Health Benefits of Primrose Oil

Can the supplement treat PMS, eczema, and diabetes?

Common Evening Primrose, Evening Star (Oenothera biennis)
Evening primrose. Alessandra Sarti/Getty Images

Evening primrose oil is extracted from the seeds of evening primrose (Oenothera biennis), a plant native to North America. It gets its name from the yellow blossoms which bloom in the evening. The oil contains gamma-linolenic acid (GLA), an omega-6 fatty acid that has both anti-inflammatory and analgesic (pain-relieving) properties.

Alternative practitioners believe that evening primrose oil can aid in the treatment of numerous health conditions, including acne, diabetic neuropathy, eczema, osteoporosis, psoriasis, premenstrual syndrome (PMS), and rheumatoid arthritis.

Evening primrose oil is not an essential oil commonly used for aromatherapy but one that can be consumed orally. It may cause side effects if overused and can interact with certain medications, including blood thinners and nonsteroidal pain relievers.

Health Benefits

Evening primrose oil has been promoted as an effective treatment for a variety of ailments, including eczema and breast pain, since the 1930s. Many of these benefits are attributed to GLA, a fatty acid found in soybeans, walnuts, seeds, and vegetable oils (like rapeseed, canola, and linseed oil). Some the claims are better supported by research than others.

Menstrual Problems

Evening primrose oil has long been used by women to treat hot flashes during menopause. Hot flashes are a form of flushing caused by reduced levels of the hormone estradiol.

While the body of evidence remains mixed, a 2013 study in the Archives of Gynecology and Obstetrics that found that a daily, 500-milligram dose evening primrose oil provided modest relief of hot flashes after six weeks.

Although the severity of hot flashes improved when compared to women provided a placebo, the duration and frequency of the episodes did not.

Evening primrose oil is also sometimes used to alleviate menstrual cramps and premenstrual syndrome (PMS). To date, there is no conclusive evidence to support these claims.

Eczema

It was in the 1980s that evening primrose oil was heavily touted as an effective treatment of eczema by Canadian entrepreneur David Horrobin (1939-2003). Despite a positive response from consumers, many of the claims since been debunked in research.

According to a 2013 review of studies from the University of Minnesota Medical School, evening primrose oil proved no more effective in treating atopic eczema than a placebo in each of the seven reviewed trials.

Many of the same conclusions have been drawn when investigating the effectiveness of evening primrose oil in treating psoriasis or acne.

Rheumatoid Arthritis

Rheumatoid arthritis is a type of autoimmune arthritis primarily affecting the joints. Some studies have suggested that GLA can reduce pain and improve function in people with mild to moderate rheumatoid arthritis. Most of the results to date have been modest at best.

A 2011 review of studies from Australia concluded that GLA found in evening primrose, borage seed, or blackcurrant seed oil provided "moderate" relief of pain and disability in people with rheumatoid arthritis.

The most promising results were seen in people who concurrently used nonsteroidal anti-inflammatory drugs, triggering a modest improvement in morning stiffness and joint articulation.

Osteoporosis

An increased intake of unsaturated fat is associated with a reduced risk of osteoporosis (bone mineral loss), especially in postmenopausal women. Primrose oil is almost entirely unsaturated fat and is believed by some to counter the bone loss seen in women with osteoporosis

An 18-month study from South Africa reported that the combined use of primrose oil, fish oil, and calcium supplements either slowed or reversed bone loss in older women (average age 79) compared to match set of women given a placebo.

According to the research, the women given primrose oil, fish oil, and calcium experienced an increase of femoral (thigh) bone density of 1.3 percent (versus a loss of 2.3 percent in the placebo group). While the bone density of the lumbar spine remained unchanged in primrose oil group, the placebo group experienced a decrease in bone density of 3.2 percent.

Diabetic Neuropathy

It was in 1993 that evening primrose oil was first proposed as a possible treatment of diabetic neuropathy (DN), an often debilitating nerve pain mainly affecting the feet and legs. Since then, there has been evidence to support some of these claims.

A 12-month study from India, involving 80 people with severe DN, concluded that a daily 500- to 1,000-milligram dose of evening primrose oil combined with 400 milligrams of vitamin E achieved pain relief in 88 percent of the participants.

However promising, the conclusions were limited by the lack of a control (placebo) group to make an evaluative comparison. Still, the findings were significant enough to warrant further research.

Possible Side Effects

Like most supplements, there hasn't been much research assessing the long-term safety of evening primrose oil. In some cases, primrose oil may cause side effects such as stomach upset, headache, nausea, and diarrhea. Most of the side effects are low-grade and resolve on their own once the treatment is stopped.

There are certain medical conditions for which evening primrose oil may pose serious health risks. Among them:

  • Evening primrose oil may increase the risk of bleeding in people with bleeding disorders or those taking anticoagulants ("blood thinners").
  • If you have upcoming surgery, you should stop taking evening primrose oil two weeks beforehand to prevent excessive bleeding.
  • People with seizure disorders and who take medications for schizophrenia should avoid evening primrose oil as it may increase the risk of seizures.
  • Pregnant women should not take evening primrose oil as it may increase the risk of miscarriage or induced labor.

Drug Interactions

Evening primrose oil can interact with a significant number of medications, either reducing the drug's efficacy or triggering side effects (primarily bleeding or seizures). These include:

  • Anti-clotting drugs like Fragmin (dalteparin)
  • Anticoagulants like Coumadin (warfarin), heparin, Lovenox (enoxaparin) and Plavix (clopidogrel)
  • Antipsychotic drugs like Compazine (prochlorperazine), Mellaril (thioridazine), Permatil (fluphenazine), Stelazine (trifluoperazine), and Thorazine (chlorpromazine)
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, Advil (ibuprofen), Aleve (naproxen), and Voltaren (diclofenac)

Advise your doctor if you are taking evening primrose oil—or any supplement—to avoid drug interactions and potentially serious side effects.

Dosage and Preparation

As a dietary supplement, there are no universal guidelines directing the appropriate use of evening primrose oil. Generally speaking, a daily dose of 500 milligrams is considered safe in adults, although many can tolerate up to 1,300 milligrams daily without any side effects. Due to the lack of research, evening primrose should be not be used in children.

Evening primrose oil is available in many health food stores or pharmacies and is typically sold in gel cap form. Bottled primrose oil is also available but is more difficult to accurately dose.

What to Look For

Dietary supplements like evening primrose oil are not required to undergo the rigorous testing that pharmaceutical drugs do. Instead, the U.S. Food and Drug Administration (FDA) imposes certain standards regarding the manufacture and labeling of the supplement. Even so, there is often considerable variation in the quality of supplements like evening primrose oil.

To ensure quality and safety, only buy supplements that have certified by an independent certifying body, such as the U.S. Pharmacopeia (USP), NSF International, or ConsumerLab.

If you are strictly vegan or vegetarian, only choose brands labeled "vegetarian safe" or "vegetarian soft gels." Unless this is stated clearly on the label, the capsule may be made with animal-based gelatin (usually beef or pig).

Other Questions

How long does evening primrose oil last?

Evening primrose oil contains a lot of unsaturated fats that are susceptible to oxidative deterioration. Because of this, the concentration of seed oil content, including GLA, tends to drop after three to four months even with refrigeration.

To extend the shelf life of the oil, keep it in its original container (typically blue to prevent sun exposure) and store it in the refrigerator. Although primrose oil can keep for up to six months in the refrigerator, buy only as much as you can use within three.

How can you tell if primrose oil has gone bad?

Any product rich in unsaturated oil can go rancid, including bottled primrose oil and primrose oil gel caps. Because primrose oil has only a faint scent, it can often be difficult to tell if it has gone bad. It may darken or smell funny, but not always. As such, you should always play it safe and discard any supplement after its use-by date.

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