Fasting and internal cleansing have been advocated as ways of improving health since ancient times and, in this respect, it may be worth remembering that very different ancient sources mention them, as in the Ebers Papyrus (c. V BC, Chap. 20), Nei Ching (c. III BC, Book 4, paragraph 14), and Herodot (c. V BC, Book 2, paragraph 77). The protocol used in this study is an adaptation of a protocol that has been used in the United States since the middle of the last century (see Colema Boards of California Inc. at https://colema.com/) and has very different components. Each of them may play a specific role in the modulation of the IM and the benefits that it produces, but, initially, our interest was to explore a possible association between these two elements (modulation and benefits), considering the protocol as a whole, as it has been offered to our patients for about 20 years. Nevertheless, we would like to mention a brief description of the effects of some of the elements consumed during the colon cleansing protocol. Cleansing elements: a) psyllium: it not only has satiety effects [30], but it is also associated with significant changes in the IM [31]; b) montmorillonite (bentonite clay) has been widely used for different human therapeutic purposes and biomaterial design [32], but it also has shown beneficial effects on gut microbiota, at least in mice [33]; c) the consumption of apple cider vinegar, has been associated with favorable effects on lipid profiles and glycemic parameters [34]. Feeding plan: a) it is well known that yoghurt consumption is beneficial and could contribute, by modulation of the gut microbiota, to reduced body weight gain and lower incidence of type 2 diabetes [35]; b) honey not only can help in the modulation of gut microbiota, but also seems to decrease low-grade inflammation (metainflammation), at least in rats [36]; c) finally, the use of probiotics is gaining popularity and general acceptance not only for the treatment of obesity [37] but, also, in relation to general health and wellbeing [38].
The change in body weight (-3.0 kg 4.2%) observed in the experimental group between T1 and T2, and preserved at T3, is probably due to the loss of fat associated with the hypo caloric diet received during the treatment (1149.9 kCal), but, also, to some degree, to water loss. The fact that the weight loss is preserved one month after finishing the cleansing protocol and without any further intervention, can possibly be explained by two facts: improving life habits of the subjects, in response to the motivation caused in the participants for the initial results, as well as by the general wellbeing reported by all of them, but, also, probably, by the modulation of the microbiota associated with the intervention. A more detailed analysis of the latter issue is pending and will be published later but, so far, the changes in the F/BR, as well as the notable increase of the prevalence of A. muciniphila in the experimental group both support this hypothesis. The association between weight loss and changes in IMB are well accepted in the scientific community, although the mechanisms are still to be elucidated [39, 40], but its potential, for instance, by means of FMT, in the management of human adiposity is considered as already established [41].
The mechanisms for observed changes such as those in fasting plasma glucose remain to be clarified, as they can be due to weight loss [42], changes in the intestinal microbiota [43] or both. Short term improvement of insulin sensitivity associated with changes in microbiota after lean donor FMT (i.e., allogenic) have been reported in the literature [44], although, as these authors state, “causality has been difficult to prove”. Other authors as [43], who found favorable changes in intestinal microbiota, glycemic control and weight loss after anti- obesity surgery, suggest, as a mechanism, the regulation of homeostasis and subsequent eubiosis by adaptation and reestablishment of bacteria-bacteria and bacteria-host connections, but they also state that “… it is still difficult to relate cause and effect: is microbiome change the cause or the effect of metabolic control after the gastrointestinal food rerouting surgical procedure”. In our study, although FBS values were in the normal range for all but one of the participants, we observed a statistical significant diminution of the mean value in the experimental group immediately (T2) and a month (T3) after treatment (from 97.0 at T1 to 80.3 at T2 and 78,3 mg*dL− 1 at T3). The volunteer with abnormal FBS (120.0 mg*dL− 1 at T1) went down to 84.0 mg*dL− 1 at T2 and to 83.0 mg*dL− 1 at T3. These findings are very encouraging and highlight the possibility of IMB modulation as a possible way to improve insulin sensitivity.
A similar reasoning applies for changes in plasma lipid profile (see, for instance, Jia et al 2021 [45] for intestinal microbiota and hyperlipidemia) and, probably, for most of the other physiological variables considered in this preliminary pilot study [40].
A limitation of this study is its small sample size, due to restrictions imposed by the COVID-19 pandemic, as well as by the financial resources available for the study. Initially, our main focus was the treatment of overweight, young adult women without comorbidities and the original aim was to offer the colonic cleansing protocol as a starting point and adjuvant for a conventional slimming program, under the hypothesis that taking it would substantially improve the response to the slimming program consisting, essentially, of diet and exercise improvements. Due to the COVID-19 pandemic, we limited the study to the mere cleansing protocol and, therefore, the possibility of combining both interventions (cleansing protocol and slimming intervention) remains open.
Due to the above mentioned limitations, this work could be considered as an exploratory descriptive pilot study, but the results endorse the convenience of a larger one in terms of the number of participants, intervention and duration of the follow up, so that it overcomes the limitations of the study and in order to achieve a stronger statistical power of the results.
The small detrimental changes observed in the control group in such a short period could probably be explained by the living conditions imposed by the pandemic, where people were confined and tended to eat more and exercise less, as already mentioned [27, 28]. Nevertheless, it has to be said that we do not have a plausible explanation for the small improvement in the F/BR observed in this group between T1 and T2, although not statistically significant. This is, in fact, the only change that is not in line with the expected results. In relation to this ratio, although different authors advocate it as a biomarker of eubiosis/dysbiosis, especially in relation to excess body fat, some concerns have been raised about its utility [46]. Nevertheless, its significant change in the experimental group can be considered as a sign of microbiota modulation, as well as the increase in the relative prevalence of the bacterium A. muciniphila, which, in our opinion, also reinforces this concept. Were it not for the restrictions imposed by the pandemic, the small detrimental effects shown in the control group (the majority of them not statistically significant), may not be present but we would not expect this condition to dramatically change the output of the study and, therefore, we would not postulate that the changes would have been more pronounced in a situation without restrictions.
There is no clinical rationale for the use of doing 5 consecutive daily colon irrigations, but our starting point for the study was to have an initial scientific approach to the results of a protocol adapted from a commercial one available in the United States for more than 80 years now. In the original one, they recommend 2 daily colon cleansings during a 7 day period, but, in a trial and error approach a couple of years ago (data not published), we concluded that 1 daily enema for 5 days was the minimum for the people to get a good feeling of wellbeing and see tangible beneficial results. As a final point, we would like to enumerate some positive and negative arguments supporting or rejecting our approach.
The main negative argument to our approach is that it does not have the necessary scientific and evidence support to be presented as an alternative for microbiota modulation, with the favorable effects associated with such modulation, as it has been considered in the literature for different conditions [18, 47]. Another negative argument are possible gastrointestinal side effects that can occur, especially those associated with whole body irrigations, as those mentioned by different authors [10, 15], which are transient and were not present in the subjects of our study.
On the other hand, we think that possible benefits of our approach are: a) it is certainly much easier to undergo as well as cheaper and safer when compared to methods like fecal (microbiota) transplantations [48]; b) its nature allows for it to be performed at home; c) it does not involve medicines (except for the small amount of magnesium sulfate used at the end); d) all products needed for the treatment can be easily purchased without the need of a prescription.