Primrose vitamin in whith spoon on wooden background

Have you ever considered taking evening primrose oil for weight loss? This supplement is marketed as a cure-all. Anecdotal evidence says that it may prevent weight gain, relieve PMS and ward off fatigue, among other beneficial effects.

What Is Evening Primrose?

Evening primrose, also known as Oenothera biennis L. or King's Cure-all, is a flowering plant with edible seeds and shoots. It's commonly used in the treatment of premenstrual syndrome, menopause symptoms, arthritis, cardiovascular problems and skin disorders. Manufacturers use its seeds to make evening primrose oil (EPO), dietary supplements and other products that support female health.

The health benefits of evening primrose are associated with its high content of fatty acids. This plant is rich in linoleic acid, gamma-linoleic acid and omega-6 essential fats, according to a research paper published in the journal Antioxidants in August 2018. It also contains flavonoids, phenolic compounds and other antioxidants with therapeutic action. Most nutrients are found in its seeds.

As the review authors note, the bioactive compounds in this plant exhibit anti-inflammatory properties and may prevent cancer cells from spreading. Gamma-linolenic acid, one of its most abundant nutrients, has been shown to reduce tumor necrosis factor α, interleukin 6 and other inflammatory markers.

Evening primrose oil is used in dietary supplements, cosmetics, shampoos and skincare products. Proponents say that it may clear acne and psoriasis, increase bone strength, reduce cholesterol and aid in weight loss. Unfortunately, most claims lack scientific proof.

The National Center for Complementary and Integrative Health (NIH) states that there's not enough evidence to support the use of this plant for any disease. It may help in treating diabetic neuropathy, but more research is needed to confirm these findings.

As the NIH points out, evening primrose oil may not be safe for pregnant women and individuals taking warfarin, an anticoagulant drug. Additionally, it may cause mild adverse reactions, such as headaches and digestive discomfort.

Evening Primrose and Weight Loss

Some brands promote evening primrose oil as a natural appetite suppressant and weight loss aid. Very few studies support this claim, though, and most of them were published in the '90s.

In fact, the only study on evening primrose oil and weight loss was published in February 1983 in the International Journal of Obesity. Unfortunately, researchers didn't find any differences in body weight between obese women who used this supplement and the control group, although this study is quite dated.

Read more: 15 Foods That Help You Peel Off the Pounds

More recent studies actually indicate an association between omega-6 fatty acids and weight gain. According to a meta-analysis featured in Obesity Reviews in April 2015, obese and overweight people have higher levels of dihomo-gamma-linolenic acid (DGLA). This compound is a polyunsaturated fatty acid derived from linolenic acid, one of the most abundant nutrients in EPO.

The Antioxidants review reported that EPO supplementation increases linolenic acid levels in the bloodstream. EPO is up to 74 percent linoleic acid and up to 10 percent gamma-linolenic acid. Therefore, it may contribute to weight gain when consumed in large doses. However, it's typically used in small amounts, so it's unlikely to affect your weight as long as you stick to the recommended dosage.

Another review, published in EBioMedicine in October 2015, suggests that polyunsaturated fatty acids may predict the onset of metabolic syndrome in overweight and obese individuals.

These compounds have been linked to insulin resistance, weight gain, increased waist circumference and body fat accumulation in people with diabetes. As the researchers note, polyunsaturated fats may cause inflammation and contribute to obesity when consumed in excess.

Potential Health Benefits

The fatty acids and bioactive compounds in evening primrose may benefit your health. Again, moderation is the key.

According to the review featured in Antioxidants, this plant is rich in gallic acid, caffeic acid, ellagic acid, quercetin and kaempferol. It also contains sterols and other phytochemicals with therapeutic properties. Its seeds are a good source of minerals and amino acids, such as lysine, tryptophan and cysteine.

Linoleic acid, for example, keeps your skin hydrated and elastic. Researchers have also found that atopic dermatitis sufferers have lower levels of gamma-linolenic acid, a potent bioactive compound in EPO. Evening primrose doesn't seem to improve the symptoms associated with this condition, though.

Read more: Why Are Linoleic Acid and Linolenic Acid Important?

Other studies suggest that gamma-linolenic acid may help reduce inflammation, which is the root cause of arthritis and various skin diseases. For example, two clinical trials cited by the association Versus Arthritis showed that EPO may temporarily relieve morning stiffness and joint pain in patients with rheumatoid arthritis.

Kaempferol, a flavonoid in EPO, may induce cancer cell death and suppress the growth of cervical cancer cells. Quercetin, another potent antioxidant, has been shown to protect against infections, inhibit platelet aggregation and boost cognitive performance. It also scavenges oxidative stress and may improve immune function. However, no studies have linked these potential health benefits to EPO.

Furthermore, evening primrose oil doesn't appear to be effective in eczema treatment. According to a review posted in Cochrane in April 2013, this natural remedy isn't any better than a placebo. In clinical trials, eczema sufferers reported mild side effects, such as diarrhea and indigestion, after taking EPO.

As you see, there is no evidence to support the role of evening primrose in disease prevention and treatment. Most studies are small, conflicting or inconclusive.

Are There Any Side Effects?

Evening primrose oil is unlikely to cause adverse reactions when used in small doses for a short period of time. However, some people may experience side effects, like nausea, loose stools and skin rash. Additionally, this product may not be safe for individuals with bleeding disorders, schizophrenia or epilepsy.

Consult your doctor before taking evening primrose supplements, especially if you're under medical treatment. This remedy may interact with antiplatelet drugs, blood thinners, antipsychotics, HIV medications and other drugs.

Be aware that dietary supplements are regulated by the FDA only after they reach the market. To reduce the risk of side effects, choose an organic brand of evening primrose oil. Stick to low doses and follow the manufacturer's instructions. If you experience adverse reactions, stop using it and reach out to your doctor.

Read more: 43 Supplements Exposed: Which Ones to Consider, Which Ones to Avoid

According to the Arthritis Foundation, this supplement takes up to six months to work. However, long-term use is not recommended. Whether you're struggling with acne, joint pain or inflammation, there are safer, more effective treatment options available.