Alpha-linolenic acid
Alpha-linolenic acid is a type of omega-3 fatty acid found in plants. It is found in flaxseed oil, and in canola, soy, perilla, and walnut oils.
Alpha-linolenic acid is similar to the omega-3 fatty acids that are in fish oil, called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Your body can change alpha-linolenic acid into EPA and DHA. However, some researchers suggest that less than 1% of ALA is converted to physiologically effective levels of EPA and DHA.
Omega-3 fatty acids -- especially EPA and DHA -- have been shown to reduce inflammation and may help prevent chronic diseases, such as heart disease and arthritis. They may also be important for brain health and development, as well as normal growth and development.
There is good evidence that fish oil containing EPA and DHA may help treat heart disease, prevent heart attack and stroke, and slightly reduce high blood pressure. Some researchers think the same may be true for alpha-linolenic acid. There is evidence that this may be so, but the evidence is not as strong as it is for fish oil.
Note: Alpha-linolenic acid is not the same as alpha-lipoic acid, an antioxidant that helps the body turn glucose into energy. This can be confusing because both alpha-linolenic acid and alpha-lipoic acid are sometimes abbreviated as ALA.
Heart Disease
One of the best ways to help prevent and treat heart disease is to eat a diet that is low in saturated and trans fats, and rich in monounsaturated and polyunsaturated fats, particularly omega-3 fatty acids. The Mediterranean Diet -- which emphasizes whole grains, root and green vegetables, daily servings of fruit, fish and poultry, olive and canola oils, and alpha-linolenic acid (found in flaxseed oil) -- is an example.
There's some evidence that eating foods high in alpha-linolenic acid may help, too. One study suggests that people who eat a diet high in alpha-linolenic acid are less likely to have a fatal heart attack. Another study found that women who ate high levels of alpha-linolenic acid (1.5 g per day) had a 46% lower risk of sudden cardiac death than those who ate the lowest amount of alpha-linolenic acid (about half a gram per day). Other population studies show that as people eat more foods with alpha-linolenic acid, heart disease deaths go down.
Researchers don't know whether taking alpha-linolenic acid supplements would have the same effect as eating foods rich in alpha-linolenic acid.
High Cholesterol
People who follow a Mediterranean-style diet tend to have higher HDL ("good") cholesterol levels. In addition, walnuts -- which are rich in alpha-linolenic acid -- have been shown to lower cholesterol and triglycerides in people with high cholesterol. However, studies with flaxseed oil, which is high in alpha-linolenic acid, have been mixed. Some studies found that alpha-linolenic acid may help lower cholesterol, while others found it didn't. Researchers don't know whether alpha-linolenic acid supplements would have the same benefits as foods with alpha-linolenic acid.
High Blood Pressure
Several studies suggest that diets or supplements rich in omega-3 fatty acids lower blood pressure slightly in people with hypertension. One population study found that eating a diet rich in alpha-linolenic acid reduced the risk of high blood pressure by about 30%.
Asthma
Preliminary research suggests that omega-3 fatty acid supplements (particularly perilla seed oil, which is rich in alpha-linolenic acid) may decrease inflammation and improve lung function in some people with asthma.
Other
Preliminary studies suggest that higher intakes of ALA is linked with improvements in dry eye that are comparable to those seen with corticosteroids. ALA is also linked with lower inflammatory markers among patients with chronic obstructive pulmonary disease.
Dietary Sources
Dietary sources of alpha-linolenic acid include:
- Flaxseeds and flaxseed oil
- Canola (rapeseed) oil
- Soybeans and soybean oil
- Pumpkin seeds and pumpkin seed oil
- Perilla seed oil
- Tofu
- Walnuts and walnut oil
Available Forms
Alpha-linolenic oil is available in cooking oils, including canola oil and soybean oil, and in medicinal oils, including flaxseed oil and dietary supplements containing flaxseed oil.
Sometimes the active ingredients in products with alpha-linolenic acid can be destroyed by exposing them to air, heat, or light. Generally, look for oil bottled in light-resistant containers, refrigerated, and marked with an expiration date. These oils are not healthful when used for cooking. Instead, use them in salad dressings and dips.
How to Take It
The recommended adequate intake of alpha-linolenic acid in the diet is listed below:
Pediatric
- Infants who are breastfed should get enough alpha-linolenic acid if the mother eats a healthy diet.
- Infant formula should contain alpha-linolenic acid.
- Children should not need supplements.
Adult
- 1 to 2 g per day
Amounts of alpha-linolenic acid in oils and foods vary. For instance:
- Flaxseed has about 2.2 g per tbsp
- Canola oil, 1.3 g per tbsp
- Flaxseed oil, 8.5 g per tbsp
- English walnuts, .7 g per tbsp
Precautions
Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable health care provider.
Because of the risk of increased bleeding, you should stop taking omega-3 fatty acid supplements before surgery. Tell your surgeon in advance that you have been taking the supplements.
People with diabetes or schizophrenia may not be able to convert alpha-linolenic acid to EPA and DHA, the forms the body uses more easily. They should get omega-3 fatty acids from foods rich in EPA and DHA.
Although studies have found that regularly eating fish -- which includes omega-3 fatty acids -- may reduce the risk of macular degeneration, one study of two large groups of men and women found that diets rich in alpha-linolenic acid may increase the risk of macular degeneration. Until researchers know more, people with macular degeneration may want to get omega-3 fatty acids from sources of EPA and DHA, rather than alpha-linolenic acid.
Similarly, studies have found that fish and fish oil may protect against prostate cancer. But a few studies suggest that alpha-linolenic acid is associated with an increased risk for prostate cancer. The evidence isn't clear, however. Other studies have found that flaxseed -- high in alpha-linolenic acid -- may benefit men at risk for prostate cancer. Until researchers know more, men with prostate cancer, or who have a father or brother diagnosed with prostate cancer, should ask their doctor before taking alpha-linolenic acid.
Most people, but not all, will benefit more from taking supplemental EPA and DHA, but talk to your doctor to determine the source and dose that is best for you.
Possible Interactions
If you are being treated with any of the following medications, you should not use alpha-linolenic acid without talking to your doctor first.
Blood-thinning medications
Omega-3 fatty acids may increase the effects of blood-thinning medications and raise the risk of bleeding. These medications include warfarin (Coumadin), clopidogrel (Plavix), and aspirin, among others.
Cholesterol-lowering medications
Getting more omega-3 fatty acids in your diet may help a group of cholesterol-lowering medications known as statins work better. Statins include:
- Atorvastatin (Lipitor)
- Rosuvastatin (Crestor)
- Fluvastatin (Lescol)
- Lovastatin (Mevacor)
- Simvastatin (Zocor)
- Pravastatin (Pravachol)
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