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Fats and oils are essential to your health and many of your body's functions. The oils most important for brain, nerves and skin include the essential fatty acids, which are available in a variety of foods that include olive oil and avocados. Flaxseeds also provide an important essential fatty acid called omega-3, which is strongest in its oil. Evening primrose, which contains omega-6s, is not usually consumed as a food, but rather its oil is taken in supplement form.

Flaxseed Oil

Flaxseed oil comes from the seeds of the flax plant. This oil provides the important essential fatty acids linolenic acid and linoleic acid, according to Shawn M. Talbott in his book "The Health Professional's Guide to Dietary Supplements." Flaxseed oil contains about 57 percent linolenic acid, which is an omega-3 fatty acid, and about 17 percent linoleic acid, an omega-6 fatty acid. It is important to get a balance of omega-3 fatty acids to omega-6 fatty acids. However, the standard American diet contains too many omega-6 fatty acids and few omega-3 fatty acids. Omega-3 fatty acids help counter inflammation and increase brain function. Flaxseed oil also contains lignan, which is a phytochemical that may help cancer prevention.

Evening Primrose Oil

Evening primrose oil comes from the herb Oenothera biennis, which has bright yellow flowers that bloom in the evening, writes Talbott. The plant grows wild in dry, arid environments, and was first documented in Britain as being used for medicinal purposes. The main oil found in evening primrose oil is gamma-linolenic acid, another essential fatty acid, though it also contains linoleic acid. People have taken evening primrose oil include to relieve PMS, hot flashes and fibrocystic breasts.

How They Differ

The main difference between flaxseed oil and evening primrose oil is that the former contains the omega-3 linolenic acid, while the latter contains the omega-6 gamma-linolenic acid, or GLA for short. Omega-3s are linked to a lower risk of heart disease, cancer and arthritis, often through their anti-inflammatory properties, notes the University of Maryland Medical Center. Though GLA is an omega-6 fatty acid, which is sometimes connected to inflammation, it is one form of omega-6 that also can reduce inflammation, but is geared more toward skin, hair, reproductive and bone health. But the University of Maryland reports that more research favors the anti-inflammatory properties of the omega-3 fatty acids found in flaxseed oil more than that of GLA found in evening primrose oil.

What to Consider

Both flaxseed oil and evening primrose oil can be healthy parts of your diet, and you can consume both at the same time. Ingesting more flaxseed oil or flaxseeds than evening primrose oil can help balance your intake of omega-3 fatty acids and omega-6 fatty acids. Possible side effects related to flaxseed oil are diarrhea if you consume large amounts and the increased risk of bleeding if you suffer from a bleeding disorder. Nausea, upset stomach or diarrhea may occur if you take too much evening primrose oil.