POLYUNSATURATED FATS

Health benefits and concerns

Atherosclerosis

People who eat diets high in alpha-linolenic acid (ALA), which is found in canola and flaxseed oil, have higher blood levels of omega-3 fatty acids than those consuming lower amounts; this may confer some protection against atherosclerosis. In 1994, researchers conducted a study in people with a history of heart disease, using what they called the “Mediterranean” diet. The diet was significantly different from what people from Mediterranean countries actually eat, in that it contained little olive oil. Instead, the diet included a special margarine high in ALA. Those people assigned to the Mediterranean diet had a remarkable 70% reduced risk of dying from heart disease compared with the control group during the first 27 months. Similar results were also confirmed after almost 4 years. The diet was high in beans, peas, fish, fruit, vegetables, bread, and cereals, and low in meat, dairy fat, and eggs. Although the authors believe that the high ALA content of the diet was partly responsible for the surprising outcome, other aspects of the diet may have been partly or even totally responsible for decreased death rates. Therefore, the success of the Mediterranean diet does not prove that ALA protects against heart disease.

Constipation

Some doctors recommend 15ml per day of flaxseed oil to help relieve constipation, though there is little scientific research to support this approach.

Cystic fibrosis (CF)

The impaired digestion of fats in CF often leads to a deficiency of essential fatty acids (EFAs). This deficiency may in turn lead to a lowered immune function, which makes children with CF more susceptible to respiratory infection. EFA deficiency can be reversed by supplementation with corn oil (1 gram per 2.2 pounds [1 kg] body weight per day), safflower oil (1 gram per 2.2 pounds [1 kg] body weight per day), linoleic acid (7.7 grams per day), and eicosapentaenoic acid (EPA from fish oil) (2.7 grams per day). EPA supplementation was particularly effective. In a double-blind trial, six weeks of supplementation with 2.7 grams per day of EPA led to reduction in sputum and improvement in lung function in children with chronic respiratory infection due to CF.

High cholesterol

Doctors and researchers are interested in alpha-linolenic acid (ALA), the special omega-3 fatty acid found in large amounts in flaxseeds and flaxseed oil. ALA is a precursor to the fatty acid EPA (also found in fish oil) which protects against heart disease. To a limited extent, ALA converts to EPA within the body. However, unlike EPA, ALA does not lower triglyceride levels (a risk factor for heart disease).

High triglycerides

Double-blind trials have consistently demonstrated that fish oil containing EPA and DHA (docosahexaenoic acid) lowers triglyceride levels. The amount of fish oil used in much of the research provided 3 grams per day of omega-3 fatty acids. To calculate how much omega-3 fatty acid is contained in a fish-oil supplement, add together the amounts of EPA and DHA. For example, a typical 1,000-mg capsule of fish oil provides 180mg of EPA and 120mg of DHA (total omega-3 fatty acids=300 mg). Ten of these capsules would contain 3,000mg of omega-3 fatty acids. Other sources of omega-3 fatty acids, such as flaxseed oil, do not lower triglycerides. While flaxseed oil has other benefits, it should not be used for the purpose of reducing triglycerides.

Benign prostatic hyperplasia (BPH)

Despite the lack of good published research, many doctors have been impressed with the effectiveness of essential fatty acids (EFAs) in cases of BPH. A typical recommendation is 1 Tbsp (15mL) of flaxseed oil per day, perhaps reduced to 1 or 2 tsp (5 to 10mL) per day after several months. Because taking EFAs increases the requirement for vitamin E, most doctors recommend taking a vitamin E supplement along with EFA supplementation.

Psoriasis

Some doctors have reported success using flaxseed oil (usually 1 to 3 Tbsp [15 to 45 mL] per day) for psoriasis, although there have been no published trials to support that observation.

Rheumatoid arthritis (RA)

Many double-blind trials have proven that omega-3 fatty acids in fish oil partially relieve symptoms of RA. The effect results from the anti-inflammatory activity of fish oil. Many doctors recommend 3 grams per day of EPA and DHA, an amount commonly found in 10 grams of fish oil. Positive results can take 3 months to become evident. In a double-blind trial, however, flaxseed oil was not effective for RA. This is probably because the omega-3 fatty acids found in fish oil (EPA and DHA), unlike the omega-3 found in flaxseed oil (i.e., alpha-linoleic acid), are effective agents against RA.

Health benefits and concerns for fats and oils
Many health benefits and concerns associated with this food are applicable to other fats and oils. Read about health benefits and concerns for fats and oils for a full description.