Omega-6 GLA: Evening Primrose, Borage & Blackcurrant Oil — A Research-Backed Guide
⚡ 60-Second Summary
GLA — gamma-linolenic acid — is an anti-inflammatory omega-6 fatty acid. The story most articles tell is that GLA bypasses a slow desaturase enzyme to make DGLA and series-1 prostaglandins, which dampen inflammation. The mechanism is real, but modern, well-powered RCTs in atopic dermatitis, breast pain, and rheumatoid arthritis have generally failed to confirm the impressive results from older small studies.
Best forms: evening primrose oil (8–10% GLA, safest default), borage oil (20–24% GLA, requires certified PA-free preparation), or blackcurrant seed oil (15–17% GLA + a small amount of stearidonic acid).
Typical dose: 240–480 mg/day GLA. Allow 8–12 weeks before deciding whether to continue.
What is GLA?
Gamma-linolenic acid (18:3 n-6) is an omega-6 polyunsaturated fat. The body normally synthesizes GLA from dietary linoleic acid via the enzyme delta-6-desaturase, then elongates GLA into dihomo-gamma-linolenic acid (DGLA), which gives rise to series-1 prostaglandins — generally anti-inflammatory or inflammation-modulating. Some adults are thought to have reduced delta-6-desaturase activity due to age, atopy, diabetes, or alcohol intake, which is the rationale for supplementing pre-formed GLA.
Practically no common foods contain meaningful GLA. The supplemental sources are all seed oils:
- Evening primrose oil (EPO) — 8–10% GLA. The most familiar source.
- Borage oil — 20–24% GLA. The most concentrated, but requires PA-free certification.
- Blackcurrant seed oil — 15–17% GLA, plus 2–4% stearidonic acid (an omega-3 metabolic shortcut).
Evidence-based benefits of GLA
1. Atopic dermatitis (eczema)
This is the historical headline use. A 1989 meta-analysis showed clear benefit, but the 2013 Cochrane review of 27 trials covering more than 1,500 participants concluded that EPO and borage oil produce no clinically meaningful improvement in eczema severity at typical doses. Some individuals still respond — particularly those with documented essential-fatty-acid abnormalities — but eczema should not be the primary reason to start GLA today.
2. Cyclical mastalgia (breast pain)
Older NHS guidance recommended EPO at 240–320 mg GLA/day for premenstrual breast pain; subsequent rigorous RCTs and a Cochrane-style review found the effect indistinguishable from placebo. NICE removed mastalgia as an indication for EPO in the UK. Mild benefit can't be ruled out, but the modern position is that GLA is not a first-line treatment.
3. Rheumatoid arthritis (modest)
Several trials of 540 mg GLA/day for 24 weeks show small reductions in tender-joint counts and morning stiffness in RA, with effect sizes smaller than fish oil. GLA is sometimes used as an add-on in patients who do not tolerate fish oil; it is not a substitute for disease-modifying anti-rheumatic drugs.
4. Diabetic neuropathy (preliminary)
One 1993 trial showed GLA at 480 mg/day improved nerve-conduction parameters in mild diabetic neuropathy. The evidence base is small and dated; modern guidelines do not list GLA as a recommended therapy.
5. Skin barrier and dryness
GLA supplementation modestly improves transepidermal water loss and skin hydration in healthy adults at 360–720 mg/day over 12 weeks. Effect size is small but consistent — useful as a hedge for adults with mild dry skin who are otherwise nutritionally adequate.
Is GLA an essential nutrient?
No. Linoleic acid (the parent omega-6) is essential, and the body normally makes GLA from it. There is no GLA RDA. Supplemental GLA is best understood as an attempt to bypass a sometimes-sluggish desaturase rather than to correct a deficiency.
Evening primrose vs borage vs blackcurrant seed oil
| Form | GLA content | Typical daily dose for 300 mg GLA | Notes |
|---|---|---|---|
| Evening primrose oil | 8–10% | 3–4 g (often 6 × 500 mg softgels) | Most studied source. No PA concern. Default safe choice. |
| Borage oil (PA-free) | 20–24% | 1.3–1.5 g | Highest GLA per gram. Choose only certified PA-free products. Don't use the unrefined oil. |
| Blackcurrant seed oil | 15–17% | 1.8–2 g | Moderate GLA + a touch of stearidonic acid (a more efficient EPA precursor than ALA). |
| Hemp seed oil | 2–4% (variable) | Not a practical GLA source | Useful for a balanced omega-3:6 ratio in food, but too dilute in GLA for therapeutic doses. |
How much GLA should you take?
- General use: 240–360 mg/day GLA
- Targeted (RA, skin): 360–480 mg/day GLA
- Upper bound studied: up to 2.8 g/day for short-term trials, but no benefit above 600 mg/day in most settings
Take with food. Allow 8–12 weeks of consistent dosing before judging effect, since GLA's downstream effects on prostaglandin signaling build slowly.
Safety, pregnancy & pyrrolizidine alkaloids
At typical doses, GLA-rich oils are well tolerated.
Common side effects
- Mild GI upset (nausea, soft stools, indigestion)
- Headache in occasional users
- Skin reactions (rare)
Borage oil and pyrrolizidine alkaloids
Borage plants synthesize pyrrolizidine alkaloids (PAs) — chemicals that can damage the liver. Properly processed borage seed oil should contain less than 1 µg of unsaturated PAs per daily dose; only buy products that are explicitly labeled "PA-free" or carry independent certification. Evening primrose oil and blackcurrant seed oil do not contain PAs.
Pregnancy and labor
EPO has historically been used to encourage cervical ripening, but modern guidelines do not recommend it. Some retrospective data suggest possible association with prolonged labor or membrane rupture; many obstetric authorities advise against routine EPO use in late pregnancy. Borage oil should be avoided in pregnancy due to PA risk and uterine-stimulant concerns.
Bleeding and surgery
GLA has a mild antiplatelet effect, generally less than fish oil. Stop 1–2 weeks before elective surgery to be conservative.
Seizure threshold
Older case reports suggested EPO might lower seizure threshold in epilepsy patients on phenothiazines; modern evidence does not support this concern at supplement doses, but caution is reasonable.
Drug and nutrient interactions
- Anticoagulants and antiplatelets — mild additive antiplatelet effect.
- Phenothiazines — historical seizure-threshold concern; modern data reassuring but caution prudent in epilepsy.
- Anti-hypertensive and ACE inhibitors — no clinically meaningful interaction.
- NSAIDs and corticosteroids — generally compatible; some evidence GLA permits dose reduction in RA.
- Omega-3 fish oil — synergistic and commonly co-supplemented; no negative interaction.
Use our free interaction checker for additional combinations.
Who might benefit — and who shouldn't bother
| Most likely to benefit | Less likely to benefit |
|---|---|
| Adults with mild atopic skin dryness | People hoping GLA replaces eczema medication |
| RA patients seeking adjunct symptom relief who can't take fish oil | Anyone already responding well to fish-oil-based omega-3 |
| Adults with documented essential-fatty-acid abnormalities | Pregnant women and people with active liver disease (especially borage) |
| Those who tolerate the cost-per-mg of GLA | People expecting omega-3-level cardiometabolic benefit |
Frequently asked questions
How much GLA should I take per day?
240–480 mg/day GLA, dosed by GLA content rather than total oil. About 3–4 g of EPO, 1.3 g of PA-free borage oil, or 1.8 g of blackcurrant seed oil delivers roughly 300 mg of GLA.
Does GLA help eczema or breast pain?
Modern reviews — including the 2013 Cochrane EPO review — find little clinically meaningful effect in either condition, despite older positive trials.
Is borage oil safer than evening primrose oil?
Only when explicitly certified PA-free. Borage naturally contains liver-toxic pyrrolizidine alkaloids that must be removed during processing.
Can I take GLA with fish oil?
Yes — they are commonly combined. At typical doses both raise their respective tissue fatty-acid pools without meaningful interference.
Will GLA help my skin look better?
Modest improvements in skin hydration and barrier function have been documented at 360–720 mg/day over 12 weeks, but effects are subtle.
Does GLA increase weight or estrogen?
No. GLA is calorically negligible at supplement doses and does not have direct estrogenic activity.
Related ingredients and articles
Omega-3
The cleaner anti-inflammatory option for most adults.
EPO & the Eczema Question
Why modern reviews changed the recommendation.
Vitamin E
Often paired with GLA in skin formulas.
Zinc
An evidence-supported skin and immune mineral.
Disclaimer: This information is for educational purposes only and should not replace medical advice. Always consult a qualified healthcare provider before starting any supplement, especially if you have a medical condition, are pregnant, or take prescription medications. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.