Fatty acids are composed of the same chemical elements as carbohydrates--carbon, hydrogen and oxygen--but in different proportions. Fatty acids contain more carbon and hydrogen and less oxygen than carbohydrates and therefore have more fuel value (nine calories per gram, more than twice as many as carbohydrates).

What is an unsaturated fatty acid? The answer to this question is illustrated below. Dietary fatty acids contain a long chain of carbon atoms. Segments of these chains are shown in the figures. Most carbons are linked by a single connection called a "single bond." Each carbon (C) in this chain is attached to two hydrogen atoms (H). A single bond is said to be saturated because the carbon cannot accept any more hydrogen atoms.

H H H H H H O
H---C--C-C--C--C--C-C---OH
H H H H H H

Saturated Fatty Acid
However, occasional carbon atoms are linked by "double bonds," and these carbon atoms are attached to only one hydrogen atom. These double bonds are called unsaturated because one of the bonds can be broken to accept hydrogens and become a single bond. When a fatty acids has only one double bond it is named monounsaturated. When it has two or more double bonds it is called polyunsaturated.

H H H H H H O
H--C--C---C==C--C--C--C--OH
H H H H

Monounsaturated Fatty Acid
(one double bond)
Saturated fats are found in all animal products, as well as coconut and palm oil. They are usually solid at room temperature. Monounsaturates are found in the oil of plants like olives, in nuts and in seeds. They are also manufactured normally within the body and are less likely to have some of the side effects associated with polyunsaturates. Polyunsaturated fats are found in plants like safflower and corn. Both monounsaturated and polyunsaturated fats are liquid at room temperature and are commonly called oils.

A specific number and configuration of atoms gives a fatty acid its identity, and there are almost three dozen that are common in the fats and oils we eat. For example, palmitic acid is the dominant saturated fat in butter; oleic acid is the dominant monounsaturated fat in olive oil; and linoleic acid in the primary polyunsaturated fat in safflower oil, corn oil and cottonseed oil.

Any edible fat is likely to contain a combination of saturated, unsaturated and monounsaturated fats--with as many as a dozen different fatty acids. It is the combination that determines the taste and texture of the fat or oil.