The analysis presented here provides an overview of the herbal ingredients contained in PFS that were used by specific consumers in six European countries, who participated in the PlantLIBRA PFS Consumer Survey 2011. The herbal ingredients are identified in those PFS consumers that a) use these products for body weight reasons, b) are overweight/obesity dieters, and c) use PFS for body weight reasons and are also dieting. The study also explores the relationship between the use/non-use of the top weight-loss PFS herbal ingredients and self-reported BMI of survey participants.
The PFS consumers who take these products for weight control are predominantly women, living in Spain, overweight and obese (with BMI ≥ 25), non-dieters, with low physical activity, never smokers, low alcohol consumers, and less frequent consumers of bakery, pastries and soft-drinks. This profile suggests that individuals who use PFS for body weight reasons are health conscious and may turn to these products with the belief that this is a safe/innocuous and effort-free strategy to lose or maintain weight, a belief that other researchers have identified [50, 51]. Other studies have reported dietary-supplement consumer profiles with similar gender results to those of the present study, but with disparate results for the other factors [9, 44, 47, 52].
The present study also found that of the total 2874 PFS products consumed, 252 (8.8 %) products were reported to be consumed for body weight reasons in the previous 12 months by 240 PFS consumers of the total sample n = 2359, i.e. a prevalence of weight-loss PFS users of 10.2 %. In a US study, Blanck et al. (2007) reported a prevalence of 8.7 % of past year use of “non-prescription weight-loss supplements” (including dietary supplements and natural or herbal weight loss aids not prescribed by a doctor), using data from the 2002 US National Physical Activity and Weight Loss Survey (n = 9,403). Of the products reported by past-year weight-loss supplement users, 73.8 % contained a stimulant including ephedra, bitter orange, caffeine, guaraná, and kola nut . In a study using data on CAM use from the 2002 US National Health Interview Survey (NHIS) Alternative Medicine Supplement (n = 31,044), Bertisch et al. (2008) reported higher prevalence of “natural herbs use” (between approximately 17 % and just over 20 % depending on BMI category, with normal weight individuals showing the highest rate); but this study focused on CAM therapies use and did not specify the format in which the natural herbs were used . Another survey of US adults, a computer-assisted telephone interview conducted by the Center for Survey Research and Analysis at the University of Connecticut in 2005–2006, reported a much higher prevalence of use: of the adults who made a serious weight-loss attempt (n = 1,444), 33.9 % reported ever having used a “dietary supplement for weight loss” (including “over-the-counter appetite suppressants, herbal products, or weight-loss supplements”, although not distinguishing between them) . Lastly, in their recent study (n = 2,732) in the city of Pelotas, Brazil, Machado et al. (2012) reported that the prevalence of use of “substances for weight-loss” was 12.8 %; however, these substances included teas, dietary supplements (unspecified) and medicines . It is important to mention that all these studies were conducted in general populations, as opposed to PFS consumers.
A comparison of results among the scarce publications evaluating the use of weight-loss supplements at the population level is limited. The studies varied in the terminology used (concepts and definitions ranged between “natural herbs”, “non-prescription weight loss supplements”, or “substances for weight-loss”), study designs, sample sizes, and data collection methodology. The present study is the first study to evaluate the use of herbal weight-loss supplements in consumers of PFS in six European countries, having harmonised the terminology and methods used across countries.
The present study estimated the prevalence of dieting for overweight/obesity in the PlantLIBRA Survey of PFS consumers : 4.8 % (n = 113) of 2359 PFS consumers in the six European countries. Similar rates were reported in one study , where 4.4 % of those currently trying to maintain the same weight were users of weight-loss dietary supplements during the past year; however, 16.1 % of those currently trying to lose weight reported past-year use of these products (around a four-fold higher rate). In addition, Pillitteri et al. (2008) observed much higher rates, reporting that of the adults who made a serious weight-loss attempt (n = 1,444), 33.9 % had used a dietary supplement for weight loss . These findings are similar to those of Machado et al. (2012), who reported a prevalence of 48.4 % for use of weight loss supplements in those who tried to lose weight . Again, comparisons between studies are difficult because of study limitations in terms of design, terms used and data collection procedures.
This is the first study in a sample of PFS consumers from six EU countries that has identified the herbal ingredients contained in products used by “consumers for weight control”, by “overweight/obese dieters” and by “overweight/obese consumers who are simultaneously consuming PFS for weight control and dieting for weight control”. Artichoke was the herbal ingredient that appeared in the greatest number of PFS consumed in all three groups (6.1, 7 and 8.6 % respectively); however, these results might be driven by the high use of these artichoke-containing products reported in Spain and Germany (see the discussion further down). In addition, green tea (3.1 %) and fennel (2.9 %) were second and third in the first group. Fennel (3.5 %) and dandelion (2.9 %) were second and third in the second group. Lastly, fennel (4.1 %) and pineapple (3.5 %) were second and third in the third group. To our knowledge, only one recent US study has reported the actual herbal ingredients contained in weight-loss supplements and the prevalence of users . They reported different herbal ingredients, with almost 74 % using a product classified as a stimulant, more than half (55 %) consuming product containing Ephedra sinica (ephedra or ma huang), one in 15 used a product containing Citrus aurantium (bitter orange), and one in 10 took Garcinia cambogia (hydroxycitric acid); other active herbal ingredients, such as conjugated linoleic acid and Ilex paraguariensis (yerba mate), were in very few of the products reported in the study .
Some literature on the effectiveness of artichoke for weight loss reveals that the scientific evidence is “insufficient to guarantee the efficacy and safety for treating obesity but could be useful to treat some of its comorbidities (i.e. hyperlipidemia)” . In their review, de Villar et al. (2003) reported that it is frequently used in slimming products and as a diuretic . According to the recent “Assessment report on Cynara scolymus L., folium”, by the European Medicines Agency (2011), other indications of traditional use (which is how it is used in Spain) include arteriosclerosis and hyperlipidemia . The same report also states that “the antioxidative, hepatoprotective and choleretic effects of artichoke leaf extracts as well as lipid-lowering and anti-atherogenic activity with increased elimination of cholesterol and inhibition of hepatocellular de novo cholesterol biosynthesis have been demonstrated in various in vitro and in vivo test systems .
Only one publication included pineapple as an ingredient of popularly consumed weight loss products, in Spain . The authors outlined the main therapeutic indications/recommendations of pineapple at that time (2003), distinguishing the “true” ones (burns, skin lesions) from the “traditional-use” ones (dyspepsia, arthralgia, arthritis, stomatitis, cellulitis, exocrine pancreatic insufficiency and obesity; including a comment of “mild diuretic effect”), and concluded that scientific evidence for weight-loss effectiveness is “untested/non-existent” . However, in a very recent publication , the authors concluded that there might be an effect at cell level, which may be a potent modulator of obesity.
Finally, no publication was found including fennel as an ingredient of weight loss supplements, despite the extensive and recent scientific literature describing its uses and properties [56, 57]. A hypothesis for the high prevalence of consumption by our consumers using PFS for weight control and dieters might involve the fact that some of the properties attributed to fennel are to “improve digestion”, “prevent bloating” and as “flavour corrector” i.e. it might be accompanying other substances in weight-loss multi-ingredient supplements to improve digestion, neutralize intestinal gas formation and enhance their flavour . Moreover, like for pineapple, advertisements promoting fennel-containing products as a slimming aid on the Internet are numerous, which may provide an additional explanation.
In Spain, the country with the highest prevalence of “body weight reason respondents” (21.5 %) and “dieters” (17.4 %) and where artichoke-containing products were most used for body weight reasons (47/79 PFS), results are consistent with the traditional use of artichoke as adjuvant of weight loss treatments, to allow a fat diet in the treatment of mild to moderate hyperlipidaemia (for reducing cholesterol) . These results are also in line with some reports in the literature, such as the “White Book of herbal shops and medicinal plants”, a report about the situation of the Spanish herbal shop sector , in which the authors report that the top-selling products are food supplements (29 %) followed by weight control products (28 %). We explored other reasons for the use of artichoke in the six survey countries and there is agreement with the recommendations of use for stomach/digestive function and cholesterol (highest in Germany) (Fig. 3). In Germany, artichoke is used in traditional herbal medicinal products used to promote digestion (against dyspepsia, digestive complaints) . Moreover, artichoke has been used in traditional medicine for centuries all over Europe as a specific liver and gallbladder remedy and several herbal drugs based on the plant are used as well for high cholesterol and digestive and liver disorders . Other uses around the world include treatment for dyspepsia and chronic albuminuria . We cannot know at this stage the health reasons behind the different prevalence of consumption of the same herbal ingredient across the six countries involved in our study, because of the low consumption levels observed in the different sample groups. In order to be able to discriminate more easily, we would need to have a higher concentration of consumers of a single product containing a particular herbal ingredient consumed for a single health condition. We could hypothesize that these differences may result from different regulatory restrictions between the countries (i.e. the same herbal ingredient might be used in PFS or in herbal medicinal products), market consumption trends, marketing strategies related to traditional/cultural beliefs, etc. However, further research is required to prove these hypotheses, involving a long-term prospective study design, a larger sample size, market, regulatory, and anthropological data, as well as, stratification by gender, season of the year, to name a few explanatory variables.
Our results show that, when the entire survey sample was used (n = 2359) to increase the power of the comparison (Tables 5 and 6), significant BMI differences were observed between consumers and non-consumers of artichoke. Also in this entire sample, differences were observed in BMI between consumers and non-consumers of green tea (third most consumed herbal ingredient of respondents of “body weight reasons”). In both cases, more consumers than non-consumers of each herbal ingredient were overweight/obese (BMI ≥ 25 kg/m2). Again, even though we could not analyse the products consumed in each country, and considering the high use of artichoke in the Spanish sample (Fig. 3), we hypothesized that the Spanish data could be influencing these differences observed through the Chi-square analysis. In order to further try and clarify this hypothesis, we performed lineal Spearman’s correlation analyses (not shown) using all 3 samples (entire survey, “respondents of body weight”, and “dieters for overweight/obesity”) between the variables of “consumption/non-consumption of the herbal ingredients of the most consumed PFS in each sample” and “BMI”; BMI was first included as a continuous variable, then as a dichotomous variable (BMI < 25; ≥25 kg/m2) and lastly, as a categorical variable of 3 categories (BMI < 25; ≥25-30; >30 kg/m2). Only the following two results yielded in these analyses were significant for products containing artichoke: 1) with BMI continuous, consumers of products containing artichoke tended to have a higher BMI (coefficient = 0.070, significance = 0.001); 2) with BMI dichotomous, consumers of products containing artichoke tended to be in the highest BMI range (coefficient = 0.048, significance = 0.019). These results show that, although significant, the correlations were not very strong (not very close to 1). This could indicate that the Spanish data was not influencing the global results as far as artichoke was concerned in the entire survey sample.
As for the “dieters” subsample only (n = 112), results presented in Table 6 show very significant BMI differences for products containing Ananas comosus (pineapple), with consumers having higher rates of normal weight (BMI < 25 kg/m2) than non-consumers. These results were in line with those observed later in the correlation analyses (not shown), which yielded the following significant results: with all 1) BMI continuous, 2) BMI dichotomous, and 3) BMI categorical, consumers of products containing pineapple tended to be in the lowest ranges of BMI, i.e. 1) coefficient = -0.250, significance = 0.008 2) coefficient = -0.329, significance = 0.000, and 3) coefficient = -0.324, significance = 0.000, respectively). These correlation results were very significant (significance < 0.01) and also stronger (closer to -1) than those for artichoke.
Finally, we took a step further and, only using the Spanish data, we performed some Chi-square tests to analyze differences in the relationship between dichotomous BMI and the consumption/non-consumption of the 5 herbal ingredients included in Tables 5 (respondents of “body weight”) and 6 (“dieters”) (not shown). The differences observed were only significant for pineapple in both subsamples, i.e. again, a higher percentage of consumers of products containing pineapple had a BMI < 25 kg/m2, but to a further extent in “dieters” vs. “respondents of body weight” (p = 0.000 vs. p = 0.012, respectively). These results concerning the consumption of pineapple-containing PFS by the “dieters” subsample could suggest an influence of the Spanish data on the global results.
Summarising, pineapple contained in products consumed by “dieters” show the strongest relationship with BMI, with those declaring to consume them tending to have a lower BMI or tending to belong to the lowest BMI range. The global results observed for this relationship are possibly influenced by its higher consumption in Spain. However, we do not know why this is happening or if there is an association influenced by other factors, and we cannot infer causality from these results due to the cross-sectional nature of the survey. Bertisch et al. (2008), who analysed the relationship between obesity and the use of CAM (including natural herbs), reported that adults with obesity had similar prevalence of use of natural herbs compared to normal-weight individuals, and after adjustment by some factors they were generally less likely to use most individual CAM modalities . Nevertheless, Bertisch et al.’s study and our study are not comparable because they evaluated the overall use of natural herbs as a CAM modality in the general population, instead of the use of herbal ingredients among PFS consumers. To our knowledge, our study is the first study that has tested BMI differences between consumers and non-consumers of particular herbal ingredients contained in PFS.
The present study has several limitations. The survey was not designed to assess weight loss. All data were self-reported, allowing the possibility of misreporting -although with regards to the products, the interviewers verified the packaging of approximately 50 % of them. There exists the possibility of misclassification of a product as a PFS when it might be in fact an herbal medicinal product, due to the unawareness by the consumer of the legal status of the product or by a post-data-collection change of status of the product. In addition, the survey did not collect composition/label data (mostly unavailable), therefore, dosages of herbal ingredients could not be calculated for BMI/dosage analyses. The definition of the product “plant food supplement” is so specific that results can really only be compared with results from other studies with this definition. The cross-sectional nature of the survey does not allow inference of causality. The design of the survey (only including PFS consumers and quota sampling) does not allow either the weighting of the data, the extrapolation of results to the general population or the comparison with general population studies. Finally, the survey had a small sample size that allowed limited stratification and no regression analyses for assessing the association between BMI and herbal ingredients consumption vs. non-consumption and identifying significant predictors.
This study has some unique strengths. It is the first study that has identified the herbal ingredients most consumed by PFS consumers from six European countries who reported taking these products for reasons of “body weight” or who were “dieting for overweight/obesity”. In addition, the “PFS product” was very clearly defined and differentiated from other herbal products, which will allow direct comparison with future studies on weight loss and PFS consumption that might be conducted. Finally, the study has identified some of the many possibilities for future research to try and explain the differences in the use of weight-loss herbal supplements across national markets within the EU. This would encourage, for example, further research into the many aspects by which the different types of herbal products used in weight-loss/control can be differentiated, ideally using purposely collected data at the national and/or European levels.