ALA (Alpha-Linolenic Acid)

When you research omega-3 fatty acids, you will quickly come across three names: ALA, EPA, and DHA. While EPA and DHA come primarily from fish and seafood, ALA — alpha-linolenic acid — is the plant-based representative of this important fatty acid family. You will find it in linseed oil, chia seeds, walnuts, and rapeseed oil. This sounds practical at first, especially if you follow a plant-based diet. However, there is a crucial catch: your body can convert ALA into the biologically active forms EPA and DHA — but only in very small amounts. In this article you will find out what this means in practice, which foods are the best ALA sources, and why plant-based omega-3 alone may not be sufficient.

What is ALA? Definition and chemical structure

ALA stands for alpha-linolenic acid. It is a polyunsaturated fatty acid from the omega-3 family. Chemically, ALA consists of a chain of 18 carbon atoms with three double bonds — hence the shorthand notation C18:3n-3. The first double bond is at the third carbon atom from the methyl end of the chain, which makes it an omega-3 fatty acid.

ALA is an essential fatty acid: your body cannot synthesise it and must therefore obtain it through food. Without adequate ALA intake, deficiencies occur. This characteristic distinguishes ALA from EPA and DHA, which the body can theoretically — albeit in small amounts — produce from ALA.

The discovery of ALA as an essential fatty acid dates back to the 1920s and 1930s, when George and Mildred Burr demonstrated through animal experiments that certain fatty acids are vital and cannot be produced by the body. ALA is therefore one of the oldest known essential nutrients in modern nutritional science.

Compared to EPA (C20:5) and DHA (C22:6), ALA is the shortest of the three omega-3 fatty acids. This structural brevity also explains why ALA can serve as a precursor for the synthesis of EPA and DHA, but the conversion requires several enzymatic steps and is correspondingly inefficient.

The best ALA sources at a glance

ALA is found exclusively in plant-based foods — this is an important difference from EPA and DHA, which are found primarily in oily fish, seafood, and algae. For a plant-based diet, ALA is therefore the main omega-3 source.

Linseed oil and flaxseeds — the richest ALA source

Linseed oil is by far the most concentrated ALA source you can use in the kitchen. Its ALA content is between 53 and 55 g per 100 g of oil — meaning more than half of linseed oil consists of alpha-linolenic acid. A single tablespoon (approx. 10 ml) already provides around 5.3 g ALA, which is many times the recommended daily intake of 1–2 g.

Ground flaxseed is also an excellent source: it contains 16 to 18 g ALA per 100 g and has the additional advantage of providing fibre, lignans, and protein. Whole flaxseeds, however, are barely digested and provide correspondingly less ALA — so always use ground or milled seeds.

Chia seeds, hemp oil, and walnuts

Chia seeds have received a great deal of attention in recent years as a superfood — rightly so when it comes to ALA. With 17 to 18 g ALA per 100 g, they are almost on a par with ground flaxseed. Two tablespoons of chia seeds (approx. 20 g) provide around 3.5 g ALA. Due to their swelling capacity, they are well suited for puddings, smoothies, or as an egg substitute in baking.

Hemp oil contains 15 to 20 g ALA per 100 g and is also characterised by a favourable omega-6 to omega-3 ratio of approximately 3:1 — ideal, since an excessively high omega-6 ratio inhibits ALA conversion (more on this in the next section).

Walnuts are the ALA-richest nut, with 9 to 10 g per 100 g. A small handful (approx. 30 g) provides around 2.7 g ALA. Studies, including a meta-analysis in the British Journal of Nutrition, have associated walnut consumption with positive effects on blood lipid levels.

Rapeseed oil as an everyday ALA source

Rapeseed oil contains 8 to 9 g ALA per 100 g — less than linseed oil, but significantly more than many other cooking oils. Its great advantage is heat stability: unlike linseed oil, rapeseed oil can be used for frying and cooking. As a standard oil for everyday cooking, rapeseed oil is one of the simplest ways to increase ALA intake as a matter of routine.

Food	ALA content (g/100 g)	ALA per serving	Serving size
Linseed oil	53–55 g	~5.3 g	1 tbsp (10 ml)
Ground flaxseed	16–18 g	~3.4 g	2 tbsp (20 g)
Chia seeds	17–18 g	~3.5 g	2 tbsp (20 g)
Hemp oil	15–20 g	~1.8 g	1 tbsp (10 ml)
Walnuts	9–10 g	~2.7 g	1 handful (30 g)
Rapeseed oil	8–9 g	~0.85 g	1 tbsp (10 ml)
Soya oil	6–7 g	~0.65 g	1 tbsp (10 ml)

The major problem: conversion of ALA to EPA and DHA

Now we come to the decisive point that distinguishes ALA from EPA and DHA — and why purely plant-based omega-3 sources are not sufficient for many people. ALA can be converted in the body to EPA and then to DHA, but this process is alarmingly inefficient.

The conversion pathway in the body

The conversion of ALA to EPA and DHA takes place mainly in the liver and requires several enzymatic steps. Two enzymes are primarily involved: delta-6-desaturase and delta-5-desaturase, as well as so-called elongases that extend the carbon chain.

The simplified pathway is as follows:

ALA (C18:3) → stearidonic acid (C18:4) → eicosatetraenoic acid (C20:4) → EPA (C20:5) → DPA (C22:5) → DHA (C22:6)

This sounds straightforward — but it is not. Studies consistently show that conversion efficiency is extremely low. According to a widely cited review by Burdge and Calder (2005, PMID: 16188209), only 5–15% of ingested ALA is converted to EPA. For DHA, conversion is even worse: less than 1% of ALA ultimately arrives as DHA in the body.

These figures mean: even if you consume generous amounts of linseed oil daily, you will not be able to build up significant DHA levels in your blood. EPA levels can at least be raised somewhat, but even here efficiency remains far below that of direct intake from fish or algae oil.

Factors that inhibit conversion

The already weak conversion is further restricted by a number of factors:

High omega-6 to omega-3 ratio: This is the most important inhibiting factor. Delta-6-desaturase is needed both for the conversion of ALA (omega-3) and of linoleic acid (omega-6, LA). In the Western diet, with an omega-6 to omega-3 ratio of often 15:1 to 20:1 — instead of the recommended 4:1 — linoleic acid massively competes for the enzyme and displaces ALA. The result: even less ALA is converted to EPA and DHA.

Age: The enzymatic activity of the desaturases decreases with age. Older people therefore convert ALA even less efficiently than younger people.

Sex: Women of reproductive age convert ALA somewhat better to DHA than men — presumably due to the influence of oestrogen on enzyme activity. Nevertheless, total conversion remains low even in women.

Alcohol: Regular alcohol consumption impairs desaturase activity and reduces the conversion of ALA to EPA/DHA.

Trans fatty acids: Industrially hydrogenated fats (trans fats) inhibit desaturases and disrupt the entire fatty acid metabolism.

Zinc deficiency: Zinc is a cofactor of delta-6-desaturase. With zinc deficiency — not uncommon in a vegan diet — conversion efficiency decreases further.

Why is ALA alone not enough?

Let us do the calculation concretely: you consume 1 tablespoon of linseed oil per day, taking in around 5,000 mg (5 g) of ALA. With a 10% conversion rate to EPA, a maximum of 500 mg EPA is produced. With 1% conversion to DHA, that would be just 50 mg DHA. EFSA recommends a daily intake of 250 mg EPA+DHA for normal cardiac function. Those 50 mg DHA are far below that figure.

And that is still the optimistic scenario: with an unfavourable omega-6 to omega-3 ratio, alcohol consumption, or older age, actual conversion rates can be significantly lower still.

ALA's own biological effects

Even though conversion to EPA and DHA is limited, ALA has its own biological significance — and this should not be underestimated. As an essential fatty acid, ALA is by definition indispensable: without it, deficiencies occur that can range from growth retardation to neurological disorders.

In addition, observational studies and some clinical investigations show that a higher ALA intake may be associated with positive effects on cardiovascular parameters. A meta-analysis in the American Journal of Clinical Nutrition (PMID: 19939984) showed that higher ALA intake was associated with a lower risk of cardiovascular disease. Studies also show that ALA-rich diets may have positive effects on LDL cholesterol and triglyceride levels.

However, the evidence for direct ALA effects is overall weaker and less consistent than for EPA and DHA. EFSA has so far not approved any independent health claim for ALA — unlike EPA and DHA, for which specific health claims have been approved. This is partly because in many studies it is not clear whether effects come from ALA itself or from the EPA converted from it.

Nevertheless, the conclusion is clear: ALA matters. As an essential fatty acid, it fulfils a structural and functional role in the body, provides energy, and is a valuable component of a balanced diet — as long as its limitations are understood. For more on the differences between the various omega-3 fatty acids, see the articles on What are omega-3 fatty acids? and EPA (Eicosapentaenoic Acid).

ALA requirements and recommendations

The German Nutrition Society (DGE) recommends that 0.5% of daily energy intake should come from ALA. With an average energy requirement of 2,000 kcal, this corresponds to approximately 1.1 g ALA per day for women and 1.6 g for men. This requirement can easily be met with the right food choices: even one teaspoon of linseed oil per day exceeds the recommendation.

EFSA has not formulated specific health claims for ALA itself — unlike EPA and DHA, for which concrete health claims regarding heart function, brain, and vision have been approved. This once again illustrates that the biological activity is much better documented for EPA and DHA.

For everyday life, this gives the following picture: you meet your ALA requirement most efficiently with a tablespoon of linseed oil daily, ground flaxseed at breakfast, or a daily walnut snack. For EPA and DHA, however, you need an independent source — either fish or, if you follow a plant-based diet, a high-quality algae oil supplement.

Algae oil: the better alternative for vegans

Here lies the elegant solution for people living on plants: algae oil. The reason why oily fish is rich in EPA and DHA is not that fish produce these fatty acids themselves. Fish accumulate EPA and DHA because they eat algae — either directly or through the food chain. The actual producers of EPA and DHA are marine microalgae.

Algae oil provides EPA and DHA directly — without the detour through the inefficient enzymatic conversion from ALA. Studies show that algae oil supplements raise DHA and EPA blood levels comparably effectively to fish oil. An analysis in the Journal of Human Nutrition and Dietetics confirmed that the bioavailability of DHA from algae oil is equivalent to that from fish oil.

Algae oil is therefore the ideal supplement for anyone following a vegan or vegetarian diet who still wants to ensure good EPA and DHA intake. How to recognise a good omega-3 oil, which quality criteria are decisive, and which products are recommended — you will find all this in our Buyer's Guide to Omega-3 Oils.

The approach "ALA from plants + DHA/EPA from algae oil" is well-founded scientifically and enables complete omega-3 coverage without animal products. Important: pay attention to the quality and EPA/DHA content of the algae oil — not every product delivers sufficient amounts.

ALA in everyday life: practical tips

To make the most of ALA-rich foods, here are some important practical tips:

Do not heat linseed oil: ALA is sensitive to heat, light, and oxygen. Never heat linseed oil — it oxidises quickly and forms unwanted oxidation products. Use it cold, for example as a dressing or drizzled over finished dishes.

Store linseed oil in the dark and cold: Buy linseed oil only in small quantities (250 ml) in opaque containers. In the refrigerator, opened linseed oil keeps for approximately 4–6 weeks. If the oil smells sharply bitter, dispose of it immediately.

Always grind flaxseeds: Whole flaxseeds are barely digested. Buy ground flaxseed or grind it fresh in a coffee grinder. Store ground flaxseed in the refrigerator and use within a few weeks.

Soak chia seeds: Chia seeds swell and are then more easily digested. Soak for at least 10–15 minutes in water or plant milk, for example as overnight chia pudding in the refrigerator.

Snack on walnuts daily: A handful of walnuts (30 g) as a daily snack provides around 2.7 g ALA and numerous other nutrients. Store walnuts in a cool, dark place, as their fatty acids are also susceptible to oxidation.

Rapeseed oil instead of sunflower oil: For cooking and frying, rapeseed oil is clearly preferable to sunflower oil — not only because of its ALA content, but also because sunflower oil is very rich in omega-6 linoleic acid, which inhibits ALA conversion. Rapeseed oil has a significantly more favourable fatty acid ratio.

If you integrate these simple habits into your daily life, you will consume adequate ALA and will also have laid the foundation for good omega-3 intake. The EPA and DHA requirement is best met additionally through oily fish or a high-quality algae oil supplement. How much EPA and DHA you need daily can be found in our dosage guide.

Frequently asked questions about ALA (alpha-linolenic acid)