Used as a rich source of omega-3 fatty acids, fish oil and fish oil supplements don't contain lignans. In fact, another major dietary source of omega-3s -- flaxseed -- contains lignans. If you want the health benefits of omega-3s plus the effects of lignans, take flaxseed and not fish oil. Consult your doctor before taking fish oil or flaxseed to discuss the potential health dangers and proper dosage.
Identification
Omega-3 fatty acids have many sources, both in supplement form and in your diet. Fish such as tuna, salmon, herring and mackerel are excellent sources of omega-3 fatty acids, but you can also get omega-3s from flaxseed and certain other plant sources, according to the University of Pittsburgh Medical Center. Lignans, however, are found mostly in flaxseeds, along with certain other plant-based sources like sesame seeds, cranberries, whole grains, pumpkin seeds and green or black tea.
Function
Omega-3s like those found in fish oil and flaxseed are essential fatty acids that appear to reduce the risk of heart attack, stroke, heart disease and other chronic illnesses, according to the University of Pittsburgh Medical Center. Additionally, omega-3 fatty acids have triglyceride-lowering and cholesterol-reducing effects, as well as blood-thinning and heartbeat-regulating actions. Fish oil may also offer anti-inflammatory actions, as well as certain neuroprotective effects that could benefit people with psychiatric conditions.
Considerations
The lignans found in the omega-3-rich flaxseed are considered phytoestrogens, plant-based substances that offer estrogen-like effects, explains the Memorial Sloan-Kettering Cancer Center. Lignans appear to influence estrogen levels in the body, affecting menstrual cycles, hormone-sensitive cancers like prostate and breast cancer, blood-glucose levels, cholesterol levels, and menopausal symptoms. Flaxseed also contains large amounts of fiber that offers laxative effects. Despite the high lignan content of flaxseeds, flaxseed oil contains little, if any, lignans, notes the University of Michigan Health System.
Uses
Because they both contain omega-3 fatty acids, fish oil and flaxseed have similar health benefits. But the presence of lignans lends special medicinal uses for flaxseed that aren't provided by fish oil. For example, lignans could help prevent certain types of cancer, as well as help treat high cholesterol, menopausal symptoms and kidney disease, according to the University of Pittsburgh Medical Center. Flaxseed is also sometimes recommended for treating constipation, lupus, stress and ulcerative colitis, says the University of Michigan Health System. Flaxseed may treat the symptoms of premenstrual syndrome as well, notes the Memorial Sloan-Kettering Cancer Center. On the other hand, fish oil might help prevent heart disease and support surgery and HIV treatment, as well as treat a wide range of cardiovascular, psychological and inflammatory conditions.
Warning
Fish oil can sometimes increase your LDL or "bad cholesterol" levels and decrease your HDL or "good cholesterol levels," says the University of Pittsburgh Medical Center. Fish oil could also alter your blood-sugar levels and increase the effects of blood-thinning medications like Coumadin. Flaxseed can cause side effects like diarrhea, gas and constipation, as well as allergic reactions in some people, cautions the Memorial Sloan-Kettering Cancer Center. You shouldn't take flaxseed during pregnancy because the lignans could cause developmental defects in the infant's reproductive system, warns the University of Michigan Health System. Flaxseed could also be dangerous for people with bowel obstructions because of its high fiber content.
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