Evening primrose oil and PCOS: a natural treatment?

Evening primrose oil is a supplement often touted as a natural remedy for a variety of ailments including PMS. But does evening primrose oil have benefits for PCOS symptoms? We look at the evidence to evaluate evening primrose oil and PCOS and investigate the potential beneficial effects of this oil for people with PCOS.

What is PCOS?

Polycystic ovary syndrome or polycystic ovarian syndrome (PCOS) affects approximately 1 in 10 people assigned female at birth. It is an endocrine disorder with many symptoms. Symptoms of PCOS include irregular periods, infertility or difficulty getting pregnant, oily skin, acne, hirsutism, hair loss on the head, skin tags and more.

PCOS cannot be cured so many people look to nutritional changes and dietary supplements to help to improve their symptoms and quality of life.

What is evening primrose oil?

Evening primrose oil is an oil made from the seeds of evening primrose plants (Oenothera biennis), a plant native to North America. Evening primrose oil has been used traditionally to treat ailments like bruises, haemorrhoids and sore throats.

This oil is a rich source of omega-6 fatty acids, particularly gamma-linolenic acid (GLA). GLA cannot be produced by the human body and must be consumed through dietary sources or nutritional supplements instead.

GLA plays several important roles in the body including being anti-inflammatory, improving skin health, improving hormonal balance, maintaining nerve function, positively impacting cardiovascular health and supporting the immune system. But what about the connection between evening primrose oil and PCOS?

What is the connection between evening primrose oil and PCOS?

As mentioned, PCOS cannot be cured. Many people look to alternative treatments for PCOS including Chinese medicine, natural remedies and alternative medicine to try alongside conventional medicine. Although limited, there are studies that suggest that evening primrose oil could have some benefits for PCOS, but more scientific studies are needed to truly understand the effects of evening primrose oil.

4 potential benefits of evening primrose oil for PCOS

Studies have been carried out to understand the effect of evening primrose oil on PCOS. Let’s take a look at four of the positive effects and analyse the strength of the evidence for the management of polycystic ovary syndrome.

Good source of essential fatty acids

Evening primrose oil is a good source of essential fatty acids, particularly omega-6. Omega-6 fatty acids are a precursor to prostaglandins which are involved in regulating inflammation. PCOS is associated with chronic inflammation so consuming foods and supplements with anti-inflammatory properties may be helpful. But it is important to note that you can get enough omega-6 in your diet from foods like vegetable oils, nuts, seeds, whole grains, meat, poultry, eggs and dairy products and supplementing is often not required.

May improve PMS symptoms

Premenstrual syndrome (PMS) is a common set of symptoms that people who menstruate often experience in the days or weeks leading up to their bleed. Symptoms include mood swings, bloating, breast tenderness and fatigue.

A 2019 study found that evening primrose oil may help to alleviate PMS symptoms including acne, bloating, irritability and breast swelling. This has been hypothesised to occur because people with PMS are sensitive to raised prolactin levels in the body. GLA in evening primrose oil is thought to prevent prolactin from causing PMS symptoms as it converts to prostaglandin E1 in the body.

Could improve blood cholesterol levels

PCOS is associated with an increased risk of developing certain conditions like high cholesterol levels. A 2018 study found that people with PCOS with vitamin D deficiency and supplemented with both vitamin D and evening primrose oil had improved triglycerides and VLDL cholesterol levels compared to a placebo group.

Of course, we don’t know whether it was just the vitamin D that improved the levels and whether evening primrose oil had an effect so more scientific research is required.

May improve hormone levels

People with PCOS have an imbalance in hormone levels, particularly sex hormones such as LH and FSH, insulin and androgens (like testosterone). People with PCOS often have raised blood sugar levels and have insulin resistance. PCOS management should focus on correcting the hormonal imbalance often seen in people with PCOS.

A 2018 study investigating the impact of evening primrose oil on PCOS in rodents found that regular supplementation improved FSH, LH and testosterone levels in rats with PCOS. They also found that supplementation reduced insulin levels and improved insulin sensitivity.

Of course, these results are only in rats so far and more evidence is needed in human PCOS patients but the pilot results are promising.

Evening primrose oil dosage

As with all supplements, the ideal dose of evening primrose oil depends on a variety of factors including age, weight, general health and the supplement concentration. Speak with a professional to establish a suitable dosage for you.

Within the scientific literature dosage varies between 500 and 3000mg per day. Always follow the specific dosage instructions provided on the supplement label unless told otherwise by your medical team.

Side effects

Generally, supplementing with evening primrose oil is considered safe but it is essential to be aware of any potential side effects or any negative effects associated with supplementation.

Gastrointestinal issues

Some people may notice gastrointestinal issues such as nausea, stomach pain or diarrhoea when taking evening primrose oil. To minimise these effects try taking the supplement alongside food.

Allergic reactions

Some people may be allergic to evening primrose oil and be unaware. If you notice any symptoms like rashes, itching, swelling or trouble breathing then seek immediate medical attention.

Headaches and pains

There have been some incidences of headaches and pains in people supplementing with evening primrose oil. 

Increased seizure risk

Evening primrose oil may lower the seizure threshold in some people. If you are susceptible to seizures then do not supplement with this oil.

Changes in blood pressure

Evening primrose oil may lower or cause fluctuating blood pressure levels. If you have concerns with your blood pressure then seek professional medical advice before supplementing.

When to avoid taking evening primrose oil

It is essential to be aware of when to avoid consuming evening primrose oil including at different life stages and whilst taking certain medications. As always before taking a new supplement or starting a new regime, speak with a healthcare provider to discuss your unique situation and ensure it is suitable for you.

Medication interactions

Those who are taking anticoagulants or antiplatelet medications should avoid taking evening primrose oil. This is because the oil may have a blood-thinning effect which could interact with various medications.

Life stages

Those who are pregnant or breastfeeding should avoid taking evening primrose oil, simply because there is not enough scientific evidence to understand the safety during these life stages. Similarly, children should avoid evening primrose oil as its safety and efficacy in this population have not been established.

Certain diseases and disorders

People who have liver or kidney disease should avoid evening primrose oil. This is because the metabolism and elimination of GLA (found in evening primrose oil) may be compromised in these conditions. People with bleeding disorders should also avoid supplementing with evening primrose oil because of its blood-thinning properties. Those who have a history of seizures should also avoid evening primrose oil supplements because it has been associated with lowering the seizure threshold in some individuals.

Key takeaways: evening primrose oil and PCOS

​Supplementing with evening primrose oil capsules may be helpful for those suffering from PMS symptoms but the evidence to support the efficacy of evening primrose oil for PCOS is just not strong enough.

We need more evidence in particular on people with PCOS using evening primrose oil supplements before we can conclusively recommend it as a useful supplement. We recommend working with a healthcare professional to develop a PCOS management plan bespoke to your symptoms and lifestyle.