Omega-3 fatty acids

Taken from Univ. of Maryland Medical Center reference guide:
 

Overview

Omega-3 fatty acids are considered essential fatty acids. They are necessary for human health, but the body can't make them. You have to get them through food. Omega-3 fatty acids are found in fish, such as salmon, tuna, and halibut, other seafoods including algae and krill, some plants, and nut oils. Also known as polyunsaturated fatty acids (PUFAs), omega-3 fatty acids play a crucial role in brain function, as well as normal growth and development. They have also become popular because they may reduce the risk of heart disease. The American Heart Association (AHA) recommends eating fish (particularly fatty fish such as mackerel, lake trout, herring, sardines, albacore tuna, and salmon) at least 2 times a week.

Research shows that omega-3 fatty acids reduce inflammation and may help lower risk of chronic diseases such as heart disease, cancer, and arthritis. Omega-3 fatty acids are highly concentrated in the brain and appear to be important for cognitive (brain memory and performance) and behavioral function. In fact, infants who do not get enough omega-3 fatty acids from their mothers during pregnancy are at risk for developing vision and nerve problems. Symptoms of omega-3 fatty acid deficiency include fatigue, poor memory, dry skin, heart problems, mood swings or depression, and poor circulation.

It is important to have the proper ratio of omega-3 and omega-6 (another essential fatty acid) in the diet. Omega-3 fatty acids help reduce inflammation, and most omega-6 fatty acids tend to promote inflammation. The typical American diet contains 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids, which many nutritionally-oriented physicians consider to be way too high on the omega-6 side. Indeed, studies suggest that higher dietary omega-6 to omega-3 ratios appear to be associated with worsening inflammation over time and a higher risk of death among hemodialysis patients.

The Mediterranean diet, on the other hand, has a healthier balance between omega-3 and omega-6 fatty acids. Many studies have shown that people who follow this diet are less likely to develop heart disease. The Mediterranean diet emphasizes foods that are rich in omega-3 fatty acids, including whole grains, fresh fruits and vegetables, fish, olive oil, garlic, and moderate wine consumption.

Uses

High cholesterol

People who follow a Mediterranean-style diet tend to have higher HDL (good) cholesterol levels, which help promote heart health. Inuit Eskimos, who get high amounts of omega-3 fatty acids from eating fatty fish, also tend to have increased HDL cholesterol and decreased triglycerides (fats in the blood). Several studies show that fish oil supplements reduce triglyceride levels. Walnuts, which are rich in alpha linolenic acid or ALA, which can convert to omega-3s in the body, have been reported to lower total cholesterol and triglycerides in people with high cholesterol levels.

High blood pressure

Several clinical studies suggest that diets rich in omega-3 fatty acids lower blood pressure in people with hypertension. An analysis of 17 clinical studies using fish oil supplements found that taking 3 or more grams of fish oil daily may reduce blood pressure in people with untreated hypertension. Doses this high, however, should only be taken under the direction of a physician.

Heart disease

The role of omega-3 fatty acids in cardiovascular disease is well established. One of the best ways to help prevent heart disease is to eat a diet low in saturated fat, and to eat foods that are rich in monounsaturated and polyunsaturated fats (including omega-3 fatty acids). Clinical evidence suggests that EPA and DHA (eicosapentaenoic acid and docosahexaenoic acid), the two omega-3 fatty acids found in fish oil help reduce risk factors for heart disease, including high cholesterol and high blood pressure. Fish oil has been shown to lower levels of triglycerides (fats in the blood), and to lower the risk of death, heart attack, stroke, and abnormal heart rhythms in people who have already had a heart attack. Fish oil also appears to help prevent and treat atherosclerosis (hardening of the arteries) by slowing the development of plaque and blood clots, which can clog arteries.

Large population studies suggest that getting omega-3 fatty acids in the diet, primarily from fish, helps protect against stroke caused by plaque build up and blood clots in the arteries that lead to the brain. Eating at least 2 servings of fish per week can reduce the risk of stroke by as much as 50%. However, high doses of fish oil and omega-3 fatty acids may increase the risk of bleeding. People who eat more than 3 grams of omega-3 fatty acids per day (equivalent to 3 servings of fish per day) may have higher risk for hemorrhagic stroke, a potentially fatal type of stroke in which an artery in the brain leaks or ruptures. Studies also suggest that omega-3 fatty acids may have antioxidant properties that improve endothelial function and may contribute to heart benefits.

Diabetes

People with diabetes often have high triglyceride and low HDL levels. Omega-3 fatty acids from fish oil can help lower triglycerides and apoproteins (markers of diabetes), and raise HDL. So eating foods or taking fish oil supplements may help people with diabetes. Another type of omega-3 fatty acid, ALA (from flaxseed, for example) may not have the same benefit as fish oil. Some people with diabetes can't efficiently convert ALA to a form of omega-3 fatty acids that the body can use. Also, some people with type 2 diabetes may have slight increases in fasting blood sugar when taking fish oil. So talk to your doctor to see if fish oil is right for you.

Rheumatoid arthritis

Most clinical studies examining omega-3 fatty acid supplements for arthritis have focused on rheumatoid arthritis (RA), an autoimmune disease that causes inflammation in the joints. Several small studies have found that fish oil helps reduce symptoms of RA, including joint pain and morning stiffness. One study suggests that people with RA who take fish oil may be able to lower their dose of non-steroidal anti-inflammatory drugs (NSAIDs). However, unlike prescription medications, fish oil does not appear to slow progression of RA, only to treat the symptoms. Joint damage still occurs.

Laboratory studies suggest that diets rich in omega-3 fatty acids (and low in the inflammatory omega-6 fatty acids) may help people with osteoarthritis. More study is needed. New Zealand green lipped mussel (Perna canaliculus), another potential source of omega-3 fatty acids, has been reported to reduce joint stiffness and pain, increase grip strength, and improve walking pace in a small group of people with osteoarthritis. For some people, symptoms worsened before they improved.

An analysis of 17 randomized, controlled clinical trials looked at the pain-relieving effects of omega-3 fatty acid supplements in people with RA or joint pain caused by inflammatory bowel disease (IBS) and painful menstruation (dysmenorrhea). The results suggest that omega-3 fatty acids, along with conventional therapies, such as NSAIDs, may help relieve joint pain associated with these conditions.

Systemic lupus erythematosus (SLE)

Several small studies suggest that EPA and fish oil may help reduce symptoms of lupus, an autoimmune condition characterized by fatigue and joint pain. However, two small studies found that fish oil had no effect on lupus nephritis (kidney disease caused by lupus, a frequent complication of the disease).

Osteoporosis

Some studies suggest that omega-3 fatty acids may help increase levels of calcium in the body and improve bone strength, although not all results were positive. Some studies also suggest that people who do not get enough of some essential fatty acids (particularly EPA and gamma-linolenic acid (GLA), an omega-6 fatty acid) are more likely to have bone loss than those with normal levels of these fatty acids. In a study of women over 65 with osteoporosis, those who took EPA and GLA supplements had less bone loss over 3 years than those who took placebo. Many of these women also experienced an increase in bone density.

Depression

Research is not clear on whether taking omega-3 fatty acids can help relieve depression symptoms. Several studies show that people who took omega-3 fatty acids in addition to prescription antidepressants had a greater improvement in symptoms than those who took antidepressants alone. Other studies suggest that omega-3 fatty acid intake helps protect against postpartum depression, among other benefits. However, some studies found no benefit.

Studies are also mixed on whether omega-3 fatty acids alone have any effect on depression. Depression is a serious illness and you should not try to treat it on your own. See a doctor for help.

Bipolar disorder

In a clinical study of 30 people with bipolar disorder, those who took fish oil in addition to standard prescription treatments for bipolar disorder for 4 months experienced fewer mood swings and relapses than those who received placebo. But another 4-month long clinical study treating people with bipolar depression and rapid cycling bipolar disorder did not show that EPA helped reduce symptoms.

Schizophrenia

Preliminary clinical evidence suggests that people with schizophrenia take omega-3 fatty acids, they experience an improvement in symptoms. However, more recent research found that EPA supplements were no better than placebo in improving symptoms of this condition.

Attention deficit/hyperactivity disorder (ADHD)

Children with ADHD may have low levels of certain essential fatty acids (including EPA and DHA). In a clinical study of nearly 100 boys, those with lower levels of omega-3 fatty acids had more learning and behavioral problems (such as temper tantrums and sleep disturbances) than boys with normal omega-3 fatty acid levels.

However, studies examining whether omega-3 fatty acids help improve symptoms of ADHD have produced mixed results. A few studies show that omega-3 fatty acids help improve behavioral symptoms. But most of these studies were not well designed. One study that looked at DHA in addition to stimulant therapy (standard therapy for ADHD) found no effect. More research is needed. In the meantime, eating foods that are high in omega-3 fatty acids is a reasonable approach for someone with ADHD.

Cognitive decline

Several studies show that reduced intake of omega-3 fatty acids is associated with increased risk of age-related cognitive decline or dementia, including Alzheimer disease. Scientists believe the omega-3 fatty acid DHA is protective against Alzheimer disease and dementia.

Skin disorders

In one clinical study, 13 people with sun sensitivity known as photo dermatitis showed less sensitivity to UV rays after taking fish oil supplements. However, topical sunscreens are much better at protecting the skin from damaging effects of the sun than omega-3 fatty acids. In another study of 40 people with psoriasis, those who took EPA with their prescription medications did better than those treated with the medications alone. However, a larger study of people with psoriasis found no benefit from fish oil.

Inflammatory bowel disease (IBD)

Results are mixed as to whether omega-3 fatty acids can help reduce symptoms of Crohn disease and ulcerative colitis, two types of IBD. Some studies suggest that omega-3 fatty acids may help when added to medication, such as sulfasalazine (a standard medication for IBD). Others show no effect. More studies are needed. Fish oil supplements can cause side effects that are similar to symptoms of IBD (such as flatulence, belching, bloating, and diarrhea).

Asthma

Studies examining omega-3 fatty acids for asthma are mixed. In one small, well-designed clinical study of 29 children with asthma, those who took fish oil supplements rich in EPA and DHA for 10 months experienced fewer symptoms compared to children who took placebo. However, most studies have shown no effect.

Macular degeneration

A questionnaire given to more than 3,000 people over the age of 49 found that those who ate more fish were less likely to have macular degeneration, a serious age-related eye condition that can progress to blindness, than those who ate less fish. Similarly, a clinical study comparing 350 people with macular degeneration to 500 without the eye disease found that those with a healthy dietary balance of omega-3 and omega-6 fatty acids, as well as more fish in their diets, were less likely to have macular degeneration.

Menstrual pain

In one study of 42 women, participants had less menstrual pain when they took fish oil supplements than when they took placebo.

Colon cancer

Eating foods rich in omega-3 fatty acids seems to reduce the risk of colorectal cancer. For example, Eskimos, who tend to have a high fat diet, but eat significant amounts of fish rich in omega-3 fatty acids, have a low rate of colorectal cancer. Animal studies and laboratory studies have found that omega-3 fatty acids prevent worsening of colon cancer. Preliminary studies suggest that taking fish oil daily may help slow the progression of colon cancer in people with early stages of the disease. If you have colorectal cancer, ask your doctor before taking any supplements.

Breast cancer

Although not all experts agree, women who eat foods rich in omega-3 fatty acids over many years may be less likely to develop breast cancer. More research is needed to understand the effect that omega-3 fatty acids may have on the prevention of breast cancer.

Prostate cancer

Population-based studies of groups of men suggest that a low-fat diet including omega-3 fatty acids (from fish or fish oil) may help prevent the development of prostate cancer.

Dietary Sources

Fish, plants, and nut oils are the primary dietary sources of omega-3 fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in cold-water fish such as salmon, mackerel, halibut, sardines, tuna, and herring. ALA is found in flax seeds, flaxseed oil, canola (rapeseed) oil, soybeans, soybean oil, pumpkin seeds, pumpkin seed oil, purslane, perilla seed oil, walnuts, and walnut oil. The health effects of omega-3 fatty acids come mostly from EPA and DHA. ALA from flax and other vegetarian sources needs to be converted in the body to EPA and DHA. However, many people's bodies do not make these conversions very effectively. This remains an ongoing debate in the nutrition community; fish and sea vegetable sources of EPA and DHA versus vegetarian sources of ALA. Other sources of omega-3 fatty acids include sea life such as krill and algae.

Available Forms

Both EPA and DHA can be taken in the form of fish oil capsules. Keep flax seed, flax seed oil, fish, and krill oils refrigerated. Whole flax seeds must be ground within 24 hours of use, so the ingredients stay active. Flax seeds are also available in ground form in a special mylar package so the components in the flax seeds stay active.

Be sure to buy omega-3 fatty acid supplements made by established companies who certify that their products are free of heavy metals, such as mercury, lead, and cadmium.

How to Take It

Dosing for fish oil supplements should be based on the amount of EPA and DHA, not on the total amount of fish oil. Supplements vary in the amounts and ratios of EPA and DHA. A common amount of omega-3 fatty acids in fish oil capsules is 0.18 grams (180 mg) of EPA and 0.12 grams (120 mg) of DHA. Different types of fish contain variable amounts of omega-3 fatty acids, and different types of nuts or oil contain variable amounts of ALA. Fish oils contain approximately 9 calories per gram of oil.

Children (18 years and younger)

There is no established dose for children. Omega-3 fatty acids are used in some infant formulas. Fish oil capsules should not be used in children except under the direction of a health care provider. Children should avoid eating fish that may be high in mercury, such as shark, swordfish, king mackerel, and tilefish. (See Precautions section.)

Adults

DO NOT take more than 3 grams daily of omega-3 fatty acids from capsules without the supervision of a health care provider, due to an increased risk of bleeding.

For healthy adults with no history of heart disease: The AHA recommends eating fish at least 2 times per week.
For adults with coronary heart disease: The AHA recommends an omega-3 fatty acid supplement (as fish oils), 1 gram daily of EPA and DHA. It may take 2 to 3 weeks before you experience benefits from fish oil supplements. You should take supplements under the direction of a physician.
For adults with high cholesterol levels: The AHA recommends an omega-3 fatty acid supplement (as fish oils), 2 to 4 grams daily of EPA and DHA. It may take 2 to 3 weeks to experience benefits from fish oil supplements. Supplements should be taken under the direction of a physician.
Precautions

Because of the potential for side effects and interactions with medications, you should only take dietary supplements only under the supervision of a knowledgeable health care provider.

Omega-3 fatty acids should be used cautiously by people who bruise easily, have a bleeding disorder, or take blood-thinning medications, including warfarin (Coumadin), clopidogrel (Plavix), or aspirin. High doses of omega-3 fatty acids may increase the risk of bleeding, even in people without a history of bleeding disorders, and even in those who are not taking other medications.

Fish oil can cause gas, bloating, belching, and diarrhea. Time release preparations may reduce these side effects, however.

People with either diabetes or schizophrenia may lack the ability to convert alpha-linolenic acid (ALA) to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the forms more readily absorbed by the body. People with these conditions should be sure to get enough EPA and DHA from their diets. Also, people with type 2 diabetes may experience increases in fasting blood sugar levels while taking fish oil supplements. If you have type 2 diabetes, use fish oil supplements only under the supervision of a health care provider.

Although studies suggest that eating fish (which includes the omega-3 fatty acids EPA and DHA) may reduce the risk of macular degeneration, a more recent study including 2 large groups of men and women found that diets rich in ALA may increase the risk of this disease. Until more information becomes available, people with macular degeneration should get omega-3 fatty acids from sources of EPA and DHA, rather than ALA.

Fish and fish oil may protect against prostate cancer, but some suggest that ALA may be associated with increased risk of prostate cancer in men. More research in this area is needed.

Some fish may contain potentially harmful contaminants, such as heavy metals (including mercury), dioxins, and polychlorinated biphenyls (PCBs). For sport caught fish, the U.S. Environmental Protection Agency (EPA) recommends that pregnant or nursing women eat no more than a single 6-ounce meal per week, and young children less than 2 ounces per week. For farm raised, imported, or marine fish, the U.S. Food and Drug Administration (FDA) recommends that pregnant or nursing women and young children avoid eating types with higher levels of mercury (such as mackerel, shark, swordfish, or tilefish), and eat up to 12 ounces per week of other fish types.

Buy fish oil from a reputable source that tests for mercury and pesticide residues in its products.

 

Possible Interactions

If you are currently being treated with any of the following medications, you should not use omega-3 fatty acid supplements, including EPA, DHA, and ALA, without first talking to your health care provider.

Blood-thinning medications: Omega-3 fatty acids may increase the effects of blood-thinning medications, including aspirin, warfarin (Coumadin), and clopedigrel (Plavix). Taking aspirin and omega-3 fatty acids may be helpful in some circumstances (such as in heart disease), but you should only take them together under the supervision of a provider.

Diabetes medications: Taking omega-3 fatty acid supplements may increase fasting blood sugar levels. Talk to your doctor if you are taking medications to lower blood sugar, such as glipizide (Glucotrol and Glucotrol XL), glyburide (Micronase or Diabeta), glucophage (Metformin), or insulin. Your doctor may need to increase your medication dose. These drugs include:

Glipizide (Glucotrol and Glucotrol XL)
Glyburide (Micronase or Diabeta)
Metformin (Glucophage)
Insulin

Cyclosporine: Cyclosporine is a medication given to people with organ transplants. Taking omega-3 fatty acids during cyclosporine (Sandimmune) therapy may reduce toxic side effects, such as high blood pressure and kidney damage, associated with this medication.

Etretinate and topical steroids: Adding omega-3 fatty acids (specifically EPA) to the drug therapy etretinate (Tegison) and topical corticosteroids may improve symptoms of psoriasis.

Cholesterol-lowering medications: Following dietary guidelines, including increasing the amount of omega-3 fatty acids in your diet and reducing the omega-6 to omega-3 ratio, may help a group of cholesterol-lowering medications called statins work more effectively. These medications include:

• Atorvastatin (Liptor)
• Lovastatin (Mevacor)
• Simvastatin (Zocor)

Nonsteroidal anti-inflammatory drugs (NSAIDs): In an animal study, treatment with omega-3 fatty acids reduced the risk of ulcers from NSAIDs. NSAIDs include ibuprofen (Motrin or Advil) and naproxen (Aleve or Naprosyn). More research is needed to see whether omega-3 fatty acids would have the same effects in people.