Text | pineapple
(i)
Can selenium supplementation prevent cancer? Is a question I often get asked in the background:
Selenium has always been a very hot concept in the health product market. Many people recommend selenium supplementation, some say that selenium supplementation can antioxidant, some say that selenium supplementation can enhance immunity, and some say that selenium supplementation can accelerate DNA repair.
Various selenium supplements on the market have also sprung up. Selenium-rich tea, selenium-rich rice, and even selenium-rich water. For a time, things were expensive to "selenium".
So, is selenium really so critical? Is selenium supplementation really useful for cancer prevention?
I will tell you the answer directly: so far, scientific research has not found that ordinary people can supplement selenium to prevent cancer.
Conversely, individual studies have found that selenium supplementation may actually increase the risk of certain cancers. Therefore, experts do not recommend that patients blindly supplement selenium.
Let's save some money and eat something really delicious.
(ii)
People who advocate selenium supplementation often tell everyone that selenium is an essential element of the human body, and without selenium, many biological functions cannot be performed smoothly. Selenium and the cell DNA repair, antioxidant function, endocrine system, immune system, etc. are related, because these system disorders and cancer is related, so in order to prevent cancer, we should supplement selenium!
Sounds like a lot of sense, doesn't it?
I often say that good pseudoscience is often science in its first sentence.
This time is no exception. Most of the above passages are correct.
Selenium is indeed an essential element of the human body. If there is a severe lack of selenium, people do get sick. The most famous example is "Keshan disease": in 1935, in Keshan County, Heilongjiang Province, a strange myocardial necrosis disease was discovered. It was later discovered that the disease was most likely due to severe selenium deficiency in some local people, coupled with viral infections. When the government followed the advice of scientists and supplemented people nearby with selenium, the disease slowly disappeared.
Therefore, there is no doubt that selenium is very important and the human body cannot be lacking! But the question is, can selenium supplements prevent cancer?
What kind of theory everyone can mention, but it is not true, the key depends on the evidence.
I said that selenium supplementation and cancer prevention are not reliable, not because of personal prejudice. In fact, I also hope that simply eating something can prevent cancer. Who doesn't like to "stay healthy without exercising, eating what you want, and then having two health supplements?" ”
But around the relationship between selenium supplementation and cancer prevention, many scientists have done research, even including some large-scale controlled studies with tens of thousands of people, but unfortunately, so far, the results have been disappointing.
In 2018, a blockbuster review article was published called "Selenium and Cancer Prevention". It analyzed data from nearly all previous studies on the issue of "selenium supplementation and cancer prevention."
What are the conclusions drawn? This is the following passage. I'll translate it for you: "Overall, we didn't find any evidence that selenium supplementation prevents cancer in humans. ”
It can be said that it is very direct.
You can look at the following table, whether it is comparing the "risk of any cancer", or the "risk of cancer death", or "the risk of colorectal cancer", the population of selenium supplementation is 1.0 times that of the group without selenium supplementation!
What is 1.0 times? In human terms, it is exactly the same, there is no difference!
One of the largest studies to date on selenium supplementation and cancer prevention is code-named SELECT. To see if selenium supplementation or vitamin E supplementation can prevent prostate cancer in men, more than 35,000 men over the age of 50 in the United States and Canada participated in the study, and they were evenly divided into 4 groups:
Group A: Take a placebo every day
Group B: Selenium supplementation daily
Group C: Vitamin E supplementation daily
Group D: Selenium supplementation + vitamin E supplementation daily
In order to experiment rigorously, the participants did not know what they were eating. The study was originally planned to be followed for at least 7 years, and the results were done for more than 5 years, and the trial was terminated prematurely, because the scientific committee analyzed the data for several years and found that there was no difference in the risk of cancer in several groups, and it was not worth doing any more.
Later, statistics even found that the group that supplemented with vitamin E increased the proportion of prostate cancer by 17% compared with those who took a placebo!
The reason behind this is not clear so far, but at least again, it shows that ordinary people really can't eat health care products.
(iii)
Everyone will definitely ask, why is selenium so important, but it is useless to supplement it?
I think the most important reason is that except for some special groups, most people in modern times are not short of selenium!
Although selenium is an essential element, many foods are rich in selenium, especially meat and eggs (seafood, offal, eggs and dairy products, etc.). If the soil has high levels of selenium, there will also be relatively high selenium in plants (grains, vegetables, etc.).
At that time, those who had "Keshan disease" in Heilongjiang, because of poverty and remoteness, not only was it difficult to obtain meat, but also the selenium content in the soil was low, and the selenium from plant sources was not enough, so it led to selenium deficiency. For such a population, selenium supplementation is very useful.
But modern times are different, our food has been enriched a lot, under normal circumstances, it is not so difficult to get enough selenium through food.
And selenium is not the more the merrier. If there is no shortage of selenium, and then additional selenium supplementation every day, it may not be good. The World Health Organization recommends a maximum daily intake of 400 micrograms of selenium for healthy adults, which can lead to "selenium poisoning" over time. Symptoms include hair, nail loss, gastrointestinal discomfort, baldness, limb weakness, liver damage, etc.
Many over-marketed health care products, in fact, behind a similar routine, is to "steal the concept".
They secretly replaced "XX element is necessary for the body" to "everyone should supplement XX element, good for the body (can prevent cancer)!" ”
Are they the same? Of course not! If there is no shortage, why make up for it?! Just like drinking water and eating are very important, but drinking too much water may be poisoned, and eating too much will directly support death.
In fact, there are many indispensable elements in the human body, not only selenium, but also potassium, sodium, magnesium, iron, zinc, copper and so on. But we don't need to deliberately supplement sodium now, why? Quite simply, because a daily diet alone is enough to get the sodium we need.
Our bigger problem now is that many people have too heavy tastes, eat too much salt, and excessive sodium bring various health problems!
(iv)
All in all, selenium is indeed very important, if it is deficient for various reasons, such as some patients with advanced gastrointestinal tumors, it will lead to selenium deficiency due to food digestion and absorption problems. If a clinical expert determines that a person is indeed deficient in selenium, it should be supplemented.
However, for healthy people, there is no scientific evidence that selenium supplementation can prevent cancer, and additional supplementation is not recommended. There are a lot of overmarketing situations in the market.
In the face of health care products, everyone will always remember eight words: what is missing to make up for, no shortage and no supplement!
Even if it is an essential element of the human body, as long as it is not lacking, do not make up for it.
Wishing you all good health! Hail to life!
bibliography:
Selenium for preventing cancer. CochraneDatabase Syst Rev. 2018 Jan 29;1(1):CD005195.
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