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Alpha-Linolenic Acid (ALA)

What is alpha-linolenic acid (ALA)?

Alpha-linolenic acid is an essential omega-3 polyunsaturated fatty acid.

ALA Sources

Chart 1. Foods High in ALA

Flaxseed oil (1 tbsp, 14 g) 7
Chia seeds (1 oz, 28 g) 5
Walnuts, English (1 oz, 28 g) 2.5
Walnut oil (1 tbsp, 14 g) 1.5
Canola oil (1 tbsp, 14 g) 1.5
Mustard oil (1 tbsp, 14 g) 1
Walnuts, black (1 oz, 28 g) 0.5

Chart 1 reference: USDA.gov [3]

Diet High in ALA and Heart Disease

There is INSUFFICIENT EVIDENCE about the effectiveness of diets high in ALA in the prevention of cardiovascular disease [14].

According to the U.S. Food and drug Administration (FDA), there is insignificant scientific evidence about the heart-protective effect of walnuts [12]. According to The Agency for Healthcare Research and Quality (AHRQ), alpha-linolenic acid (ALA) from flaxseed, walnuts and soybeans is much less effective in preventing heart disease than fish oil, which contains EPA and DHA [13].

ALA and Cholesterol

High ALA intake is not associated with lower total and LDL cholesterol or triglyceride levels [15], so its eventual beneficial effects may be conveyed by reducing the levels of C-reactive protein (CRP) – a marker of inflammation [1].

ALA Supplements (Flaxseed and Walnut Oil)

Nonprescription flaxseed (linseed) oil and walnut oil supplements containing alpha-linolenic acid (ALA) are available.

Health Benefits of ALA Supplements

There is INSUFFICIENT EVIDENCE about the effectiveness of flaxseed oil in the prevention or treatment of anxiety, atherosclerosis (hardening of the arteries), attention deficit-hyperactivity disorder (ADHD), cancer (breast, prostate), constipation, coronary heart disease, diabetes mellitus type 2 [16], dry eyes and skin, high blood pressure, HIV/AIDS, pneumonia or polycystic ovary syndrome (PCOS), or in increasing exercise performance or promoting weight loss [1,11].

The eventual beneficial effects of ALA are not caused by ALA itself, but by eicosapentaenoic (EPA) and docosahexanoic acid (DHA), which are produced from ALA in the human body, however, the conversion of ALA to EPA and DHA is relatively inefficient [2,4].

Some, but not all, studies have shown that a diet high in ALA might be heart-protective for those who rarely eat fish (which are a good source of ALA derivatives EPA and DHA) [1,9,10].

ALA Safety and Side Effects

Flaxseed oil is LIKELY SAFE for most adults. The main possible side effect of large doses of ALA supplements (>30 g/day) is diarrhea [1,11]. Allergic reactions to flaxseed and flaxseed oil are possible. Various studies have shown a possible connection between the use of alpha-linolenic acid and risk of prostate cancer [5,6,7,8].

The safety of flaxseed oil in pregnancy and lactation has not been evaluated, so pregnant and breastfeeding women should better avoid it.

  1. Essential fatty acids  Linus Pauling Institute
  2. Letter Regarding Eggs with Enhanced Omega-3 Fatty Acid Content and a Balanced 1:1 Ratio of Omega-3/Omega-6 Fatty Acids and Reduced Risk of Heart Disease and Sudden Fatal Heart Attack  US Food and Drug Administration
  3. List of foods high in alpha-linolenic acid (ALA)  US Department of Agriculture
  4. Brenna JT et al, 2009, alpha-Linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans  PubMed
  5. Kim do Y et al, 2008, The ketogenic diet and epilepsy  PubMed
  6. Koralek DO et al, 2006, A prospective study of dietary alpha-linolenic acid and the risk of prostate cancer (United States)  PubMed
  7. Altar-Bashi NR et al, 2004, Alpha-linolenic acid and the risk of prostate cancer. What is the evidence?  PubMed
  8. Brouwer IA et al, 2004, Dietary α-Linolenic Acid Is Associated with Reduced Risk of Fatal Coronary Heart Disease, but Increased Prostate Cancer Risk: A Meta-Analysis  The Journal Of Nutrition
  9. Zatonski W et al, 2007, Rapid declines in coronary heart disease mortality in Eastern Europe are associated with increased consumption of oils rich in alpha-linolenic acid  Springer Link
  10. Campos H et al, 2008, α-Linolenic Acid and Risk of Nonfatal Acute Myocardial Infarction  Circulation
  11. Flaxseed oil  WebMD
  12. 2004, Qualified Health Claims: Letter of Enforcement Discretion – Walnuts and Coronary Heart Disease  US Food and Drug Administration
  13. Coates PM, 2004, AHRQ Evidence Reports Confirm that Fish Oil Helps Fight Heart Disease  Agency for Healthcare Research and Quality
  14. Pan A et al, 2012, α-Linolenic acid and risk of cardiovascular disease: a systematic review and meta-analysis  PubMed
  15. Wendland E et al, 2006, Effect of alpha linolenic acid on cardiovascular risk markers: a systematic review  PubMed
  16. Wu JH et al, 2012, Omega-3 fatty acids and incident type 2 diabetes: a systematic review and meta-analysis  PubMed

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