In brief: Do fish oil supplements containing omega-3 fatty acids significantly improve heart health, brain health and a host of other conditions? Here’s what the science says.
Fish oil is the third most widely used supplement in the U.S. According to a study published in 2015 by the National Institutes of Health (NIH), nearly one in twelve Americans used fish oils in 2012.
Omega-3 fatty acids are a group of polyunsaturated fatty acids (PUFA) that are essential for health and are required for some functions in the body. Research studies suggest that omega-3 fatty acids may help in a wide range of diseases, including rheumatoid arthritis, asthma, depression, cancer, ADHD, cardiovascular disease and various autoimmune diseases.
There is some evidence that omega-3 fish oil supplements may help to relieve the symptoms of rheumatoid arthritis. For most other conditions for which the supplements have been studied, either definitive conclusions have not yet be reached, or studies have shown them not to be beneficial.
List of 9 Facts About Omega-3s
1. Two Types of Omega-3s.
Omega-3 fatty acids, called omega-3s for short, come from both food and dietary supplements. Fish oil supplements contain DHA and EPA omega-3s, and flaxseed oil supplements contain ALA omega-3s. Fish oil supplements contain DHA and EPA omega-3s, and flaxseed oil supplements contain ALA omega-3s.
Omega-3 fatty acids are divided into two distinct types: long-chain and short-chain. The long-chain omega-3s DHA and EPA and are found mostly in fish, especially fatty fish such as tuna, trout, and salmon; and shellfish such as oysters, crab, and mussels.
The short-chain omega-3 fatty acid ALA (alpha-linolenic acid) is mostly found in vegetable oils and seeds, such as soy oil, chia seeds, and canola oil.
Omega-3s are important for healthy bodily functions, including digestion, fertility, muscle activity, blood clotting, and cell division and growth. ALA is an essential fatty acid. Because the human body cannot manufacture it, people must obtain it from supplements or food. DHA (docosahexaenoic acid) is essential for brain development and function. The third most common omega-3 fatty acid is eicosapentaenoic acid (EPA).
2. The Healthiest Omega-3s are DHA and EPA
Vegetarians have a tough time. ALA, found in vegetables is far less beneficial than DHA and EPA, both found in fish. A vegetarian has to eat a lot more ALA to gain the same benefits provided by fish oils.
3. Fish Is The Healthiest Source of Omega-3 Fatty Acids
Evidence suggests that a heart-healthy diet should include seafood rich in DHA and EPA fish oils. Research studies showed that people who ate seafood at least once a week were less likely to die of heart disease than those who rarely or never ate it. The USDA’s 2015-2020 Dietary Guidelines for Americans recommends that adults eat 8 or more ounces of seafood per week because it provides healthy fish oils. The USDA, FDA, and NCCIH recommend smaller amounts of seafood for young children and have issued a special advisory concerning pregnant or breastfeeding women and fish consumption.
4. Heart Disease
While the omega-3 fatty acids found in whole fish have been shown to be healthy, fish oil supplements containing DHA and EPA have not been shown to protect against heart disease in the general population. There has been a substantial amount of research on omega-3s supplements, and their role in heart disease. The findings of individual studies have been inconsistent. Researchers aren’t sure if fish oil in supplement form protects a healthy person against heart disease. The American Heart Association (AHA) recently issued an advisory on omega-3 fish oil supplements, stating that they are not useful in the primary prevention of heart disease. While the AHA has long recommended eating fish to prevent heart disease, it is not so sure about fish oil supplements, believing them to be helpful only for particular categories of patients with specific heart diseases.
5. Rheumatoid Arthritis
A 2012 systematic review concluded that DHA and EPA, the primary omega-3 fatty acids found in fish oil, may be helpful in alleviating symptoms of rheumatoid arthritis (RA). Many study participants who took fish oil reported reduced joint swelling and pain, less morning stiffness, and a reduced need for anti-inflammatory drugs.
6. Fish Oils And Brain Health
The omega-3 fatty acid DHA plays a significant role in brain function and eye health. While there is ongoing research on fish oils and diseases of the eye and brain, the medical community has not found enough solid evidence to conclude either way. Researchers are still actively investigating.
While researchers don’t know yet if fish oil supplements protect the brain, they have discovered something else that does. Massive observational studies have shown that the caffeine in coffee significantly protects the brain, helping to prevent Alzheimer’s and Parkinsons’s Disease.
Fish Oil Supplements in Brain & Eye Health
Researchers are studying omega-3 fatty acids and their role in diseases of the nervous system and brain, such as cognitive decline and multiple sclerosis. A large study, called Age-Related Eye Disease Study 2 (AREDS2) has investigated the role of omega-3s in both brain health as well as eye health. In 2015, AREDS2 researchers concluded that taking DHA and EPA in supplement form did not slow cognitive decline in older adults.
Omega-3s in Mental Health
Researchers are also investigating the role of omega-3 fatty acids and in various mental health disorders, including attention-deficit hyperactivity disorder (ADHD), bipolar disorder, borderline personality disorder, autism, schizophrenia, and depression. No firm conclusions have been reached as of yet.
7. Fish Oils and Other Diseases
Research On Fish Oil Supplements in Eye Health (AMD)
Age-related macular degeneration, or AMD for short, is a disease of the eye that can cause vision loss. Studies have shown that people who eat seafood-rich diets are less likely to develop the advanced stage of AMD. The authors of the AREDS2 study concluded that taking fish oil supplements containing DHA and EPA did not slow the progression of AMD in people who were at high risk of developing the advanced stage of the disease.
Fish Oils and Prostate Cancer
While some research has linked the omega-3 fatty acids DHA and EPA with an increased risk of prostate cancer, the evidence is far from certain. Researchers are still investigating a possible link between omega-3 fatty acid consumption and prostate cancer. According to the NCCIH:
There is conflicting evidence about whether omega-3 fatty acids found in seafood and fish oil might increase the risk of prostate cancer.
The National Center for Complementary and Integrative Health (NCCIH), is a division of the U.S. National Institutes of Health. It reviews scientific evidence on supplements and publishes its findings as a guide to the public.
Fish Oil Supplements and Other Conditions
Omega-3 fish oil supplements have also been studied in the prevention and treatment of a variety of conditions including asthma, allergies, diabetes, cystic fibrosis, menstrual cramps, kidney disease, lupus, obesity, osteoporosis, ulcerative colitis, and Crohn’s disease. Additionally, omega-3s have been studied in the prevention or treatment of the severe weight loss associated with advanced cancer. As well, omega-3 fatty acids have been thought to improve outcomes in organ transplant patients. Based on the currently available evidence, no conclusions have drawn about whether omega-3 supplements are helpful for these diseases and conditions.
8. Omega-3 Safety Concerns
While there are exceptions (see general precaution, below) for people who are taking medicine that affects blood clotting, have allergies to seafood, and women who are pregnant or breastfeeding, fish oil supplements are generally safe, according to the NCCIH which states in general:
Omega-3 fatty acid supplements usually do not have negative side effects. When side effects do occur, they typically consist of minor gastrointestinal symptoms, such as belching, indigestion, or diarrhea.
General Precaution Regarding Omega-3 Fatty Acids
Omega-3 supplements are not advised for people who take medicines that affect blood clotting, pregnant or breastfeeding women, or people allergic to seafood. Anyone considering taking omega-3 fish oil supplements should consult their physician first. The NCCIH bottom line:
The bottom line: Including seafood in your diet is healthful. Whether omega-3 supplements are beneficial is uncertain.
The NCCIH gives the following two precautions for people contemplating omega-3 supplements:
If you are considering omega-3 supplements, talk to your health care provider.
It’s especially important to consult your (or your child’s) health care provider if you are pregnant or breastfeeding, if you take medicine that affects blood clotting, if you are allergic to seafood, or if you are considering giving a child an omega-3 supplement.
Omega-3 Fatty Acids and Bleeding Time
According to the NCCIH, omega-3 fatty acid supplements may extend bleeding time, the amount of time it takes for a wound to stop bleeding. The NCCIH adds:
People who take drugs that affect bleeding time, such as anticoagulants (“blood thinners”) or nonsteroidal anti-inflammatory drugs (NSAIDs), should discuss the use of omega-3 fatty acid supplements with a health care provider.
Fish Oils vs. Fish Liver Oils
According to the NCCIH, fish liver oils, such as cod liver oil, are not the same as fish oil, saying:
Fish liver oils contain vitamins A and D as well as omega-3 fatty acids. Both of these vitamins can be toxic in large doses. The amounts of vitamins in fish liver oil supplements vary from one product to another.
9. Eating Whole Fish And Pregnancy
The U.S. Food and Drug Administration also advises children and pregnant women to limit consumption of high mercury fish and encourages these groups to substitute low-mercury fish and limit consumption.
Fish is rich in long-chain omega-3 fatty acids nutrients that are vital to a growing fetus. For pregnant women, eating fish is a double-edged sword: fish contains nutrients essential to fetal growth, but potentially contains hazards. The solution, according to the NCCIH, is to consume low mercury fish. The NCCIH advises that
“women who are pregnant or breastfeed should consume 8 to 12 ounces of seafood per week from a variety of seafood types that are low in methyl mercury,” adding, “Pregnant or breastfeeding women should limit the amount of white tuna (labeled as albacore) to no more than 6 ounces per week.” and “They should not eat tilefish, shark, swordfish, and king mackerel because they are high in methyl mercury.”
FDA Recommendations – Mercury and Fish
For middle-aged and older adults, the FDA believes that the benefits of fish outweigh the potential risks, as long as EPA guidelines are followed. Additionally, the FDA says that eating a variety of fish helps minimize adverse effects from potential contaminants.
Take Home Message
- A diet rich in seafood is much healthier than fish oil supplements.
- Researchers are still investigating the role of omega-3s in preventing a variety of diseases.
- Pregnant and breastfeeding women should avoid consuming high-mercury fish.
Related Article: The Dirty Secret of Omega-3 Fish Oil Supplements
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References / Article Sources
National Center for Complementary and Integrative Health, U.S. National Institutes of Health; “Omega-3 Supplements: In Depth“; NCCIH Publication Number D482; Last Update: August 2015; Available Online.
United States Department of Agriculture (USDA), Department of Health and Human Services (HHS) “Dietary Guidelines for Americans, 2015-2020, 8th Edition.” 2016, ISBN: 9780160934650.
National Center for Complementary and Integrative Health, U.S. National Institutes of Health; “7 Things To Know About Omega-3 Fatty Acids”; Last Update: September 24, 2015; Available Online.
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