Basics & Facts
Omega-3 fatty acids are a group of polyunsaturated fatty acids that are essential for cell growth, muscle function, digestion, blood clotting and brain development among other bodily functions. Omega-3s cannot be made by the human body, so they need to come from foods or supplements. There are three main types of omega-3s:
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
A small amount of ALA is converted into EPA and DHA in the body.
Sources of Omega-3
The main foods sources of ALA in the American diet are canola and soybean oils. Other food sources with a significant amount of ALA are:
- Flaxseeds and flaxseed oil
- Firm tofu
- Mustard oil
EPA and DHA come from mostly fatty fish including:
- Rainbow trout
Shellfish, including oysters and Dungeness crabs, contain omega-3s in smaller amounts.
Toxins are a concern to some people who eat large amounts of fish, particularly mercury and other environmental contaminants. For most people, the level of contaminants consumed is not high enough to pose problems, but it can be harmful to developing fetuses and infants. Pregnant and breastfeeding women are therefore encouraged to limit how much they eat of certain kinds of fish, such as tuna and swordfish, which tend to have higher levels of toxins.
(Also read: 8 Main Foods To Avoid When Pregnant.)
Omega-3 supplements have not been shown to contain toxins, however, and have become very popular on store shelves in a variety of forms. ALA comes in mainly flaxseed oil preparations (also known as linseed oil) and DHA and EPA are available in fish oil supplements or those labeled as omega-3s. A vegetarian source of DHA is algae oil. Per the label, the content of any of these omega-3s can vary from bottle to bottle and because dietary supplements are not FDA-regulated, the purity and amounts of each ingredient cannot be assured or verified.
Years of research have shown that a diet high in omega-3 fatty acids can have a number of health benefits. Studies of supplements, however, have not been as conclusive. A summary of major findings is as follows:
Heart disease: The strongest evidence of omega-3’s health benefits concerns a significantly reduced risk of heart disease among people who have a high intake from food. Because of this, the American Heart Association recommends that people (whether or not they have heart disease) consume omega-3 rich fish two times a week at a minimum. People with coronary artery disease are encouraged to have 1 gram/day of EPA and DHA even though the evidence of the efficacy of supplements is not as strong as that of food sources.
Rheumatoid arthritis: In many studies, people with this painful joint disease reported less stiffness, swelling and pain when they took supplements containing omega 3s from fish oil sources.
Infant development: Enough evidence exists to show that in pregnant and breastfeeding women, having adequate DHA in particular is linked with better brain and eye health in developing fetuses and infants. The U.S. Department of Health and Human Services’ Dietary Guidelines for Americans recommends that pregnant and breastfeeding women eat between eight and 12 ounces of seafood each week (avoiding fish high in mercury).
Other conditions are actively being investigated because of promising preliminary findings:
- Mental disorders such as bipolar disease, schizophrenia and depression
- Alzheimer’s disease and other dementia-related illnesses
- Age-related macular degeneration
- Dry eye syndrome
So far, most research indicates that the omega-3s found in fatty fish (DHA and EPA) seem to confer the most health benefits, rather than ALA.
It is known for sure that babies who get insufficient amounts of omega-3s from their mothers during the fetal stage are at an increased risk of eye and nervous system problems. With regard to adults, a major research study sponsored in part by the Centers for Disease Control and Prevention found that having a low level of omega-3 fatty acids is one of the main dietary factors affecting mortality in the U.S.—mainly due to ill effects on the cardiovascular system. Another study showed that dietary omega-3 deficiency was associated with metabolic and cognitive problems. According to the University of Maryland Medical Center, the following symptoms are associated with omega-3 deficiency:
- Memory problems
- Dry skin
- Heart problems
- Low mood
- Poor circulation
Aside from not eating enough omega-3 containing foods or supplements, deficiencies can occur in people with health conditions that interfere with fat absorption or metabolism.
Omega-3 supplements, even when taken in normal amounts, can produce some minor side effects such as belching, upset stomach and diarrhea. According to the National Institutes of Health, it is unclear if people with allergies to fish or shellfish can safely take supplements. People who take fish liver oil (such as cod liver oil) should use caution because these preparations contain vitamins A and D, both of which can be toxic if taken in high doses.
Flaxseed oil, a common ALA supplement, can cause loose stools if taken in high amounts. In some instances, severe allergic reactions have occurred in some people.
DHA and EPA in particular can interfere with medications that affect blood clotting. Long bleeding times and strokes have been reported in people taking high amounts (about 6.5 grams/day). In some studies, omega-3s have been associated with suppressed immunity so caution is advised in people who have compromised immunity for any reason. Regardless, the Food and Drug Administration has ruled that up to 3 grams/day of EPA and DHA is generally safe for most people.
The Recommended Daily Allowance of each of the major omega-3s has not been determined by the Food and Nutrition Board because not enough scientific data exists to say for sure how much each age group needs. Instead, an Adequate Intake (AI) is reported, which is an estimate of what is needed for healthy people in each group.
- Infants 0 to 12 months: 0.5 grams (gms)/day of ALA, EPA and DHA
- Children 1 to 3 years: 0.7 gm ALA
- Children 4 to 8 years: 0.8 ALA
- Male children 9 to 13 years: 1.2 ALA
- Female children 9 to 13 years: 1.0 ALA
- Male teens 14 and up: 1.6 ALA
- Female teens 14 and up 1.1 ALA
Pregnant and breastfeeding women may have different requirements and should discuss omega 3s with their doctor.
Regardless of how you get omega 3s (whether it’s through food sources or supplements) it’s best to spread out the sources throughout the day so the body can use these nutrients best. As with other supplements, a doctor’s advice is always a prudent move.