Alpha-Linolenic Acid (ALA)
Also known as: α-linolenic acid, 18:3n-3, Omega-3 fatty acid
Overview
Alpha-linolenic acid (ALA) is a short-chain omega-3 fatty acid found primarily in plants. ALA is an essential fatty acid (EFA), meaning the body cannot synthesize it and it must be consumed in the diet. Foods high in ALA include various nuts/seeds and their oils, such as walnuts, flaxseed, hemp seeds, chia seeds, and canola oil. Smaller amounts can be found in kiwi fruit, spinach, watercress, and grass-fed beef. ALA consists of an 18-carbon chain with three double bonds, making it a polyunsaturated fatty acid. Within the body, ALA can have many functions. It can be broken down for energy via the β-oxidation metabolic pathway; be incorporated into cell membranes, affecting their fluidity and cell signaling; influence gene expression; and be metabolized into other bioactive compounds, such as oxylipins (chemical messengers) or other omega-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), although this occurs at a low rate. While both DHA and EPA (primarily found in fish oil) have many reported health benefits, the effects of ALA are less clear.
Benefits
Animal models suggest that ALA might modulate blood lipid levels by reducing lipid synthesis while also stimulating lipid metabolism, and may reduce inflammation by reducing the production of inflammatory mediators through inhibition of nuclear factor kappa B (NF-kB). In theory, reductions in inflammation and blood lipids could be protective against cardiovascular disease, but a protective effect hasn’t been consistently found with ALA supplementation. ALA can also be metabolized into other bioactive compounds, such as oxylipins (eicosanoids), which are a diverse group of lipid mediators that have immune-modulating effects.
How it works
ALA may have small cardiovascular benefits, but the research is fairly mixed. In short-term trials (2–3 months), ALA seems to minorly reduce triglycerides (although less efficiently than fish oil), LDL-cholesterol, and total cholesterol. However, these effects are not observed in longer trials. ALA may reduce the risk of heart arrhythmias, but has not been found to reduce blood pressure or the risk of cardiovascular events (e.g., heart attack, stroke). Additionally, ALA may reduce markers of inflammation including C-reactive protein and TNF-alpha; however, these effects are inconsistent and are mostly observed in people with higher baseline levels of these biomarkers. Some observational studies have suggested that higher reported intakes of ALA are associated with reduced all-cause and cardiovascular disease mortality, but this has not been found in randomized controlled trials (RCTs).
Side effects
As part of the regular diet, the Institute of Medicine has established an adequate intake (AI) level for ALA of 1.6 grams for men and 1.1 grams for women. This represents the daily amount that is thought to be nutritionally adequate. ALA is highly bioavailable in foods and oils, but flax and chia seeds should be ground before consumption to ensure the ALA is available for absorption. The optimal dosage for ALA as a supplement is not well established and is likely influenced by baseline levels of intake. For reducing triglycerides or LDL-cholesterol, a 2021 meta-analysis of RCTs found that ALA dosages of 3–8 grams daily were the most effective; however, the benefit on lipid levels was not observed beyond 3 months. Further complicating the issue is the form in which ALA is provided. In clinical trials, ALA is provided in a variety of ways, including as ALA-enriched margarine, in walnuts, in ground flax or chia seeds, or in their oils. Due to the heterogeneous nature of these dosage forms and the presence of other bioactive compounds, the consumption of, for example, 3 grams of ALA in walnuts may not produce the same effects as consuming 3 grams of ALA in flaxseed oil.
Dosage
ALA is generally considered to be safe and well-tolerated; however, there is a lack of research reporting on adverse effects. There are some important limitations to ALA research. Most trials provide ALA as foods or oils (e.g., flaxseed, walnut, canola, ALA-enriched margarine), which means there are other bioactive compounds present, such as different fatty acids, fiber, vitamins and minerals, and polyphenols. These compounds could influence the observed effects and make it challenging to disentangle the effects of ALA from the food as a whole. Additionally, ALA is ubiquitous in the diet, and many clinical trials do not account for baseline intakes of ALA which could impact the observed effects (or lack thereof).
FAQs
What is alpha-linolenic acid?
Alpha-linolenic acid (ALA) is a short-chain omega-3 fatty acid found primarily in plants. ALA is an essential fatty acid (EFA), meaning the body cannot synthesize it and it must be consumed in the diet. Foods high in ALA include various nuts/seeds and their oils, such as walnuts, flaxseed, hemp seeds, chia seeds, and canola oil. Smaller amounts can be found in kiwi fruit, spinach, watercress, and grass-fed beef. ALA consists of an 18-carbon chain with three double bonds, making it a polyunsaturated fatty acid. Within the body, ALA can have many functions. It can be broken down for energy via the β-oxidation metabolic pathway; be incorporated into cell membranes, affecting their fluidity and cell signaling; influence gene expression; and be metabolized into other bioactive compounds, such as oxylipins (chemical messengers) or other omega-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), although this occurs at a low rate. While both DHA and EPA (primarily found in fish oil) have many reported health benefits, the effects of ALA are less clear.
What impacts the conversion of alpha-linolenic acid to DHA and EPA?
In the body, ALA can function as a precursor for the production of the long-chain omega-3 fatty acids EPA and DHA. However, these conversions are limited; they have been estimated to occur at rates of <8% and <4% for EPA and DHA, respectively. There are many factors that can impact the efficiency of this conversion, such as sex, genetic polymorphisms, disease states, and habitual fatty acid consumption.
What are the signs and symptoms of alpha-linolenic acid deficiency?
ALA is an essential fatty acid that must be consumed in adequate amounts to prevent deficiency. In the United States, the majority of adults meet or exceed the recommended adequate intake of ALA, and deficiency is uncommon. When deficiency does occur, it may lead to dry, scaly skin, vision problems, and neuropathy. In rodent models of ALA deficiency, impaired learning abilities have been observed, but this hasn’t been found in humans.
What are alpha-linolenic acid’s main drawbacks?
ALA is generally considered to be safe and well-tolerated; however, there is a lack of research reporting on adverse effects. There are some important limitations to ALA research. Most trials provide ALA as foods or oils (e.g., flaxseed, walnut, canola, ALA-enriched margarine), which means there are other bioactive compounds present, such as different fatty acids, fiber, vitamins and minerals, and polyphenols. These compounds could influence the observed effects and make it challenging to disentangle the effects of ALA from the food as a whole. Additionally, ALA is ubiquitous in the diet, and many clinical trials do not account for baseline intakes of ALA which could impact the observed effects (or lack thereof).
How does alpha-linolenic acid work?
Animal models suggest that ALA might modulate blood lipid levels by reducing lipid synthesis while also stimulating lipid metabolism, and may reduce inflammation by reducing the production of inflammatory mediators through inhibition of nuclear factor kappa B (NF-kB). In theory, reductions in inflammation and blood lipids could be protective against cardiovascular disease, but a protective effect hasn’t been consistently found with ALA supplementation. ALA can also be metabolized into other bioactive compounds, such as oxylipins (eicosanoids), which are a diverse group of lipid mediators that have immune-modulating effects.
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