Experts call omega-3 fatty acids “essential.” This means that we need them to maintain our health, but our bodies can’t produce them, so we have to consume them.
If they’re essential, they must be doing something important in your body. But what exactly do omega-3s do?
In this two-part feature, we won’t enter into the debate about omega-3 supplements — we’ve covered that elsewhere.
You can find the second part of our omega-3 feature here.
Below, we’ll focus on why your body needs omega-3s. In this first part, we’ll cover the basics of omega-3s, take a brief historical tour, then examine their vital role in your cells' membranes and your retinas.
Buckle up for a biochemical banquet.
What are omega-3s?
Omega-3s are polyunsaturated fatty acids. Polyunsaturated means they have lots of double bonds. Saturated fats have no double bonds, and monounsaturated fats have one.
The number of double bonds in a fatty acid changes how it works in your body, and we'll dig into this later on.
The three most important forms of omega-3 are:
Alpha-linolenic acid (ALA): This is in plant foods, like soybean and canola oil.
Eicosapentaenoic acid (EPA): This is in fish and other seafood.
Docosahexaenoic acid (DHA): This is also in fish and other seafood.
EPA and DHA are sometimes called marine omega-3s, for obvious reasons. They’re the most important omega-3s for your health.
And in most regions of your body, DHA is present in higher concentrations than EPA.
ALA doesn’t provide the same range of benefits as EPA and DHA. Your body can convert some ALA to EPA and DHA, but it’s a slow process.
But how did we find out that these fatty acids are essential?
The birth of essential fats
In the early 1900s, people saw fats as a source of calories and little else, certainly not essential for health. But in the 1920s and 1930s, this started to change.
A wife and husband team — Mildred and George Burr — conducted carefully controlled studies that advanced our understanding of fats.
They found that when they fed rats diets that lacked fats, the rodents got ill and usually died within a few months. The Burrs also showed that oils, including corn and cod liver oils, could cure them.
They called the fats responsible “essential fatty acids,” and the name stuck. The Burrs were the first to identify linoleic acid (an omega-6) as an essential fatty acid.
Although controversial at the time, their findings became a jumping-off point for further research.
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Still today, scientists are diving into the details. In this two-part feature, we’ll outline just some of the functions that experts can now attribute to omega-3s.
But because omega-3s are present in every tissue in your body, we still don’t know everything that they do.
We should also note that some of the functions we’ll cover have only been demonstrated in animal models. So, it might be different in humans.
Either way, we hope to provide a snapshot of just how pivotal omega-3s are for health.
Once you’ve consumed something that contains omega-3s, they eventually make their way into the membranes of all the cell types in your body.
From skin cells to liver cells to nerve cells, omega-3s make themselves at home.
But some cells have a greater proportion of omega-3s than others, namely the cell membranes of your retina, brain, and myocardium — the muscles of your heart.
Properly functioning cell membranes are vital. You simply wouldn’t be alive without them.
And because cell membranes need omega-3s to function correctly, the role that these fatty acids play in your membranes is one of their most important.
Why membranes matter
When you think of a cell membrane, you might imagine something like a simple plastic bag containing all the structures within the cell.
In reality, cell membranes are complex, fluid structures that have many important jobs.
For instance, they protect the cell and keep its internal environment stable.
Cell membranes also ensure that the things the cell needs — like nutrients — can get inside, and things it doesn’t need, like toxic substances, leave.
Cells also have to respond to their environments, and their membranes play a part here, too: They carry receptors that can detect incoming messages and relay them to other parts of the cell or to other cells.
What are phospholipids?
The main components of cell membranes are phospholipids. These consist of a “head” that contains phosphate and “tails” derived from fatty acids, like omega-3s. In diagrams, they sort of look like tadpoles with two tails.
Omega-3s have many double bonds in their carbon chain, and each double bond forms a kink in their tails.
This means that they can’t stack as tightly as fatty acids with fewer double bonds, like saturated fats.
This loose stacking helps keep cell membranes more fluid. And maintaining membrane fluidity is vital in making sure cell membranes can do all their jobs.
If a cell membrane isn’t fluid enough, it’s a problem. For instance, without enough fluidity, the many proteins that live and work within membranes can’t do what they’re supposed to.
Cell membranes are studded with proteins that carry out many functions. This includes receptors that receive information and pores that allow certain compounds into or out of the cell.
How fluid the membrane is affects how these proteins function.
So, omega-3s’ kinked tails change the membrane’s fluidity and affect how membrane proteins work.
This then influences how the cell behaves — and how it responds to signals from hormones, nerves, and the like.
Talking about how membrane fluidity affects protein function feels quite abstract. So, we’ll outline one important example to help shed a little light.
Omega-3s in your eye
As we mentioned earlier, your retina houses a higher proportion of omega-3s than many of your other body parts.
In particular, you have lots of DHA in the cell membranes surrounding a membrane protein called rhodopsin.
Rhodopsin detects light and helps convert it into a signal that gets sent to your brain. So, it’s vital for vision.
To turn light into a signal, rhodopsin has to physically change shape, and DHA helps the protein make this change. DHA also changes how permeable and fluid the retina cells’ membranes are.
So, by influencing the properties of the cell membrane, DHA helps you see.
But omega-3s seem to protect our eye health in other ways, too.
For instance, animal studies suggest that omega-3s might help reduce inflammation, help regrow blood vessels after injury, extend the life of photoreceptor cells, and play other roles.
And DHA is important right from the start of life. Scientists have shown that it’s essential for the development of your retina and brain.
So, infants who don’t get enough DHA may have visual and cognitive impairments.
Already, we’re getting a sense that omega-3s are busy — present in cell membranes throughout your body and vital for brain development. And we’re only just getting started.
In part two, we’ll begin by covering their activity in your brain. Then, we’ll examine how omega-3s reduce inflammation and protect your heart health.
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