Can evening primrose oil (EPO) affect cholesterol levels?

Effect of Evening Primrose Oil on Cholesterol Levels

Evening primrose oil has no significant effect on cholesterol levels in the general population, though it may modestly increase HDL cholesterol in hyperlipidemic individuals and reduce triglycerides at doses ≤4g/day. 1

Mechanism and Composition

• Evening primrose oil (EPO) contains gamma-linolenic acid (GLA), which makes up approximately 9% of its fatty acid content, along with linoleic acid (about 72%) 2
• GLA is an omega-6 fatty acid that has been proposed to have anti-inflammatory properties and potential effects on lipid metabolism 3

Evidence on Cholesterol Effects

General Population

• A systematic review and meta-analysis of randomized clinical trials found that EPO supplementation had no significant overall effect on total cholesterol, LDL cholesterol, HDL cholesterol, or triglycerides in the general population 1
• An earlier study in hyperlipidemic patients showed that EPO supplementation at increasing doses (2.4ml, 4.8ml, and 7.2ml) over three months did not change serum cholesterol, HDL cholesterol, or triglyceride mean values 2

Specific Populations

• In hyperlipidemic subjects specifically, EPO supplementation was found to significantly increase HDL cholesterol levels (weighted mean difference = 5.468 mg/dl) 1
• At doses ≤4 g/day, EPO supplementation showed a significant reduction in triglycerides (weighted mean difference = -37.28 mg/dl) 1
• In animal studies, EPO demonstrated more potent hypocholesterolemic effects than safflower oil, with increased excretion of neutral steroids during the first two weeks of feeding 4

Comparison to Other Dietary Fats

• Current dietary guidelines emphasize that the types of fatty acids consumed are more important than total fat content for cardiovascular health 3
• Replacing saturated fatty acids with polyunsaturated fatty acids (like those found in EPO) may reduce coronary heart disease risk by 2-3% 3
• However, specific evidence for EPO's effects is limited compared to other oils like olive oil, which has stronger evidence for cardiovascular benefits 3

Limitations and Considerations

• The quality of evidence for EPO's effects on cholesterol is generally low, with small studies showing inconsistent results 1, 2, 5
• One study in men with low dihomo-gamma-linolenic acid levels found that EPO was not an effective hypocholesterolemic agent 5
• Most dietary supplement studies lack the rigor of pharmaceutical trials, making definitive recommendations difficult 3

Clinical Implications

• EPO should not be recommended as a primary intervention for managing cholesterol levels due to insufficient evidence 1
• For patients requiring cholesterol management, established approaches such as dietary modification (reducing saturated fats, increasing unsaturated fats from sources like olive oil) and pharmacological therapy when indicated remain the standard of care 3
• If patients are interested in using EPO for potential modest lipid benefits, doses ≤4g/day may provide some triglyceride-lowering effects in certain populations 1

Potential Additional Benefits

• In hyperlipidemic rabbits, EPO supplementation reduced hypercholesterolemia, increased HDL cholesterol, and demonstrated anti-thrombotic effects 6
• EPO may have other health effects unrelated to cholesterol, though these require further investigation 3