Flaxseed oil is an alternative source of heart healthy omega-3 fatty acids -- if you can't take fish oil. In addition to alpha-linolenic acid, flaxseed oil also contains lignans, weak estrogenic substances that may also have health benefits. Flaxseed oil pressed from the seed doesn't supply any lignans, unless the oil contains ground flaxseed. Filtering the oil removes any lignans. Some manufacturers do not filter their oil, to preserve the lignans.
Lignans in Flaxseed
Lignans have weak estrogenic properties that are beneficial to preventing cardiovascular disease. The effects of lignans on hormone-related breast, ovarian, endometrial and prostate cancer have been mixed in clinical studies. According to the Linus Pauling Institute, some studies have shown a reduction in cancers in people with the highest intake of lignans and others have shown no correlation.
Manufacturers that filter their flaxseed oil claim filtering removes the impurities that cause flaxseed oil to go rancid very quickly when exposed to heat, light or air. Spectrum, which manufactures flaxseed oil, adds clean ground flaxseed back into the oil after triple-filtering it to remove any impurities left after pressing. The company's website states that adding back clean ground flaxseed to the product gives it a fuller, nuttier taste in addition to preserving the nutrients in the plant.
Manufacturers that don't filter their flaxseed oil claim unfiltered flaxseed oil retains lignans in the small bits of ground flaxseed already in the oil. Lightly-filtered or unfiltered flaxseed oil retains lignans, claims chiropractor Marcus Ettinger on the California Academy of Health website. Ettinger offers a chemical analysis of the company's flaxseed oil, which shows it contains 1.5 percent lignans.
If you want the benefit of lignans from flaxseed, putting flaxseed on your breakfast cereal or in your granola is probably a better way to get those benefits than taking flaxseed oil -- which may contain little or no lignans. On the other hand, if you're concerned about the estrogenic effects of lignans but want to increase your omega-3 fatty acid intake without taking fish oil, take filtered flaxseed oil. Filtered flaxseed oil contains omega-3 fatty acids without the lignans.