Fish Oil Benefits, Dosage and Side Effects - Dr. Axe

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Fish Oil Benefits for Cancer, ADHD, Pregnancy & More


Fish oil benefits

Out of 12 dietary, lifestyle and metabolic “preventable causes of death” that were examined in a 2009 study, omega-3 fatty acid deficiency ranked as the sixth highest killer among Americans. Research shows that omega 3-fatty acids, which can be obtained from taking fish oil and consuming fish, can help ward off a number of common causes of death, such as heart disease and stroke.

What are the benefits of fish oil? Studies suggest these include decreasing the risk of not only cardiovascular diseases, but also symptoms of depression, hypertension, attention deficit hyperactivity disorder (ADHD), joint pain, arthritis and chronic skin ailments like eczema.

Fish oil intake has also been associated with aiding the body in weight loss, fertility, pregnancy and increased energy. Prescription fish oil has even been approved by the U.S. Food and Drug Administration to lower unhealthy high triglyceride levels.

Most of these fish oil benefits exist because it’s one of nature’s richest sources of omega-3 fatty acids, which have anti-inflammatory effects.

What Is Fish Oil?

Fish oil comes from the tissues of oily fish. When it comes to human consumption of fish oil, you can get it from eating fish or from taking a supplement.

The best sources of omega-3 oils are cold-water, fatty fish, such as salmonherring, white fish, sardines and anchovies.

Fish oil is a concentrated source of omega-3 fats, which are also called ω-3 fatty acids or n-3 fatty acids. To get more scientific, omega-3s are long-chain polyunsaturated fatty acids (PUFAs).

Our bodies are able to make most of the fats we need need, but that’s not true for omega-3 fatty acids. When it comes to these essential fats, we need to get them from omega-3 foods or supplements.

Fish oil benefits are attributed to two very important omega-3 PUFAs: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA and EPA are sometimes called the “marine omega-3s” because they mainly come from fish.

Fish oil vs. krill oil

The types of fish that are most commonly used to make fish oil supplements include salmon, cod liver, mackerel, sardines, halibut, pollock and herring.

Krill is another small, shrimp-like creature that is used to make krill oil, another marine source of omega-3 fats. Krill oil has a red color and naturally contains astaxanthin, a type of antioxidant that is added to some fish oils.

While both fish and krill oil provide omega-3s, they are of different chemical forms. The type found in fish oil is mostly triglycerides, while the type found in krill oil is mostly in the form of phospholipids.

This seems to change how the fats are absorbed. Some research suggests that krill oil may be better absorbed than fish oil.

However, because findings have been mixed, at this time experts still tell us that there isn’t sufficient evidence to say that krill is necessarily better.

Nutrition Facts

As mentioned, the main nutritional value of fish oil is its high omega-3 fatty acid content, particularly of DHA and EPA.

Nutritional information varies by product and fish source, so you’ll want to check supplement labeling for specific details.

A one-teaspoon serving of fish oil from sardines (about 4.5 grams) typically contains approximately:

  • Calories: 40.6
  • Total Fat: 4.5 g
  • Saturated Fat: 1.3 g
  • Polyunsaturated Fat: 1.4 g
  • Monounsaturated Fat: 1.5 g
  • Vitamin D: 0.4 mcg (3% DV)
  • Omega-3 fatty acids: 1,084 mg (DV varies by age and gender)
  • Omega-6 fatty acids: 90.6 mg (DV varies by age and gender)

*Daily Value: Percentages are based on a diet of 2,000 calories a day.

Fish oil also typically contains vitamin A and other nutrients depending on the particularly fish used to make the supplement.



When it comes to mental health, what is fish oil good for? There’s some evidence suggesting that omega-3 fatty acids may help alleviate symptoms of ADHD and related developmental problems, as well as many other mood and mental health problems over one’s lifetime.

A 2012 study involving children from 6 to 12 years of age with ADHD found “statistically significant improvements” among those taking omega-3 supplements in the following categories: restlessness, aggressiveness, completing work and academic performance.

Another study found that increasing omega-3 intake, specifically DHA, may improve literacy and behavior in children with ADHD. Fish oil is believed to work via its effects on brain function, which makes sense when you consider that 60 percent of the brain is composed of fats.

2. Alzheimer’s disease and cognitive health

For several years now, the fish oil and Alzheimer’s disease connection has been studied with consistent results. The essential fatty acids vital for brain function that are found in fish oil can not only slow cognitive decline, but can help prevent brain atrophy in older adults.

A study published in the FASEB Journal found that fish oil may act as a natural weapon to help fend off the onset of cognitive decline and Alzheimer’s disease.

Another study conducted by researchers at Rhode Island Hospital that examined the relationship between fish oil supplementation and indicators of cognitive decline found that the adults taking fish oil (who had not yet developed Alzheimer’s) experienced significantly less cognitive decline and brain shrinkage compared to adults not taking fish oil.

3. Arthritis

Omega-3 supplements may help relieve symptoms of rheumatoid arthritis, especially joint pain.

One study also showed that omega-3 fish oil supplements worked just as well as non-steroidal anti-inflammatory drugs (NSAIDs) in reducing arthritic pain. Fish oil may be a safer alternative to NSAIDs when taken long term for pain management, considering it has very low risk for side effects.

4. Cancer

Scientific studies demonstrate that fish oil may help prevent and eliminate various cancers, including colon, prostate and breast. It may also make conventional cancer drugs more effective.

Intravenous fish oil lipid emulsions, in particular, are rich in omega-3 polyunsaturated fatty acids, which exhibit anti-inflammatory and immunomodulatory effects.

A scientific review published in 2013 looked at omega-3 polyunsaturated fatty acids and prostate cancer prevention. Researchers concluded that there’s a great deal of evidence suggesting that omega-3s have antiproliferative effects — which means they inhibit cancer cell growth — in cancer cell lines, animal models and humans.

Another scientific review in 2014 evaluated study findings on omega-3 intake in relation to the prevention and treatment of breast cancer, the most prevalent cancer among women. The review found that EPA and DHA, as well as ALA, can differentially inhibit breast tumor development.

According to this review, there is solid evidence to support the use of omega-3s as “a nutritional intervention in the treatment of breast cancer to enhance conventional therapeutics, or potentially lowering effective doses.”

Additionally, a 2017 study found that “very high fish consumption in early adulthood to midlife may be associated with decreased risk of breast cancer.”

Fish oil also looks to be helpful for another type of cancer experienced by women: endometrial cancer. A 2015 study published in the American Journal of Clinical Nutrition revealed that “long chain omega-3 intake associated with reduced endometrial cancer risk only in normal-weight women.”

5. Cardiovascular disease

Omega-3 fish oil has anti-inflammatory properties, which may help prevent or manage a plethora of cardiovascular diseases.

According to a 2019 systematic review, DHA (compared to EPA) seems to be an especially beneficial bioactive compound for heart, cardiovascular and brain function.

Some studies have found that fish consumption can protect against heart disease, in spite of a large intake of fat and cholesterol. Fish oil has been shown to impact on several risk factors associated with coronary heart disease, including hypertension, high levels of triglycerides and high LDL cholesterol.

Omega-3 fatty acids are also associated with improved survival rates for heart attack victims, according to some research. A study published in the medical journal Circulation showed that people who took a high dose of fish oil each for six months following the occurrence of a heart attack actually improved their hearts’ overall functioning and also reduced biomarkers of systemic inflammation.

Although the National Center for Complementary and Integrative Health reports that “research indicates that omega-3 supplements don’t reduce the risk of heart disease,” it also tells us that “people who eat seafood one to four times a week are less likely to die of heart disease.”

Fish oil also can help manage blood pressure levels, according to research.

6. Depression and anxiety

A 2017 study published in Critical Reviews in Food Science and Nutrition noted: “There is mounting evidence to suggest that n-3 PUFAs play a role in depression and deserve greater research efforts.”

Most studies suggest a small to modest beneficial effect of PUFAs on depressive symptoms compared to placebo.

Omega-3 fatty acids have been shown to be critical for development and function of the central nervous system. Evidence from randomized, placebo-controlled trials suggests deficiency of dietary in omega-3 PUFAs may contribute to development of mood disorders, and supplementation may provide a new treatment option for depression and other mood-related problems.

According to a 2017 study published in the Journal of Integrative Neuroscience, there are several mechanisms by which omega-3 PUFAs are thought to induce an antidepressant effect, including by having anti-inflammatory actions and direct effects on membrane properties in the brain.

7. Diabetes complications

A study published in Brain Research shows how far-reaching fish oil can be for people with diabetes. Researchers found that fish oil can help reduce the risk of diabetics from developing cognitive deficit because it protects the hippocampus cells from being destroyed.

The study also showed that fish oil could help reduce oxidative stress, which plays a central role in the development of diabetes complications, both microvascular and cardiovascular.

8. Eye/vision-related disorders

Studies demonstrate that a combination of lutein plus zeaxanthin and omega-3 fatty acids can help reduce age-related macular degeneration.

Results have been mixed regarding whether omega-3s can help to slow down progression of advanced macular degeneration (AMD). However, DHA is a major lipid component of retinal photoreceptors in outer segments of the eyes. It has been shown to have anti-inflammatory and anti-angiogenesis properties that can protect against AMD.

9. Skin and hair

Fish oil benefits for skin include the ability to nourish the skin with fats and fat-soluble vitamins that help maintain a smooth, elastic texture. There is also evidence that fish oil prevents signs of photoaging (wrinkles), potentially as well as skin cancer, allergic reactions, dermatitis, cutaneous wounds and melanogenesis.

One of the biggest reasons fish oil leads to healthier skin is the fact that it can reduce inflammation. Research has shown that fish oil supplements can even reduce sun-induced inflammation and provide sunburn relief.

The deficiency of EPA and DHA in diet contributes to skin conditions, such as dandruff, thinning hair, eczema and psoriasis, as well as age spots and sun spots.

In one study, individuals taking fish oil equivalent to 1.8 grams of EPA had a significant reduction in symptoms of eczema after 12 weeks. Researchers posit that these effects may be due to fish oil’s ability to reduce leukotriene B4, an inflammatory substance that plays a role in eczema.

10. Fertility and pregnancy

How might fish oil help you sexually? Recent studies have shown that the consumption of omega-3 fish oil may help improve fertility in both men and women.

One of the greatest benefits for men is due to DHA, which is a byproduct of omega-3 fatty acids that plays a key role in the mobility and health of sperm.

Fish oil has also been shown to support fertility in women by reducing inflammation, balancing hormones and regulating their cycles. It may also be helpful in the treatment of conditions like polycystic ovarian syndrome and endometriosis, which can cause infertility.

Fish oil is also extremely beneficial for pregnant women and their children. Throughout pregnancy and also while breastfeeding, a woman’s omega-3 needs are even higher than usual.

According to the American Pregnancy Association, most U.S. women are deficient in EPA and especially DHA going into pregnancy and get even more depleted during pregnancy, as the placenta supplies the fetus with DHA from the mother’s tissue.

Omega-3 DHA is a critical building block of the fetal brain, eyes and nervous system. Once the baby is born, omega-3s continue to be vital to healthy brain development and immune function.

Omega-3 fatty acids also seem to reduce the chance of premature delivery. EPA and DHA intake can help support healthy labor and delivery outcomes.

This omega-3 duo also helps normalize mood and overall well-being in the mother after giving birth.

11. Weight loss/management

Australian researchers published results of a study examining the effects of fish oil on weight loss in combination with diet and exercise in the May 2007 issue of the American Journal of Clinical Nutrition. The results showed that a combination of fish oil supplements and regular exercise can reduce body fat while also improving heart and metabolic health.

The fish supplementation group had lowered triglycerides, increased HDL cholesterol and improved blood flow. Overall, adding fish oil to a current exercise program (and an overall healthy lifestyle) looks like it can decrease body fat as well as cardiovascular disease risk.

Another small study had all volunteers consume the same exact control diet and substituted fish oil for visible fats (things like butter and cream). The volunteers consumed six grams of fish oil each day for three weeks.

Researchers found that body fat mass decreased with the intake of fish oil.

The researchers concluded that dietary fish oil reduces body fat and stimulates the use of fatty acids for the production of energy in healthy adults. This means it may also be helpful for those looking to improve their body composition via exercise and bodybuilding.

12. Bones and muscles

A 2020 meta-analysis sought to evaluate the effect of omega-3 fatty acids on “sarcopenia-related performances among the elderly.”

By examining a series of randomized, controlled trials, researchers found there were minor benefits for muscle mass gain and improved walking speed for people who consumed at least two grams of omega-3 supplements daily, particularly when supplementing for more than six months.

Further research seems to confirm these findings, with a 2023 systematic review relaying that “the majority of the study results appeared to indicate that omega-3 fatty acids are beneficial for muscle health.”

In addition, a 2013 study found that omega-3 consumption may benefit bone mineral density, particularly in the spine, in older adults. Another study published in 2021 found that habitual use of fish oil supplements can reduce the risk of fractures, particularly in people predisposed to fracture risk.

However, experts note that the benefits of fish oil for skeletal and bone health depend on the EPA and DHA content in the supplement.

13. Liver health

Several studies have shown that fish oil and omega-3s can help protect the liver and improve symptoms of non-fatty alcoholic liver disease (NAFLD). For instance, a 2019 analysis provided the following conclusion: “These studies suggest that dietary supplementation with C20–22 ω3 PUFA should be considered as a viable and effective option to lower liver fat in obese adults and children with NAFLD.”

Meanwhile, a 2020 double-blind, randomized, placebo-controlled clinical trial saw the PUFAs in fish oil “were effective in reducing [alkaline phosphatase] and liver fibrosis without altering the expression of circulating miR-122 in individuals with NAFLD.”

Finally, a 2022 study found that fish oil supplementation was able to help improve liver damage in people with NAFLD.


Many of Americans’ health problems can be traced back to having an omega fat imbalance, specifically of omega-3 and omega-6 fats. Omega-6 fats aren’t necessarily bad for you, but if they’re consumed in large amounts without omega-3s they can cause inflammation, which leads to chronic illness.

Today, the average American has a 20:1 ratio of omega-6 to omega-3s, when a healthy ratio is more ideally around 4:1 or even better yet 2:1. Put in other numerical terms, the typical American diet tends to contain 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids.

The biggest cause of omega-3 deficiency is the overconsumption of foods high in omega-6 fatty acids. Omega-6 comes from things like fried foods, fast foods and boxed foods that contain vegetables oils (like soybean oil, canola oil, sunflower oil, cottonseed oil and corn oil).

Research has shown that having a lower ratio of omega-6/omega-3 fatty acids can reduce the risk of many common chronic diseases, including ADHD, asthma, arthritis, autoimmune diseases and more.

Dosage Recommendations

The best way to achieve a good balance of omega-3 and omega-6 is by getting fish oil from wild-caught fish, such as salmon. However, it is also beneficial for some people to supplement with a high-quality omega-3 fish oil or cod liver oil.

How much fish oil should you take per day?

  • Currently, there isn’t a set standard recommendation for how many omega-3s we need each day, but suggestions range from a fish oil dosage of 500 to 1,000 milligrams daily.
  • How easy is it to get these recommended amounts? To give you an idea, there are more than 500 milligrams of total omega-3s in one can of tuna fish and one small serving of wild-caught salmon.
  • Ideally aim to eat at least two servings of fatty fish each week to fulfill your omega-3 needs. This is a recommendation that is encouraged by organizations such as the American Heart Association.
  • If you’re not able to get enough fish oil benefits through your diet, fish oil pills can be a good option. When taking fish oil, more is not always better. Remember that you want it to stay in a balanced ratio with omega-6 fats.
  • When should you take fish oil supplements? The time of day is not important, so take it when it’s most convenient, ideally with a meal.

Risks, Side Effects and Drug Interactions

Omega-3s from supplements usually produce only mild side effects, if any at all, when taken at recommended doses.

The American Heart Association considers taking up to three grams of fish oil per day safe. It advises that patients taking more than 3 grams of omega-3 fatty acids from capsules should do so only under a physician’s care.

Most physicians would say that taking more than two grams (or 2,000+ milligrams) daily is a mega dose.

While they are generally tolerated well, fish oil side effects can include:

  • belching
  • bad breath
  • heartburn
  • nausea
  • loose stools/diarrhea
  • rash
  • nosebleeds

Taking a high-quality supplement may reduce the likelihood of any unwanted side effects. It’s also a good idea to take fish oil pills with meals to reduce side effects.

Before taking this product, you should speak with your doctor if you currently take any medication or have any ongoing health concerns. You should also speak to your doctor if you have a known fish or shellfish allergy.

If you have a bleeding disorder, bruise easily or take blood-thinning medications, you should use these supplements with extra caution, since large doses of omega-3 fatty acids can increase bleeding risk. This bleeding risk also applies to people with no history of bleeding disorders or current medication usage.

If you have type 2 diabetes, you should only use supplements under your doctor’s supervision. Individuals with type 2 diabetes can experience increases in fasting blood sugar levels while taking fish oil supplements.

Avoid low-quality supplements

Also, not all fish oils are created equal. Most fish oils are highly processed and can oxidize easily because omega-3 fats are polyunsaturated, have a low heat threshold and can easily go rancid.

For that reason, you want to buy a fish oil in triglyceride form that also contains antioxidants to preserve them, like astaxanthin or essential oils.

  • A high percentage of omega-3 oils on the market today may contain mercury and pesticide residues plus hydrogenated oils.
  • Look for astaxanthin as part of any high-quality fish oil supplement.
  • To avoid supplements containing mercury or other harmful contaminants, purchase supplements from a reputable source that clearly tests for these health-hazardous contaminants in its products. These tests should be ideally conducted by a third-party, and a certificate of analysis should indicate the levels of purity from environmental toxins.

Is fish oil for dogs and pets safe?

Just like with humans, omega-3 fats found in fish have been shown to have beneficial effects in treating illnesses in dogs and pets, according to PetMD. Research suggests that omega-3s for dogs can help with the treatment of infections, cancer, joint, heart, kidney, skin and gastrointestinal problems, in addition to having positive effects on wound healing, skin health and coat quality.

However, too much may have adverse effects on health. The National Research Council has established a “safe upper limit” of EPA and DHA for dogs, which is a daily dose between 20–55 milligrams per pound of body weight (of combined EPA and DHA).

In order to prevent side effects like digestive upset, stick to giving your dog no more than this amount.

Final Thoughts

  • Omega-3 fatty acids are essential to our health, but our bodies cannot make them so we must get them from our diets. If diet is not enough to meet your needs, then a high-quality fish oil supplement is the next best option.
  • Fish oils supplements can be used as prevention to health problems as well as a treatment. Scientific studies have and continue to back up all of the incredible benefits of fish oil, ranging from helping with eczema and fertility to heart disease and many types of cancer.
  • The best fish oil supplements are ones manufactured under strict standards with thorough testing for health-hazardous contaminants like mercury.
  • Currently, there isn’t a set standard recommendation for fish oil dosage, but most suggestions tell us to aim for a daily dose that provides between 500 to 1,000 milligrams of omega-3s.

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