Scientific Opinion on the substantiation of health claims related to dried
plums of ‘prune’ cultivars (Prunus domestica L.) and maintenance of
normal bowel function (ID 1164, further assessment) pursuant to Article
13(1) of Regulation (EC) No 1924/2006[sup]1[/sup]
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3
European Food Safety Authority (EFSA), Parma, Italy
ABSTRACT
Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies was
asked to provide a scientific opinion on a list of health claims pursuant to Article 13.1 of Regulation (EC) No
1924/2006 in the framework of further assessment related to plums of „prune‟ cultivars (Prunus domestica L.)
and maintenance of normal bowel function. The food that is the subject of the claim, prunes (dried plums of
„prune‟ cultivars (Prunus domestica L.)) is sufficiently characterised. The claimed effect, maintenance of normal
bowel function, is a beneficial physiological effect. The proposed target population is the general population. In
weighing the evidence, the Panel took into account that two human intervention studies showed an effect of dried
plums on bowel function, that one study with considerable limitations showed an effect of dried plums on stool
consistency, but not on other measures of bowel function, that another study with considerable limitations did not
show an effect of dried plums on bowel function when compared to dried apple, and that there is good evidence
for plausible mechanisms by which some components of prunes may contribute to the claimed effect. On the
basis of the data presented, the Panel concludes that a cause and effect relationship has been established between
the consumption of dried plums of „prune‟ cultivars (Prunus domestica L.) and maintenance of normal bowel
function. In order to obtain the claimed effect, about 100 g of dried plums (prunes) should be consumed daily.
The target population is the general population.
© European Food Safety Authority, 2012
1. Charakterystyka żywności / składnika
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Suszone śliwki mogą przyczyniać się do prawidłowego funkcjonowania jelit
The food that is the subject of the health claim is prunes (dried plums of „prune‟ cultivars (Prunus domestica L.)).
The content in prunes of water, total carbohydrates, protein, fat and amino acids, as well as a number of different sugars, minerals, vitamins, carotenoids, organic acids, and phenolic compounds, is given in the literature (Dikeman et al., 2004; Stacewicz-Sapuntzakis et al., 2001). The composition with regard to a number of components with purported effects can be measured. Prunes contain dietary fibre (according to four American studies: average 6.45 g/100 g, range 6.0–7.3 g/100 g) which includes soluble and insoluble fibre, sorbitol (average from six sources/varieties 14.7 g/100 g, range 9.4-19.3 g/100 g), and phenolic compounds (ca. 184 mg⁄100 g) such as neochlorogenic and chlorogenic acids. The water content of dried prunes is about 20-23 %5 (for data and references see also: Stacewicz-Sapuntzakis et al., 2001; US Department of Agriculture, 2009).
The Panel considers that the food, prunes (dried plums of „prune‟ cultivars (Prunus domestica L.)) which is the subject of the health claim, is sufficiently characterised.
3. Naukowe uzasadnienia wpływu na zdrowie człowieka - Prawidłowe funkcjonowanie jelit
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Suszone śliwki mogą przyczyniać się do prawidłowego funkcjonowania jelit
In its earlier opinion (EFSA Panel on Dietetic Products Nutrition and Allergies (NDA), 2010), a total of 16 references were cited to substantiate the claim, of which 14 were narrative reviews, publications providing only background information, or studies unrelated to the food for which the claim was made, from which no conclusions could be drawn for the scientific substantiation of the claim. Of the two human intervention studies provided which were considered as being pertinent to the claim, one reported no effect of dried plums on bowel function (Lucas et al., 2004), whereas the other showed some effect of dried plum consumption on faecal weight compared to grape juice (control) (Tinker et al., 1991). Based on the information initially submitted, the Panel concluded that the evidence provided was insufficient to establish a cause and effect relationship between the consumption of dried plums of „prune‟ cultivars (Prunus domestica L.) and maintenance of normal bowel function.
In the framework of further assessment, three additional human intervention studies as well as references which addressed proposed mechanisms by which some components identified in prunes could contribute to exert the claimed effect were provided. One human intervention study with a cross-over design (Sairanen et al., 2007) assessed the effect of consuming daily 260 g of a test yoghurt containing 12 g galacto-oligosaccharides, 12 g prunes and 6 g linseed, or 260 g of a control yoghurt without the afore-mentioned combined constituents, on defecation frequency in elderly subjects with self-reported constipation. The Panel considers that no conclusions can be drawn from a study on a fixed combination of constituents for the scientific substantiation of a claim on prunes alone. The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claim.
Two references reported on human intervention studies (Attaluri et al., 2011; Howarth et al., 2010) investigating the effects of prunes on bowel function.
This evaluation is based on the scientific references provided in the present and the previous submission which addressed the effects of dried plums of „prune‟ cultivars (Prunus domestica L.) on maintenance of normal bowel function, and on the mechanisms by which dried plums could exert the claimed effect in the target population.
In total, four human intervention studies which reported on the effects of prunes on measures of bowel function were submitted (Attaluri et al., 2011; Howarth et al., 2010; Lucas et al., 2004; Tinker et al., 1991).
The study by Tinker et al. (1991) was an eight-week, open-label, cross-over intervention in which 41 adult men (29-79 years) with mild hypercholesterolaemia were randomised to consume daily either 12 prunes (~100 g; ~6 g dietary fibre by analysis) or 360 ml grape juice (low-fibre control) for four weeks each in order to assess the effects of prunes on blood cholesterol concentrations. Biochemical parameters and 72-h faecal samples were collected at baseline and at the end of each intervention period. There were no drop-outs. Treatment differences were assessed by repeated-measures analysis of variance (RM-ANOVA) grouped by diet sequence. The baseline and prune periods were compared with the grape juice period. Faecal wet and dry weights were significantly higher after the prune period than after the grape juice period (faecal wet weight as g/72 h (mean±SEM): 628±44 vs. 514±34, respectively p=0.001; faecal dry weight as g/72 h: 140±9 vs. 120±8, respectively, p=0.006) and higher than baseline values (faecal wet weight as g/72 h (mean±SEM): 550±42.7; faecal dry weight as g/72h: 123±7.1). Interactions between diet sequence and dietary intervention were not statistically significant for faecal weight. The Panel considers that this study shows an effect of dried plums on bowel function as indicated by increased faecal weight.
Attaluri et al. (2011) described an eight-week cross-over study with blinded data analysis. Forty chronically constipated subjects (m/f=3/37, mean age 38 years) were recruited from the community. Subjects were instructed to maintain their usual lifestyle including diet and physical activity.
Laxatives and other remedies for constipation were discontinued for at least one week prior to study enrolment. Subjects were randomised to consume dried plums (50 g twice daily with meals (about 12 plums daily), equivalent to about 6 g per day of fibre) or psyllium (11 g twice daily with 240 ml of water, equivalent to 6 g per day of fibre) for three weeks each, with a wash-out period of one week in between, after a one-week run-in. Subjects were then followed for six weeks (no intervention), during which they were asked to continue with their usual diets and remedies to treat constipation. They were asked to maintain a daily stool and symptom diary during the eight-week study period and during the last week of the six-week follow up. At the end of each intervention period, subjects were asked to fill in a global constipation symptom score (a validated Rome III outcome measure). Rules for the use of rescue laxatives were defined and their use documented in the stool diaries. There were no drop-outs in the study. The investigators who analysed the data were blinded to treatment group allocation. The primary outcome measure of the study, which was used for power calculations, was the mean number of complete spontaneous bowel movements (CSBMs, defined as bowel movements with sensation of complete evacuation and with no laxative/enema in the preceding 24 h) per week. Secondary outcomes were global constipation symptom scores, taste survey scores, stool consistency (Bristol stool form scale), and straining scores. In addition, the number of bowel movements per week, the number of spontaneous bowel movements (no laxative/enema in the preceding 24 h) per week, and the number of complete bowel movements (sensation of complete evacuation) per week were also assessed from the stool diaries. One-week measurements obtained at baseline, during the third week of each intervention period, and at the end of follow-up were compared using two-tailed paired Student‟s t-test with Welch‟s correction for unequal variances and one-way analysis of variance. Negative binomial regression analysis was used to assess carry-over effects for primary and secondary outcome variables. No carry-over effects were identified for primary or secondary outcomes. The Panel notes that the statistical analysis performed was not appropriate for assessing differences between the two interventions, i.e. dried plums and psyllium. As compared to pre-intervention baselines, the intervention with either dried plums or psyllium resulted in a significant increase in mean CSBMs per week (1.8 vs. 3.5, p=0.001 and 1.6 vs. 2.8, p=0.001, respectively). For both interventions, CSBM-per-week values returned to pre-treatment baseline during the wash-out period. Significant changes with the dried plum intervention in some of the secondary outcome measures such as stool consistency and improved straining scores as compared to baseline are in line with the observed effect on bowel movements. The Panel notes that dried plums showed an effect on bowel function similar to psyllium, for which there is evidence to support a laxative effect (Brandt et al., 2005; Fleming and Wade, 2010; Ramkumar and Rao, 2005). The Panel considers that this study shows an effect of dried plums on bowel function.
One reference (Lucas et al., 2004) described a secondary study that was part of an intervention trial in 58 post-menopausal women not on hormone replacement therapy and free of any gastro-intestinal or eating disorders. The objective of the study was to evaluate the effects of dried plums on markers of bone turnover. Subjects were randomised to consume either 100 g of dried plums (Prunus domestica L.) (about 10-12 plums, 7 g dietary fibre) or 75 g of dried apples (6.5 g dietary fibre) daily for three months. Subjects were asked to fill in a validated questionnaire regarding their weekly bowel habits, including stool frequency, estimated faecal bulk, consistency of stool (7-point scale), strain and pain during bowel movement, and feeling of constipation after bowel movement. Mean stool frequency in this population sub-group was normal (around 11 per week). Data were analysed by RM-ANOVA. Thirty-eight women completed the study. No significant differences were found between the two treatment groups or between different time-points within each group for any of the parameters used to assess bowel function. The Panel notes that this study had a number of limitations. The study design reduced the likelihood that an effect of prunes on bowel function could be observed, for example, the effect of prunes was determined in comparison with dried apple which had a similar amount of dietary fibre, and self-reported outcomes are not a sensitive measure of changes in bowel function in this group which had normal bowel function. In addition, the Panel notes the high drop-out rate in this study, that no information was provided on how the missing data were taken into account in the statistical analysis, and that the information provided was insufficient to judge the appropriateness of
the statistical analyses. The Panel considers that this study with considerable limitations did not show an effect of dried plums on bowel function when compared to dried apple.
A cross-over study (Howarth et al., 2010) was designed to investigate the effect of different snacks on energy and nutrient intake, as well as their impact on body weight and bowel habits. A total of 29 females (25 to 54 years) were randomised to consume twice daily one 100 kcal snack of either prunes (84 g/day, number of plums not indicated; 6 g/day dietary fibre) or low-fat cookies (1 g/day dietary fibre) for two weeks each, with a two-week wash-out period in between after a three day baseline run-in. The primary outcome of the study (used for power calculations) was differences in energy intake between snack types. Intake of macronutrients, intake of dietary fibre, changes in body weight, and changes in bowel habits were secondary outcomes. Dietary intake (via food records) was assessed at baseline and every other day for a total of seven days per treatment period. Information on bowel habits (via a self-reported seven-day bowel habit questionnaire) was collected at baseline and daily during the second week of each treatment period. Bowel habit parameters included stool consistency, straining during bowel movement, pain during bowel movement, completeness of evacuation, overall feeling of constipation, and stool frequency. Mean stool frequency in this population sub-group was normal (around 1.2 per day). Twenty-six women completed the study and entered data analysis, which was performed in the population of completers only. Differences in dietary intake and bowel habits between baseline and the interventions were assessed by RM- ANOVA with post hoc paired-comparison t-tests. Subjects reported significantly softer stools with dried plum consumption compared to low-fat cookie intake and baseline values (p≤0.05). No other significant decreases were reported for any other bowel habit parameter. The Panel notes that this study had a number of limitations, for example, self-reported outcomes are not a sensitive measure of changes in bowel function in this group which had normal bowel function, and the information provided was insufficient to judge the appropriateness of the statistical analyses. The Panel considers that this study with considerable limitations showed an effect of dried plums on stool consistency but not on other measures of bowel function.
Several references which proposed mechanisms by which some components of prunes could contribute to the claimed effect were identified (Couteau et al., 2001; Livesey, 2001; Parkar et al., 2008; Stacewicz-Sapuntzakis et al., 2001; Welsch et al., 1989). Prunes contain dietary fibre, both soluble and insoluble, and sorbitol (Stacewicz-Sapuntzakis et al., 2001). Insoluble components of dietary fibre resist breakdown by the microflora and exert a physical effect on faecal bulk by their presence, and by retaining water within the cellular structure, whereas the soluble components are extensively degraded by the microflora resulting in a substantial stimulation of microbial growth and thereby an increased faecal bulk (Cummings, 2001). Increased faecal mass will increase the diameter of the lumen of the colon, thereby decreasing intraluminal pressure and allowing increased forward flow of the faeces (Gregory and Strong, 2005). Sorbitol is poorly absorbed in the small intestine and acts as an osmotic laxative (Livesey, 2001; Mahan and Escott-Stump, 2007; US Food and Drug Administration, 1993). While individual variation is observed with regard to the laxative threshold for sorbitol, laxative effects have regularly been observed with a dose of 20 g and more, and in some studies with a dose of 5-10 g (Badiga et al., 1990; Bauditz et al., 2008; Hyams, 1983; Jain et al., 1985). The Panel considers that there is good evidence for plausible mechanisms by which some components of prunes (i.e. sorbitol and dietary fibre) may contribute to an improvement in bowel function.
In weighing the evidence, the Panel took into account that two human intervention studies showed an effect of dried plums on bowel function, that one study with considerable limitations showed an effect of dried plums on stool consistency, but not on other measures of bowel function, that another study with considerable limitations did not show an effect of dried plums on bowel function when compared to dried apple, and that there is good evidence for plausible mechanisms by which some components of prunes may contribute to the claimed effect.
The Panel concludes that a cause and effect relationship has been established between the consumption of dried plums of „prune‟ cultivars (Prunus domestica L.) and maintenance of normal bowel function.
