What is in the oil
Evening primrose oil is pressed from the seeds of Oenothera biennis. Its main fatty acids are linoleic acid (LA) and gamma-linolenic acid (GLA), both omega-6 fatty acids. The label shows how much of each the product contains. Oil from different batches varies a little, which is why Swanson gives GLA as a usual range.
Evening primrose oil products compared
| Product | Daily dose on the label | Oil per day | GLA per day | Pack lasts |
|---|---|---|---|---|
| OstroVit Evening Primrose Oil 1000 mg, 60 softgels | 1 softgel with water | 1000 mg (LA 700 mg) | 90 mg | 60 days |
| Swanson Evening Primrose Oil 1300 mg, 100 softgels | 1 softgel, 1 to 2 times a day | 1300 to 2600 mg | 104 to 260 mg, usually | 50 to 100 days |
| Swanson Evening Primrose Oil 500 mg, 100 softgels | 2 softgels, 2 to 3 times a day | 2 to 3 g | 160 to 300 mg | 16 to 25 days |
Compare by GLA per day and by the price per day, not by the milligrams on the front of the bottle. The 500 mg Swanson softgel needs four to six softgels a day to reach its dose.
Other ingredients
All three products use a gelatin softgel with glycerol, so they are not vegan. OstroVit also adds 10 mg of vitamin E (83% of the 12 mg NRV) as DL-alpha-tocopheryl acetate, which stabilises the oil.
What the EU allows us to say
The EU has not authorised a health claim for evening primrose oil or for gamma-linolenic acid. Under Regulation (EC) No 1924/2006 we therefore describe the oil, the fatty acids and the dose, not an effect on the body. The one claim that touches this category belongs to the vitamin E in the OstroVit softgel, not to the oil:
- Vitamin E contributes to the protection of cells from oxidative stress.
Regulation (EU) No 432/2012 allows it because the OstroVit softgel provides at least 15% of the NRV for vitamin E.
Warnings on the labels
- OstroVit: not for children, pregnant or breastfeeding women.
- Swanson (both): not recommended for pregnant or breastfeeding women; if you take prescription medicines, talk to your doctor before use.
Other oils and fatty acids are in omega-3 and fish oil. Combined formulas for women are in vitamins for women.
Questions
What is GLA?
Gamma-linolenic acid is an omega-6 fatty acid present in evening primrose oil. The label states how many milligrams a daily dose contains.
Is evening primrose oil the same as fish oil?
No. Fish oil provides the omega-3 fatty acids EPA and DHA, evening primrose oil provides omega-6 fatty acids. They are different products.
Why do the pack lengths differ so much?
The daily dose ranges from one softgel to six, and some labels give a range. A 100-softgel bottle lasts from 16 to 100 days depending on the product and the dose you choose.
When should I take it?
Follow the label. OstroVit says one softgel a day with enough water. Swanson labels give a number of softgels per day and no set time.
Why do you not write about the benefits?
Because no EU-authorised claim exists for evening primrose oil. We write what is on the label.
Sources
- Regulation (EC) No 1924/2006 (nutrition and health claims on foods)
- Regulation (EU) No 432/2012 (list of permitted health claims)
- EFSA: Health claims
Content reviewed by Inese Kalniņa, dietitian.
2026-10-01