Many parents have the feeling that their children are developing earlier now compared to their own years. A number of studies have shown that this feeling is not an illusion, as the age of onset of puberty has been advancing, especially for girls. 2006 Danish survey found that the average age of onset of puberty for girls was 9 years and 10 months, almost a year earlier than in a similar survey in 1991. What is causing earlier and earlier pubertal development? Before we answer this question, let’s understand how pubertal development begins. The center that controls pubertal development is an area of the hypothalamus called the arcuate nucleus, which contains neuroendocrine neurons that make and release gonadotropin-releasing hormone. Stimulated by gonadotropin-releasing hormone, the pituitary gland begins to produce luteinizing hormone and follicle stimulating hormone. These two hormones are released into the bloodstream and stimulate the ovaries to make estradiol (the main estrogen) and the testes to make testosterone (the main male stimulus), thus allowing the bodies of girls and boys, respectively, to begin pubertal development. This control process is actually very complex, and there are many details that are still unclear. But it is now known that pubertal development is achieved by disinhibiting the brain from the arcuate nucleus. The arcuate nucleus is active before and during the period just after birth, but a few months after birth, the function of the arcuate nucleus is inhibited until the age of 8 to 10 years, when this inhibition is lifted and so pubertal development begins. If there is a tumor in the brain that does not inhibit the function of the arcuate nucleus, precocious puberty can occur. Many other factors can affect the function of the arcuate nucleus, for example, leptin, which is secreted by fat cells, stimulates the arcuate nucleus to make and release gonadotropin-releasing hormone. In addition to the hypothalamic-pituitary-gonadal route of control, there is a second route of control of pubertal development, which is the secretion of certain androgens by the adrenal glands that also affect pubertal development. However, many people find it difficult to understand the complexity of pubertal development and simply attribute precocious puberty to the fact that the foods they eat now contain many hormones. Even some doctors think so too. For example, a children’s hospital in Beijing sent out a microblog saying, “How to prevent precocious puberty? Exogenous hormone intake should be controlled; for example, foods that contain a lot of estrogen, such as milk and milk products, soybeans, honey, chicken, and anti-seasonal fruits, should be eaten in moderation and not in excess.” This health advice is very much to the taste of the general public, but extremely unprofessional. The main components of honey are sugar and water, which account for more than 99% of the total, leaving trace amounts of protein, organic acids, aromatic substances, minerals, pigments, etc. It does not contain estrogen. When it comes to honey, some people associate it with royal jelly, which is often cited as the culprit for premature sexual development. In fact, royal jelly does not contain estrogen, but it does contain androgens, but the amount of androgens contained in one gram of royal jelly is only a few hundred thousandths of the amount of androgens synthesized in a man’s body in a day, which is insignificant. Broilers in chicken farms are often rumored to be using hormones because they grow fast and are ready for market in a few dozen days. In fact, the reason why broilers grow fast is because of the good breed, reasonable feed ingredients and suitable feeding environment, not because of feeding hormones. The use of hormones in chicken farming is prohibited, and even if they are used illegally, they are not beneficial to the growth of chickens and no one will use them. The use of sex hormones does not stimulate the growth of chickens, while the use of growth hormones is possible. However, growth hormone is a protein that will be digested orally and cannot be absorbed and used by the body, so it can only be injected, and it has to be injected several times a day to be effective. Obviously, it is impossible for someone to have the energy to inject the hormone several times a day to the chickens in a chicken farm, not to mention that growth hormone is very expensive, and the value of 1 mg exceeds the price of chickens, so it is impossible for someone to do this kind of business at a loss. So the US Food and Drug Administration does not even allow the sale of chicken meat with the label “no hormones” because hormone use is not allowed and no one will use it. The use of sex hormones in cattle and sheep farming is also allowed because it stimulates growth and improves feed utilization. Unlike growth hormones, sex hormones are steroidal compounds that can be absorbed orally and by injection, and are also very cheap, so they are commonly used in cattle and sheep farming. However, the residual amount of sex hormones in meat is extremely low, and the residual amount of estrogen in 100 grams of beef is less than 1 ng (1 ng equals one billionth of a gram), so the U.S. Food and Drug Administration stipulates that if sex hormones are used in cattle and sheep breeding, they can be marketed without a withdrawal period. Milk also contains estrogens, and they also work in the human body, but the amount of estrogen in milk is also very low, at a concentration of about a few tens of picograms per milliliter (1 picogram equals one trillionth of a gram). Even if you drink a liter of milk a day (which is certainly not possible for the average person), even if all the estrogen in milk is absorbed by the body (which is actually impossible), it is only a few tens of nanograms, whereas children before puberty are already producing estrogen in their bodies, and the amount of estrogen produced each day is already about 10 micrograms, which is hundreds of times more than in milk. So the amount of estrogen in milk is insignificant and completely negligible and will have no effect on the body. Plant growth regulators are sometimes used in fruit cultivation to promote results, and since plant growth regulators are also called plant growth hormones, it gives people the association that eating fruits will give them hormones. In fact, although plant hormones are also called hormones, their chemical composition is completely different from that of animal hormones, and they do not play the role of hormones in the human body. Some plants contain estrogen-like ingredients, sometimes called phytoestrogens, but they do not play a role in regulating growth in plants and are not phytohormones, except that their chemical structure happens to be similar to estrogen, and once they enter the human body, they can bind to estrogen receptors and play estrogen-like effects, but such effects are very weak. The isoflavones in soy are phytoestrogens, but their estrogenic activity is very weak, so unless one eats a lot of them, there is nothing to worry about. It can be seen that it is not justified to blame early pubertal development on the presence of hormones in the diet. So what is it that makes kids today reach puberty earlier than their parents and grandparents did? The main reason is that they are much more well nourished than their predecessors, even to the point of excess, so they weigh more and have more body fat. Once the weight and amount of fat reach a certain level, the body feels ready for reproduction and enters puberty early. Conversely, if the body is in a state of malnutrition, the first thing to ensure their own survival, rather than reproduction of offspring, the time to enter pubertal development will be delayed. This is easy to understand from the point of view of evolutionary biology, and many studies have confirmed it: the start of pubertal development is related to the high weight, and obesity is a risk factor for precocious puberty. Another reason is that there are many chemicals and drugs in the environment that can cause endocrine disruption in humans, so-called endocrine disruptors or “environmental hormones”. For example, organochlorine pesticides, brominated flame retardants used as additives in plastics, have been tested in animal experiments and epidemiological surveys that they can interfere with the human endocrine system and cause precocious puberty, so their use has been restricted or even banned. DDT and its metabolites, in particular, have long been found to cause premature sexual maturation. However, it is still controversial how much these environmental hormones actually affect the human body. Some baby bottles and plastic water bottles are made from hard, clear polycarbonate resin, which is made by polymerizing bisphenol A. In addition, epoxy resins used for the interior of cans and milk powder cans also contain BPA. small amounts of BPA can penetrate into the food inside the bottle. BPA has a chemical structure similar to estradiol and is able to bind to estrogen receptors to produce estrogenic activity. A number of studies (mainly animal studies) have shown that even low dose exposure to BPA in pregnant women and infants may affect the development of the brain and endocrine system in infants and children. Low doses of BPA may also have health effects in adults, increasing the risk of heart disease, diabetes and liver damage. After this issue became a concern, manufacturers of baby bottles have taken the initiative to stop using BPA in products such as baby bottles, and some governments have banned it from being used in the production of baby bottles. The U.S. Food and Drug Administration also banned the use of BPA in the production of baby bottles in 2012, but the reason is that manufacturers are no longer using it to produce bottles, rather than for safety reasons. The FDA believes that although BPA may be harmful to fetuses, infants and children, the BPA content in plastic products is too low to have an adverse effect on humans, so it does not prohibit the use of BPA in other food packaging. As a consumer, for insurance purposes, there are ways to minimize the intake of BPA. When choosing bottles for babies, use BPA-free ones. Those hard, transparent bottles usually contain BPA, while softer, translucent bottles usually do not contain BPA, which is more likely to be released when exposed to acid or heat. Therefore, when shopping for tomato juice, fruit juice, carbonated beverages and other foods, do not choose can packaging with a resin lining, choose glass bottles, cartons, polyethylene packaging will be safer, and do not heat food containers made of polycarbonate. As with many medical and health issues, early sexual maturity and early puberty in children is a complex issue, and making categorical and categorical recommendations without scientific basis or even against the facts will only cause unnecessary panic. Medical providers who are supposed to have more expertise than the average consumer should be even more cautious in what they say.