An associate professor at Peking University’s Faculty of Medicine posted an article on the Internet questioning the authorities’ practice of “forcing folic acid supplements” after seeing an advertisement for free folic acid supplements funded by the Chinese government outside his home. According to him, most people already get enough folic acid from food, and high levels of folic acid may promote the growth of cancer cells, leading to an increase in tumors. He is therefore outraged, saying, “Is our country really so rich that we can spend money indiscriminately and let people get sick?” In fact, China is still only recommending folic acid supplementation, but not strong folic acid supplementation. It is the United States that is strongly supplementing folic acid, which, in this associate professor of medicine’s opinion, is simply poisoning. So what exactly is this folic acid that he makes so horrible about? Is it really that scary? In 1931, British physiologist Lucy Wells was doing research in India when she discovered that poor women there were prone to a form of pernicious anemia when they became pregnant, and that there was a nutritional factor in yeast that could prevent and treat this disease. This factor was initially called the “Wells factor”, and 10 years later it was first isolated from spinach leaves and named folic acid. Folic acid is a B vitamin that is essential for cell division to synthesize DNA. If too little folic acid is consumed from the diet, the synthesis of DNA is reduced, which in turn reduces cell division. All dividing cells are affected by this, but those that divide rapidly are more severely affected, such as anemia when red blood cell production is reduced. What later made folic acid famous was a birth defect called neural tube defects. In the human embryo, at week 3, an area called the neural plate appears, which sinks in the middle part and bulges at the edges, forming a neural fold. The neural folds gradually merge medially on both sides and close to form the neural tube by about day 27. The neural tube later differentiates into the brain and spinal cord. If the neural tube does not close, there is a neural tube defect. This is one of the most serious and common birth defects, with one to two out of every 1,000 births having neural tube defects: in some cases, the brain does not develop properly, and almost none of these malformations survive; in more cases, the spinal bones do not develop properly and the spinal cord protrudes or is exposed, called spina bifida. Spina bifida can present with symptoms such as paralysis, incontinence, and mental retardation. The occurrence of neural tube defects is associated with a variety of factors. In the 1950s, researchers noted that one of the important factors was malnutrition. The incidence of neural tube defects was always higher in poor populations. Also, babies conceived in the winter and early spring had a higher rate of spina bifida. Was it because the mother did not have easy access to fresh vegetables and fruits at the time of conception? By the 1960s, researchers doing animal experiments found that a deficiency of folic acid could lead to neural tube defects. Studies on people then began. Several clinical trials done in the 1980s and early 1990s showed that supplementing pregnant women with high doses of folic acid before and early in pregnancy was effective in preventing neural tube defects, reducing the incidence of neural tube defects by 60 to 75 percent. The higher the amount of folic acid consumed by pregnant women, the lower the risk of developing neural tube defects. Based on these findings, the U.S. Public Health Service recommended in 1992 that all women of childbearing age consume 400 micrograms of folic acid daily. Folic acid is widely available in a variety of foods, and foods rich in folic acid include dark green leafy vegetables, citrus, legumes and whole grains. Unfortunately, folic acid in food is very unstable and more than half of its activity is lost during harvesting, storage, processing and cooking. Folic acid is a water-soluble vitamin and is more likely to be lost when cooked in water. Moreover, natural folic acid is not readily absorbed by the body, with only about 50% being absorbed by the body. Taking leafy vegetables with the highest folic acid content as an example, although their folic acid content can be as high as 160 micrograms/100 grams, it is obviously difficult to eat 1 kg of leafy vegetables per day to meet the folic acid requirements of pregnant women after taking into account the instability and absorbability of food folic acid. Thus, contrary to what that associate professor at BYU said, most people have difficulty getting adequate folic acid from food. According to USDA estimates, most American women of childbearing age get only 200 micrograms of folic acid per day from food. Fortunately, humans successfully synthesized folic acid back in 1945. Synthetic folic acid is extremely stable, can be stored for several years without loss of activity, and is almost 100% absorbed by the body. Taking folic acid preparations is much more reliable than taking folic acid as a dietary supplement. Although doctors generally recommend that pregnant women take folic acid preparations, neural tube defects occur in the first month of pregnancy, before the pregnant woman even knows she is pregnant and it is too late to take folic acid supplements until she finds out she is pregnant. To avoid this, folic acid supplements should be taken before pregnancy, but about half of all pregnancies are unplanned, and to be on the safe side, all women of childbearing age should take folic acid supplements daily. However, not every woman of childbearing age is aware of the importance of folic acid, and even if they are, only a few are able to take folic acid preparations consistently on a daily basis. Adding folic acid to foods and “fortifying” everyone with folic acid is the most thorough approach. The U.S. Food and Drug Administration made a decision in 1996 to mandate the addition of a certain amount of synthetic folic acid to food products starting in January 1998. Based on the amount added, it was estimated that each American would thus receive about 200 micrograms of additional folic acid per day, which, when combined with other food intake, would basically meet the folic acid requirements of a pregnant woman’s body. The effect was dramatic, with a 26% reduction in the incidence of neural tube defects in the United States one year after mandatory folic acid supplementation was implemented. Canada took the same measure in 1998, and the effect was even more pronounced, with a 46% reduction in the incidence of neural tube defects. While it is possible that universal folic acid supplementation may cause excessive folic acid intake in some individuals, it is alarming to suggest that high folic acid leads to increased tumor incidence. There are no known side effects of high folic acid intake. But high folic acid may interfere with the diagnosis of vitamin B12 deficiency. About one in five older adults who are deficient in vitamin B12 show initial symptoms of anemia. If they consume too much folic acid, they will not become anemic, and their doctor may therefore not detect their vitamin B12 deficiency and delay treatment. However, the daily intake of folic acid would have to be as high as 1 mg or more for this to occur, which is unlikely to happen at the current level of folic acid additions. Public health policy is a trade-off, and sometimes other populations have to make certain sacrifices for the health of the next generation.