Osteoarthritis Pain Abatement By Focusing On Healthy Dietary Intake
Overview
The impact of dietary changes on pain and joint function in adults with osteoarthritis (OA) is a growing area of interest. This systematic review evaluated whether diets high in plant phenols and omega-3 fatty acids could reduce osteoarthritis pain and improve joint function more effectively than diets high in saturated fatty acids, omega-6 fatty acids, and refined carbohydrates.
A comprehensive search of databases including CINAHL, Clinical Trials, Cochrane Library, Dissertation & Thesis Global, Embase, Medline, PubMed, Scopus, and Web of Sciences from January 2015 to May 2023 resulted in the identification of 7,763 articles. Following an independent review process, eight clinical trials (seven randomized and one non-randomized) were included in the final analysis. Due to variability in outcome measures, a meta-analysis was not feasible. This review synthesizes the effects of various diet interventions on pain and physical function in adults with osteoarthritis pain. The diets in the included trials varied in their content of fatty acids and polyphenols. The evidence suggests that encouraging the consumption of omega-3 fatty acids and polyphenols could positively impact osteoarthritis pain and physical function in adults with this condtion.
Findings indicated that participants adhering to diets rich in phenols and omega-3 fatty acids reported notable improvements in pain relief and physical function. The most significant improvements were observed in those consuming the highest levels of omega-3 fatty acids.
In conclusion, while the evidence is limited due to potential bias, there is an indication that advising adults with OA to replace refined grains and processed foods with whole plant foods, fish, and plant oils may reduce osteoarthritis pain and improve physical function. Continuous follow-up may be necessary to maintain adherence to these dietary modifications.
Introduction
Osteoarthritis (OA) is the primary cause of disability among older adults, with its prevalence increasing by 48% since 1990. The condition is characterized by joint pain, stiffness, and functional impairment. Effective management aims to alleviate osteoarthritis pain, maintain joint function, and support daily activities. Without proper intervention, OA can progress to an advanced stage, potentially necessitating surgical joint replacement.
Recent research suggests that diet modification could play a complementary role in OA treatment. Weight loss of 5%–20% has shown positive effects on pain reduction and functional improvement in overweight or obese individuals. There is a growing interest in nutrient balance beyond simple caloric reduction, as certain nutrients impact the environment of articular chondrocyte cells.
Oxidative stress, a condition where free radicals outnumber antioxidants, can lead to inflammation in chondrocytes, causing the release of proinflammatory mediators that exacerbate pain and contribute to cellular degradation. This chronic oxidative stress leads to structural changes in the joint and surrounding tissues, resulting in persistent inflammation and pain.
Antioxidants can mitigate oxidative stress in chondrocytes, interrupting the cytokine cascade and reducing inflammation. Over time, antioxidants help balance cartilage cell synthesis and degradation. These beneficial compounds are found in plant foods as vitamins, minerals, and polyphenols, with the highest concentrations in the seed coat, bran, bark, fruit, kernel, and leaf portions. Refined carbohydrates, which lack these portions, have lower polyphenol content. Research by Valsimou et al. indicates that multiple polyphenols work synergistically to reduce oxidative stress in chondrocytes.
However, the impact of phenols on OA-related pain and physical function varies. Some systematic reviews, such as those by Morales-Ivorra et al., Xu et al., and Zeng et al., show that diets rich in phenol-containing foods correlate with reduced pain and better joint function. In contrast, studies by Guan et al. found no consistent pain reduction in clinical trials with phenol-rich foods like strawberries and pomegranate juice.
Fatty acids also play a crucial role in chondrocyte metabolism. Saturated fats are associated with increased inflammatory cytokines and OA-like symptoms, while omega-3 polyunsaturated fats help reduce oxidative stress and protect chondrocytes. Conversely, omega-6 fatty acids may promote chondrocyte degradation. Balancing the intake of omega-6 and omega-3 fatty acids is essential for maintaining chondrocyte homeostasis.
Evidence from human observational studies supports these findings. For example, Miao et al. demonstrated a link between dietary stearic acid and inflammation in rat chondrocytes. Similarly, Eaton et al. and Lu et al. observed associations between dietary fat intake and joint space loss in adults with knee OA.
Given the influence of phenols and fatty acids on OA markers, dietary proportions of these nutrients significantly impact chondrocyte homeostasis. This study aims to assess how dietary modifications affect pain and physical function in adults with OA. It is hypothesized that a diet rich in phenols and omega-3 fatty acids will lead to less pain and improved joint function compared to a diet high in saturated fat, total fat, refined carbohydrates, and omega-6 fatty acids.
Method
The protocol for this systematic review followed the Cochrane Handbook for Systematic Reviews of Interventions and adhered to the PRISMA 2020 Checklist steps as illustrated in Figure 1. It was conditionally registered in PROSPERO on 24 February 2023, with final approval granted on 3 July 2023 (CRD42023394983). The databases searched included CINAHL, Clinical Trials, Cochrane Library, Dissertation & Thesis Global, Embase, Medline, PubMed, Scopus, and Web of Sciences. An initial search in PubMed, Web of Science, and Scopus was followed by an analysis of keywords and indexed terms using MESH. Subsequently, a comprehensive search was conducted using all identified keywords across all databases (Appendix A). Inclusion criteria were restricted to English-language articles on human studies involving adults, published since January 2015. Prior systematic reviews did not identify clinical trials before 2017. Relevant literature reviews’ reference sections were also checked. All search results were managed using EndNote, and an additional search in Google Scholar added the first 200 results to the EndNote Library.
From these searches, 7271 records were identified and imported into EndNote; after deduplication, 4465 articles remained for screening. The first reviewer (K.S.) screened 4116 titles for eligibility, while both reviewers (K.S. and C.H.) assessed the remaining 349 titles and abstracts using Rayyan software. Screening excluded 4453 articles for not meeting eligibility criteria or being duplicates. Among excluded titles and abstracts, 35.2% involved ineligible populations, 30.8% had non-diet interventions, 25.7% had unsuitable study designs, and 7.5% had irrelevant outcomes. One study was in Spanish, and two had durations under six weeks (Appendix B). Twelve full-text articles were reviewed (K.S., C.H.) (Appendix C), with five excluded for reasons such as being abstracts, not focusing on OA, or lacking sufficient information on dietary interventions. An updated search on 26 May 2023 identified three additional studies, one of which was included in the synthesis. The PRISMA flow diagram was updated (Appendix B).
Eight articles, dated between 2015 and 2023, were retained for the study. Two studies21, 22 used the same participants but were both included to provide data on short- and long-term dietary intervention effects.
Data were extracted by the primary investigator (K.S.) and tabulated in Excel, including study author, publication year, design, purpose, population demographics, diet intervention, findings, attrition, adherence, conclusions, and comments on confounding or validating variables. A second reviewer (C.H.) critically analyzed the extracted data for accuracy and presentation.
Two reviewers (K.S., C.H.) independently assessed the seven randomized clinical trials for risk of bias using Cochrane RoB2 tools. They evaluated measures to reduce bias, including randomization, allocation concealment, intervention adherence, outcome assessment blinding, attrition, and reporting biases. Articles were rated as low risk, unclear, or high risk, with reviewers agreeing on the judgments. They also used the Cochrane ROBINS1 tool for the non-randomized clinical trial, assessing biases in randomization, participant selection, intervention classification, deviations, and data reporting, reaching agreement on the risk of bias classification.
The extracted data were reviewed for homogeneity and the feasibility of pooling outcome data. A meta-analysis was not conducted due to varied outcomes across studies. The primary investigator (K.S.) analyzed the data narratively using SWIM reporting guidelines, tabulating study characteristics, participant demographics, clinical characteristics, diet intervention types, frequencies, and durations.
Diets were categorized based on phenol and omega-3 fatty acid content. High phenol/high omega-3 diets included plant-based, DGA, anti-inflammatory, and Mediterranean diets, characterized by whole plant foods, limited saturated fats, and whole grains. Low phenol/low fat diets were defined by low-fat content but allowed refined carbohydrates. Low phenol/high fat diets included high animal food content with high saturated fat levels. Diet effects were evaluated using ACR-validated tools for assessing OA pain and physical function, including AIMS2, KOOS, WOMAC, and VAS.
Inclusion Criteria
Clinical trials assessing diet impact on osteoarthritis pain or physical function due to OA were included.
Exclusion Criteria
Exclusions applied to animal studies, participants under 19, non-OA arthritis, acute pain, supplement-based interventions, non-whole food diets, non-specific or weight loss diets, and studies without pain or joint mobility outcomes or less than six weeks duration.
Result
Seven of the eight studies reviewed were randomized controlled trials (RCTs), while one was a nonrandomized, single-arm study. These studies included a total of 778 participants, with ages ranging from 52 to 72 years, and a majority being female (86.5%). Most participants in five studies were predominantly white (66%–100%), whereas two large studies mainly included African Americans (86%). One study did not report race.
Participants were excluded for reasons such as joint replacement history, recent weight loss, adherence to other diets, or presence of non-OA pain and specific comorbidities like rheumatoid arthritis, diabetes, fibromyalgia, organ failure, and cancer. The mean BMI of participants ranged from 29 to 35 kg/m², and all experienced moderate disability and pain at the start. Seven studies controlled for pain medications, but only one accounted for dietary supplement use.
All studies included at least one group instructed to follow a high-phenol/high-omega-3 fatty acid diet, with variations in the specific diets. Common components included unrefined plant foods, with limited animal products, commercial bakery items, and processed grains. Plant oils were eliminated in the plant-based diet, used sparingly in the DGA diet, and liberally in the Mediterranean and anti-inflammatory diets. These diets, particularly those using plant oils liberally, had the highest phenol and omega-3 fatty acid content.
Dietary interventions were implemented through education and ongoing communication by dietitians or trained individuals, with trial durations ranging from 6 weeks to 18 months (median 12 weeks). Adherence, tracked via dietary logs, was highest in shorter studies, with 100% adherence reported in a 6-week study and 96% in a 9-week study. The lowest compliance (65%) was reported in a 12-week study. Attrition rates varied from 0% to 21%, primarily due to non-adherence to dietary interventions.
All participants were classified as overweight or obese and lost weight across all diet interventions, with weight loss ranging from 1.3 to 8.7 kg. The greatest weight loss was observed in a low-phenol/high-fat diet study over 12 weeks. Another study showed that a low-calorie, high-phenol/high-omega-3 fatty acid diet led to greater weight loss compared to a standard low-calorie diet.
Pain reduction was reported across all studies, with significant reductions noted in those with over 80% adherence to the high-phenol/high-omega-3 fatty acid diet. Improvements in pain scores were more pronounced in diets with higher phenol and omega-3 fatty acid content, particularly those including plant oils. However, one study with lower adherence did not achieve statistically significant pain reduction. Similarly, physical function improved in all groups following the high-phenol/high-omega-3 fatty acid diet, with significant results in five studies. The greatest improvements were noted in studies allowing liberal use of plant oils.
The risk of bias assessment using the ROB2 tool indicated a high level of bias in the RCTs, mainly due to outcome measurement issues. The NRCT, assessed with the ROBINS-I tool, showed a low level of bias in several areas but had a high risk overall due to its design.
Conclusion
The systematic review reveals that adults consuming diets rich in plant phenols and omega-3 fatty acids experience less pain and improved joint function compared to those with diets high in refined carbohydrates, saturated fats, and total fats.
In eight clinical studies, participants were directed to replace or entirely remove refined carbohydrates and grains. Seven of these trials also advised increasing intake of phenol and omega-3 rich foods while reducing saturated fats. Across all studies, those who replaced refined foods with whole or unrefined plant foods reported less pain and better joint function.
Unlike previous cross-sectional studies, these trials quantified participants’ replacement of unrefined plant and animal foods with diets high in phenols and omega-3 fatty acids. The trials provided new insights into how dietary shifts can affect osteoarthritis (OA) symptoms. The most significant dietary changes were noted among participants following either a low-phenol/high-fat diet with 20–50 g of carbohydrate or an all-plant food diet. Participants on other diets showed moderate dietary changes. Those instructed by Hughes et al. and Fitzgibbons et al. to follow high-phenol/high-omega-3 fatty acid diets showed a 3%–5% improvement in their Healthy Eating Index (HEI) scores. Cooper et al. observed increased vegetable intake by 1.2 servings and fruit intake by 0.13 servings, along with a decrease in refined and whole grain consumption.
Overall, participants with even minor increases in fish, fruit, vegetables, and whole grains reported significant pain relief and improved physical function. The nutrient composition of these adjusted diets suggests a synergistic effect among polyphenols, omega-3 fatty acids, and micronutrients with antioxidative properties. Sadeghi et al. and Dolatkhah et al. provided detailed nutrient content, showing significant differences in saturated fat, magnesium, sodium, fiber, manganese, beta carotene, vitamin E, magnesium, zinc, vitamin A, and vitamin C consumption between the control and intervention groups.
The findings indicate that moderate dietary changes can reduce pain and enhance physical function, with pain scores improving by 20% in most groups. However, the extent of these benefits may vary depending on the severity of OA symptoms and individual patient factors. Therefore, while dietary interventions can offer mild improvements, their impact may be limited.
Dietary interventions, particularly those emphasizing interpersonal communication and written resources, demonstrated high adherence and low attrition rates. These interventions could also be beneficial for associated conditions like cardiovascular disease. Furthermore, diet education and nutrition counseling might support patient efforts in exercise and weight loss, which are crucial for managing OA.
Weight loss of 10%–20% has been linked to significant pain relief and improved physical function, with a 25% reduction in pain reported for a 20% weight loss. The studies reviewed indicated up to 10% weight loss, suggesting that longer interventions could yield further benefits.
Nevertheless, the findings are limited by a high risk of bias and the need to account for weight loss and micronutrient intake from diet or supplements. Blinding participants to diet interventions and using patient-reported outcomes present inherent challenges. Additionally, the varying stages of OA and affected joints among participants add to the complexity. Although the review supports high-phenol/omega-3 fatty acid diets for reducing pain and improving function, the evidence is not robust due to these limitations.
Future research should address these limitations, potentially through crossover designs and controlled dietary supplement use, and employ objective measures of physical function. Including detailed nutritional composition and servings in studies will enhance clarity.
Promoting dietary patterns rich in whole plant foods may benefit adults with OA by reducing pain, preserving joint function, preventing disability, and potentially delaying or avoiding joint replacement surgery. Long-term adherence to these diets may require ongoing counseling.
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