Flaxseed Oil: 5 Benefits and Side Effects (Caution for 4 Specific Groups)

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What is Flaxseed Oil?

Flaxseed oil, also known as linseed oil, is a colorless to pale yellow oil obtained from the dried and mature seeds of the flax plant (Linum usitatissimum). Flaxseed oil is a sought-after edible oil, serving as a nutritional supplement and a source of alpha-linolenic acid (ALA), an omega-3 fatty acid.
Cold-pressed flaxseed oil is rich in alpha-linolenic acid, a polyunsaturated fatty acid with three double bonds (C18H30O2). It is associated with cognitive enhancement, improved memory, eye protection, better sleep, inhibition of thrombotic diseases, prevention of myocardial infarction and stroke, reduction of blood lipids, blood pressure lowering, inhibition of hemorrhagic stroke, and allergy prevention [1] [2] [3] [4].

What are the Nutritional Components of Flaxseed Oil?

Flaxseed is rich in dietary fiber, with 2.7 grams of fiber per 10 grams of flaxseed. Adding it to bread and cereals can increase the fiber content. The unique feature of flaxseed oil lies in its unusually high content of alpha-linolenic acid, which has a unique reaction with oxygen in the air. Specifically, the fatty acids in typical flaxseed oil include:

Alpha-linolenic acid: 51.9-55.2% (Omega-3)
Oleic acid: 18.5-22.6% (Omega-9)
Linoleic acid: 14.2-17% (Omega-6)
Palmitic acid: 7% [5]

What are the Recommended Evidence-Based Effects and Benefits of Flaxseed Oil?

Reducing the Growth of Cancer Cells

💡Some animal studies suggest that flaxseed oil may reduce the growth of cancer cells. In one study, mice given 0.3 ml of flaxseed oil for 40 days were found to prevent the spread of cancer and the growth of lung tumors [6].
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💡In another small animal study, flaxseed oil was shown to block the formation of colon cancer in rats [7]. Additionally, flaxseed mixed with a mixture of seeds and plant oils rich in alpha-linolenic acid may have a preventive effect on colon cancer in mice.
Beneficial for Heart Health

Flaxseed oil can improve heart health by reducing blood pressure and increasing arterial elasticity.

💡In a study of 59 people comparing the effects of flaxseed oil and safflower oil, which is rich in omega-6 fatty acids, supplementation with 1 tablespoon (15 ml) of flaxseed oil for 12 weeks resulted in significantly lower blood pressure levels than supplementation with safflower oil [8].

💡Some studies have found that flaxseed oil can also improve arterial elasticity. Aging and elevated blood pressure are often associated with reduced vascular elasticity, and these benefits may be due to the high concentration of omega-3 fatty acids in flaxseed oil. Numerous studies suggest that omega-3 fatty acids can improve heart health, with benefits such as reducing inflammation and lowering blood pressure [9] [10] [11] [12].
Treatment of Constipation and Diarrhea

Flaxseed oil helps in the treatment of constipation and diarrhea.

💡A recent animal study found that flaxseed oil can act as both a laxative and an anti-diarrheal, promoting regularity [13].

💡Another study provided flaxseed oil, olive oil, or mineral oil to 50 constipated hemodialysis patients. After 4 weeks, flaxseed oil increased bowel frequency and improved stool consistency, proving to be as effective as olive oil and mineral oil [14].

However, research on the effects of flaxseed oil on constipation and diarrhea is currently limited to animal studies and specific conditions, and further research is needed to evaluate its effectiveness in the general population.
Improving Skin Health

Studies have found that supplementing with flaxseed oil can help improve skin smoothness and treat certain skin conditions such as dermatitis.

💡A small study supplementing 13 women with flaxseed oil for 12 weeks showed improved skin smoothness and reduced sensitivity to stimuli and roughness at the end of the study [15].

💡Another recent animal study found that giving flaxseed oil to mice with dermatitis for 3 weeks alleviated symptoms such as redness, swelling, and itching [16].
Reducing Inflammation

Flaxseed oil has anti-inflammatory properties, and its omega-3 fatty acid content helps reduce inflammation in certain populations.

💡Studies show that flaxseed oil significantly reduces levels of C-reactive protein (a marker for inflammation) in obese individuals [17].

Are There Any Side Effects of Flaxseed Oil?

For most adults, flaxseed oil is safe, but it is recommended to consult a doctor before use for the following groups:

If you have prostate cancer, it is advisable to discuss the use of flaxseed oil with your doctor [18].
Pregnant or breastfeeding women and those with hormone-related conditions should avoid using flaxseed oil as its safety is unknown.
Flaxseed oil has anticoagulant effects. If you have bleeding disorders or are scheduled for surgery, consult a healthcare professional before use.
Flaxseed oil may cause a decrease in blood sugar. If you have diabetes or any other conditions affecting blood sugar levels, consult a healthcare professional before use. [19] [20]