Seed Oils: Definitions for most of the important terminology
OR: many different ways to say the same thing
What follows is my attempt to define all (or most of) the important terms relating to seed oils in simple language. I started with the more basic terms which are followed by more in the weeds kind of terms. These are more important for reading the literature on seed oils (because "seed oils" isn't really used in any of the papers, it can be trickier to find relevant articles if you don’t know the terminology). I'm planning on updating and improving this list over time, so any feedback would be greatly appreciated.
Fatty Acids: When we talk about the different fats in food, what we're really talking about are fatty acids. These are organic (in the chemistry sense of the term) compounds consisting of a hydrocarbon chain (literally hydrogens and carbons in a chain) and a terminal (at the end) carboxyl group (a carbon, two oxygens and a hydrogen). The main important thing here is there are a few different types of fatty acids, which can be distinguished by some key features which I'll mention below.
PUFA (Polyunsaturated Fatty Acid): This is the first of three main types of fatty acids. These are fatty acids that contain more than one double bond in their backbone. Where those double bonds are in the backbone determine whether it's an n-3 or n-6 PUFA. IMPORTANT NOTE: All seed oils are PUFAs but not all PUFAs are seed oils. This is an important distinction which can be misinterpreted (deliberately or accidentally) to misrepresent the data on seed oils.
Lots of different ways to say “seed oils”:
Seed Oils: Seed oils are a type of cooking oil which are made from different seeds and contain high levels of linoleic acid.
Linoleic Acid: The main omega-6 polyunsaturated fatty acid found in seed oils.
Linoleate: Typically refers to the salt (or ester) form of linoleic acid. Same molecule as linoleic acid, but different chemical form.
n-6 PUFA / Omega 6: Polyunsaturated fatty acids where the first double bond is six carbons from the methyl end.
Other Kinds of PUFAs (which aren’t seed oils):
n-3 PUFA / Omega 3: Polyunsaturated fatty acid where the first double bond is three carbons away from the methyl end of the fatty acid.
Linolenic Acid: Refers to alpha-linolenic acid (ALA), an omega-3 fatty acid. It serves as a precursor to other omega-3 fatty acids, EPA and DHA. Not to be confused with linoleic acid, they are definitely not the same thing.
Other kinds of Fatty Acids:
Saturated Fatty Acid (SFA): This is the second main kind of fatty acid. SFA have no double bonds between any carbon atoms.
Monounsaturated Fatty Acids (MUFA): Contain one double bond in their carbon chain. They are usually liquid at room temperature
Trans Fatty Acid (TFA): Unsaturated fatty acids that contain at least one trans configuration double bond. Found in partially hydrogenated oils. Typically manufactured and terrible for our health (although natural TFAs do exist).
Important Terms for Reading Papers on Seed Oils:
Lipid Peroxidation: A process in which free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process leads to the production of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), among other compounds, which can further damage cells by modifying proteins, DNA, and other molecules. Lipid peroxidation is associated with aging and various diseases, including atherosclerosis, liver disease, and Alzheimer's disease.
Reactive Oxygen Species (ROS): Chemically reactive molecules containing oxygen. Examples include peroxides, superoxide, hydroxyl radical, and singlet oxygen. ROS are produced as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress (such as UV or heat exposure), ROS levels can increase dramatically. This may result in significant damage to cell structures, a situation known as oxidative stress. ROS are balanced by the antioxidant systems of the body but when overproduced, they can cause damage to DNA, RNA, proteins, and lipids, contributing to the development of various diseases, including cancer, cardiovascular diseases, and neurodegenerative disorders.
Malondialdehyde (MDA): A chemical compound considered a marker for oxidative stress and lipid peroxidation. It is generated as a byproduct when polyunsaturated fatty acids in cell membranes are damaged.
4-Hydroxynonenal (4-HNE): Another byproduct of lipid peroxidation, known for its role in signaling cell death and contributing to various diseases due to its ability to react with DNA, proteins, and other important cellular molecules.
Oxidative Stress: An imbalance between free radicals and antioxidants in your body, which can lead to cell and tissue damage.
Anti-Oxidants: Molecules that inhibit oxidation and neutralize free radicals, thus preventing cell damage. They are found in various foods, including fruits, vegetables, nuts, and grains, and play a crucial role in maintaining health and preventing diseases.
Free Radical Cascades: Chain reactions initiated by free radicals, which are unstable atoms or molecules that have unpaired electrons. These cascades can cause damage to cells, proteins, and DNA, contributing to aging and various diseases.
Oxidation: A chemical reaction involving the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. In the context of fatty acids, it refers to the process by which fatty acids are broken down or degraded, often leading to the production of free radicals.
Eicosanoids: Signaling molecules made by oxidation of 20-carbon fatty acids. They have complex roles in inflammation, immunity, and as messengers in the central nervous system.
Arachidonic Acid: An omega-6 fatty acid found in animal products (in very small amounts). It is a precursor for eicosanoids, which are signaling molecules that play numerous roles in inflammation and immunity.