

§ 2. Fatty acids

The general chemical formula for fatty acids is
CH₃-(CH₂)_n-COOH, [where n is usually an odd number between 11 and 17]
which is a hydrocarbon [a chain of Carbon (C) atoms with Hydrogens (H) attached] with a acid radical (COOH) replacing an H at the terminal end of the hydrocarbon chain. The acid radical is a Carbon (C) double-bonded to an Oxygen (O) and single-bonded to a hydroxyl (OH) [I will sometimes use the symbol -(C=O)-OH for -COOH], leaving one unused bond location on the Carbon [for a valence of ± 1]. Chemists number the Carbons from the acid end [also called the alpha-end], but nutritionists number the carbons from the opposite end [called the omega-end because alpha (α) is the first letter of the Greek alphabet, and omega (Ω) is the last letter of the Greek alphabet]. Some of the characteristics of the fatty acids are derived from the hydrocarbon properties, so we need to look at the hydrocarbons as well as at the fatty acids to fully understand the chemistry involved. The first 4 hydrocarbons (metane, ethane, butane & propane) are gases at room temperature, although butane and propane can be liquified by pressure (as in butane lighters, and LP gas or liquified propane). The next several are liquids [gasoline, light machine oil, automotive oil] at room temperature, but at 18 or more carbons, they are semi-solids [consistency of butter, and lubricating grease]. The hydrocarbon with 40 to 70 C's is called asphalt. By the way, the ‘octane’ rating number on gasoline is the percentage of energy released on burning [average of theoretical and ‘research,’ or controlled burn in a calorimeter] compared to the 8-Carbon hydrocarbon, or Octane]. The following table lists the first 8 hydrocarbons and their fatty acid equivalents, and you should probably scroll quickly down to the next paragraph, ignoring the table as if it were intended to amuse me more than it would you.

The hydrocarbons are considered to be “saturated” when they are saturated with Hydrogens. When they are not saturated there will be at least one double bond between adjacent Carbons. The effect of double bonding which interests us is to lower the melting point, so a saturated fatty acid such as CH₃(CH₂)₁₃COOH that is semisolid (lard) at room temperature, would be liquid (corn oil) if it were unsaturated such as CH₃(CH₂)₅CH=CH(CH₂)₆COOH Note: in Chemistry these molecules [hydrocarbons or fatty acids] are either saturated or unsaturated; there is no distinction between ‘monounsaturated’ and ‘polyunsaturated.’ The term “polyunsaturated” was first used by an advertising agency hired to promote [if memory serves me well] a well-known brand of margarine. Other than ‘one or more’ versus ‘zero,’ how many double bonds is far less important to Nutrition and Wellness than is the location of the first double bond counting from the omega-end (Ω). The unsaturated oils are named by the location of the first double bond: omega-3, omega-6, or omega-9. There may be additional double bonds, but it does not matter to the functioning of the fatty acids in the Human body. Most Ω-6 plant (or animal) oils also have a double bond at Ω-9, and the Ω-3 plant (or animal) oils usually have double bonds at Ω-6 & Ω-9. The following chemical formulae illustrate each of the biologically significant fatty acid types:
          C#¹ , C#² , C#³ , C#⁴ , C#⁵ , C#⁶ , C#⁷ , C#⁸ , C#⁹ , C#¹⁰ , C#¹¹
  (Sat..) CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-COOH
  (Ω-9) CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-COOH
  (Ω-6) CH₃-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-CH=CH-CH₂-COOH
  (Ω-3) CH₃-CH₂-CH=CH-CH₂-CH=CH-CH₂-CH=CH-CH₂-COOH
  The saturated fatty acids, rich in cholesterol, are typically found from animal sources [“lard”], and are associated with arthrosclerosis… and heart attacks & strokes; the unsaturated fatty acids are from vegetable (& some animals, especially fish) sources [oils], and contribute less to arterial plaque. However, Grandmother's flaky pie crusts were made with good old pig lard; pie crusts made with corn oil resemble cardboard [a good grade of cardboard, but cardboard none-the-less]. There is also an aesthetic difference: imagine, if you will, a stack of pancakes hot off the griddle [if you're trying to lose weight, you can imagine a short stack]. Now picture the pat of butter (saturated and Ω-9 fatty acids) melting into the pancakes as the maple syrup runs off the stack and onto the plate. Now repeat the image, but this time that stack of beautiful golden-brown pancakes hot off the griddle gives off a wisp of steam as it is placed in front of you. Anticipating the delicious breakfast to follow, you grab the jar of corn oil (mostly Ω-9 with some Ω-6's) and pour it onto the pancakes. Whoa! Instantly soggy and disgusting - “I'm not going to eat that, let's get Mikey…” So now we had to choose heart attack or aesthetically pleasing pancakes, with butter melting its saturated fatty acids into the pancakes. Ah, but we were wrong. It is not the high cholesterol in saturated animal fats that causes heart attacks. It is the saturated and Ω-9 fatty acids that plaque out best on arterial walls. Ω-6 fatty acids do not plaque out as much, and Ω-3 fatty acids actually dissolve existing plaque, decreasing the risk of heart attack.
  The most heart attack friendly fatty acids (saturated, plus with high cholesterol) come from red meat, where ‘red’ does not describe the color - pork may be “other white meat,” but it is the reddest meat in terms of speeding up that heart attack. White meat, such as chicken, rabbit, some fish [catfish, perch], are Ω-6 sources with little cholesterol; the heavier plant oils (most famously, corn) is also Ω-6 with no cholesterol. The best Ω-3 oils are, in order of decreasing Ω-3 density,
    1. white fish [again ‘white’ is not a color, but a good source of Ω-3 oils; the best way to determine if a fish is ‘white’ is if it can be flaked when cooked properly]. Salmon (with pink flesh) is definitely a white fish. Shellfish also count as white fish
    2. Almonds, pecans, & other tree nuts
    3. peanuts, and any non-low fat peanut butter not enriched with Salmonella [the ‘low fat’ peanut butters I have read the labels on have reduced the density of Ω-3 oils and replaced them with Ω-6 oils, making them just as dense in fat, but less healthy]. Sunflower seeds are also a good Ω-3 source
    4. plant oils: canola (which has a slight buttery flavor), sunflower, safflower, flaxseed, soybean, olive [olive oil is not the highest in Ω-3 oil, but has a very effective trade organization promoting it], peanut (especially for frying potato chips). These are listed here as low density because you should not consume large quantities of added oils
  You need to know that Illustration 18.5 (pg 18-6) in Nutrition Now, 5^th ed. shows saturated fats, Ω-9 oils (as monounsaturated) and lumps Ω-6 & Ω-3 oils (as polyunsaturated). Therefore, it does not depict the amounts of Ω-3's and Ω-6's separately. As noted on pg 18-8 in that text, a 2000 study has suggested that the ratio of Ω-6 to Ω-3 is important, and should approximate (as a guess, not documented) 4 to 1 or less, but more than 1 to 1. Unfortunately, information available to consumers of food stuffs about the ratio of Ω-6 to Ω-3 is largely non-existant.
  Two specific Ω-3 oils are important to CNS (Central Nervous System = brain and spinal cord) maintenance and blood clotting control, plus anti-inflammatory function. These are DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). Both are found at high density in fish oils [except fish liver oil, as in Gramma's cod liver oil]. I think (but am not sure) that at least DHA is commercially extracted from seaweed for use in baby formulas. As will be my advice repeatedly on nutrient intake, Food is the preferred source for nutrients [including Ω-3 oils]; supplements are NOT. Food comes from plants and animals and have been our nutrient source for well over 1,000,000 years; supplements grow in factories and we simply have not had time (in generations) to adapt to artificial nutrients.

    Remember our stack of pancakes with butter melting into them, and syrup flowing off onto the plate? We wanted the nice thin, runny maple syrup rather than the ‘thickest’ Mrs Butterworth's™ due to the unacceptably high corn syrup content of thick syrups [think Karo™, 100% corn syrup]. When we replaced the cholesterol-rich saturated butterfat with Ω-6 corn oil [Crisco™], we ended up with soggy and disgusting pancakes that we didn't want to eat. “Never fear, Underdog is here,” and so are the dedicated Chemists who provide us with an endless supply of non-foods for our food supply. We can, with the magic of modern Chemistry, make perfectly good plant oils look more like butter by hydrogenation (then adding FD & C Yellow no. 5 and Yellow no. 6)! “And what,” you should be asking, “is hydrogenation?” Hydrogenation involves breaking one of the bonds in a double bond, then adding 2 Hydrogens. “Partially hydrogenated” means there are fewer double bonds, but there still remains at least one double bond; “fully hydrogenated” means that all of the double bonds have been converted to single bonds, and no more hydrogens can be added - the molecule is saturated. To illustrate, let's start with an Ω-6 corn oil:
  naturally occurring Ω-6:
CH₃-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-CH=CH-CH₂-COOH
  partially hydrogenated Ω-6 [and Ω-9 for comparison]:
CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-COOH
CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-COOH
  fully hydrogenated Ω-6 [and saturated for comparison]:
CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-COOH
CH₃-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-COOH
  Notice the naturally occurring Ω-6 fatty acid is ‘polyunsaturated,’ and is an essential fatty acid because it is a normal component of cell membranes which are found in high amounts in nerve cells. After being partially hydrogenated, it is ‘monounsaturated,’ and looks exactly like an Ω-9 fatty acid, so should be expected not to contribute to nerve cell membranes, but to plaque out on arterial walls, cause blockages and heart attacks. As a fully hydrogenated Ω-6 fatty acid it is now saturated, and looks exactly like a saturated fatty acid, so should be expected not to be an essential fatty acid but to be fully as effective at producing heart attacks and strokes as was the butterfat we were trying to avoid by using margarine as a butter substitute! If that were the entire story, we could say that if you like the flavor of butter, eat butter; if you prefer the flavor of margarine, eat margarine; if you don't want a heart attack, eat dry toast for the rest of your life. “And now, the rest of the story…” the long chain of the fatty acids is not straight as drawn in 2-dimensions. In 3-d [with your 3-d goggles] the molecule zigs and zags. At each C - C bond the 2^nd C could zig to the right or zag to the left. Yet in biologically produced fatty acids, the bonds tend to zag to the left, making them levo-rotary, or left-handed and politically correct [called cis-fats]. But, when made in the laboratories of our friendly, dedicated Chemists out to improve our lives, these molecules both zig and zag, so only about half are good levo-rotary (cis-fat) molecules, while the other half have gone over to the dark side and are dextro-rotary, or right-handed [called trans-fats] which is evil. [See, all that discrimination against left-handedness is driven by right-handed Jedi on the dark side of the force (if you are right-handed disregard this sentence)]. Dextro-rotary (trans-fat) is not good because all your enzymes are designed to deal with levo-rotary molecules. Under the Lock & Key Hypothesis, enzymes do not “fit” dextro-rotary molecules, and do not process them at all. The poor, neglected dextro-rotary trans-fats, shunned by the levo-rotary enzymes, are left to roam not the streets but the arteries where they join the street gang Plaque. Translated to English, this means that persons who eat butter are more likely to have heart attacks than do people who don't eat butter. However, persons who do eat margarine are more likely to have heart attacks than are people who eat butter. So now we have: if you like the flavor of real butter (from happy cows, the California type), eat butter. If you really want to have that heart attack soon and get it over with, eat more trans fats. If you would prefer to wait for your heart attack (perhaps until after you die from other causes), eat dry toast for the rest of your life. Or eat butter, but put creamy peanut butter on your hot toast without butter. The peanut butter melts nicely into the toast, tastes good, and counter-acts the negative effects of the butter. [Our friendly, dedicated Chemists are not really evil, and are working on methods to produce levo-rotary hydrogenated fatty acids. Crisco™ announced in 2007 that they had developed a new version of their shortening with only 0.49 grams trans-fats, so it had to be labeled 'zero grams trans-fat,' and that they wanted their customers to know that it is 0.49 g more than zero]
  The whole dextro-rotary versus levo-rotary thing was first discovered with synthetic versions of Insulin and Thyroxin. After observing that it took twice the dose rate of the synthetic insulin or thyroxin to get the same effect as the natural molecules, the chemists re-examined their molecules and discovered rotary-ness. They then altered the manufacturing process to produce mostly (if not entirely) the levo-rotary molecules.

§ 3. Triglycerides (fats & oils)

Triglycerides are three fatty acids attached to a glycerol. Gylcerol is an alcohol with three -OH groups:

CH₂OH
 |
CHOH
 |
CH₂OH

A fatty acid can be dehydrated onto this molecule by removing the -H from the -OH on the -COOH (1'-C end of the fatty acid and the -OH from the 1'-C end of the glycerol:

CH₂OH   HOOC-(CH₂)_n-CH₃
 |
CHOH
 |
CH₂OH

yielding a monoglyceride:

CH₂-O-(C=O)-(CH₂)_n-CH₃
 |
CHOH
 |
CH₂OH

repeating this on the 2'-C of the monoglyceride yields a diglyceride;
and then again on the 3'-C of the diglyceride to make the triglyceride:

CH₂-O-(C=O)-(CH₂)_n-CH₃
 |
CH-O-(C=O)-(CH₂)_n-CH₃
 |
CH₂-O-(C=O)-(CH₂)_n-CH₃

  You may be aware that oil and water don't mix. If you doubt this, try this experiment at home: mix roughly equal amounts of wine vinegar (a solution of acetic acid in water) with extra virgin olive oil, and add some Italian seasoning. Shake vigorously, and spread over a bed of mixed lettuce varieties. Pass the container of the vinegar & oil to the person on your left, and observe whether or not the mixture has separated. Then enjoy your salad. Now that you've had some salad, we can note that the hydrocarbon (omega end of the fatty acid) is not soluble in water (and is oil soluble), but the acid group (-COOH) on the alpha-end of the fatty acid is water soluble. The chemical term for a molecule that is water soluble on one end and oil soluble on the other is detergent. Dish detergent, such as Dawn™, works by dissolving the oil soluble ends of the detergent molecules in the grease on the dishes, leaving the water soluble ends sticking out as a surface (of the grease globule) that is water soluble, so the entire grease globule dissolves in the dish water.
  So a fatty acid is a detergent, but when dehydrated onto a glycerol, the water soluble end is covered by the glycerol, and the water soluble alcohol groups (-OH) on the glycerol are covered by the fatty acid. As a triglyceride, the entire structure is no longer water soluble. Another name for triglyceride is fat. Fatty acids are slightly soluble in water and can be transported in the blood stream; while fats are completely insoluble in water and can no longer be picked up by the blood stream and transported. This makes fats an excellent long term storage of rather stable, energy-dense molecules. If your long-lost ancestors were Cro-Magnons [which they were (Cro-Magnons were ‘Modern Humans’)] who happen to live closer to the Pleistocene glaciers than most other Cro-Magnons [like the ones in southern France making cave paintings (a.k.a. graffiti)], they would have needed some means of storing large quantities of energy-dense material to support Life during the long winters (similar to the famous Winter of 2008-2009 in Northern Indiana, between Donaldson and Lake Michigan. You may remember this particular winter if you were anywhere near Donaldson, IN, that season).
  Unfortunately, since the oil-soluable ends of fatty acids (especially the saturated, Ω-9 & trans-fat ones) can dissolve in the cell membranes of the lining of your arteries, then other saturated, Ω-9 & trans-fat fatty acid molecules can dissolve in the oil-soluable ends of these fatty acids to produce long-term fatty acid storage as arterial plaque [sufficiently long-term to be a ‘Life Time supply’, due to the premature death due to heart attack]. The Ω-3 fatty acids also dissolve in the plaque, but remain dissolved in the fluids (water) in the blood stream,so the ‘stored’ fatty acids in plaque are returned to the blood stream to be removed by the liver and kidneys.

§ 4. dietary sources of lipids

Saturated fats and Ω-9 fatty acids come primarily from animal sources [including dairy], which are also the best dietary sources of cholesterol [plants, in general, contain little to no cholesterol]. From a nutrition point of view, the ‘redness’ of meat refers to the cholesterol-density, and saturated fat density. The ‘white’ meats have low density of cholesterol and saturated fats, but remain Ω-9 fatty acid dense. All fish are white-meat sources, but some are classified as ‘white-fish.’ The best way to determine if a fish is a ‘white fish,’ is to cook it properly [relatively low heat, and cooked until it is just thoroughly cooked], then attempt to flake it [flaking a fish involves placing your fork along the side-line on the fish and pulling toward the belly (of the fish) with pressure. If it is a white fish, the flesh will come off as flakes; if it is not a white fish, the flesh will come off as lumps]. Those fish with a strong oily smell are probably not white fish. Over-cooking almost any animal will dehydrate the flesh making it tough, and destroy both the flavor and most of the nutrient value. Under cooking red meat will not kill the Botulinum bacteria; while under cooking white meats does not kill the Salmonella bacteria. Botulinum produces a powerful toxin [called Botox, for BOtulinum TOXins. These toxins cause muscle paralysis; death occurs due to the paralysis of heart muscle. This is clearly why cosmetic Botox injections make such good sense -who wants to be a corpse with wrinkles on their face? [Hint: a good mortician can get rid of those ugly wrinkles without killing you; since you'll already be dead by the time of your appointment]. Salmonella toxins tend to produce moderate to severe gastric symptoms (diarrhea, cramping, projectile vomiting). Although they can kill you, the death is not as abrupt as the cardiac arrest associated with botulism; and death usually results from severe dehydration. Neither botulism nor salmonella poisoning are pleasant experiences. I recommend avoiding both.
  The dietary sources of Ω-6 & Ω-3 fatty acids include white fish [the kind that flake] and plant sources. Not only are the white fish the highest density source of Ω-3 fatty acids, they are, in my opinion, the best tasting fish. White fish are cold water predators: salmon and trout (a genus in the salmon family), pike, flounder, talipia, mahi-mahi, whitefish, sole, etc. If you don't like fish as part of your food supply, you should try to learn to like them. They will make you live longer, and with fewer signs of aging; they are brain food in that they reduce the risk of non-Alzheimer's age-related dementia. Your second choice for Ω-3 fatty acids is tree nuts & peanuts. A good blend of Ω-6 and Ω-3 fatty acids can be found in dark, leafy green vegetables (dark green lettuce varieties, Brussel sprouts [yes, it's cabbage]) and cruciferous vegetables (cauliflower, broccoli) and whole grain (non-bleached, non-enriched) grains; but you still need fish and nuts to boost the Ω-3 fatty acid intake.
The term “reduced fat” on the front of food packaging should not be taken to mean healthier. Most reduced fat products also come with increased carbs; just as reduced carb foods also come with increased fats. Many ‘reduced fat’ products, according to their nutrition facts label, seem to substitute less healthy fats for the naturally occurring Ω-3 & Ω-6 oils.

§ 5. nutrient values of lipids

Fat constitutes our primary form of long term energy storage, which is intended to be released only in an emergency, such as cave-man winter when food was scarce at best. Modern Humans release long term fat storage in response to prolonged illness, since winter never comes (in that we will probably never see a period of a few to several months without a food supply). Curiously [for most people], the trigger for increased fat deposition is reduced carbohydrate density in the food intake [naturally occurring food supply reaches its maximum carbohydrate density in late summer]. As a result, many reduced carb weight management programs cause fat deposition rather than the desired reduction in body measurement (waist size for example). On the other hand, one of the triggers for satiety (cessation of desire to eat) is increased serum fatty acids; so many low fat weight management programs fail due the failure to achieve satiety, leading to continual munching [of mostly high carb density snack ‘foods’]. A couple of side effects of maintaining adequate adipose deposits are (1) insulation to assist in maintaining body temperature, and (2) “padding” which protects soft tissues including a number of rather key vital organs.
  The essential fatty acids are involved in cell reproduction (forming cell membranes for the newly forming cells) and therefore healthy skin, adequate red blood cells, sperm production for Human reproduction, and maintaining healthy nervous tissues (particularly in the Brain & CNS). Dietary fatty acids assist in absorbing fat soluble vitamins. Some (Ω-3 & Ω-6) fatty acids combine in the blood serum with proteins forming lipoproteins. The lipoproteins are either high density, HDLs (the good guys ["H" for Healthy]) or low density, or LDLs (the bad guys ["L" for Lousy]. HDL's seem to function as anti-oxidants and as anti-inflammatory agents; LDL's are now believed to be oxidants, promoting aging and declining health.
You get your cholesterol from the frankfurters you ate and from your Uncle Frank. All Humans can produce cholesterol [from Ω-6 fatty acids, mostly] at a rate which is determined by your family tree (Genetics), hence ‘Uncle Frank.’ However, you must understand that you need cholesterol both as an ingredient in cell membranes and as a precursor to the steroidal hormones, notably estrogen, testoserone, and human growth hormone. Unfortunately, the best cholesterol producers can make only enough for normal production of steroidal hormones and for repair of damage to skin tissue (blood clot & scar formation). During growth phases [sometimes called childhood] additional cholesterol is required from dietary sources. The Yuppies (1980's) mistakenly thought that if low cholesterol diets were good for preventing heart attacks in 40-ish to 40-somethings people, it should be much better to start younger, say 6 to 8 year olds. They successfully produced a population of stunted young adults, from which we concluded that dietary cholesterol is required during growth periods. It has been suggested by relible sources that the slowing of the healing processes in the elderly are due to a decline in cholesterol production, again requiring additional dietary cholesterol in the over 40 population. And, we now know that serum cholesterol has absolutely no predictive value in heart attack risk (although persons with elevated cholesterol have diets which favor the production of LDL's, which do have high predictive value for heart attack risk).
Side effects associated with fats and oils are pleasant flavor and texture in foods. A negative side effect is that fats spoil more rapidly than most other nutrients, and become rancid giving the food an unpleasant aroma [this is not entirely negative, because most people will discard food as soon as the fats in it have become rancid, and before the proteins have spoiled enough to cause serious food poisoning].

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