What is alpha-linolenic acid (ALA)?
Alpha-linolenic acid (ALA) is a plant-based omega-3 fatty acid with 18 carbon atoms and three double bonds. It is essential, meaning the body cannot make it, and it converts only a small share into the long-chain fatty acids EPA and DHA.
What is ALA and where does it come from?
ALA (alpha-linolenic acid) is the parent compound of the omega-3 family, a polyunsaturated fatty acid (18:3 n-3). Humans cannot synthesise it, so it counts as an essential fatty acid.
Rich plant sources are:
- Linseed (flaxseed) oil and seeds: the oil is more than half ALA.
- Chia seeds and hemp oil
- Walnuts and walnut oil
- Rapeseed (canola) oil: lower in ALA than linseed oil but widely used in cooking.
These oils are sensitive to light, heat and oxygen, so store them cool, dark and tightly closed.
How much ALA becomes EPA and DHA?
The body can elongate ALA in several enzymatic steps to EPA and DHA, but the process is inefficient. Reviews report conversion to EPA of roughly a few percent up to about 10 %, and to DHA mostly lower, often below 1 % to a few percent. Figures vary widely between studies and individuals. In single tracer studies in young women they were considerably higher, about 21 % for EPA and 9 % for DHA (Burdge & Wootton, 2002). Women tend to convert more than men in studies, and dietary omega-6 fatty acids compete for the same enzymes.
For this reason ALA alone often does not secure the supply of EPA and DHA, which matters especially for people who eat no fish.
ALA compared with EPA and DHA
Quick comparison of the three omega-3 fatty acids.
| Fatty acid | Chain length | Typical source | Made by the body? |
|---|---|---|---|
| Fatty acid ALA | Chain length 18 carbons, 3 double bonds | Typical source Linseed oil, chia, walnuts, rapeseed oil | Made by the body? No (essential) |
| Fatty acid EPA | Chain length 20 carbons, 5 double bonds | Typical source Fatty sea fish, algae oil | Made by the body? Only low conversion from ALA |
| Fatty acid DHA | Chain length 22 carbons, 6 double bonds | Typical source Fatty sea fish, algae oil | Made by the body? Only very low conversion from ALA |
Authorisation and recommendations
In the EU, the following claim is authorised for ALA: ALA contributes to the maintenance of normal blood cholesterol levels. The beneficial effect is obtained with a daily intake of 2 g of ALA. EFSA sets the adequate intake of ALA at 0.5 % of total energy.
This is general nutrition information, not individual advice. If you have questions about your own intake, speak to a doctor.
ALA is not the same as EPA and DHA. People on a purely plant-based diet can take the long-chain omega-3s directly from algae oil; see fish oil as the classic source for comparison.