Biol 135 Lecture: IV. Structure, Function and Source of Macronutrients

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Lipids

Biol 135 Lecture: IV. Structure, Function and Source of Macronutrients.

B. Lipids

Lipids are found everywhere in nature and are absolutely fundamental to good human health and nutrition. They constitute a diverse group of compounds which are related more by their physical properties rather than by their chemical properties. They function as energy storage, insulation and protection, fuel for metabolism and indispensable components of essential vitamins, hormones and regulators in the body.

In a Healthy, Balanced Whole Food Diet, there should never be a need to reduce your fat intake or cut back on any healthy lipids. The consumption of healthy lipids is vital to good nutrition and good health.

Whole Food / Refined Food
Unrefined, entire original “item” / Heavily processed from original form
All original nutrients remain intact / Most (if not all) original nutrients removed
Unprocessed, not chemically treated / Chemically treated (in processing & for shelf-life)

A really easy way to tell the difference between and “Bad Fat” and a “Good Fat” is to ask yourself where did it come from, directly, exactly, where? If it came from a “processing plant”, like margarine does, this should tip you off that regardless of what was originally used the product, it has become quite different after processing. Compare this to something that came directly from a healthy animal. And your choice is as easy as falling off a log! Note: If you have never tried walking on a log, you will find it is incredibly easy to fall off, it’s only natural really!

Many things about health are connected to using the common sense you have, a simple yet valuable method for determining the truth. In order to trust this method however, you must be active at protecting yourself from false information! The type of information gained from watching television, for example. This source of information will bombard you day and night with misleading information! Via television programs, advertising and news reports! There is no requirement for any program on television to be truthful – seriously, even the evening news is not obliged to tell you the truth! (Florida State vs. Fox News):

ORGANIC CONSUMER ASSOC, March 7, 2004. Title: “Florida Appeals Court Orders Akre-Wilson vs. Fox Television; Couple Warns Journalists of Danger to Free Speech, Whistle Blower Protection”. From a 1996 Investigative Report, litigation ensued. During appeal, FOX asserted that there are no written rules against distorting news in the media. They argued that, under the First Amendment, broadcasters have the right to lie or deliberately distort news reports on public airwaves. This was upheld.

There are many many other examples establishing that there is no requirement for telling the truth on television: This is a good time to understand that fact. Regardless of the person or institution or agency delivering the information, the issue is not the reputation or the power of the entity, the issue being able to distinguish lies from the truth! As some wise person once said: “Let truth be the authority and not authority be the truth”. The more informed you become the easier it will be for you to detect a lie and the faster you will be able to assess a situation for what it really is and make sound decisions.

A perfect example of believing in authority to our own detriment is accepting the Big Fat Myth that still impacts our diet and health today - that cholesterol and saturated fats are bad for you. In addition, that poly-unsaturated vegetable oils should take the place of those naughty fats!

The trend to significantly reduce fats in our diet, especially saturated animal fats, took hold in the early 1960’s due to the studies by Dr. Ancel Keys that purported to find a causal link between diets high in animal fat and cardiovascular disease. This belief has never been shown to be true. In the “What is Nutrition” lecture notes, there is a re-visiting of that amazing study to show that even 50 years ago it should have been flagged for incredibly poor scientific methodology and for drawing farcical conclusions. For some time, real health mavericks have known that blaming animal fat consumption for our poor nutritional health was ridiculous and indeed removing beneficial saturated fats from our diets was significantly deleterious to human health. Now, over 50 years after the initial findings that were heavily promotion by all of the powerful health and medical groups, it is becoming more and more obvious that the information was not scientifically accurate. Still to this day, despite it being on the cover of Time Magazine that “Scientists Got it Wrong”, this mythos that fat causes heart disease continues to be an accepted lie. This lie is repeated in every textbook I’ve read about nutrition, including all the 2015 editions. Just one of the reasons to forgo a text for this class and write my own.

a)1961b) 1984c) 2014

Figure 1. Shows Time Magazine covers of: a) Dr. Ancel Keys in 1961, he claimed that saturated fats in the diet clogged arteries and caused heart disease; b) Perpetuation of the ‘Bad Cholesterol’ Myth in the 1980’s;and c) a published ‘correction’ of labeling “Fat the Enemy” in 2014.

Figure 2. Shows (left)the rates of butter and margarine consumption per capita per year, and (right) the number of deaths from diseases of the heart from the turn of the 20th century.

As the graphs in Fig 2.indicate, the campaign to target animal fats (like butter), as bad for your health has been a success! In addition, there was and still is a force that has also encouraged American’s to replace butter with heavily processed margarines that contain hydrogenated vegetable oils. This has literally been the removal of something good and beneficial and replacing it with something toxic and deleterious. Please note the time frame of the graph on the right. At the same time that the consumption or butter and margarine were swapped out, the successful eradication of heart disease did not occur and has not occurred - even the American Heart Association has to show that the numbers for heart disease have gone up. In fact, Heart Disease is the number one killer of Americans. Number one! If the “Fat causes heart disease” myth were true, we would certainly not expect the numbers of people dying from heart disease to continue to rise. But wait, there’s more.

Since as a nation we have embarked on this low dietary fat crusade for over 50 years, if heart disease has continued to be a major health issue, then are we at least less fat? As a result of the reduction in the percentage and types of fats in our diet surely we are less fat as a result of eating less fat? No - Darn it! Americans are actually fatter because of it! How is that possible? It is possible by the simple fact that if you remove good fats from your diet and replace them with refined highly processed carbohydrates (like sugars and starchy grains), any excess carbohydrates will get converted almost immediately in your body to, you guessed it, FAT. So the truth of the matter is you can eat zero fat and still gain weight in fat.

Figure 3. As the graph shows, calories from fat have decrease by about 10%, but the prevelance of obesity has continued to increase. There is a notable incline in obesity during the mid 1980’s, after the introduciton of High Fructose Corn Syrup (HFCS) to many beverages and after the introduciton of Diet Sodas, containing artificial sweetenrs.

In general, lipids are insoluble in water, meaning they do not dissolve in water, but typically will float on top of water since they are less dense. They are soluble in non-polar organic solvents (alcohol, ether, etc.). Lipids are essential dietary constituents because of their many important roles in the body, they provide high energy value and also they deliver fat soluble vitamins and are the building blocks for cell membranes, steroid hormones, etc. Lipids include fatty acids, triglycerides, phospholipids, sphingolipids, sterols, waxes, glycolipids and lipoproteins.

Overview of Lipids in Human Nutrition

1. Fatty Acids– these are made up of chains of carbon, for 2 to 24 Carbons long. The building blocks of lipids are Fatty acids and Glycerol

Saturated fats– have all the H atoms possible, i.e., there are no double bonds.

Unsaturated fats– do not have maximum H atoms, contain at least one double bond.

2. Glycerides– important energy storage molecule. Made from glycerol and fatty acids

a)Monoglyceride one fatty acid and glycerol.

b)Diglyceride two fatty acids and glycerol.

c)Triglyceride three fatty acids and glycerol.

3. Phospholipids – fundamental component t of all cell membranes. This is created by adding a polar phosphate containing fatty acid to a diglyceride.

4. Sterols –contain a4 fused carbon ring structure, most important example is Cholesterol.

Fatty Acids

One of the fundamental building blocks of nutritional lipids are fatty acids. They have the general formula CH3(CH2)n COOH where n can be any even number from 2 to 24.

The structure of a fatty acid includes the carboxylic acid group (COOH) on one end of a chain of carbon and hydrogen atoms, with a methyl group (CH3) of the other end. Fatty acids can be freely floating around but more commonly they are found bound in triglycerides and phospholipids.

There are two basic types of fatty acids: Saturated andUnsaturated. Saturated fatty acids do not have any double bonds, whereas unsaturated can have one (monounsaturated) or more than one (polyunsaturated) fatty acid.

Figure 1.Shows the structural differences between a saturated and unsaturated fatty acid. What is the configuration of the double bond in this unsaturated fatty acid? Answer: ______.

Use the space below to draw out the saturated fatty acid Lauric Acid:

Use the space below to draw out the unsaturated fatty acid Linoleic acid:

More details about Fatty Acids

There are over 20 different fatty acids. They can vary by the length of the chain; whether carbons have double or single bonds between them; or by the total number of double bonds.

In a saturated fatty acid, almost all of the carbon atoms are bonded to hydrogen. A good example is lauric acid which has 12 carbons and is solid at room temperature.

Unsaturated fatty acids have one or more double bond between carbons, it is less saturated with hydrogen, and tends to be liquid at room temperature.

Monounsaturated fatty acids have one double bond. An example is Oleic acid which has 18 carbons (olive oil is an example).

Polyunsaturated fatty acids have more than one double bond and examples are the essential fatty acids linoleic acid(found in walnuts, almonds, brazil nuts, sesame seeds, sunflower, pumpkin or poppy seeds; also the following oils: walnut, wheat germ, blackcurrant seed, evening primrose and grape seed oils). Another example isalpha-linolenicacid (found in flaxseeds, flaxseed oil, pumpkin seeds and pumpkin seed oil, perilla seed oil, walnuts, and walnut oil).

Saturated and monounsaturated fats are more easily used by your body than polyunsaturated fats.

Figure 2.This flow chart shows theclassification and organization of the different types of fatty acids in human nutrition and in the human body.

Fatty Acids may be classified by the number of carbon atoms as:

Length of carbon chains:

• Short-chain fatty acids (SCFAs): Less than eight carbons
• Medium-chain fatty acids (MCFAs): Eight to 14 carbons
• Long-chain fatty acids (LCFAs): 16 or more carbons
• Very-long-chain fatty acids (VLCFAs): More than 22 carbons

A fatty acid's chain length and saturation control its melting point. As chain length increases, melting point increases. Likewise, fats that are solid at room temperature (butter, coconut oil) have longer chain lengths than fats that are liquid at room temperature (fish oil, olive oil). With chain lengths being equal, unsaturated fats have lower melting points than saturated fats.

Saturated fatty acids are do not have any double bonds and may be represented by the general formula CH3(CH2)n COOH where n can be any even number from 2 to 24. The most common ones are:

Lauric acidCH3 (CH2)10 COOH(12 Cs)- found in coconut oil, breast milk.

Myristic acid CH3 (CH2)12 COOH(14Cs) - found in coconut, palm kernel oil, butter, cheese, whale blubber.

Palmitic acid CH3 (CH2)14 COOH(16 Cs) - found in poultry, beef, game meats.

Stearic acid CH3 (CH2)16 COOH(18 Cs)- found in cocoa butter, beef tallow, lard, butter, beef, pork, lamb.

Of the saturated fatty acids palmitic acid and stearic acid are the most widely distributed. Monounsaturated fatty acids contain one double bond. The most common dietary monounsaturated fatty acid is oleic acid which has the formula: CH3 (CH2)7 CH=CH (CH2)7 COOH.

The polyunsaturated fatty acids contain two or more double bonds. Linoleic acid, linolenic acid and arachidonic acid are important examples of polyunsaturated fatty acids, as they are essential fatty acids.

Essential Fatty Acidsare unsaturated fatty acid that is essential to human health, but cannot be manufactured in the body, abbreviated EFA. There are three types of EFAs:

1. Arachnoidic Acid

1. Linoleic Acid*

1. Linolenic Acid

*When linoleic acid is obtained in the diet, it can be converted to both arachnoidic and linolenic acid.

Exercise: List the dietary sources of these three EFA’s

Essential Fatty Acid / Source in our Diet
Arachnoidic Acid
Linoleic Acid
Linolenic Acid

The Chemical Instability of Polyunsaturated Fatty Acids (PUFAs)

Your tissues are made up mostly of saturated and monounsaturated fats, therefore your body requires more of them than polyunsaturated fats (which is true of all mammals). The main dietary Polyunsaturated Fatty Acids(PUFAs) are omega-3 and omega-6 fats. Although your body does need these, it needs them in relatively small quantities.One of the problems with PUFAs is that they are very chemically unstable, and highly susceptible to being altered and denatured by what's around them. Think about what happens to the oils in your pantry—they are susceptible to going rancid as a result of oxidation. In your body, PUFAs undergo a similar process when exposed to the toxic byproducts of proteins and sugars—especially fructose. This is why most fish oil supplements have such a short shelf life, and many are already oxidized before they hit the bottle. Consuming oxidized fats can do your body more harm than good.

When you eat too many PUFAs, they are increasingly incorporated into your cell membranes. Because these fats are unstable, your cells become fragile and prone to oxidation, which leads to all sorts of health problems, such as atherosclerosis. Now let's take a look at the most common PUFAs in your diet—the omega fats.

The Omega Fats

Opposite the acid end is the "omega end" of a fatty acid (see figure below).

The location of the first double bond from the omega end dictates whether a fatty acid is an omega-3, omega-6, omega-9 (oleic acid), or another member of the "omega family." Both omega-3s and omega-6s come in both short-and long-chain varieties.

Omega-3 Fats

• Plant Based: The shorter-chain form of omega-3 is alpha-linolenic acid (ALA), the only omega-3 found in plants (except for some algae). Foods rich in ALA include flaxseed oil (53 percent), canola oil (11 percent), English walnuts (9 percent), and soybean oil (7 percent). ALA is essential.

• Animal Based: The longer-chain forms of omega-3 are found mostly in animals and they are eicosapentaenoic and docosahexaenoic acids (EPA and DHA) and are highly unsaturated, mainly found in fish, shellfish and krill. DHA is the primary structural component of your brain and retina, and EPA is its precursor. Your body can make some EPA and DHA from short-chain ALA, but does so inefficiently. Recent studies suggest less than one percent of ALA is converted, if you are consuming the typical Western diet. DHA is found in cod liver oil, fatty fish, and in smaller concentrations in the organs and fats of land animals.

Omega-6 Fats

• Shorter-chain: The shorter-chain form of omega-6 is linoleic acid (LA), which is the most prevalent PUFA in the Western diet, is abundant in corn oil, sunflower oil, soybean oil and canola oil. All of the oils you should avoid.

• Longer-chain: The longer-chain form of omega-6 is arachidonic acid (AA), which is an important constituent of cell membranes and a material your body uses to make substances that combat infection, regulate inflammation, promote blood clotting, and allow your cells to communicate. AA is found in liver, egg yolks, animal meats and seafood.

Traditionally, only two fats were considered "essential"—ALA (an omega-3 fat) and LA (an omega-6 fat). However, we now know it's the long-chain derivatives—arachidonic acid, DHA, and EPA—that your body needs the most. Although you have the enzymes to convert LA into these longer-chain fats (ALA, DHA and EPA), the conversion isn't efficient enough for optimal brain growth and development. This has led to a recent rethinking of what fats to consider "essential" and recommendations for adding more long-chain fats to your diet, to better meet these biological demands.