COVID-19 pandemic is still a world-widespread health problem. At the time of writing (31.07.2020), there were in total over 16,8 million reported cases of COVID-19 around the world with over 660’000 of them having resulted in death [1]. Countries like the USA, India, and Brazil seem to be struggling the most as they had around 60’000, 52’000, and 41’000 new daily cases, respectively. In the face of this global health burden, scientists, governments, and health experts are looking for effective prevention and intervention measures.

Recently, in news and social media of various countries, a new agent was presented as a cure for COVID19 – Lactoferrin [2-5]. Public response was very enthusiastic as one Australian company manufacturing dairy products enriched with lactoferrin revealed record-breaking sales results for this year [6]. Their sales for the first quarter of this year increased seven-fold when compared with respective months last year. It was induced by very optimistic titles of articles like “MUST READ! Immune System: Natural Protein Found In Mother’s Milk and Colostrum Called Lactoferrin Could Help Protect Against Various Viruses” from Thailand Medical News [4] or “Coronavirus, studio sull’immunità dei bimbi: il segreto è la lattoferrina. Ecco la proteina che può contenere il contagio” (“Coronavirus, a study on the immunity of children: the secret is lactoferrin. Here is the protein that can contain the infection”) from Italian Il Messaggero [3] or a Facebook post entitled “Fight COVID-19 with a Glass of Milk!!!” by the American dairy breeding industry community, The Bullvine [2]. The Facebook post got almost 500 likes and was shared around 1’400 times even though it is marked as “False information” by Facebook moderators.

Lactoferrin belongs to the protein family binding and transporting iron called transferrins. Unlike other transferrins, lactoferrin is mostly found in milk and other fluids, instead of blood plasma [7, 8]. It is mostly present in colostrum – the first form of the milk produced after giving birth (7 g/L) and mature human milk (1 g/L). Its high concentration in human milk and its iron-binding properties lead to the belief that it is very effective as an antimicrobial agent and that it’s very effective at boosting immunity.

There is a plethora of studies showing various levels of effectiveness of lactoferrin against different microbes [9-13]. These studies show lactoferrin as a promising compound even against viruses responsible for AIDS [10] and the previous SARS epidemic [12]. There are also two recent studies testing lactoferrin’s influence on the SARS-CoV-2 virus [14, 15]. These two publications were presented in the bioRxiv portal, which means they haven’t been peer-reviewed yet. On top of that, all of these studies were performed in vitro, meaning in a controlled environment outside the living organism.

Unfortunately, experiments performed on humans treated with different doses of lactoferrin showed less promising results [16-20]. When used against hepatitis C [16, 17, 19] or bacteria Helicobacter pylori, which is responsible for gastric diseases [18, 21], lactoferrin showed marginal or no effect on treated patients. When used against not-specified “summer cold”, lactoferrin presented minimal positive influence when tested on a small group of people [20]. On the other hand, people that took lactoferrin had more incidences of gastroenteritis, also commonly known as “stomach flu”.

In addition to that, there were two studies checking the influence of lactoferrin intake on the immune system [22, 23]. In both of these studies, tests were performed on very small groups of participants, showing minor or no effects on the tested parameters related to the immune system.

We are in a desperate need for a way to fight the COVID-19 pandemic. Lactoferrin was presented in the media as a possible magical solution for that problem. Unfortunately, it was based not on research but on a (misunderstood) scientific literature review about lactoferrin [24]. As of right now, there is one completed clinical trial regarding the influence of lactoferrin on patients with COVID-19 [25]. Results have not yet been published. Currently (31.07.2020), there are three more clinical trials regarding lactoferrin’s influence on COVID-19 patients [26-28]. Unfortunately, none of these trials started to recruit patients yet.

There are no vaccines or medications that were shown to be effective against COVID-19 at the moment [29]. That makes it very tempting to report on any studies as a ready solution to the problem even if they present just preliminary results. However, we should be careful with this kind of approach, as it is very likely to be ineffective but could also be potentially harmful.