Dietary Supplement Use and Associated Factors Among Adults Working in Urban Settings in Tanzania: A Cross-Sectional Study

Abstract

ABSTRACT Background: Dietary supplements are products consumed to provide nutrients or other substances that the user may not consume in sufficient amounts through normal diets. Despite their increased global popularity, there is still scant information regarding the use of dietary supplements and associated factors among adult populations in Tanzania. This study aimed: to assess the extent of dietary supplement use and factors associated with use among adults working in urban settings. This was a cross-sectional study involving 419 adults working in public and private institutions within the Ilala District of Dar es Salaam who were selected using stratified and simple random sampling techniques. The study’s data was collected using quantitative methods through a self-administered questionnaire. Data analysis was done through descriptive statistics for frequencies, means, standard deviations, and proportions; cross-tabulations with chi-square tests for comparing observed differences in supplement use; and multivariable logistic regression for identifying factors associated with supplement use. A P-value of <.05 was considered statistically significant in the analysis. The prevalence of dietary supplement use among working adults was 46.5%, where 36.9% reported regular and 63.1% occasional supplement use, respectively. Seven types of dietary supplements were identified to be consumed, of which 45.1% of the respondents consumed more than one type of dietary supplement. Multivitamins (64.1%) were the most frequently reported type of supplement consumed, followed by Mineral (34.9%) and Herbal/Botanical (26.7%) supplements. The most commonly reported reason for dietary supplement use among working adults was to improve overall health (67.1%). A third of the users (35.9%) admitted to self-prescribing dietary supplements without seeking professional medical advice. The use of dietary supplements was significantly associated with being female (AOR = 2.243, 95% CI 1.415-3.555, P = .001) and knowledgeable of supplements (AOR = 6.756, 95% CI 4.092-11.154, P < .001). Overall, the use of dietary supplements is popular among adults working within urban settings, but its use is exacerbated by perceived knowledge and self-prescription instead of health professional advice. Therefore, there is a need for further studies to explain better the underlying drivers for perceived knowledge on decision-making. There is also a strong need for extensive health education to prevent inappropriate or excessive use of supplements which might lead to potential adverse events. Introduction: Tanzania has continued to encounter increasing malnutrition, particularly under-nutrition and over-nutrition, and diet-related non-communicable diseases. The National Nutrition Survey shows that the prevalence of over nutrition (overweight or obese) among women aged 15 to 49 years has increased in the past 2 decades from 11.3% in 1992 to 31.7% in 2018, and it is higher among wealthier populations and those living in urban areas.1 The sub-Saharan Africa (SSA) region has also experienced an increase of 67% in the burden of non-communicable diseases in the past 3 decades, where the most affected populations are of economic and social working age and situated in urban settings.2Worldwide, consumers’ desire good health and improved nutrition amid a demanding working environment and increasing healthcare costs, particularly in developing countries. The emergence of consumers adapting to healthy lifestyles has influenced them to seek alternative forms of medicinal and nutritional products.3 Dietary supplements are products consumed to provide nutrients or other substances that the user may not consume in sufficient amounts through normal diets. They are considered alternative forms of medicine and nutrition because of their dietary composition and the expected health promotion benefits that come with their consumption.4The regulation of dietary supplements differs across many countries where they are either produced or imported. In Tanzania, dietary supplements are regulated under the Food, Drugs, and Cosmetics Act of 2003 and the Standards (Imports Registration and Batch Certification) Regulations of 2021. These legislations safeguard public health interests by ensuring the safety and quality of dietary supplements before their distribution, including directions on their safe and appropriate use because they can potentially cause high health risks to vulnerable groups with impaired physiological conditions.5,6The global demand for dietary supplements has recently increased because they were initially consumed by athletes, gym attendants, and bodybuilders. However, they have extended to consumers of working-age groups who seek well-being and vitality and are influenced by their socio-demographic and lifestyle characteristics.7 The dietary supplements currently in the global market and widely consumed are segmented but not limited to vitamins, fish oils, minerals, proteins, herbs, or botanicals like Ginseng, Ganoderma, and the like.8,9Globally, over the past 40 years, there has been an observed increase in dietary supplement use from 25% to 70%.10-13 these proportions are higher among people with non-communicable diseases, the elderly, women, and university students.11,12,14,15 The increase in dietary supplement use can influence consumers to abandon conventional diets and medically approved treatments, thus leading to adverse reactions. Dietary supplement use is of public health concern because excessive, inappropriate, or unsupervised consumption can lead to adverse reactions and ailments.16,17In Sub Saharan Africa context, studies reported the prevalence of dietary supplement use in Ghana among stroke survivors (29.4%), in Kenya among urban adults aged 18 to 64 years (14.4%), in Uganda among professional athletes participating in individual and team sports (13.4%), and in South Africa among university dietetics students (23.0%). These studies further reported that dietary supplements were used to improve inadequate diet, maintain overall health, manage weight and build muscle, and prevent diseases through a strengthened immune system.18-21In Tanzania, studies have been done primarily on using micronutrient supplementation to prevent nutrition deficiencies among pregnant women and school children.22-24 However, there is limited information with regard to dietary supplements and the factors associated with use among adult populations in Tanzania despite their increased popularity, particularly in urban settings, where inappropriate or unsupervised use can lead to adverse reactions or worse. Hence, this study aimed to assess the extent of dietary supplement use among the working population within urban settings and the factors associated with this consumption because limited studies have researched this population. It is vital to acknowledge that urban adults have access to vast information that can drive them to make decisions on their health and lifestyle choices. Methods: This cross-sectional study was conducted in Ilala District, 1 of the 5 districts in Dar es Salaam region, located in eastern Tanzania. The district has 3 divisions, namely, Ukonga, Ilala, and Kariakoo, which are subsequently divided into 26 administrative wards. The population of the district is estimated at 1 775 049 people. There are 611 412 and 92 162 adults aged above 25 years employed in the private and public sectors, respectively in Ilala District. Sampling Probability sampling techniques were employed in this study. The primary sampling units for this study were institutions in the service industry within Ilala District. Separate lists of public and private institutions were obtained from the Ilala District council offices. Stratified random sampling was employed on both lists of public and private institutions, which served as a sampling frame for this study, and a total of 28 private and public institutions were selected for the convenience of the study. In each selected institution, a list of full-time staff was obtained from the respective administrative/human resources officer, and the employees were selected through simple random sampling. Only pre-selected employees available for work on that particular day were considered for the study, and other employees replaced those who were pre-selected but absent. The study participants were proportionately sampled from each institution to reach the estimated sample size of respondents. The employees’ weight and height measurements were taken in each institution before leaving the questionnaires with them. Due to limited information on dietary supplement use in Tanzania, the prevalence of dietary supplement use reported from other studies conducted in Sub-Saharan Africa could not be used because they were from different target groups (eg, elderly adults, gym attendants) to this study. Therefore, sample size estimation considered an expected prevalence of 50%, power of 90%, and 0.05 precision yielding 427 as the sample size. Data Collection the Research and Publication Committee of the Muhimbili University of Health and Allied Sciences (MUHAS) gave the study ethical clearance. Field data was collected using a pretested, self-administered questionnaire (with closed and open ended questions) developed in English and translated into Kiswahili. This tool was adapted from a 2015 study reported by Valentine from Illinois State University due to the similarities in study approach and research topic. The questionnaire gathered information on the socio-demographic and economic characteristics, lifestyle/behavioural characteristics, perceived knowledge of supplement use, supplement consumption patterns, and social-environmental characteristics. The weight and height measurements were taken using SECA scale by trained research assistants before leaving the questionnaires with the respondents to determine their respective Body mass index (BMI). Permission was obtained from local authorities in Ilala District and Executive directors in selected organizations before conducting any measurements on consenting respondents. All the respondents were measured without shoes and heavy clothing like suit coats and jackets. The respondents filled out the questionnaires in person within their organizations and were not required to provide their names or telephone contacts. All information was treated as confidential. Before their participation, the study’s aim and benefits were explained thoroughly to the respondents, including their right to voluntary participation. Each respondent was requested to provide consent; only those who consented were included in the study. Data management and analysis the completed questionnaires were checked for consistency and completeness on the day of data collection, and errors were corrected in the field. Data cleaning was done and then followed by sorting, coding, and entering into SPSS version 18. Dietary supplement use was the outcome variable where respondents who used any supplement within the past 12 months were coded as 1, and those who did not were coded as 0. Independent variables included socio-demographic, socio-economic, lifestyle/behavioral, self-perception issues, and perceived knowledge of supplement use. Descriptive statistics were done to generate frequencies, means, and standard deviations to describe the sample population. The proportions of dietary supplement use by categories of independent variables were compared using cross-tabulation with chi-square tests to determine the significance of their observed differences. Multivariable logistic regression was used to identify factors associated with dietary supplement use among the adults working in Ilala District. The statistical significance level was set at P-value of .05 or less. Results: The study analysis involved 419 respondents working in diverse institutions within Ilala District who were successfully approached. A large proportion of respondents (60.1%) were from public institutions while the rest were in private organizations. More than half (56.6%) of these respondents were female. Three quarters of the respondents (76.6%) had a bachelor’s degree or a higher level of education (Two thirds of the respondents (66.1%) were between the age of 20 and 39 years, and the mean age of the respondents was 37.5 ± 10.58 years. A large proportion (72.1%) of the respondents reported earning a monthly income of more than Tshs. 800 000/= (approximately $344). The mean BMI was 27.46 ± 0.25 kg/m2, where about a quarter (25.8%) of the respondents was obese, and more than a third (39.9%) were overweight.