Almost two-thirds of the respondents indicated having used DS’s, SNPS, or both in the previous twelve months. DS’s were used more frequently than SNPs, with improving health being the most important motivating factor. The most frequently reported products used were, for DS’s, vitamin and mineral supplements, and, for SNPs, energy drinks. DS use was most frequently reported by women and older people. On the other hand, men, young people, and those exercising most frequently reported the highest use of SNPs. Women tended to indicate general health considerations more frequently compared to men as their main reason, whereas men reported physical performance purposes as their main reason for use more often than women. Remarkably, even sedentary respondents reported a relatively high prevalence of SNP use.
4.1. Prevalence and Reasons
Combined use of DS and SNP intake of specific groups and populations has been previously reported, ranging from 22% to 98% based on different methods [1
], while we measured a substantial percentage of 61% (combining both DS’s and SNPs) in the current study. Only a few studies have focused on the sport-specific use of DS’s and SNPs in non-athletes [1
]. Although the combined DS and SNP use in the present study is lower than in most recent studies with athletes [2
], it is much higher than the reported 4.8% in a small group of non-athletic controls (n
= 60) as presented previously [1
]. This may be explained by geographical differences indicating the relevance of this type of study for specific regions worldwide.
Overall DS use in this Dutch sample (49%) is similar to DS use of a representative sample of the US population (i.e.
, 52% [19
]) and data based on the latest Dutch Food Consumption Survey (VCP) [20
]. This VCP was also questioning dietary supplement use throughout the year, and showed a range of 26–36% for men and 34–54% for women across different age groups. The results of the present study are at the upper end of the results of the VCP, most likely due to including or not including specific types of DS’s (for example ergogenic supplements), but also reflecting some of the differences in our population with those of the VCP (maybe as a result of including those interested in a questionnaire about health and exercise), despite the fact that we included a representative sample of the Dutch population. As observed previously, multivitamins, vitamin C, and vitamin D were most frequently reported [19
Gender differences found in the present study are in line with results found earlier in a study including 1689 non-athletes as controls of an athletic population [8
]. These authors reported a difference in total nutritional supplement use—a combination of DS’s and SNPs—between men (32%) and women (52%) [8
]. We found a similar gender difference although the total prevalence of DS and SNP use was higher in our study, and the difference between both groups was much smaller: 60% vs.
64% for men and women, respectively. Interestingly, the women in our study reported higher DS use compared with men (36% vs.
20%), while men reported a higher prevalence of SNPs. This gender difference was also previously detected by others [2
]. An explanation might be that DS’s are more frequently linked to health, whereas SNPs are more frequently associated with physical performance. This would be in line with our observations that women reported “health” more often as the reason for use, while men reported “physical performance.” In contrast, some studies did not find a gender difference [3
] or in fact found the opposite [1
], which may also depend on the definitions used for DS’s and SNPs.
It is interesting to note that, compared with older respondents, younger respondents use more SNPs or both SNPs and DS’s. This contrasts with some previous investigations that indicated a higher prevalence of nutritional supplement use in adult athletes compared with adolescents [23
]. It can be speculated that SNPs, such as sports drinks and energy drinks, have become increasingly popular among younger individuals in recent years. This might be attributed to marketing strategies of companies producing these type of products that are appealing to young athletes, resulting, for example, in parents buying these drinks at the supermarket for their children to replenish energy and fluid at half-time during their sports activities on the weekend.
Our findings are also in line with the National Health and Nutrition Examination Study. That study revealed comparable trends for those being active (>120 times a year in the present study vs.
vigorous in NHANES), reporting the highest percentages for total DS use, but also for the top ranked products like multivitamin/mineral and vitamin C [19
4.2. Strengths and Limitations
The novelty of this paper is that we examined the use of DS’s and SNPs in a representative sample of a general population in relation to reasons for use, i.e., health purposes, physical performance purposes, both, or other reasons, for the total category of DS’s, SNPs, or combined use of DS’s and SNPs. To the best of our knowledge, this is the first study investigating the general reason for use (health, performance, or both) of both DS’s and SNPs in a general population. Besides this, we used a sound sampling strategy with a strong response rate.
An important added value of the present study is that it evaluated the prevalence of intake of DS’s and SNPs separately, as well as the different types of products used—an insight which has generally not been provided in other large cohort publications [19
]. For example, there does not seem to be any nutritional substantiation for energy-containing SNPs used by the majority of the non-exercising population. Combining DS’s and SNPs will not provide this insight.
The estimated proportions with a confidence interval (CI) of 95% are relatively small, which increases the likelihood that the true value of the respondents will actually lay close to the reported average percentage.
As we did not investigate frequency of use or quantity, this should be investigated in the near future. As a consequence, our results reflect the total prevalence of respondents using a product at least once in this period. This may inflate the results for prevalence of use; on the other hand, others have questioned nutritional supplement use in the last 12 months [27
], which can be seen as indicative for the (absolute) prevalence of this type of product and the difference in proportion between products and categories.
Since we were limited by the number of questions that could be included in the questionnaire, we chose to pre-select the most relevant types of DS’s and SNPs. In the case of SNPs, sports energy bars are missing in this category because we focused on fluid-based SNPs; therefore, the prevalence of SNP use in our study could be underestimated, but should at least give a representative picture of fluid-based SNP use. It could be debated why, for example, ergogenic supplements such as creatine and B-alanine were classified as DS’s, as others would put these in the SNPs category because of their sports-performance-enhancing claims. On the other hand, some but not all of these ergogenic supplements could be used for health purposes as well. For example, there is a relation between the nitrate in beetroot juice and blood pressure. Quercitin is a polyfenol that could also be related to health and caffeine and seen from a healthy life style perspective, for example, to stimulate energy metabolism to enhance body weight loss. As there is not a single definition, either legal or within nutritional science, of what constitutes a dietary supplement [28
], we chose to combine all supplements based on tablets, capsules, drops, and so on in small doses, mostly defined in mg or mcg. As the included sport nutrition products were defined as those delivering substantial energy, macronutrients, fluid, or a combination of the three. In this case, classifying ergogenics as DS’s could affect the prevalence of sport-specific use as a reason. On the other hand, the prevalence of the reason for physical performance regarding DS’s is only 14%, compared with 79% using DS’s for health purposes. The contribution of these ergogenic supplements on sport-specific use can be stated as limited. Still, this can be seen as a limitation that could have been prevented if we divided these categories beforehand.
As health is the main reason for use of DS’s, SNPs, or both, these observations suggest that the general population has the impression that both DS’s and SNPs are considered a healthy choice. An obvious question is whether the majority of this population needs these products, and whether the products used actually enhanced their sporting performance or influenced their health.