Omega-3 fatty acids (also known as n-3 fatty acids) are polyunsaturated fatty acids that are essential nutrients for health. We need omega-3 fatty acids for numerous normal body functions, such as controlling blood clotting and building cell membranes in the brain, and since our bodies cannot make omega-3 fats, we must get them through food. Omega-3 fatty acids are also associated with many health benefits, including protection against heart disease and possibly stroke. In addition to these established benefits for cardiovascular disease, omega-3 fatty acids in high doses (e.g 6 to 10 capsules per day) are used to treat depression. New studies are identifying potential benefits for a wide range of conditions including cancer, inflammatory bowel disease, and other autoimmune diseases such as lupus and rheumatoid arthritis.

 There are several omega-3 fatty acids including alpha linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and others. The human body cannot synthesize omega-3 fatty acids but can convert alpha linolenic acid into the other omega-3 oils. Alpha linolenic acid is therefore a nutrient essential for life and is sometimes called vitamin F. Alpha linolenic acid is found in dark green leafy vegetables, flax seed oil and certain vegetable oils. ALA from flaxseed oil is converted in the body to EPA and then DHA at an efficiency of (5%-10%), and (2%-5%) respectively. Additional sources of ALA with a high omega-3 to omega-6 ratio include chia seed oil, perilla oil, sachia inchi, purslane, lingon berry, sea buckthorn and hemp seed oil. The human body may be able to convert more ALA to EPA and DHA if the ratio of omega-6 oils to omega-3 oils in the diet is near (1:1).

Sources of omega-3 fatty acids:

There are two major types of omega-3 fatty acids in our diets: One type is alpha-linolenic acid (ALA), which is found in some vegetable oils, such as soybean, rapeseed (canola), and flaxseed, and in walnuts. ALA is also found in some green vegetables, such as Brussels sprouts, kale, spinach, and salad greens. The other type, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), is found in fatty fish. The body partially converts ALA to EPA and DHA.
 The Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) are found primarily in oily cold-water fish such as tuna, salmon, and mackerel. Aside from fresh seaweed, a staple of many cultures, plant foods rarely contain EPA or DHA.

We do not know whether vegetable or fish omega-3 fatty acids are equally beneficial, although both seem to be beneficial. Unfortunately, most Americans do not get enough of either type. For good health, you should aim to get at least one rich source of omega-3 fatty acids in your diet every day. This could be through a serving of fatty fish (such as salmon), a tablespoon of canola or soybean oil in salad dressing or in cooking, or a handful of walnuts or ground flaxseed mixed into your morning oatmeal.

Omega-3 fatty acids from food or from supplements?

Certainly foods, since the plants and fish that contain omega-3 fats have other good nutrients, such as protein, vitamins and minerals. People who do not eat fish or other foods rich in omega-3 fatty acids should consider taking an omega-3 supplement of 500 mg per day; fish oil is used in supplements, but there are also vegetarian supplements that have ALA. Studies suggest that people who have already had a heart attack may benefit from higher doses of omega-3 supplements (basically, double the 500 mg), so if you do have heart disease, consult your healthcare provider about whether taking a higher dose of omega 3s makes sense for you

Health Benefits of Omega-3 Fatty Acids
Scientists made one of the first associations between omega-3 fatty acids and human health while studying the Inuit (Eskimo) people of Greenland in the 1970s. The Inuit consumed a very high fat diet but suffered far less from coronary heart disease, rheumatoid arthritis, diabetes mellitus and psoriasis than their European counterparts.

Omega-6 fatty acids (also known as n-6 fatty acids) are also polyunsaturated fatty acids that are essential nutrients, meaning that our bodies cannot make them and we must obtain them from food. They are abundant in the Western diet; common sources include safflower, corn, cottonseed, and soybean oils.

Omega-6 fatty acids lower LDL cholesterol (the "bad" cholesterol) and reduce inflammation, and they are protective against heart disease. So both omega-6 and omega-3 fatty acids are healthy. While there is a theory that omega-3 fatty acids are better for our health than omega-6 fatty acids, this is not supported by the latest evidence. Thus the omega-3 to omega-6 ratio is basically the "good divided by the good," so it is of no value in evaluating diet quality or predicting disease.

Essential means that these fatty acids must be consumed in the diet because humans cannot manufacture them from other dietary fats or nutrients, nor can they be stored in the body. They must be consumed daily to meet the body's requirements. They are macronutrients, required in amounts of grams per day (compared to micronutrients such as vitamins, which are required in milligrams per day). EFAs provide energy and are also components of nerve cells, cellular membranes, and are converted to hormone-like substances known as prostaglandins

The prevalence of heart disease in populations has been shown to be inversely proportional to the relative concentration of linoleic acid in the diet.
Both linoleic acid and its derivatives are obtained from plant and animal sources. Plant sources include unprocessed, unheated vegetable oils such as corn, sunflower seed, safflower, soy, sesame, and cottonseed oils. They are also found in plant materials such as evening primrose, black currant seeds, and gooseberry oils as well as in raw nuts and seeds, legumes, and leafy greens. Animal sources of omega-6 fatty acids (although in smaller amounts than in plants) are lean meats, organ meats, and breast milk.

Omega-3 fatty acids are a form of polyunsaturated fat important to overall health. As it pertains to heart disease, their main benefit is their ability to reduce the risk of heart rhythm problems in certain groups of people, thus reducing the risk of sudden cardiac death. In addition, omega-3s may help reduce triglycerides, lower blood pressure slightly and reduce blood clotting.

Mild Hypertension
Several studies have shown that eating 200 g of fatty fish or taking six to 10 capsules of fish oil daily will lower blood pressure (BP). Therefore, omega-3 can benefit patients with borderline high blood pressure. Omega-3 oils also effectively prevent hypertension in cardiac patients after transplantation.

Rheumatoid Arthritis
Because omega-3 fatty acids inhibit the action of inflammatory prostaglandins and leukotrienes, they can help control arthritis symptoms. Significant reduction in the number of tender joints and morning stiffness, as well as an increase in grip strength, have been observed in patients taking fish oil capsules. Studies have shown that patients taking fish oil supplements for rheumatoid arthritis require fewer pain medications; some are able to discontinue their nonsteroidal anti-inflammatory treatment. Despite the beneficial effects of omega-3 fats, regular antirheumatic drugs and nonsteroidal anti-inflammatory medications most likely still are required to control this chronic condition.

Diabetes
Early studies in laboratories indicate that omega-3 fatty acids in fish oils might prolong life in people with automimmune disorders like diabetes. A new study looked at substituting fish oil for corn oil in diets and found a tendency to suppress immune system dysfunction and prolong life. More studies are required to prove the diet's benefits in humans.

Asthma
Taking high dose omega-3 fatty acids can reduce inflammation of the airways and reduce asthma attacks. According to Donald Rudin, the author of the book titled Omega-3 Oils, allergic disorders such as asthma may be triggered by too much omega-6 and too little omega-3 fats in our body. Excessive amounts of omega-6 prostaglandins cause the body to produce antibodies that cause allergic reactions. Flaxseed or fish oil supplements can keep the omega-6 fats in check and decrease the inflammatory reactions associated with asthma.

Mental Disorders
According to some studies, many common mental disorders, such as depression, bipolar disorder (manic-depression), attention-deficit hyperactive disorder (ADHD), anxiety, or schizophrenia, may be triggered by deficiencies of omega-3 fatty acids and/or B vitamins. The rates of depression are low in countries that eat a lot of fish, while the rate of depression steadily rises in the United States as Americans eat increasingly more processed food and less fresh fish and vegetables containing omega-3 fats. In one study, 53% of bipolar patients on placebo (olive oil) became ill again within four months, while none of the patients who were given 9.6 g daily of omega-3 fatty acids (as fish oil) did. Supplements containing omega-3 fats also reportedly have been effective in children with ADHD precipitated by essential fatty acid deficiencies. Furthermore, a 25% decrease in schizophrenic symptoms was observed in patients receiving eicosapentanoic acid (EPA), one of the omega-3 fatty acids contained in fish oil.

Cancer Prevention
Omega-3 fatty acids inhibit tumor growth when injected into animals. Flaxseed oil, which is a plant source of omega-3 fatty acids, has been shown to prevent cancer of the breast, colon and prostate. The Mediterranean diet, which is heart healthy, also can decrease risk of getting cancer. Omega-3 fats, it seems, strengthen the immune systems and inhibit the inflammation and blood circulation of the tumors.

For those who don’t eat fish, a fish oil supplement or an algae supplement can provide omega-3 fatty acids. However, supplements aren’t cheap, and the amount of DHA and EPA in supplements varies widely. Except for people who have established heart disease, the evidence of heart disease prevention is stronger when one eats fish instead of taking supplements. Supplements can pose risks, too. Taking more than 3 grams of fish oil a day may increase the risk of bleeding, worsen heart rhythm problems in those who have arrhythmias or cause other side effects.
Consuming excessive amounts of fish-oil capsules can result in excessive bleeding, gastrointestinal distress, anemia, or strokes.

Both omega-3 and omega-6 fatty acids are essential, i.e. humans must consume them in their diet. Omega-3 and omega-6 compete for the same metabolic enzymes, thus the omega-6:omega-3 ratio will significantly influence the ratio of the ensuing eicosanoids (hormones), (e.g. prostaglandins, leukotrienes, thromboxanes etc.), and will alter the body's metabolic function. Metabolites of omega-6 are significantly more inflammatory (esp. arachidonic acid) than those of omega-3. This necessitates that omega-3 and omega-6 be consumed in a balanced proportion; the ideal ratio of omega-6:omega-3 being from 1:1 to 1.5:1. Studies suggest that the evolutionary human diet, rich in seafood, nuts and other sources of omega-3, may have provided such a ratio.

For most of the time humans have been on earth we have eaten foods containing omega-6's and omega-3's in a ratio of about 2:1. However, over the last 50 years in North America, the ratio has changed to from 2:1 to 10-20:1. Our diet now includes huge amounts of oils that are extracted from plants and used for cooking or in prepared foods. These oils (such as corn oil, safflower oil, cottonseed oil, peanut oil, soybean oil) are primarily omega-6s. We have decreased our intake of omega-3's, found primarily in whole grains, beans and other seeds, and seafood.

Typical Western diets provide ratios of between 15:1 and 50:1 - i.e., dramatically skewed toward omega-6. Here are the ratios of omega-6 to omega-3 fatty acids in some common oils: canola 2:1, soybean 7:1, olive 13:1, sunflower (no omega-3), flax 1:3 cottonseed (almost no omega-3), peanut (no omega-3), grapeseed oil (almost no omega-3) and beware of corn oils 46 to 1 ratio of omega-6s to omega-3s which is the extreme reverse of desireable ratios.

Eating too much omega-6 and too little omega-3 causes clots and constricts arteries to increase risk for heart attacks, increases swelling to worsen arthritis, and aggravates a skin disease called psoriasis. It may block a person's ability to respond to insulin, causing high insulin and blood sugar levels and obesity. It increases hormone levels of insulin like growth factor-1 that causes certain cancers.