Fish oil is a food supplement that’s rich in two essential omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Omega-3s are crucial for the healthy functioning of your cells and for producing important hormones.
And eating foods like fish and shellfish is the best way to get EPA and DHA omega-3s into your diet.
There’s strong evidence that eating more of these foods can improve your heart health. And they contain a range of other nutrients beyond EPA and DHA.
Although it’s generally better to get omega-3s from food, some people may benefit from taking omega-3 supplements. Below, we look at who might benefit and why.
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Omega-3s and their potential benefits
When people talk about the possible health benefits of fish oil, they generally mean the benefits of the oil’s omega-3 fatty acids.
Fatty acids are the building blocks of the fats that your body needs to function properly.
Omega-3s are essential fatty acids. Your body can’t make them, so it has to get them from your diet.
Omega-3s are also a vital part of the membranes in every single one of your body’s cells.
They’re also involved in producing hormones that regulate how your arteries work, inflammation, and blood clotting.
Below, we’ll round up what researchers have discovered about the possible health benefits of fish oil and its omega-3s: EPA and DHA.
Some studies look at supplements, and others look at getting omega-3s from food.
It’s worth noting that a 6-ounce serving (around 170 grams) of wild salmon contains almost as much omega-3 as two 1,000-milligram omega-3 fish oil capsules.
So, if you opt for food sources of omega-3s, you’d still be getting the benefits that fish oil might offer.
Experts link eating more fish with having better heart health. But when it comes to fish oil supplements, things are a little less clear.
A review of 79 clinical trials found little or no evidence that supplements containing EPA and DHA lowered the risk of a heart attack, stroke, or dying from heart disease.
Meanwhile, a large-scale study found an association between taking 2-g doses of EPA twice a day and a small but significant improvement in heart health outcomes. The participants also took medications that lowered cholesterol, called statins.
There’s also good evidence that regularly taking supplements containing EPA and DHA can help lower triglyceride levels. Having high levels of these fats is linked with a greater risk of heart disease.
One large review looked at a range of different studies. Some lasted a few weeks, others ran for a few months. Some asked participants to take daily supplements containing around 2–4 g of omega-3s. Others asked them to take up to 15 g of fish oil every day.
The review found that, overall, the interventions led to much lower levels of triglycerides in the participants’ blood, regardless of whether they’d started out with high or normal levels of triglycerides.
And omega-3s may benefit heart health in several other ways. For example, they may help lower blood pressure and improve blood vessel function.
There’s some evidence that omega-3s have powerful anti-inflammatory properties.
Over time, persistent inflammation contributes to different chronic health conditions, such as type 2 diabetes and heart disease.
Omega-3s may help improve the symptoms of inflammatory conditions, such as rheumatoid arthritis.
One small study involving 60 people with this condition found that those who took fish oil supplements for 12 weeks had less joint swelling and pain than participants who didn’t take a supplement.
In older, small studies, researchers have reported similar findings.
Scientists analyzing multiple studies have found that increasing your intake of omega-3s — by changing your diet or taking supplements — may be linked to better cognitive functions, such as memory and focus. It may also be linked with a reduced risk of Alzheimer’s disease.
One large study included adults aged 60–73, and it found that those who regularly took fish oil supplements were significantly less likely to develop any form of dementia than people who didn’t take the supplements.
Age-related macular degeneration
Age-related macular degeneration is an eye disease that damages part of the retina, leading to blurred central vision.
A review of 21 studies found that people who got more EPA and DHA in their diets had a 14% lower risk of developing an early form of this condition — and a 29% lower risk of developing a late form.
Researchers have found some links between the amount of fish and omega-3s in your diet and the risk of developing depression — but the association isn’t clear-cut.
The researchers found that those who had more omega-3s in their diets had a significantly lower risk of depression.
Another extensive study in Spain looked at people with overweight or obesity.
The researchers found that the participants had a reduced risk of depression if their diets contained a moderate amount of fish or omega-3s — but not if their intake was low or high.
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Dietary sources of omega-3s
Some people may benefit from taking fish oil supplements, but in general, it’s better to get your omega-3s from food.
There’s good evidence that regularly eating fish can reduce your risk of heart disease.
This is because whole foods — like fish and plant sources of omega-3s — also contain a range of other nutrients with their own health benefits.
Seafood sources of omega-3s
Fatty fish and other types of seafood are the best sources of EPA and DHA.
There are no official daily allowances for these essential fatty acids. But the Dietary Guidelines for Americans recommends that people eat 8 oz (around 227 g) of fish or shellfish every week.
So, if you eat seafood, here are some types that contain omega-3s:
herring: 1.7 g of omega-3s in a 3-oz serving
mackerel: 1 g in a 3-oz serving
rainbow trout: 0.8 g in a 3-oz serving
salmon: 1.8 g in a 3-oz serving
oysters: 0.7 g in a 3-oz serving, which also contains some alpha-linolenic acid (ALA)
Plant sources of omega-3s
The main omega-3 in plants is ALA. Our bodies can only convert a small amount of the ALA we eat into EPA and DHA.
Still, ALA has its own health benefits.
Experts recommend that adult females get 1.1 g of ALA every day and that adult males get 1.6 g. But people who are pregnant or breastfeeding need more.
The best sources of ALA include:
flaxseed (linseed) oil: 7.3 g of ALA in a tablespoon
chia seeds: 5 g in a 1-oz serving
walnuts: 2.6 g in a 1-oz serving
flaxseeds (linseeds): 2.4 g in a tablespoon
canola (rapeseed) oil: 1.3 g in a tablespoon
soybean oil: 0.9 g in a tablespoon
To learn more about which foods are best for your body, take our free quiz.
Should I consider supplements?
For most people, it’s best to get EPA and DHA omega-3s from whole foods. So, regularly eating fish and other seafood is the best way to get the omega-3s that your body needs.
But some people may benefit from supplements at certain points in their lives.
You might want to consider taking EPA and DHA supplements if you’re in any of these groups:
People who are pregnant or breastfeeding: EPA and DHA are essential for the healthy development of babies. If you’re worried about eating fish while pregnant, you might want to talk to a healthcare provider about an omega-3 supplement.
Older adults: There’s reasonably good evidence, which we go into above, that taking omega-3 supplements later in life could help reduce the risk of cognitive decline and dementia.
People who don’t eat seafood: If this is you, you might benefit from an omega-3 supplement. But having a very healthy vegetarian (or any other plant-based) diet is already linked with a lower risk of heart disease, independent of your omega-3 intake.
Risks and side effects of omega-3 supplements
Doctors consider good quality omega-3 supplements to be safe for most people.
But if you have certain health conditions or are taking certain medication, there are risks.
These risks include:
Drug interactions: If you take omega-3 supplements and a blood-thinning medication (like warfarin) or a nonsteroidal anti-inflammatory drug (like ibuprofen) it may take longer for a cut to stop bleeding.
Atrial fibrillation: This heart rhythm disorder increases your risk of a stroke. And there’s some evidence that people with high triglyceride levels have a greater likelihood of developing atrial fibrillation if they also take omega-3 supplements.
Seafood allergies: It’s unclear if taking fish oil supplements is safe for people with seafood allergies.
If you might fall into any of the groups above, ask a healthcare professional before you start taking omega-3 supplements.
Fish oil can also have mild side effects for some people, including:
an unpleasant aftertaste or fishy burps
Frequently asked questions about fish oil
Below, we delve into some common questions about the health effects of fish oil.
Before we start, it’s worth noting that the research in some of these areas is very limited.
Also, you’d likely get any possible benefits of the oil from eating fish and shellfish.
Does fish oil help with hair growth?
Having good nutrition is one of the many factors at play in having healthy hair. And there’s some limited evidence that fish oil could help with hair growth.
In one small study, some female participants took supplements containing omega-3 for 6 months. The researchers found that these participants had less hair loss and more hair density and thickness than those who didn’t take the supplements.
Does fish oil increase testosterone?
Omega-3s play a role in reproductive health and may have an effect on male testosterone levels.
In one small study, the total testosterone of participating males increased after 12 weeks of taking a DHA-enriched fish oil supplement.
A larger study involving young adult men found that those with a history of taking fish oil supplements had higher testosterone levels than those who didn’t take these supplements.
The difference was greater for the people who took the supplements more often.
How does fish oil affect your skin?
Some researchers suggest that the omega-3s in fish oil may contribute to the health of your skin by helping maintain your body’s fluid balance.
Omega-3s may also help slow skin damage from sun exposure.
Fish oil supplements have high levels of the omega-3 essential fatty acids EPA and DHA.
Research has shown that taking them regularly can help lower triglyceride levels, and it may contribute to good heart health in other ways.
For most people, it’s best to get the omega-3s that your body needs by eating seafood.
But some of us, including those who are pregnant or breastfeeding, may benefit from taking omega-3 supplements.
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