Evening primrose oil is just a legend, many kinds of effects are advocated by manufacturers.

One reader left me a message saying that his wife was infatuated with Evening Primrose Oil and had asked friends to bring it back from the United States, saying that it was also highly respected in the United States. The reader was a little confused: his wife had eaten for half a year without seeing any "effect". What's the good thing about this thing?

Evening primrose is a plant with yellow flowers in the evening. This unique characteristic has made it a focus of attention for a long time. Evening primrose oil has a long history in Europe and the United States. It is commonly used to treat eczema, anti-inflammatory, menopausal symptoms, premenstrual syndrome, and so on. In modern times, people have been used to treat cardiovascular diseases, diabetes, asthma and even cancer.

However, in the United States, it is sold under the name of "dietary supplements". That is to say, it does not need to be examined and certified, as long as no one has an immediate problem, the competent authorities will not ask. But it can't claim to be able to treat any disease - if those functions claimed in China appear in the United States, manufacturers will be prosecuted.

Evening primrose oil is mainly composed of linoleic acid and gamma linolenic acid. Both are polyunsaturated fatty acids, which are healthier than animal oil from the point of view of edible oil. However, linoleic acid is not rare. Many vegetable oils, such as soybean oil, contain about half of them. Evening primrose oil is higher in content, but the human body can only distinguish the total intake, not the oil from which it comes. Therefore, considering the vegetable oils used in the normal diet, linoleic acid in evening primrose oil does not make sense.

Many of the health functions are related to gamma linolenic acid. There is little research on gamma linolenic acid, and many functional descriptions are based on "speculation" rather than scientific data. The quality of some sporadic experiments is not good enough to explain the problem. For example, one study used it to treat pancreatic cancer, a control experiment of more than 40 people, concluded that patients injected with gamma linolenic acid lived longer. But a similar experiment of more than 200 people did not have this effect. Generally speaking, other experimental studies on the health of gamma linolenic acid do not exceed this quality, and it is impossible to judge whether gamma linolenic acid is "useful" or "useless".

Many people like to say that one component has no effect and can not deny the "overall effect" of multi-component formation - logically, of course, this is correct, but we must prove it through scientific experiments, rather than "possible" as a fact. So far, there have been many studies on skin symptoms such as eczema, and there are also some results of "effective" research. A few years ago, the American Medical Library (NLM) concluded that "there is good evidence to support this use", but pointed out that "large-scale, well-designed experiments are needed before strong recommendations can be made". In the August 2014 update, this effect was placed at the "maybe ineffective" level. The use of Evening Primrose Oil, previously approved by the United Kingdom, was cancelled in 2003 after years of discussions that found insufficient evidence of validity.

Other aspects of "efficacy" have more than 20 reported in the literature, and they are often used by manufacturers to advocate "what research shows". However, these literatures only show that "some people have studied this kind of effect" and do not show that "this kind of effect exists at all". According to the literature summary of the American Medical Library, evening primrose oil has been evaluated as "probably effective" in improving neurological impairment caused by diabetes mellitus and "slowing down osteoporosis in the elderly", and the latter needs to be supplemented with fish oil and calcium. For asthma, diabetes, weight loss, cardiovascular, menopausal symptoms, premenstrual syndrome and so on, it is "probably ineffective" or "there is not enough evidence to make a judgment"