The safety of long-term intake of Nisin

As a natural antibacterial peptide derived from the fermentation of Streptococcus lactis, nisin is widely used in food preservation. Consequently, the safety of its long-term intake and its health effects have always been the core of research and attention. Currently, sufficient evidence indicates that it has high safety within the scope of regular dietary intake, while also providing clear indirect health benefits. Only under extreme conditions does it pose minimal potential impacts.

From the perspective of long-term intake safety, nisin’s molecular properties and metabolic pathways determine its low-risk nature. First, it is naturally degradable: upon entering the human digestive tract, it is rapidly broken down by regular digestive enzymes (such as pepsin and trypsin) into amino acids or small-molecule peptides. These decomposition products are identical to those from the digestion of ordinary proteins—they do not accumulate in the body and do not require complex metabolism via organs like the liver or kidneys, thus avoiding risks of metabolite toxicity or organ burden. Second, evaluations by global authoritative regulatory bodies further consolidate its safety foundation: the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the U.S. Food and Drug Administration (FDA), and other institutions have classified Nisin as a "Generally Recognized as Safe" (GRAS) substance. Through long-term animal experiments, a clear No Observed Adverse Effect Level (NOAEL) has been established. Experiments show that even when animals are continuously fed with doses far exceeding human daily dietary exposure (humans typically ingest a few micrograms to tens of micrograms of Nisin per kilogram of body weight via food, while the NOAEL in animal experiments can reach hundreds of milligrams per kilogram of body weight), no issues such as growth retardation, liver or kidney dysfunction, gastrointestinal mucosal damage, or genotoxicity (e.g., gene mutations, chromosomal aberrations) are observed. Additionally, large-scale population epidemiological observations have found no association between long-term consumption of Nisin-containing foods and digestive system diseases, allergic reactions, or other chronic illnesses—further confirming its safety in long-term human diets.

In terms of health effects, Nisin’s core value lies in two key dimensions: "indirect health protection" and "reducing potential risks." First, it effectively inhibits the growth of harmful bacteria in food, lowering the risk of foodborne illnesses. It exerts specific inhibitory effects on Gram-positive bacteria (such as Listeria and Staphylococcus aureus—which cause food poisoning—and Clostridium botulinum, which produces highly toxic botulinum toxin). This can delay or prevent the proliferation of these pathogenic bacteria in foods (e.g., dairy products, meat, canned goods), reducing food spoilage and the probability of acute gastroenteritis, food poisoning, and other diseases caused by consuming contaminated food. This is directly significant for ensuring food safety and reducing short-term health risks. Second, it reduces the use of synthetic chemical preservatives, alleviating indirect health burdens. As a natural antibacterial agent, Nisin can replace or reduce the addition of synthetic chemical preservatives (such as benzoates and sorbates) in food. Long-term excessive intake of certain synthetic preservatives may have potential impacts on the metabolic systems of sensitive populations (e.g., children, the elderly). Therefore, the use of Nisin indirectly reduces long-term human exposure to chemical preservatives, aligning with the healthy dietary trend of "natural and low-burden."

However, it is also necessary to objectively view the minimal potential impacts of Nisin under specific scenarios. First, mild gastrointestinal reactions in extremely few sensitive individuals: for people with weak gastrointestinal function or irritable bowel syndrome (IBS), intake of Nisin far exceeding regular dietary doses (e.g., direct consumption of high-concentration nisin preparations rather than intake via food) may cause transient abdominal distension or mild abdominal discomfort. This may be related to its mild irritation to the intestinal mucosa or transient regulation of local flora, but such reactions are self-limiting—they resolve within hours after stopping intake—and rarely occur at regular food addition levels. Second, minimal impacts on intestinal flora: in vitro experiments show that high-concentration Nisin may slightly inhibit some Gram-positive beneficial bacteria in the intestine (e.g., a few Lactobacillus strains). However, in vivo studies indicate that low-dose nisin in daily diets has almost no impact on the overall structure, diversity of intestinal flora, or the quantity of core beneficial bacteria (e.g., Bifidobacterium). Its impact is far smaller than that of common factors such as dietary structure and antibiotic use, and the intestinal flora has the ability to self-repair and regulate, preventing long-term flora imbalance.

As a natural, degradable food preservative, the long-term intake safety of nisin has been verified through multiple lines of evidence, including molecular mechanism research, animal experiments, and population observations. Regular dietary intake not only poses no health risks to the human body but also indirectly protects health by inhibiting harmful bacteria and reducing the use of chemical preservatives. Only in cases of extremely high doses or in specific sensitive populations may transient, mild discomfort occur. There is no need to worry about its regular application in food—it is a food additive with both safety and health value.