*5.2. Nutrition Treatments for Chronic Pain*

Evidence suggests that following a predominately plant-based eating pattern (e.g., vegetarian, vegan, or flexitarian eating pattern) or a Mediterranean eating pattern (characterized by a high consumption of fruit, vegetables, legumes, wholegrains, dairy, olive oil, moderate consumption of fish, and small amounts of red meat) or an optimizing diet quality are most effective at reducing pain experiences [53]. The evidence available in the scientific literature is also supported by practice guidance toolkits [18]. However, these guidelines are limited to specific chronic pain conditions such as osteoarthritis, rheumatoid arthritis, and fibromyalgia. These toolkits also recommend predominately plant-based eating patterns, healthy fats and oils, and consuming a wide variety of nutritious foods. The evidence presented in the literature and toolkits can be synthesized into dietary recommendations that health professionals can provide to people experiencing pain (Table 2).

The evidence also indicates that reducing and limiting the intake of added sugar and energy-dense, nutrient poor, or ultra-processed foods will reduce the underlying mechanisms such as inflammation and oxidative stress that contribute to chronic pain experiences [94,171]. Ultra-processed foods undergo several industrial food processes and contain high amounts of sugar, chemically modified protein (e.g., hydrolyzed proteins), oil products (e.g., hydrogenated oils), and food additives [172]. They also contribute to a poor diet quality, metabolic health, and the development of chronic health conditions [173]. Examples of these foods include soft drinks, sweet or savory packaged snacks, and processed meats. National dietary guidelines recommend limiting the consumption of these foods, both in the amount consumed and in the frequency of consumption. In addition, the World Health Organization (WHO) recommends that adults limit their added sugar intake to less than 10% of their total caloric intake [174]. This includes foods such as table sugar, syrups, sweet packaged snacks and baked products, and sugar-sweetened beverages.

It is also important to consider the barriers or practical implications to adhering to a particular eating pattern. These include: ability and access to shop, prepare and cook food, pain flare-ups, cost, culinary skills, sleep, gastrointestinal symptoms, food intolerances, environment, motivation, and mood [53,175]. As part of a multidisciplinary team, a dietitian can work with the patient and their health care team to develop a sustainable plan that improves pain experiences, other health outcomes, and that can be adhered to over a long period of time [175].

Social determinants of health, such as education, socioeconomic status, access and quality of essential services, and the social environment, also play a role in an individual's ability to access nutritious and affordable food. Food insecurity is the inability to reliably access adequate and affordable nutritious food and it is associated with chronic pain and poor mental health. Findings from a recent survey of 200 adult food bank users in the United States, found that 53% of respondents reported experiencing chronic pain [176]. In this study, after controlling for age and gender, depression, and chronic pain significantly predicted food insecurity. A study which analyzed data from approximately 80,000 Canadians aged ≥12 years found that those who were food-insecure were 1.3 times more likely to experience chronic pain and almost 2.7 times more likely to have used prescription opioids in the last year [177]. This demonstrates that multidisciplinary teams must explore barriers, practical implications, and social determinants of health when it comes to nutrition and pain.

Other health professionals, such as psychologists, occupational therapists, and physiotherapists can also provide valuable advice and guidance that will work, in combination with the advice and guidance provided by the dietitian, to address some of these practical implications. For example, a psychologist can help address mood and motivation, an occupational therapist can undertake a functional assessment and provide advice on how to participate in nutrition and food-related activities, such as cooking, and physiotherapists can assist by facilitating people to build their strength and mobility which will help with accessing food.

A common denominator for all health professionals is behavior change. These practical implications can also be considered barriers that may make behavior change difficult. Behavior change is a fundamental part of the biopsychosocial and lifestyle approaches to pain management. Models and frameworks, such as the Behavior Change Model [178], can be used to understand and implement behavior change to overcome these barriers. It is important that all health professionals in a multidisciplinary team are familiar with behavior change models and incorporate behavior change techniques in their practice.
