Rumors
There are many "selenium-rich products" on the market that claim to have health benefits such as "anti-cancer". Many places and many businesses are vigorously promoting it as a "high-end product".
However, a recent hot search has raised questions about this type of product.
Next, let's sort out "selenium and health" and "selenium-rich food".
Analytics
Let's talk about the answer first: it is really unnecessary to pursue selenium-rich foods, so let's talk about it in detail.
1. Selenium is an essential element for the human body
Life activities are based on proteins, and there are dozens of proteins in the human body that contain selenium. The involvement of selenoproteins is required for many physiological activities.
Selenium deficiency can cause severe symptoms. For example, in Keshan County, Heilongjiang Province, it was found that there were a large number of "abnormal heart diseases" (known as "Keshan disease"). When the disease was found to be related to selenium deficiency in the region, sodium selenite supplementation was promoted from the 70s of the 20th century, which effectively prevented the disease. By the 80s of the 20th century, Keshan had basically eliminated the existence of the disease.
In addition to Keshan disease, selenium deficiency can cause other symptoms. There is some evidence that selenium deficiency may also be associated with male infertility. There is a bone and joint disease in some regions of **, as well as in Siberia, which is speculated to be related to selenium deficiency in these regions as well. In addition, selenium deficiency may increase the risk of cretinism in infants by exacerbating symptoms of iodine deficiency.
2. How much selenium does the human body need?
Selenium occurs naturally in nature and is absorbed by the body as plants grow into human food. The human body can absorb selenium in organic form as well as inorganic form. The former is mainly proteins that contain selenium, and the latter is usually selenate and selenite. In general, organic selenium is more absorbed than inorganic selenium. However, the absorption rate of inorganic selenium is not low.
Among foods, seafood and organ meats are the richest in selenium**, while muscle meats, grains, and dairy products also provide some. In plants, the amount of selenium depends mainly on how much it is in the soil, as well as factors such as the pH of the soil and the form in which selenium is present. Therefore, its content is not an intrinsic property of the plant, but more importantly depends on the area where it is grown. In animals, selenium comes from the food eaten, so the amount of selenium in animal products varies. However, animals have a certain ability to regulate the storage of selenium in the body, so the selenium content in animal food is not as affected by geography as plants.
For both men and women, an intake of 55 micrograms per day is sufficient for adults. Pregnant women and mothers need slightly more, with the US setting standards of 60 and 70 micrograms, respectively. In most parts of the country, people can get enough from regular foodSo "selenium deficiency" has not become a public health problem.
3. Can selenium supplementation prevent cancer?
The selling point of selenium-rich products and selenium supplements is not "to meet the needs of the human body", but to "eat more to prevent cancer". Because selenium is associated with cancer-related physiological activities such as DNA repair, apoptosis, endocrine, immune system, and antioxidant, it is not surprising to speculate that "selenium supplementation prevents cancer", but the actual results are not ideal.
Some epidemiological studies do show that selenium intake is inversely associated with the incidence of certain cancers (e.g., colorectal cancer, prostate cancer, etc.). StillDue to the limitations of the survey methodology and the quality of the data, these data are far from being a "reliable basis".
There have also been some randomized controlled trials conducted by research institutions, but the results have been inconsistent. For example, in a randomized, double-blind controlled study of 1,312 American adults over a period of 6 years, the results showed that taking 200 micrograms of selenium per day reduced the incidence of prostate cancer by 52% to 65%. However, another similar trial in the United States, Canada and Puerto Rico, involving 35,533 men over the age of 50, found "no effect".
There are many studies on "selenium supplementation to fight cancer", but on the whole, the scientific conclusion that can be made based on them is that "it is not enough to officially supplement selenium to fight cancer".
After reaching the recommended "adequate intake", additional selenium supplementation is unreliable, so is it of health value? Other "health effects" that have been studied by the scientific community are also "unclear and inconclusive". It has also been found that even if you supplement 600 micrograms of selenium per day, only the selenium level in the blood increases, but the activity of those selenoproteins in the cells does not increase accordingly. In other words, the extra selenium, although it can enter the bloodstream, may not enter the cells to function.
4. Are selenium-rich products reliable?
The amount of selenium in the soil is not high in most parts of China, so the selenium intake of the population in most areas is not high. The "safe upper limit" of selenium set by the United States is **400 micrograms, and people in most parts of China are far from this amount. In other words, if you want that "just in case" hope, it is unlikely that eating selenium-rich products or selenium supplements will be harmful.
Yeast selenium is made by culturing yeast so that selenium exists in the form of selenoproteins. In terms of absorption, it will be higher than inorganic selenium such as sodium selenite. However, after all, the human body absorbs the total amount, and the absorption rate of inorganic selenium is low, but it is cheap, as long as you eat a large amount, you can make up for the lack of low absorption rate.
"Selenium-rich tea" is a tea produced in some regions, in which its selenium content is significantly higher than that in other regions. In general tea, the average selenium content is about 150 micrograms per kilogram, while the national standard for selenium-rich tea requires the selenium content to be between 250 and 4,000 micrograms per kilogram. The selenium content of selenium-rich tea on the market is roughly around 1,000 micrograms per kilogram. Such a tea does meet the standard of "selenium-rich", but it is not realistic to expect it to "replenish selenium". The average person uses about 10 grams of tea leaves per day, which contains about 10 micrograms of selenium. Only about 10% of this selenium can be brewed into tea, which is about 1 microgram. In other words, unless you eat the tea leaves, drinking selenium-rich tea can only account for about 2% of the body's daily selenium needs - it can only be said that it is better than nothing.
Another common selenium-rich food is "selenium-rich rice". The selenium content of ordinary rice is about 35 micrograms per kilogram, while the national standard for selenium-rich rice is 70 to 300 micrograms. If you eat 300 grams of rice per day, then regular rice can provide 10 micrograms of selenium, while selenium-rich rice can provide 20 to 90 micrograms. That is, it is effective to supplement with selenium through selenium-rich rice. But it's important to note that selenium is also found in other foods, and the body may also get enough of it. If you need to supplement selenium, whether it is worth eating selenium-rich rice depends on the comparison of selenium-rich rice with other selenium supplements.
Other selenium-rich products, such as selenium-rich eggs, selenium-rich apples, selenium-rich corn, etc., still need to look at the actual content and usual consumption of selenium.
5. Is the "selenium-rich" claimed by the merchant reliable?
That's a problem
Under the Weibo on this topic, a netizen left a message saying:
Screenshots of the network.
If this is just a netizen's "hearsay" and unreliable, the famous anti-counterfeiter Wang Hai accused two "Internet celebrity merchants" of inflating the selenium content of selenium-rich products, which should be a "real hammer".
Screenshots of the network.
One is a selenium-rich egg with a nominal value of 422 micrograms of 100 grams, the actual value of 26 micrograms of 100 grams; The other is selenium-rich corn with a nominal value of 351 microgram 100 grams, measured value 225 micrograms to 100 grams, the actual values are significantly lower than the allowable deviation range, which is considered "nominal inconsistency" or "false labeling".
Selenium-rich foods are "not inherently bad." If it is similar to ordinary food**, it will not reach the "intake control amount" after eating it; But if it is sold because of "rich selenium", then it is not worth spending for ordinary consumers, and it is good to give people who are not bad for money to gain a sense of psychological superiority.
For example, this "selenium-rich egg" sells for 26 in a nearby supermarket9 a box, much more expensive than ordinary eggs.
Screenshots of the network.
However, compared with other "high-end eggs" in the supermarket, it is roughly the same price. In other words, eating ordinary eggs is to get nutrition economically; Eating "selenium-rich eggs" and other "high-grade eggs" can obtain "psychological pleasure" in addition to nutrition.
Conclusion
Adults of both sexes can meet their health needs with a daily intake of 55 micrograms of selenium. In most parts of the country, people can get enough from regular food, so "selenium deficiency" has not become a public health problem.
In addition, there are many studies on "selenium supplementation to fight cancer", but the scientific conclusion that can be made based on them is that "it is not enough to confirm that selenium supplementation can fight cancer". So now people want to buy selenium-rich foods, but they can only be comforted.
Author: I am Yun Wuxin, Ph.D. in food engineering, and senior R&D personnel in the food industry.
Review: Ruan Guangfeng, Director of Science and Technology Department, Kexin Food and Nutrition Information Exchange Center.
Editor in charge: Wu Yan.