Alpha-linolenic acid, or ALA, is an essential fatty acid, which means that it is essential to human health but cannot be manufactured by the body. For this reason, ALA must be obtained from food. ALA, as well as the fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), belongs to a group of fatty acids called omega-3 fatty acids. EPA and DHA are found primarily in fish while ALA is highly concentrated in certain plant oils such as flaxseed oil and to a lesser extent, canola, soy, perilla, and walnut oils. ALA is also found in wild plants such as purslane. Once ingested, the body converts ALA to EPA and DHA, the two types of omega-3 fatty acids more readily used by the body.

It is important to maintain an appropriate balance of omega-3 and omega-6 (another essential fatty acid) in the diet as these two substances work together to promote health. These essential fats are both examples of polyunsaturated fatty acids, or PUFAs. Omega-3 fatty acids help reduce inflammation and most omega-6 fatty acids tend to promote inflammation. An inappropriate balance of these essential fatty acids contributes to the development of disease while a proper balance helps maintain and even improve health. A healthy diet should consist of roughly two to four times more omega-6 fatty acids than omega-3 fatty acids. The typical American diet tends to contain 11 to 30 times more omega-6 fatty acids than omega-3 fatty acids and many researchers believe this imbalance is a significant factor in the rising rate of inflammatory disorders in the United States.

Some signs of alpha-linolenic acid deficiency include loss of motor coordination, tingling in the extremities, vision impairment, and behavioral changes.

Studies suggest that ALA and other omega-3 fatty acids may be helpful in treating a variety of conditions. The evidence is strongest for heart disease and problems that contribute to heart disease, but the range of possible uses for ALA include: heart disease, high cholesterol, high blood pressure, acne, arthritis, asthma, eating disorders, breast cancer, burns, inflammatory bowel disease (IBD), depression, menstrual pain. Although further research is needed, preliminary evidence suggests that omega-3 fatty acids may also prove helpful in protecting against certain infections and in treating a variety of conditions including ulcers, migraine headaches, attention deficit/hyperactivity disorder (ADHD), preterm labor, emphysema, psoriasis, glaucoma, Lyme disease, and panic attacks.

People with either diabetes or schizophrenia may lack the ability to convert ALA to EPA and DHA, the forms more readily used in the body. Therefore, people with these conditions should obtain their omega-3 fatty acids from dietary sources rich in EPA and DHA.

Although studies have found that regular consumption of fish (which includes the omega-3 fatty acids EPA and DHA) may reduce the risk of macular degeneration, a recent study including two large groups of men and women found that diets rich in ALA may substantially increase the risk of this disease. More research is needed in this area. Until this information becomes available, it is best for people with macular degeneration to obtain omega-3 fatty acids from sources of EPA and DHA, rather than ALA.

Similar to macular degeneration, fish and fish oil may protect against prostate cancer, but ALA may be associated with increased risk of prostate cancer in men. More research in this area is needed.