Irritable Bowel Syndrome (IBS) is a chronic disorder affecting an estimated 15 – 22% of western populations, and is the major cause of referrals to gastroenterology clinics in the western world [1]. The symptoms may include abdominal pain, diarrhoea, urgency to have a bowel movement, a feeling of incomplete evacuation after a bowel movement, flatulence and bloating. Some sufferers experience constipation, or an alternation between constipation and diarrhoea. IBS is more common among women than men, with a 2:1 female: male ratio [2]. Current medical treatments are directed at symptomatic relief, and although these can give some relief, there is no one treatment which has been shown to be lastingly effective. Although IBS is not a life-threatening disease, the symptoms and the effects of the symptoms on daily life can have a great impact on sufferers [3]. IBS is also associated with large healthcare and economic costs in terms of hospital investigations, repeated visits to GPs, prescription medicines, and loss of time from work [4]. Although hospital investigations for more serious diseases such as cancer or Inflammatory Bowel Disease are negative in people with IBS, some abnormalities in the gut have been found. For instance, some patients have been found to have a degree of mucosal inflammation, which may be in response to some foods [5]. It is possible that people with IBS have immunological reactions to dietary antigens as food elimination based on serum immunoglobulin G antibodies has been found to result in a significant decrease in symptoms of IBS. Both numbers of mast cells and their mediators have been shown to be increased in intestinal mucosa in patients with irritable bowel syndrome, especially in the close proximity of intestinal nerves [6]. Kalliomäki [6] suggests that food antigens induce mast cells to secrete mediators which regulate gastrointestinal motility, resulting in alterations in peristalsis and an increase in abdominal pain and discomfort. Furthermore, the mast cell-derived mediators have effects on immune cell functions. It may be then, that the nutrition of people with IBS is more important than has been traditionally thought. As people with IBS tend to believe that their symptoms are affected by diet, they often attempt to manage their disorder by dietary control. However, the only consistent advice given to people with IBS is usually simply to eat a "healthy" diet which includes fruit, vegetables and fibre. In an early study of people with IBS, Dancey & Backhouse [7] found that although the majority of their sample of 148 people (70%) stated that they were trying to follow a "healthy" diet with large amounts of fruit and vegetables; for many of these people, such a strategy had not led to symptom improvement, and in an attempt to control their IBS, 14% were eating very restricted diets. Some of these diets involved avoiding complete groups of foods, e.g. carbohydrates. Whilst such a strategy may reduce bloating, for instance, such a diet is not likely to enhance wellbeing. As well as eating a sufficient quantity of a wide variety of foods from each food group, micronutrients and nucleotides may also be important for health, especially in the sub-well. It is nucleotides which are the focus of this study.

Nucleotides are substances which are synthesised endogenously – they have important effects on the growth and development of cells which have a rapid turnover, such as those in the immune system and the gastrointestinal tract. The intestinal epithelium is a rapidly proliferating tissue with a high cellular turnover rate. A complete cell cycle in humans is 24 hours, with a replacement of the entire enteric epithelium within 3–6 days. In healthy people, dietary nucleotides are probably not essential, and in fact most will be metabolised and rapidly excreted from the system. However, under certain circumstances (e.g. in the sub-well, diseased, or under conditions of stress or poor diet) dietary nucleotides may be what Maldonado, Navorro, Narbona, & Gil [8] call "semi-essential", optimising the function of the gastrointestinal and immune systems. In relation to the gastrointestinal system work has shown that dietary nucleotides enhance the intestinal absorption of iron [9]. Dietary sources of nucleotides are nucleoproteins and nucleic acids, and these are found to varying degrees in many foods – lamb, liver, mushrooms (but not fruit and other vegetables) all are rich in nucleotides. Rapidly dividing tissue requires a constant supply of nucleotides in order to manufacture essential nucleic acids. Exogenous supplies of nucleotides may optimise tissue function particularly during recovery from mucosal injuries when the endogenous supply may limit the synthesis of nucleic acids.

Holen & Jonsson [10] found that dietary nucleotides had beneficial effects, especially when the nutrition supply was inadequate. Work with infants has shown that the incidence and duration of acute diarrhoea is lower in infants when dietary nucleotides are included in their diets [11]. Previous work on the effect of nucleotide supplementation in animals has found that such supplements are important for the repair mechanism of immune cells [12]. In piglets, nucleotide supplementation had effects on the gastrointestinal system by increasing villi height and crypt depth. [13]. Evans, Tian, Gu, Jones & Ziegler [14], using rats to model short-bowel syndrome, found that nucleotide supplementation is associated with increased jejunal adaptive growth after massive small bowel resection in rats. Dietary nucleotides have been found to help athletes by reducing the release of stress related hormones and chemicals in the body, and by maintaining a higher level of antibodies, which enables the immune system to work more effectively [15]. In people with a chronic illness such as IBS whose primary symptoms relate to the gastrointestinal tract, nucleotide supplementation may improve symptoms via improved gut function or by an enhancement of the immune system.

There are particular problems in assessing the benefits of treatments of people with IBS, and some of the problems of this patient group in relation to clinical trials have been discussed in detail by Spiller [16]. People with IBS show great variability in frequency and severity of symptoms, both when compared to others and also from day-to-day in their own symptoms. Spiller [16] has shown there are clear benefits to participating in clinical trials; people with IBS tend to be helped by placebo alone. This is thought to be due to a reduction in anxiety and/or depression as a result of help and reassurance given by the people running the trial. If this is the case, then anxiety and depression should reduce over the length of the trial. One would also expect that, if symptoms improve, then psychological well-being should in some way improve also. Thus although our primary aim was to determine whether nucleotide supplementation improved the symptoms of irritable bowel, we also wished to determine whether ratings of anxiety and/or depression would show any change as a result of symptom change.

The average person with IBS spent approximately £15.00 during the six months trial on medications, supplements, minerals and vitamins and visited the G.P.'s surgery approximately seven times, the majority of the consultation times being for reasons other than IBS.

Analysis of symptoms

Mean ratings for the symptom series for each condition with 95% C.I.'s for the symptoms are represented below (see Figure 2).

A repeated measures ANOVA on each of the symptoms was carried out. Sphericity was not assumed and therefore the Greenhouse-Geisser correction for degrees of freedom was used. The difference between conditions for abdominal pain (F_2,67 = 3.71; Eta² = .10), urgency to have a bowel movement (F_2,64 = 3.82; Eta² = .10) and a feeling of incomplete evacuation (F = _2,67 = 3.52; Eta² = .09) were significant at p < .05. Diarrhoea (F_2,58 = 3.08; Eta² = .08), Flatulence (F_2,70 = 2.89; Eta² = .07), Bloating (F_2,68 = 2.61; Eta²= .07) and Constipation (F_2,49 = .31; Eta² = .01) were not statistically significant at p < .05.

The percentage improvement of both placebo and IntestAidIB over baseline is shown below (see Figure 3).

Symptom severity for all symptoms (except constipation) are in the expected direction of baseline>placebo>IntestAidIB.

The study has shown that there is a consistent improvement in most of the symptoms of irritable bowel syndrome following nucleotide supplementation with IntestAidIB. There was a very low drop-out rate (18%); none of the participants who completed the study reported any side-effects. A feeling of urgency to have a bowel movement and abdominal pain showed the most improvement over baseline and placebo, and since abdominal pain is the symptom most likely to prompt people to seek medical help, this is a important finding. A feeling of incomplete evacuation after a bowel movement also improved following treatment by the neutroceutical product. However, whilst statistically significant, improvements are modest, and this may be due to several factors. Firstly, people with IBS are not a homogenous group, and show great variability in frequency and severity of symptoms, both from each other, and individually. This makes it difficult to detect effects of interventions. Secondly, the placebo response was strong – Spiller [16] states that it takes approximately 12 weeks for the placebo effect to reduce. Perhaps a longer trial – and with a larger dose – effects might have been stronger. However, this is speculative and further trials need to take these factors into consideration.

Participants were a mixed group of people who have a current diagnosis of IBS, some of whom still attend a gastroenterological clinic, and some of whom do not. They were not obtained from tertiary centres and carried on with their normal life taking their usual medications. Although their symptoms were not perhaps as severe as tertiary patients, their symptoms were bothersome enough for them to enter the clinical trial, and the symptoms were severe enough for the participants to buy a range of products aimed at relieving their symptoms. We expect that the effects found in this simple would be stronger if replicated with participants from tertiary centres.

The benefits over placebo compare favourably with benefits found in some drug trials. For example, Tegaserod (a drug which acts as a selective agonist at 5HT receptors in the gastrointestinal tract) was found to produce 4.7% advantage over placebo in the participants' assessment of global relief of IBS [24]. Although many such drugs are well tolerated, there were no side effects at all reported in the present study, which is a considerable advantage. The percentage improvement varied according to the symptoms – between 4 and 6%. The symptom improvements shown are unlikely to be the result of a decrease in anxiety or depression which has sometimes been cited as a reason for any improvement in trials, as anxiety and depression in the present study did not decrease significantly as the trial progressed (irrespective of condition). The effect – at least at this dosage – does not seem strong enough to lead to an improvement in psychological state since depression, anxiety, general health and illness intrusiveness did not differ between the conditions.

The strong placebo effects found in the present study are similar to those in other IBS- studies [16]. We suggest that the percentage improvement over and above the placebo effect is a physiological effect of the nucleotide supplement on the gut. However, whilst results were consistent and some symptoms were statistically significant, these effects may not be strong enough to be perceived as a great improvement by the participants, who will try to assess the benefits of such a supplement against a background of extremely variable symptoms. The mechanism by which nucleotide supplementation might improve gut function could be via increased mucosal protein, DNA and villus height – as has been found in animal studies [14, 25] Evans et al [14] state that rodent models are useful in translational research to identify potential new treatments to increase gut mucosal growth that is potentially relevant to humans with short bowel syndrome (this is not related to IBS). They state "...an increase in the surface area that would correlate with the increased villus height and crypt depth may conceivably correspond to an increase in available nutrient transporters, which may translate into increased nutrient uptake" (Although people with IBS have not been shown to have damage to the gut, nucleotide supplementation may improve gut function nonetheless by such a mechanism. However, this is purely speculative, and the present study set out only to determine whether symptoms of IBS were improved with nucleotide supplementation. Further studies, preferably dose-dependent studies, will need to be carried out to determine the mechanism by which any improvements occur.

A neutroceutical product, IntestAidIB, was found to improve six of the measured seven symptoms of IBS compared to both baseline and placebo. However, only abdominal pain and urgency to have a bowel movement showed statistically significant effects at the p < .05 level. Although the improvements in symptoms were consistent, the effects were not strong, and psychological measures showed no improvement either as a result of the experimental condition, or due to the benefits of taking part of a clinical trial. Further studies need to replicate and extend these results, seeking to clarify the mechanism by which improvements occur.