From the perspective of modern medicine, the mechanism by which iron supplements trigger gastrointestinal disorders or constipation is clearly understood. Generally, supplements in the form of non-heme iron are absorbed in the stomach, and any unabsorbed iron travels down the gastrointestinal tract, causing several problems.
First, iron ions directly irritate the lining of the gastrointestinal tract, which can cause nausea, gastric discomfort, and abdominal pain. The chemical reaction that occurs upon contact with gastric acid can also irritate the gastric mucosa, easily leading to unpleasant symptoms such as heartburn or feeling bloated.
Second, unabsorbed iron moves to the large intestine, causing significant changes in the gut microbiome. Iron serves as an essential nutrient for the growth of certain pathogenic bacteria. When excessive iron enters the intestine, it promotes the proliferation of harmful bacteria and disrupts the balance of beneficial bacteria, resulting in gut dysbiosis. This dysbiosis causes gas formation, abdominal distension, and changes in intestinal motility, which can manifest as defecation disorders such as constipation or diarrhea.
Third, as a potent oxidizing agent, iron can induce oxidative stress. Unabsorbed iron ions generate reactive oxygen species (free radicals) that can directly damage intestinal mucosal cells, causing hypofunction of the intestinal mucosa and inflammation. This can also be associated with leaky gut syndrome, which increases intestinal permeability and ultimately harms overall gut health. In addition, physical and chemical actions, such as iron interfering with water absorption during digestion, hardening stools, or hindering intestinal motility, also aggravate constipation.
Thus, while iron is an essential nutrient, taking it indiscriminately without considering your individual digestive system status or intestinal environment can harm gastrointestinal health and cause discomfort, so caution is warranted.
