Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid. A diet rich in ALA and ALA supplements, both reduce the risk and complications of many chronic diseases, including heart disease, obesity, diabetes, and cancer. However, certain forms of ALA may adversely affect some people. Read more to find out how ALA impacts your health.
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) [R].
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 [R].
These fatty acids promote eye health, as well as brain and nervous system development. They also reduce the risk of high blood pressure, high cholesterol, stroke, and cancer, improve memory, slow aging and decrease the risk of heart disease [R].
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 causes:
- Reduced vision [R]
- Weakness [R]
- Inability to walk [R]
- Pain in the legs [R]
- Blurry vision (in monkeys) [R]
- Scaliness of skin [R]
- Excessive cholesterol and inflammation [R]
To prevent deficiency, your diet should contain between 0.2 to 0.3% of total calories from ALA [R].
Health Benefits of Alpha Linolenic Acid
1) ALA Prevents 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 (DB-RCT) 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 [R].
In a similar study (DB-RCT) 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 [R].
ALA (diglyceride) activates genes involved in fat break down and increases heat production in the gut, resulting in increased calorie-burning [R].
In mice, substituting ALA (flaxseed oil) for corn oil in their diets decreased fat mass [R].
In rats, ALA protected kidneys from complications due to obesity (by increasing ALA-derived oxylipins) [R].
2) ALA Improves The Skin
Low ALA is associated with dry and uncomfortable skin and poor skin quality [R].
Flaxseed oil has a high ALA content, which supports skin health. Flaxseed decreases skin cell inflammation and promotes regeneration [R].
In a study (DB-RT) of 13 women, flaxseed oil supplementation improved skin sensitivity, hydration, and overall condition [R].
In another study (DB-RCT) of 45 women, 12 weeks of flaxseed oil ingestion reduced skin redness and roughness [R].
Flaxseed also lowered skin cell inflammation and increased skin cell repair [R].
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 [R, R].
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 [R].
In mice, ALA supplementation protected the skin from UV damage [R].
3) ALA May Reduce Cancer Risk
In a study of 350 colon cancer patients and 350 controls, higher ALA levels in the blood were associated with a reduced risk of colon cancer (57%) and rectal cancer (59%) [R].
In a study of 121 female breast cancer patients, patients with the highest amounts of ALA in their breast tissue had an 80% reduced risk of the cancer spreading to other tissues [R].
Another similar trial of 123 women with breast cancer and 59 healthy controls found that breast tissue with the highest levels of ALA had 65% reduced breast cancer risk [R].
Flaxseed oil reduced the development, number, severity, and size of skin cancer in mice. It also increased antioxidants and improved detoxification enzyme levels in skin and liver tissue [R].
In laboratory, ALA exposure reduced colon and breast cancer cell spread and growth and increased cancer cell death (apoptosis) [R].
However, high ALA levels in prostate tissue are associated with more aggressive prostate cancer [R].
ALA and Prostate Cancer Risk
A meta-analysis of population studies (about 220,000 people) showed a slight protective effect high ALA intake of about 5% reduced risk [R].
However, another meta-analysis of other population studies (about 130,000 people) showed an approximate 60% increased risk of prostate cancer [R].
ALA supplementation as flaxseed appeared to reduce prostate cancer growth pre-surgically in 134 men with prostate cancer (RCT) and did not increase prostate ALA tissue levels. However, it did increase EPA levels in the prostate by about 50%. [R].
4) ALA Protects Against Diabetes
ALA, given as 1 gram of flaxseed oil daily, improved wound healing, reduced inflammation, and increased insulin sensitivity as well as reduced fasting insulin levels in a study (DB-RCT) of 60 patients with diabetic foot ulcers [R].
Storage of ALA in fat tissue reduced the risk of insulin resistance (HOMA-IR) in a study of 716 people [R].
However, dietary ALA intake was only associated with reduced insulin resistance in people with BMI<25 or with smaller waist sizes in a study of 3,383 people [R].
ALA supplementation resulted in improvements in insulin sensitivity and increases in a protein involved in metabolism (adiponectin) in a study (DB-RCT) of 20 patients with type 2 diabetes [R].
Women with polycystic ovaries (PCOS) might have a higher risk for diabetes and high insulin and glucose levels. In a study (DB-RCT) of 60 women with PCOS, flaxseed oil supplementation lowered their insulin levels [R].
However, in a study (DB-RCT) of 32 type 2 diabetes patient, high-dose ALA flaxseed oil failed to reduce glucose, HbA1C, insulin resistance, or insulin levels compared to safflower placebo [R]
Another study (DB-RCT) of 32 patients with type 2 diabetes did not find ALA helpful in reducing glucose or insulin resistance [R].
5) ALA Protects Against Stroke
High ALA intake was associated with a 35 to 50% reduced stroke risk in a cohort study of 20,069 middle-aged people living in the Netherlands [R].
In mice and rats, ALA:
- Reduced stroke symptoms and tissue damage [R]
- Protected against brain damage [R]
- Improved blood flow and circulation (via activation of TREK-1 potassium channel) [R]
- Protected neurons from cell death [R]
- Improved chances of survival after stroke [R]
6) ALA Improves Heart Health
High amounts of dietary ALA in large population studies was related to:
- Reduced risk of heart disease [R]
- Lower blood pressure [R]
- Lower triglycerides [R]
- Less plaque in the arteries [R]
- Reduced chances of fatal heart attacks [R]
Heart rhythm may benefit from dietary ALA as well [R].
In rats, a combination of supplemental ALA and fish oil protected their hearts from life-threatening or malignant arrhythmia (irregular heartbeats) [R].
Supplemental ALA reduced triglyceride levels and improved triglyceride to HDL ratios, known heart disease risk factors, in 74 healthy people with normal cholesterol profiles [R].
ALA also reduces LDL (bad) cholesterol, a risk factor for heart disease, when given as camelina oil in a study (RCT) of 68 people with high cholesterol [R].
In a study (DB-RCT) of 37 people with mildly high cholesterol, ALA given as flaxseed oil improved LDL levels [R].
Although short-term supplementation of 15 grams of ALA per day did not change clotting risk factors in 17 vegetarian men, it did increase blood levels of EPA and reduced inflammatory fat ratios [R].
However, only fish oil, but not ALA, helped prevent heart damage in rats [R].
7) ALA Reduces High Blood Pressure
ALA supplementation given with a strict diet significantly reduced blood pressure (systolic and diastolic) in a study (RCT) of 127 patients with mild hypertension [R].
High blood pressure may be caused by omega-3 deficiencies. Supplemental ALA as canola or flaxseed oil helped prevent omega-3 deficiency-related high blood pressure in mice [R].
In rats, both flaxseed and flaxseed oil reduced blood pressure [R].
8) ALA Reduces 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 [R].
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 (DB-RCT) of 645 healthy volunteers [R].
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 [R].
High-dose supplemental ALA in a 12-week study (RCT) 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 [R].
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 [R, R].
In pigs, high intake of ALA reduced production of an inflammatory marker (arachidonic acid) in the body by 40% [R].
9) ALA May Improve Gut Health
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 [R].
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 [R].
Both sage and fish oil reduced inflammatory markers (IL-6, COX-2, TNF-alpha), when compared to corn oil [R].
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) [R].
ALA-rich flaxseed protected the lining of the gut, increased antioxidant enzymes, and reduced oxidative stress in mice with colitis [R].
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 [R].
However, in mice, whole flaxseed may increase injury and inflammation in acute colitis [R].
10) ALA May Improve Kidney Function
In rats, ALA as flax or flaxseed oil [R]:
- Improved kidney function
- Improved kidney levels of omega-3 fats
- Reduced inflammatory markers
- Decreased cholesterol
ALA for Treatment of 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 [R].
A longer-term trial showed similar kidney benefits in 40 patients with lupus from supplemental flaxseed, but this trial had a high dropout rate [R].
Flaxseed also reduced risk of dying and reduced kidney dysfunction in a mouse study of spontaneous lupus [R].
11) ALA May Prevent Allergic Reactions
High intake of ALA reduces the risk of allergic reactions in 568 humans [R].
ALA given as linseed oil reduced histamine release in mice [R].
ALA also reduced the release and production of histamine in rat cells [R].
As a precursor to EPA, ALA may decrease allergic sensitivities and nasal inflammation [R].
In a mouse study of allergic dermatitis, fermented flaxseed oil reduced redness, itching, swelling and skin damage [R].
In horses with allergic skin lesions, flaxseed oil reduced skin wounds and redness (DB-RCT) [R].
12) ALA Reduces Risk of Respiratory Infections
Proper metabolism of fats may be required to fight viruses [R]
High intake of ALA was associated with a reduced risk of pneumonia in a cohort study of 38,378 men [R].
In a 2-year study (DB-RCT), supplemental ALA and omega-6 (linoleic acid) or placebo (olive oil) reduced fever and school absences in 38 children with recurrent respiratory infections [R].
13) ALA May Help Treat Stomach Ulcers
In rats, ALA-rich flaxseed oil was more effective than medicine for reducing gastric (stomach) ulcers due to alcohol [R].
ALA can also inhibit the growth of H. pylori, a type of bacteria that can cause stomach ulcers [R].
14) ALA Improves Eye Health
Sea buckthorn oil (rich in ALA) improved dry eye symptoms in a study (DB-RCT) of 100 patients with dry eye [R].
Topical ALA reduced eye inflammation and dryness in mice [R].
In rats, ALA from flaxseed helped protect the retina from UV damage [R].
15) ALA Reduces 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% [R]
- Lowered fatigue [R]
- Reduced depression by 50% (prospective cohort, 2,469 patients) [R]
16) ALA Improves 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 [R].
In a study (DB-RCT) of 50 patients, daily supplementation with 4 mL of flaxseed oil helped relieve constipation [R].
17) ALA May Reduce Depression Risk
High ALA intake reduced the risk of depression in a cohort study of 54,632 women, with a stronger effect in those with low omega-6 (linoleic acid) intake [R].
18) ALA May Improve Rheumatoid Arthritis
19) ALA May Increase Lifespan
ALA given to C. elegans, a type of roundworm, increased lifespan (by activating NHR-49/PPARα and SKN-1/Nrf2 transcription factors) [R].
20) ALA and 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 [R].
However, a small dose of ALA/linoleic acid versus placebo (vitamin C) in a study (DB-RCT) of 73 children with ADHD did not result in improvements in behavior [R].
Another study (DB-RCT) of 40 children failed to show improvements in ADHD, but had a high number of patients who quit the study [R].
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) [R].
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.
Drug and Supplement Interactions
High doses of supplemental omega-3 fats may increase the blood-thinning effects of warfarin [R].
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 [R].
Linoleic Acid Interaction with ALA
In pigs, high intake of linoleic acid reduces the production of EPA from ALA [R].
Decreasing linoleic acid helped improve production of EPA from ALA in mice [R].
Sources of ALA
- Flaxseed and flaxseed oil
- Chia seeds
- Canola oil
- Hemp seeds
- Soybean oil
- Camelina oil
- Nuts, especially walnuts
- Sea buckthorn oil
- Sage oil
Flaxseed oil is the most commonly used as supplemental ALA.
Baking temperatures appear to be safe for ALA in flaxseed oil [R].
However, frying temperatures diminish the quality oils high in ALA [R].