I have never liked seafood. It smells bad to me. I’m so sensitive to that smell that I don’t even like sitting next to someone who is eating seafood. Even the idea of taking a fish oil capsule makes me queasy because I don’t want to end up tasting or smelling fish if I belch. So I was greatly relieved to discover that human beings don’t need to eat fish or take fish oil! The diseases that fish oil is supposed to help prevent are rare to nonexistent among people who eat a low-fat, plant-based diet. Also, a recent study showed that vegans (people who don’t eat any animal foods) had plenty of the long-chain omega 3 fatty acids in their bloodstream, even though they weren’t eating any of the long-chain omega 3 fatty acids and were eating relatively little of their precursor, alpha-linolenic acid. (For an explanation of the essential fatty acids, click here.)
Fish oil is fat from a fish. An oil is just a fat that is liquid at room temperature. The fat from fish tends to stay liquid at room temperature because it is rich in polyunsaturated fatty acids. (For an explanation of the different kinds of fats, click here. Fish oil contains a lot of omega 3 fatty acids, which are much less plentiful than omega 6 fatty acids in the standard American diet. Like humans, however, fish CANNOT make their own supply of omega 3 fatty acids. The omega 3 fatty acids in fish came from the plants at the bottom of their food chain.
Your body can make all the saturated and monounsaturated fatty acids that it needs. However, it can’t make omega 6 or omega 3 fatty acids. The only two fatty acids that are considered essential (which means that they have to be found ready-made in your food) in human nutrition are an omega 6 fatty acid called linoleic acid and an omega 3 fatty acid called alpha-linolenic acid. However, it’s extremely rare to find anyone with a real dietary deficiency of either one. It’s the sort of thing that happens only in tube-fed patients who are being fed fat fat-free solutions or being given an unbalanced fat supplement. Their needs for these essential fatty acids can be met by rubbing a small amount of vegetable oil on their skin.
Your body uses the omega 6 and omega 3 fatty acids as raw materials to make eicosanoids and leukotrienes, which are signaling molecules that play important roles in inflammation and immunity. These molecules also serve as messengers in the nervous system. Because the eicosanoids that are made from omega 6 fatty acids interact with the ones made from omega 3 fatty acids, it’s probably important to get a reasonable balance between these two kinds of fatty acid in the diet. The most sensible way to do this is to cut way back on fat consumption and eat lots of fresh vegetables. For an extra margin of safety, you can add a spoonful of ground flaxseed to your cereal in the morning. Flaxseed is a good source of alpha-linolenic acid.
The omega 3 fatty acid that is found in plants is alpha-linolenic acid. Like fish, human beings can lengthen the carbon chain of alpha-linolenic acid to produce other fatty acids that the human body needs: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA is found in the cell membranes in the nervous system, including the retina of the eye. EPA is used to make some important eicosanoids that help to moderate the effects of the eicosanoids that are made from omega 6 fatty acids.
The Food and Nutrition Board of the National Academy of Sciences does not consider DHA or EPA to be essential nutrients, which means that those fatty acids don’t have to be found in your food. For a technical discussion of which fatty acids are essential and how much of each you need, see this report from the Food and Nutrition Board of the National Academy of Sciences: https://www.nap.edu/read/10490/chapter/10
Because of the complicated roles that the essential fatty acids and DHA and EPA play in the immune and nervous system, there’s been a lot of interest in using supplements of these fatty acids as drugs. As with any drug treatment, the decision of how and when to use these supplements should be based on clinical trials, whenever possible. Since most of the diseases that fish oil is being used to treat are rare in populations that eat a low-fat, plant-based diet, it makes sense to try correcting the diet before using fish oil supplements.
It is theoretically possible that some people, especially those who have trouble absorbing fat from their food or who have a rare metabolic disorder, might benefit from taking some form of fat supplement. However, many people refuse for various reasons to use fish products. Fortunately for those people, DHA and EPA supplements made from marine algae are available.