Welcome to the second part of our two-part feature on the wonders of omega-3 fatty acids. In it, we ask why omega-3s are “essential."
In other ZOE articles, we’ve covered the links between consuming enough omega-3s and health. In this feature, we’re asking how these health effects happen.
What makes omega-3s special, and how do they protect us against disease?
In the first part, we covered the basics of omega-3s, a little bit about their discovery, and why they’re vital for the proper functioning of your cells' membranes.
In this part, we’ll start with the omega-3s in your brain. Then, we’ll move on to their role in inflammation. We'll finish by looking at how omega-3s affect heart health.
Before we get going, we should mention that a lot of the relevant research is based on animal models. So, the story might be different for humans.
Right, let’s begin in the brain.
Omega-3s in your brain
As we learned in part one of this deep dive, omega-3s are present in every type of tissue in your body.
Your nervous system has particularly high levels of docosahexaenoic acid (DHA) — the most common form of omega-3 in your body.
And if there are a lot of omega-3s in there, you can assume they’re doing something important.
Scientists are still getting to grips with the roles of omega-3s in the brain, but it seems that they’re important in a number of ways.
Development and maintenance
We mentioned in part one that omega-3s are essential during the development of your nervous system in early life. But they remain important throughout your life.
The cells in your nervous system die and are refreshed continually — although more slowly than other tissues in your body.
So, we need a steady supply of DHA to ensure that everything can be built as needed.
Your brain is a hardworking organ, receiving around 20% of the blood that’s pumped from your heart.
Some compounds derived from EPA and DHA seem to play a role in increasing blood flow in the brain.
One study found that people with higher levels of omega-3s in their blood had increased blood flow in parts of their brain that are involved in storing and retrieving memories.
The blood-brain barrier
This virtual barrier separates the central nervous system from the rest of your body. It helps keep infections and toxins from reaching your brain.
Some early animal studies found evidence that DHA might help support the blood-brain barrier.
As we saw in part one, DHA can influence how cell membrane proteins function, and this includes the membranes of nerve cells, or neurons.
The membranes of your neurons have protein channels that let charged particles (ions) in and out.
The highly orchestrated opening and closing of these ion channels produces the electrical signals that nerves use to pass messages around your body.
There are many types of these ion channels, and DHA can influence how readily they open and close, affecting the function of your brain and nervous system.
When a nerve fires, it releases chemicals called neurotransmitters. These chemicals move across a space between nerves called the synapse. Neurotransmitters pass on information from one nerve to the next.
DHA is essential for the formation of synapses during development, and it remains important throughout your life.
Because of DHA’s influence on cell membranes, it can help neurotransmitters bind to receptors in membranes more successfully.
Also, animal studies in the 1990s found that when rats were deficient in omega-3s, they had lower levels of the neurotransmitters serotonin and dopamine in some parts of their brains.
Inflammation is a healthy response to threats like injuries or infections. However, if inflammation continues for long periods in the absence of a threat, it can damage cells and tissues.
Because inflammation is vital for protecting health but can be harmful if it persists, your body keeps a tight rein on it.
And omega-3s and omega-6s are part of this important balancing act. First, let’s return to your brain.
Omega-3s' anti-inflammatory effect may be important for brain health.
For instance, there’s some evidence that inflammation in your brain, also called neuroinflammation, might be linked to psychiatric conditions like depression.
And some animal research suggests that omega-3s might help reduce depression by limiting neuroinflammation.
Although there’s limited evidence in humans, some scientists hope that omega-3s might form part of future treatments for depression.
As we’ve seen, omega-3s form part of cell membranes. Omega-6s, which are also essential fatty acids, do the same.
One of the most well-studied and important omega-6s is arachidonic acid. Like DHA, it helps keep membranes fluid, affects how membrane proteins work, and supports brain health.
When a cell receives certain signals, its membranes release arachidonic acid, which is converted into hormones called eicosanoids.
Overall, eicosanoids produced by omega-6s tend to promote inflammation. So, this is where omega-3s come in. They also produce eicosanoids, but theirs have an anti-inflammatory effect.
Importantly, omega-3s and omega-6s compete for space in the membrane. So, having more omega-3s in your cell membranes means that fewer inflammatory compounds are released.
Now, we need to add a caveat here because seed oils, which are rich in omega-6s, have received a bad rap over the years. Some people suggest that their pro-inflammatory eicosanoids are responsible for a range of chronic diseases. And that’s not entirely fair.
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Although arachidonic acid eicosanoids are slightly pro-inflammatory, consuming them doesn’t cause increased inflammation.
When we wrote about the drama surrounding seed oils, we spoke with ZOE’s Chief Scientist Dr. Sarah Berry.
She explained that “As long as you’re consuming adequate omega-3, it’s perfectly fine to be consuming omega-6. Based on current evidence, it will not cause an unfavorable inflammatory response. Omega-6 has a protective effect against many chronic diseases.”
Aside from competing with omega-6s, omega-3s tamp down inflammation via other routes, too.
For instance, omega-3s can “turn down” genes that promote inflammation.
Also, animal studies show that when omega-3s are present in the membranes of some immune cells, those cells release less inflammatory proteins called cytokines.
So, by a number of mechanisms, omega-3s help keep inflammation in check, which helps protect you against diseases, including cardiovascular diseases, which we’ll look at next.
Omega-3s and heart health
Studies investigating whether omega-3 supplements protect heart health have produced conflicting results.
However, consuming enough omega-3s in your diet is important for maintaining heart health.
Omega-3s probably help protect your heart and blood vessels in a number of ways.
Following on from the section above, omega-3s’ ability to reduce inflammation is likely key.
Atherosclerosis and inflammation
Atherosclerosis is the buildup of a fatty compound on the lining of your arteries. As these so-called plaques grow, they increase the risk of a heart attack or stroke.
In fact, atherosclerosis is the most common cause of cardiovascular disease.
Also, omega-3s help lower levels of triglycerides (fat) in your blood. Elevated levels of triglycerides are associated with an increased risk of cardiovascular diseases.
Experts are still figuring out how omega-3s lower levels of fat in your blood, but they do have some theories.
The leading theory goes like this: Your liver produces particles that contain triglycerides and releases them into your bloodstream. Omega-3s slow this production down, which reduces how much reaches your bloodstream.
There’s also some evidence from animal studies of another mechanism: Omega-3s help produce compounds that may reduce how much fat is broken down in your gut.
And if it’s not broken down, it passes out in your poop rather than being absorbed into your blood.
Aside from reducing inflammation and blood triglycerides, omega-3s might also protect heart health in other ways. For instance, they may help reduce blood pressure and prevent blood clots.
Omega-3s might also help prevent abnormal heart rhythms called arrhythmias.
As we mentioned earlier, DHA can influence how ion channels work in nerves. And scientists think that omega-3s might also affect how ion channels work in the heart cells responsible for contractions.
So, these fatty acids might help stabilize your heart rhythm.
As you’ve probably gathered, there are many links between omega-3s and heart health. And we have a lot left to discover.
What should you do?
While scientists continue to unearth the roles of these fatty acids in our bodies, there’s one thing we know for sure: They’re essential. So, you should consume them.
In general, ZOE recommends a “food first” approach. So, rather than reaching for a supplement, try to get your omega-3s from food. We have an article that explores good food sources of omega-3s.
However, some people may need to take supplements to ensure that they get enough of these fatty acids. For instance, people who are pregnant or breastfeeding.
If you're worried about getting adequate amounts, ask a doctor for advice.
Despite the length of this two-part feature, we’ve only scratched the surface of what omega-3s do in your body.
If you only take one thing away from these articles, it should be that omega-3s are amazing.
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