Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid. A diet rich in ALA and ALA supplements is often recommended to reduce the likelihood of heart disease, obesity, diabetes, and cancer. Read on to learn more about the sources and benefits of an ALA-rich diet and ALA supplementation.
What is Alpha-Linoleic Acid (ALA)?
Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid. It is necessary for our health, but our bodies can’t produce it. We need to take it through food (and supplements) [1].
ALA is found in flaxseed oil, chia seeds, sage, some vegetables, and nut oils. It is converted in the body into the unsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), which reduce inflammation [2].
These fatty acids promote eye health, as well as brain and nervous system development. They also reduce blood pressure, cholesterol, and incidence of stroke and cancer, improve memory, slow aging, and probably prevent heart disease [2].
The omega-3 index is the percentage of EPA and DHA total fatty acids in the blood. An omega-3 index greater than 8% is associated with a 90% lower rate of heart disease-related death [3, 4].
ALA Deficiency
Alpha-linolenic acid is considered essential in the diet because it is an omega-3 building block of the fatty acids EPA and DHA.
ALA deficiency can cause:
- Reduced vision [5]
- Weakness [5]
- Inability to walk [5]
- Pain in the legs [5]
- Blurry vision (in monkeys) [6]
- Scaliness of skin [7]
- Excessive cholesterol and inflammation [8]
To prevent deficiency, your diet should contain between 0.2 to 0.3% of total calories from ALA [8].
Health Benefits of Alpha-Linolenic Acid
Omega-3 fatty acids are considered essential nutrients, and most of our dietary omega-3s tend to be in the form of ALA. That said, regulations set manufacturing standards for ALA supplements but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
Possibly Effective For
1) Obesity
ALA, like other fatty acids in the diet, is usually attached to two or three glycerols; they are classified as diglyceride or triglyceride depending on the number of glycerols they have.
In a study of 177 obese people, 12 weeks of supplemental ALA (diglyceride, but not triglyceride form), reduced intra-organ fat mass, body weight, waist size, and blood triglycerides [9].
In a similar study of 114 overweight people, 12 weeks of ALA (diglyceride) supplementation also reduced fat mass, body weight, waist size, and triglyceride blood levels by increasing fat burning [10].
ALA (diglyceride) activates genes involved in fat break down and increases heat production in the gut, resulting in increased calorie-burning [11].
In mice, substituting ALA (flaxseed oil) for corn oil in their diets decreased fat mass [12].
In rats, ALA protected kidneys from complications due to obesity (by increasing ALA-derived oxylipins) [13].
2) Cancer Prevention
In a study of 350 colon cancer patients and 350 controls, higher ALA levels in the blood were associated with a reduced incidence of colon cancer (57%) and rectal cancer (59%) [14].
In a study of 121 female breast cancer patients, patients with the highest amounts of ALA in their breast tissue were 80% less likely to experience metastasis (migration of cancer cells to other tissues) [15].
Another similar trial of 123 women with breast cancer and 59 healthy controls found that breast tissue with the highest levels of ALA was 65% less likely to develop breast cancer [16].
Flaxseed oil reduced the development, number, severity, and size of skin cancer in mice. It also increased antioxidants and improved detoxification enzyme levels in the skin and liver tissue [17].
In the laboratory, ALA exposure reduced colon and breast cancer cell spread and growth and increased cancer cell death (apoptosis) [18].
However, high ALA levels in prostate tissue are associated with more aggressive prostate cancer [19].
Prostate Cancer
A meta-analysis of population studies (about 220,000 people) showed a slight (5% reduction) protective effect of high ALA intake [20].
However, another meta-analysis of other population studies (about 130,000 people) showed an approximate 60% increased rate of prostate cancer [21].
ALA supplementation as flaxseed appeared to reduce prostate cancer growth pre-surgically in 134 men with prostate cancer and did not increase prostate ALA tissue levels. However, it did increase EPA levels in the prostate by about 50% [22].
None of this is to say that if you supplement with ALA, you will not get cancer. Cancer is a complex disease with myriad genetic, environmental, dietary, and other risk factors which we do not yet fully understand. However, existing research seems to indicate that people who eat more ALA and who have more ALA in their bodies are less likely to develop cancer, all else being equal.
3) Stroke Prevention
High ALA intake was associated with a 35 to 50% reduced incidence of stroke in a cohort study of 20,069 middle-aged people living in the Netherlands [23].
In mice and rats, ALA:
- Reduced stroke symptoms and tissue damage [24]
- Protected against brain damage [25]
- Improved blood flow and circulation (via activation of TREK-1 potassium channel) [26]
- Protected neurons from cell death [27]
- Improved chances of survival after stroke [25]
4) Heart Health
High amounts of dietary ALA in large population studies were related to:
- Lower rates of heart disease [28]
- Lower blood pressure [29]
- Lower triglycerides [30]
- Less plaque in the arteries [31]
- Fewer fatal heart attacks [32]
Heart rhythm may benefit from dietary ALA as well [33].
In rats, a combination of supplemental ALA and fish oil protected their hearts from life-threatening or malignant arrhythmia (irregular heartbeats) [34].
Supplemental ALA reduced triglyceride levels and improved triglyceride to HDL ratios, known heart disease risk factors, in 74 healthy people with normal cholesterol profiles [35].
ALA also reduces LDL (bad) cholesterol, a risk factor for heart disease, when given as camelina oil in a study of 68 people with high cholesterol [36].
In a study of 37 people with mildly high cholesterol, ALA given as flaxseed oil improved LDL levels [37].
Although short-term supplementation of 15 grams of ALA per day did not change clotting markers in 17 vegetarian men, it did increase blood levels of EPA and reduced inflammatory fat ratios [38].
However, only fish oil, but not ALA, helped prevent heart damage in rats [39].
Blood Pressure
ALA supplementation given with a strict diet significantly reduced blood pressure (systolic and diastolic) in a study of 127 patients with mild hypertension [40].
High blood pressure is a possible symptom of omega-3 deficiencies. Supplemental ALA as canola or flaxseed oil helped prevent omega-3 deficiency-related high blood pressure in mice [41].
In rats, both flaxseed and flaxseed oil reduced blood pressure [42].
ALA was effective and safe to take along with blood pressure medications in mice [43, 44].
5) Inflammation
Inflammation contributes to the causes and severity of many diseases, including heart disease, diabetes, cancer, brain conditions, depression, and autoimmune diseases. Reducing inflammation with ALA may improve these disease outcomes [45].
A 4-week ALA-supplemented diet reduced inflammatory markers (TNF-alpha and IL-1beta) by 30% compared to a diet high in omega-6 fats (sunflower oil) in a study of 645 healthy volunteers [46].
ALA supplementation via linseed oil also reduced inflammatory markers (C-reactive protein, interleukin-6 and blood amyloid A) in a study (RCT) of 50 people with high cholesterol levels [47].
High-dose supplemental ALA in a 12-week study of 60 older adults undergoing strength training reduced inflammation (IL-6) and improved knee muscle strength compared to placebo (corn oil). However, the placebo group had improved bone density while the ALA group did not [48].
Both ALA and omega-6 fats (alpha-linoleic acid) in the diet were related to lower levels of inflammation (C-reactive protein) in men, while only omega-3 intake as a whole reduced inflammation in women [49, 50].
In pigs, a high intake of ALA reduced the production of an inflammatory marker (arachidonic acid) in the body by 40% [51].
6) Pneumonia & Respiratory Infections
Proper metabolism of fats may be required to fight viruses [52]
People with the highest intake of ALA were least likely to develop pneumonia in a cohort study of 38,378 men [53].
In a 2-year study, supplemental ALA and omega-6 (linoleic acid) or placebo (olive oil) reduced fever and school absences in 38 children with recurrent respiratory infections [54].
7) Multiple Sclerosis Symptoms
In various cohort studies of multiple sclerosis patients, ALA, as a component of flaxseed oil, was associated with:
- Reduced chances of relapse by 53% and reduced disease activity by 55% [55]
- Lowered fatigue [56]
- Reduced depression by 50% (prospective cohort, 2,469 patients) [57]
8) Depression
High ALA intake was inversely associated with depression in a cohort study of 54,632 women, with a stronger effect in those with low omega-6 (linoleic acid) intake [58].
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of ALA for any of the below-listed uses. Remember to speak with a doctor before taking ALA supplements, and never use them in place of something your doctor recommends or prescribes.
9) Skin Health
Low ALA status is associated with dry and uncomfortable skin and poor skin quality [59].
Flaxseed oil has a high ALA content, which supports skin health. Flaxseed decreases skin cell inflammation and promotes regeneration [60].
In a study of 13 women, flaxseed oil supplementation improved skin sensitivity, hydration, and overall condition [61].
In another study of 45 women, 12 weeks of ALA-rich flaxseed oil supplementation reduced skin redness and roughness [62].
Flaxseed also lowered skin cell inflammation and increased skin cell repair [60].
Eczema is a common skin disorder with dry, uncomfortable, and red skin. Flaxseed oil lowered saturated fatty acid levels in both horses and human skin cells, which may reduce rash areas and help clear irregular skin [63, 60].
ALA amounts are decreased in fat tissue of patients with psoriasis compared to normal controls; they also have lower circulating levels of ALA and omega-6 fats [64].
In mice, ALA supplementation protected the skin from UV damage [65].
10) Diabetes
ALA, given as 1 gram of flaxseed oil daily, improved wound healing, reduced inflammation, increased insulin sensitivity, and reduced fasting insulin levels in a study of 60 patients with diabetic foot ulcers [66].
Storage of ALA in fat tissue was inversely related to insulin resistance (HOMA-IR) in a study of 716 people [67].
However, dietary ALA intake was only associated with reduced insulin resistance in people with a BMI of under 25 or with smaller waist sizes in a study of 3,383 people [68].
ALA supplementation resulted in improvements in insulin sensitivity and increases in a protein involved in metabolism (adiponectin) in a study of 20 patients with type 2 diabetes [69].
Women with polycystic ovaries (PCOS) appear to be more likely to develop diabetes and high insulin and glucose levels. In a study of 60 women with PCOS, flaxseed oil supplementation lowered their insulin levels [70].
However, in a study of 32 type 2 diabetes patients, high-dose ALA flaxseed oil failed to reduce glucose, HbA1C, insulin resistance, or insulin levels compared to safflower placebo [71].
Another study of 32 patients with type 2 diabetes did not find ALA helpful in reducing glucose or insulin resistance [72].
11) Inflammatory Bowel Disease
Adding omega-3-rich foods including ALA to the diet of 230 IBD (ulcerative colitis and Crohn’s disease) patients increased blood ratios of omega- 3 to omega-6. This reduced inflammation; it also reduced disease activity and increased disease absence rates [73].
In rats, sage oil (rich in ALA) decreased colon tissue damage, increased repair, and decreased the amount of dying tissue better than fish or corn oil [74].
Both sage and fish oil reduced inflammatory markers (IL-6, COX-2, TNF-alpha) when compared to corn oil [74].
Reducing the omega-6 to omega-3 ratios by providing a high ALA diet reduced disease activity and inflammation in rats with induced colitis (IBD) [75].
ALA-rich flaxseed protected the lining of the gut, increased antioxidant enzymes, and reduced oxidative stress in mice with colitis [76].
In rats with ulcerative colitis, ALA substitution for one-third of the omega-6 diet content reduced disease activity, oxidative enzyme activity (myeloperoxidase), inflammatory markers (TNF-alpha and IL1-beta), and increased amounts of omega-3 inside colon cells [75].
However, in mice, whole flaxseed increased injury and inflammation in acute colitis [77].
12) Kidney Function
In rats, ALA as flax or flaxseed oil [42]:
- Improved kidney function
- Improved kidney levels of omega-3 fats
- Reduced inflammatory markers
- Decreased cholesterol
Lupus-Induced Kidney Problems
An ALA-rich flaxseed diet (30 g/day) improved markers of kidney function, reduced total and LDL cholesterol, and excessive blood clotting in 9 patients with lupus-induced kidney inflammation [78].
A longer-term trial showed similar kidney benefits in 40 patients with lupus from supplemental flaxseed, but this trial had a high dropout rate [79].
Flaxseed also reduced the rate of death and reduced kidney dysfunction in a mouse study of spontaneous lupus [80].
13) Allergies
High intake of ALA was inversely associated with allergic reactions in 568 humans [81].
ALA given as linseed oil reduced histamine release in mice [82].
ALA also reduced the release and production of histamine in rat cells [83].
As a precursor to EPA, ALA may decrease allergic sensitivities and nasal inflammation [81].
In a mouse study of allergic dermatitis, fermented flaxseed oil reduced redness, itching, swelling and skin damage [84].
In horses with allergic skin lesions, flaxseed oil reduced skin wounds and redness [85].
14) Eye Health
Sea buckthorn oil, a supplement rich in ALA, improved dry eye symptoms in a study of 100 patients with a dry eye [86].
Topical ALA reduced eye inflammation and dryness in mice [87].
In rats, ALA from flaxseed helped protect the retina from UV damage [88].
15) Constipation and Diarrhea
Flaxseed oil has both a laxative property and can help resolve diarrhea, possibly due to the support of the function of potassium channels [89].
In a study of 50 patients, daily supplementation with 4 mL of flaxseed oil helped relieve constipation [90].
16) ADHD
In a pilot study of 60 children, ALA given with vitamin C improved blood levels of EPA and DHA and resulted in improved behavior in ADHD [91].
However, a small dose of ALA/linoleic acid versus placebo (vitamin C) in a study of 73 children with ADHD did not result in improvements in behavior [92].
Another study of 40 children failed to show improvements in ADHD but had a high number of patients who quit the study [93].
Animal Research (Lacking Evidence)
No clinical evidence supports the use of ALA for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
17) Stomach Ulcers
In rats, ALA-rich flaxseed oil was more effective than medicine for reducing gastric (stomach) ulcers due to alcohol [94].
ALA can also inhibit the growth of H. pylori, a type of bacteria that can cause stomach ulcers [95].
18) Rheumatoid Arthritis
Flaxseed oil reduced symptoms of arthritis and inflammation in animal studies of rheumatoid arthritis [96, 97].
19) Lifespan
ALA given to C. elegans, a type of roundworm, increased lifespan (by activating NHR-49/PPARα and SKN-1/Nrf2 transcription factors) [98].
Limitations and Caveats
ALA supplements can contain other beneficial plant components, as is the case with flaxseed oil and beneficial lignans. Some of the benefits attributed to ALA may be related to the plant source and other biologically active compounds.
Some of the benefits were researched in animals or cells, but not humans.
Safety & Precautions
There are no known side effects of including ALA-rich foods in the diet. However, certain forms of ALA (milled whole flaxseed) may be irritating to people with inflammatory bowel disease (IBD).
Drug and Supplement Interactions
High doses of supplemental omega-3 fats may increase the blood-thinning effects of warfarin [99].
Probiotics may positively influence the metabolism of ALA. Use of probiotics (Bifidobacterium breve) increased ALA levels in fat tissue and increased DHA production and tissue levels in rats [100].
In mice, the addition of a probiotic supplement (Bifidobacterium breve) to ALA also increased the amount of anti-cancer compounds (CLA) in fat tissue and decreased liver triglyceride levels [101, 102].
Possible Linoleic Acid Interaction
In pigs, a high intake of linoleic acid reduces the production of EPA from ALA [51].
Decreasing linoleic acid helped improve the production of EPA from ALA in mice [103].
ALA and Gene Variation
ALA supplementation as flaxseed increases EPA amounts in the blood, and this accounts for many of its benefits. This conversion may be less efficient in those with the following SNPs [104]:
These variants are associated with markers of heart disease. However, the same study also showed that people with these variants can benefit (raise their EPA) with high dietary ALA supplementation [104].
Sources of ALA
The recommended daily intake of omega-3 fatty acids (as ALA) is 1.6 g per day for men and 1.1 g per day for women, with an increase to 1.4 g per day during pregnancy and lactation [105].
Dietary Sources
Natural sources include [106, 36, 86, 74]:
- Flaxseed and flaxseed oil
- Chia seeds
- Canola oil
- Hemp seeds
- Soybean oil
- Pecans
- Camelina oil
- Mayonnaise
- Nuts, especially walnuts
- Sea buckthorn oil
- Sage oil
Flaxseed oil is commonly used to supplement ALA.
Baking temperatures appear to be safe for ALA in flaxseed oil [107].
However, frying temperatures diminish the quality oils high in ALA [108].
Supplement Dosage
Supplemental ALA comes in a wide variety of doses: between 200 mg and 14 grams per day [91, 48].
Dietary and supplement intake between 6 to 12 grams daily was linked to reduced markers of heart disease. Supplements of 3 g daily improved EPA levels [28, 1].
ALA is readily converted to EPA, but the conversion to DHA is very inefficient [109, 103, 110].
Women convert ALA to EPA more efficiently than men [111, 112].
User Experiences
Users find that supplemental ALA reduces triglycerides, helps with dry eyes, improves sleep quality and daytime alertness. One user found it helpful in reducing heart palpitations.
Some people recommend taking it with food. However, some users experienced bloating, gas and nausea.
