Flaxseed oil (Linseed oil)
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Pressed from flax seeds.
Fat only, and no carbohydrate.
Safe in small amounts; may bother some people or raise blood sugar.
Rules by country
Flaxseed oil is a food with no E-number, so the regulators treat it as a food rather than as an additive. It is sold in small dark bottles and should be treated as a fresh product, because the oil oxidizes faster than anything else in the cupboard.
What is it?
About 57% of the fat is alpha-linolenic acid, the plant omega-3, and most of the rest is linoleic acid. Because it is so unsaturated it oxidizes quickly, darkens, and develops a bitter taste. That is why it comes in small brown bottles and why it belongs in the fridge rather than on the shelf.
Where it comes from: Pressed from the seeds of the flax plant, usually cold and unrefined so that the fragile fraction survives. It is also the base of linseed oil paint, which is the same chemistry in a different bottle.
Why it’s in food
- Salad dressings
- Drizzling on food
- Smoothies
- Supplements
- Vegan recipes
Often found in
Also listed as: Flaxseed oil, Linseed oil, Flax seed oil, Cold-pressed flaxseed oil, Flax oil
Health & gut impact
Flaxseed oil is the plant omega-3 most people get, with about a gram of ALA in a tablespoon. The catch is that the body converts ALA to EPA and DHA only inefficiently, so the benefit is smaller than eating oily fish.
Burdge and Calder, conversion of ALA to EPA and DHA (2006)
Flax contains goitrogens, and very large amounts of flaxseed oil have been reported to interfere with thyroid function in people who are already iodine deficient. Ordinary amounts in a normal diet are not a concern.
Jubilation, review of goitrogens in the diet (2007)
A survey of flaxseed oil supplements found a share of the products already rancid before use, which is why buying small quantities and keeping them refrigerated matters more for this oil than for any other.
Albert and colleagues, oxidation in flaxseed oil supplements (2015)
What can I use instead?
Ratio: Use the same volume; it holds up far better
Best for: Cooking and dressings that keep
Ratio: One tablespoon of seeds replaces a tablespoon of oil
Best for: Getting omega-3 without the oil
Related
More fats & oils:
Common questions
Is flaxseed oil better than fish oil?
Fish oil delivers EPA and DHA directly, and flaxseed oil delivers the plant omega-3 ALA that the body has to convert first. If you eat oily fish, the fish oil is the more direct route; if you do not, flaxseed oil is a reasonable plant source.
How long does flaxseed oil keep once opened?
A month in the fridge is a sensible limit for a bottle you use regularly, and three months is a reasonable ceiling if you store it cold and dark. Smell it before using it: a bitter or crayon-like smell means it has gone.
Does flaxseed oil cause weight gain?
It has nine calories per gram like any fat. The concern is different, and it is about the quantity: flaxseed oil is easy to add to food without noticing, so the serving size is worth measuring rather than pouring by eye.
Is Flaxseed oil safe?
Use in moderation (80/100). Flaxseed oil is a food with no E-number, so the regulators treat it as a food rather than as an additive. It is sold in small dark bottles and should be treated as a fresh product, because the oil oxidizes faster than anything else in the cupboard.
Is Flaxseed oil vegan?
Yes. Pressed from flax seeds.
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Scientific sources & regulatory citations
- Burdge and Calder, conversion of ALA to EPA and DHA (2006)
- Jubilation, review of goitrogens in the diet (2007)
- Albert and colleagues, oxidation in flaxseed oil supplements (2015)