Evening Primrose Oil
Evening primrose oil in softgels, liquid oil and blends with starflower oil. We explain what GLA per capsule means, why cold-pressed oil with vitamin E stays fresher, and how to take it consistently, with food, over several weeks.Read more →
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What the GLA in evening primrose oil actually means
Evening primrose oil is pressed from the seeds of Oenothera biennis, a yellow flowering plant that opens its blooms in the evening. The seed oil is mostly linoleic acid, with a smaller share of gamma-linolenic acid, usually shortened to GLA. GLA is an omega-6 fatty acid. Your body can build it from the linoleic acid in everyday cooking oils, but the speed of that step differs from person to person. A supplement supplies GLA that is already formed. That is the reason people buy this oil instead of sunflower oil.
The strength sits in the GLA, not in the size of the capsule
Packs compete on numbers: 500 mg, 1000 mg, sometimes 3000 mg. Those figures only say how much oil the softgel holds. The useful number is the GLA content, which in evening primrose oil is normally 8 to 10 percent of the fatty acids. A 1000 mg softgel at 9 percent gives you roughly 90 mg of GLA. Blends with borage seed oil, sold in the UK as starflower oil, sit higher, because borage seed is naturally richer in GLA. So compare milligrams of GLA, not milligrams of oil.
How we choose evening primrose oil
We look at three things. The form first: cold-pressed oil, because pressing without heat or solvents treats the fatty acids gently. Then the dosage: the GLA has to be stated in milligrams on the label, not hidden behind the weight of the oil. Then the combination: vitamin E inside the softgel, since GLA oxidises easily and vitamin E keeps the oil stable. We buy directly from the brands, so what arrives is authentic, and every product passes our compliance team before it goes live. We test products ourselves and independent labs spot-check batches. You can read how we select our brands.
Who buys it, and what to expect
In the UK this oil has a long history with women who take it around their period or during the menopause, and with people who eat little GLA from food. Be realistic about the pace. Fatty acids work into your cell membranes slowly, so judge the result after eight to twelve weeks of daily use rather than after a fortnight. We also keep the record straight: European food law has authorised no health claim for GLA or for evening primrose oil, and the UK medicines regulator withdrew the two prescription evening primrose oil medicines in 2002 because the evidence for eczema and breast pain fell short. That does not make the oil useless as a source of GLA. It means the honest promise is a reliable daily amount of GLA, and the judgement about how you feel stays with you. If you want the wider picture, our omega-6 pages sit next to this one.
A few practical points before you order:
- Softgels made with bovine gelatin are not suitable for vegans, so check the shell if that matters to you.
- UK labels often advise anyone with epilepsy to speak to their doctor first. The same is sensible if you use blood-thinning medicine.
- Store the bottle cool and dark, because this oil turns rancid faster than most.
Other pressed plant oils and botanical extracts are grouped in our herbal supplements range.
Frequently asked questions
It is the oil pressed from the seeds of the evening primrose plant, Oenothera biennis, a plant from North America whose flowers open towards dusk. The seeds are small and oily, and it takes a lot of them to fill a bottle. People take the oil for one component in particular: gamma-linolenic acid, or GLA, an omega-6 fatty acid that is scarce in an ordinary diet. Most products are softgel capsules; liquid oil also exists.
