Walk into any pharmacy, and you’ll see them. Massive, translucent yellow bricks of oil sitting in oversized plastic tubs. It’s kinda strange when you think about it. We’ve spent decades trying to get the "fishy" taste out of our diets, yet millions of people voluntarily swallow concentrated mackerel and sardine fat every single morning.
So, why do people take fish oil anyway?
Is it just a leftover habit from the days of cod liver oil and wooden spoons? Not exactly. Most people are chasing two specific molecules: eicosapentaenoic acid and docosahexaenoic acid. You probably know them as EPA and DHA. These are the "active ingredients" that make fish oil worth the occasional fishy burp. We don't make these very well on our own. Our bodies are actually pretty bad at converting plant-based omegas (like the ALA in flaxseeds) into the stuff our brains and hearts actually use.
That’s why the fish oil industry is a multi-billion dollar behemoth. People want a shortcut to the benefits of a Mediterranean diet without necessarily eating grilled sardines three times a week.
The Heart of the Matter: Inflammation and Arteries
For a long time, the standard answer to why do people take fish oil was simple: heart health. This all started back in the 1970s with some observations of Greenland Inuit populations. Researchers like Dr. Jørn Dyerberg noticed that despite eating a diet incredibly high in fat (lots of seal and whale meat), these communities had remarkably low rates of heart disease.
The secret was the omega-3s.
Basically, fish oil helps lower triglycerides. That’s a big deal because high triglycerides are a major red flag for cardiovascular trouble. It’s not just about the numbers on a blood test, though. EPA and DHA are built into the membranes of every cell in your body. They make those membranes more fluid and flexible. Think of it like swapping out old, brittle plastic for high-quality silicone.
There’s also the inflammation factor. Most of us are walking around with a bit too much "fire" in our systems. Modern diets are packed with omega-6 fatty acids (found in vegetable oils like soy and corn), which can be pro-inflammatory if they aren't balanced out. Fish oil acts as a counterweight. It produces signaling molecules called resolvins and protectins. The names give it away—they literally help "resolve" inflammation.
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However, it’s not a magic shield.
Recent large-scale trials, like the REDUCE-IT study, showed that high doses of a specific, purified EPA (Vascepa) significantly reduced cardiovascular events. But—and this is a big but—other trials using standard over-the-counter blends haven't always shown the same dramatic results. It turns out that the quality and the specific ratio of the oil matter a lot more than the flashy label on the bottle.
Your Brain is Mostly Fat
If your heart is the engine, your brain is the high-tech computer submerged in oil. About 60% of the human brain is fat. A huge chunk of that is DHA.
This is a massive reason why do people take fish oil during pregnancy and early childhood. DHA is crucial for the structural development of the retina and the cerebral cortex. If a baby doesn't get enough during those "brain growth spurts," it can actually impact cognitive development and visual acuity later on. Honestly, it’s one of the few supplements that almost every OB-GYN agrees on.
But what about adults?
As we get older, our brains tend to shrink. It’s a depressing reality of biology. Some research suggests that people with higher levels of omega-3s in their blood have larger brain volumes in the hippocampus—the part of the brain responsible for memory and learning. It’s like providing the raw materials for repairs.
There’s also the mental health angle. You’ll see people taking fish oil to help manage depression or anxiety. While it’s definitely not a replacement for therapy or medication, some clinical trials have found that EPA-rich oils can be as effective as some antidepressants for specific types of mood disorders. It likely works by making it easier for neurotransmitters like serotonin and dopamine to move across cell membranes. If the "gate" is stuck because the fat in the membrane is too stiff, the signal doesn't get through.
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The Joint Pain and Performance Connection
You’ll often see athletes or older adults with "creaky" knees reach for the fish oil. This goes back to that inflammation discussion. If you have rheumatoid arthritis, the evidence for fish oil is actually quite strong. It can reduce morning stiffness and joint pain to the point where some patients can actually lower their dose of non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen.
For the gym rats, it’s about recovery. Intense lifting causes micro-tears and a localized inflammatory response. That’s why you’re sore. By damping down that systemic inflammation, fish oil might—theoretically—help you get back to the squat rack a day sooner. It’s subtle, but in the world of high-performance sports, subtle is enough.
What Most People Get Wrong: The Quality Trap
Here is where things get a little murky. If you buy the cheapest bottle of fish oil you can find, you might actually be doing more harm than good.
Fish oil is highly unstable. It hates light. It hates heat. It hates oxygen. When fish oil is exposed to these things, it oxidizes. In plain English: it goes rancid.
If you’ve ever opened a bottle and it smelled like a dumpster behind a seafood shack, throw it away. Consuming oxidized oil can actually increase oxidative stress in your body, which is the exact opposite of what you want.
Also, look at the back of the bottle. You might see "1,000mg Fish Oil," but then look at the breakdown of EPA and DHA. Sometimes, that 1,000mg only contains 300mg of actual omega-3s. The rest is just filler fat or other "stuff" from the fish. You want a high concentration of the good stuff. Otherwise, you’re just swallowing a bunch of extra calories for no reason.
How to choose a good one
- Third-party testing: Look for the IFOS (International Fish Oil Standards) seal. It means a lab checked it for heavy metals like mercury and lead, and ensured it isn't rancid.
- The form matters: Look for "Triglyceride form" rather than "Ethyl Ester." Your body absorbs the triglyceride form much better because that's how it occurs in nature.
- Dark bottles: Always. If it’s in a clear bottle sitting under bright grocery store lights, it’s a gamble.
The Risks: It’s Not for Everyone
There's no such thing as a "perfect" supplement. Because fish oil "thins" the blood slightly by making platelets less sticky (which is good for preventing strokes), it can be a problem if you’re already on blood thinners like Warfarin or if you have an upcoming surgery. Surgeons usually tell you to stop taking it two weeks before you go under the knife.
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There is also some emerging, though debated, research regarding a slight increase in the risk of atrial fibrillation (a heart rhythm issue) in people taking very high doses. It’s a reminder that more isn't always better.
Practical Steps for Success
If you’re considering why do people take fish oil and thinking about starting yourself, don't just grab the first bottle you see.
First, try eating the fish. Two servings of fatty fish a week (salmon, sardines, mackerel, anchovies) usually provide enough omega-3s for the average person. If you hate fish, then the supplement makes sense.
Aim for a combined total of at least 500mg to 1,000mg of EPA and DHA per day for general health. If you’re dealing with high triglycerides or intense joint pain, you might need more, but that’s a conversation for your doctor.
Always take it with a meal that contains some fat. Since it’s an oil, your body needs gallbladder activity and digestive enzymes to break it down. If you take it on an empty stomach with just a glass of water, you’re much more likely to experience those dreaded "fish burps" because the oil is just sitting on top of your stomach acid.
Keep your bottle in the fridge. It keeps the oil stable and significantly reduces the chance of it going rancid before you finish the bottle. It’s a small step that makes a huge difference in the quality of the supplement you’re putting into your body.
Ultimately, people take fish oil because it’s a foundational nutrient that our modern, processed-food-heavy environment has stripped away. It’s not a miracle cure for a bad lifestyle, but it’s a very effective way to "grease the wheels" of your biological machinery.
Actionable Next Steps:
- Check your current supplement for an IFOS seal or third-party certification.
- Calculate the actual mg of EPA + DHA on your label, not just the "Total Fish Oil" amount.
- Move your fish oil bottle to the refrigerator to preserve its freshness.
- If you aren't already, take your dose with your largest meal of the day to maximize absorption and prevent digestive upset.