Brief reportDietary correlates of chronic widespread pain in Meru, Kenya
Introduction
Chronic pain is one of the most common and disabling medical conditions worldwide [1]. Data from the World Health Organization suggest that across 17 developed and developing countries, the population attributable risk for “yearly days out of role” was significantly higher for chronic pain than that of 19 other health conditions assessed [2]. Low- and middle-income countries (LMICs) could be disproportionately affected by chronic pain because of differences in exposures and treatment options available. Chronic pain may also have an impact on affected individuals in developing countries to a greater extent than in the developed world because of the need for more physical labor.
Chronic widespread pain has been linked to central sensitization, which is a self-propagating upregulation of excitatory neurotransmission in the central nervous system [3]. This not only causes widespread pain but also negatively affects sleep, cognition, and mood as well [4]. This type of pain often presents with an unknown etiology, and individuals with central sensitization in LMICs may suffer disproportionately because of a lack of treatment options [5].
Most developing countries lack access to pain specialists, sophisticated imaging studies, expensive medications, and surgeons, limiting their ability to evaluate and treat pain adequately. One underexplored treatment option for chronic pain is dietary modification, especially for pain conditions that are more diffuse or systemic in nature, such as fibromyalgia. Dietary factors may play more prominent roles in developing countries because communities often lack adequate access to clean water and appropriate amounts of healthy food, increasing susceptibility to dehydration and malnutrition, which may affect neurotransmission and pain response. They may also be at higher risk for certain food-based exposures.
To date, most research suggests that the prevalence of pain in developing countries is similar to the United States and other developed nations. Studies on pain in various countries indicate that the overall pain prevalence is similar in developed (37% overall) and developing (41% overall) countries [6], [7], [8]. In a recent review article, chronic pain prevalence in LMICs was estimated to be around 33%, with a 4% prevalence rate for fibromyalgia [9]. This closely resembles prevalence estimates for overall pain (30%) [10] and for fibromyalgia (5%) [11] in the United States.
Community members in Meru, Kenya, have been concerned that they are experiencing abnormally high rates of chronic pain in the community and asked our research group to conduct a preliminary assessment of pain in the region. We used community-based sampling methods to assess local households in random areas of the Kithoka region of Meru, Kenya, to gain a very preliminary look at the potential prevalence of pain in the region, as well as the identification of shared dietary exposures, as one area of potential intervention. Of 89 individuals surveyed, 54 (61%) reported chronic pain lasting 3 mo or longer, with 30% of those surveyed meeting the criteria for fibromyalgia [12]. The prevalence rate identified in this very small sample was significantly higher than the chronic pain rates of 33% reported in other developing countries [9] and double the estimates of 30% from the United States [10], and self-report of fibromyalgia symptoms was six times higher than the US population estimate of 5% [11].
Common dietary exposures among those reporting pain in the surveyed group were found to be frequent use of mixed seasoning spices called Mchuzi mix and very low intake of water. Mchuzi mix contains added monosodium glutamate (MSG), which is used as a flavor enhancer in foods. Glutamate is well known in the field of nutrition as a negatively charged amino acid; however, glutamate is also the most common neurotransmitter in mammalian nervous systems [13]. Increased dietary consumption of free glutamate (in the form of additives) has the potential to enhance glutamatergic neurotransmission [14], which plays a pivotal role in central sensitization [3] and widespread chronic pain [15]. Dehydration has also been linked to increased brain activity related to painful stimuli [16]. Thus, there is good biological plausibility for how dietary exposure to MSG and inadequate water intake may be able to affect chronic pain.
Herein, we report the results of a quasi-experimental pilot study that tested the effects of removal of dietary MSG, increased water intake, or a combination of both, relative to acetaminophen (as the main treatment option available in Meru, Kenya), to determine the percentage of people with self-reported improvement in pain. Biological hypotheses and future directions based on this work are also discussed.
Section snippets
Methods
The research study was reviewed and approved by both University of Michigan and American University institutional review boards in the United States and was approved in Kenya by the Kenya Methodist University Scientific and Ethics Review Committee. All participants gave written informed consent; in the case of illiteracy, verbal consent was witnessed and formally recorded. English is the primary language of Kenya; however, some participants only spoke Swahili or the local dialect of Kimeru.
Results
Table 1 describes the study population. The majority of participants were women (90%), and the average age was 56 (±18) years. Age appeared to marginally differ across groups (P = 0.07), with older individuals being more likely to be in the acetaminophen or water only groups. Marginal differences were also noted for body mass index (BMI), with the acetaminophen group having the lowest BMI of 18 kg/m2 (P = 0.09). Education significantly differed across groups, with the acetaminophen group also
Discussion
The results of this very preliminary pilot study suggest that a dietary intervention is feasible in the rural Kithoka region of Meru, Kenya. If the results presented here hold in a larger clinical trial, it would suggest that a low-glutamate diet combined with adequate water intake may be an effective low-cost treatment option for chronic pain. Future research should recruit widespread chronic pain participants with exposure to MSG and test the effects of this dietary intervention against
Conclusions
The results of this preliminary research suggest that dietary contributions to widespread chronic pain should be studied in more depth in Meru, Kenya. Ideally, future research would include a formal prevalence estimate in a large random sample of the community, detailed evaluation of common exposures (including dietary exposures), and further work to conduct a large-scale blinded intervention testing the effects of removing MSG and increasing water intake relative to acetaminophen. Using
Acknowledgments
The authors would like to acknowledge the incredible support we received from the Kithoka community in Meru, Kenya, which helped make this research possible, including clan elders, clinic staff, translators, and residents.
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This work was partially supported by an International Travel Grant from American University, United States. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.