Doctors, scientists, and technical people take morbid delight in using terminology which the general public does not always understand fully. However, they get away with it, because people are loath to question them, not wanting to appear ill-informed. Thus, the media throws around terms like fats, lipids, oils, omega-3 fats, and the like, with abandon. And nobody takes them to task.
Speak clearly, please
Fat, lipid, and oil: These are commonly used terms, and their meaning needs to be crystal clear.
Our diet has three major constituents: protein, fats, and carbohydrates. We need fats to ensure our bodily structure and metabolism.
This is chemically an ester, which is a compound formed by the combination of an acid with an alcohol. In the case of a fat, the acid is a fatty acid, and the alcohol is glycerol.
So a fat is basically a glyceride. If we have three fatty acid chains combining with glycerol, we have a triglyceride, which is another term which nobody explains, but which you see all the time on your report if you have a “cholesterol blood test.”
What, then, is a lipid?
A lipid is an organic compound having certain characteristics. Before we go further, let us refresh our understanding of organic and inorganic compounds.
Organic, inorganic, what’s the difference!
Chemistry consists mainly of organic and inorganic compounds.
Compounds associated with living beings are organic. They always have carbon atoms as part of their structure, while most inorganic molecules don’t.
Almost all of the organic compounds contain bonds between carbon and hydrogen (C—H). Some, however, do not, like urea.
Some examples of organic compounds are fats, lipids, sugars, proteins, nucleic acids, enzymes, etc.
Examples of inorganic compounds are metals, salts, and other molecules not containing carbon-hydrogen bonds.
Back to lipids
So lipids are organic compounds. They have carbon to hydrogen bonds, and they also have oxygen. The number of hydrogen atoms in a lipid molecule is always more than double the number of oxygen atoms.
The carbon to hydrogen bond in a lipid is a special one, called a nonpolar covalent bond. This means that the carbon and hydrogen atoms share a pair of electrons equally. The importance of this is that the molecule of a lipid is made fat soluble. It will not dissolve in water, though.
Types of lipids
Biologically, we have four important lipids. They are fats, steroids, phospholipids, and waxes.
So fat is a type of lipid.
All fats are lipids, but not all lipids are fats.
Then what is an oil?
Fats are usually solid at room temperature.
A fat which is liquid at room temperature is called an oil.
Oils can have saturated, monounsaturated, and polyunsaturated fatty acids. Being liquid at room temperature, they tend to have more unsaturated fats than saturated ones.
Yes, fat can be essential, in that the body would not function without a healthy dose of fat.
However, biochemically, the term “essential fatty acid” is applied to those fats which cannot be made by the body. Therefore, we have to eat them as part of our diets. There are two of them: alfpha-linolenic acid (an omega-3 fat) and linolenic acid (an omega-6 fat).
Other fats needed by us can be made by our bodies using these essential fats and other substances.
Are we saturated yet?
Saturated fat is bad, unsaturated is good: You have heard this refrain most of your life. It is not necessarily true.
But what is a saturated fat anyway?
Atoms join with other atoms to make molecules. And molecules are what make up matter.
There are laws which govern this union. If a carbon atom is able to join with all the hydrogen atoms it possibly can, it is called saturated. It is happy. In that case, it combines with other carbon atoms with what is called a single bond, chemically shown as C—C. However, if it cannot combine with all the hydrogen atoms it is capable of, it ends up joining with other carbon atoms using a “double bond.” This is shown as C=C. This makes it unsaturated. The same is true of “triple bonds.”
How do you bond with others?
In a fatty acid molecule, if a carbon atom joins with another carbon atom using a double bond (or triple bond), that fat is called “unsaturated.” Otherwise (with carbon-to-carbon single bonds only) it is “saturated.”
If in one fatty acid molecule, there is only one double bond between two carbon atoms, that is called a “mono-unsaturated fat.”
The presence of more than one double bond makes the fat a “poly-unsaturated fat.”
What is this omega business?
If you are an adult, you must have heard of omega-3 and omega-6 fatty acids. One is supposed to be good, the other one not so good.
But what are they?
It is all about the ending
The fatty acids chains have two ends: the beginning and the tail. The beginning is the so-called acid end, and the tail is the methyl end. Since we are all in love with the Greeks, we call the beginning the “alpha end” (since alpha is the first letter in the Greek alphabet), and the tail is the “omega end.” Omega, of course, is the last letter of the Greek alphabet. This end is also called the n-end.
This is a polyunsaturated fat. Which means that the fatty acid chain has more than one double bond (C=C).
The omega part means that you start looking at the tail end (omega end) of the chain. Then look at the third carbon atom from that end. If the first double bond occurs at this location, you are dealing with an omega-3 fatty acid.
Why is this important? Read on.
Apply the same process as above. If the first double bond is at the 6th carbon atom from the tail end, you have an omega-6 fatty acid. Again, this is a polyunsaturated fat.
What’s the big deal?
Mono-unsaturated fatty acids are felt to be better for your health than poly-unsaturated fats. Among the poly-unsaturated fats, the omega-3s are again supposed to be better than the omega-6s.
In fact, many experts feel that in the ancient era, humans had much more omega-3s in their diets than omega-6s, and that nowadays this ratio has been reversed, leading to several ill-effects on our health.
And what about trans fats?
About this, not much debate exists. These fats are universally condemned as the worst types of fats for our heart health. Many localities in the US have legislated to ban them, or severely cut down on their presence in our food supply.
What’s so “trans” about the fat?
It is basically a chemical arrangement.
There are two types of arrangements of hydrogen atoms in unsaturated fatty acids (which have at least one double bond).
The “cis” type occurs when the two hydrogen atoms are on the same side of the double bond in the chain. “Cis” in Latin means “on this side.”
The “trans” type occurs when the hydrogen atoms are on opposite sides of the double bond (“trans” means “across” in Latin).
Again, what’s the big deal?
The trans configuration in unsaturated fatty acids creates problems. So why was it created? For convenience.
Of course, there are some naturally occurring trans fats also. These are produced in the guts of some animals. Meat and milk from these animals can have small amounts of trans fats.
Then we have artificial trans fats, which are created by the hydrogenation of vegetable oils.
Adding hydrogen to a liquid vegetable oil makes the product more solid, and increases its shelf life.
In some instances, trans fatty acids can alter the taste and texture of food in a manner which consumers like.
Oils containing trans fats are often used by fast-food chains and restaurants around the world, because such oils can be reused several times in commercial fryers to deep-fry food.
Trans fat = Bad fat
The hydrogenation of vegetable oil leads to a product which has serious implications for heart disease.
The trans fats produced in this manner can reduce the amount of “good cholesterol,” or HDL cholesterol, and increase the amount of “bad cholesterol, or LDL, in your blood stream.
- The terms fats, oils, lipids, trans fats, omega-3, and omega-6 are frequently seen by the public, but not always fully understood. It is important to be clear about what they mean.
- Fats can be saturated or unsaturated, and their ratio in our diet is important.
- The ratio of omega-3 and omega-6 fats in our diets is also important.
- Trans fats are the worst kinds of fats, and should be avoided as far as possible.
Food sources of different fats
We will discuss details of this, and their health implications, in subsequent posts.