*5.3. Scope of Practice*

Dietary changes vary in their simplicity and sustainability. Some changes are easy, and others are harder to implement and sustain over time. These changes can be categorized into general healthy eating, basic, or complex recommendations for chronic pain, and personalized medical nutrition therapy as outlined in Figure 3.

**Figure 3.** Nutrition and the chronic pain scope of practice.

In a multidisciplinary team, all health professionals should understand all of the components involved in pain management, including nutrition. However, it must be acknowledged that all health professionals have a particular area of expertise. Dietitians are experts qualified to provide medical nutrition therapy using the nutrition care process. In the nutrition and chronic pain scope of practice, all health professionals, should understand general healthy eating and have a basic understanding of nutrition-related recommendations for chronic pain. Pain management teams include medical, nursing, physiotherapy, psychology, and other allied health professionals and all have a significant role in providing relevant and appropriate health education to patients, including nutritional recommendations. However, a comprehensive understanding of nutrition-related recommendations for chronic pain and personalized medical nutrition therapy, should be provided by credentialed dietitians (e.g., Accredited Practising Dietitian or Registered Dietitian) who have undertaken approved study at university and registered with their respective national dietetic association (e.g., Dietitian's Australia or British Dietetic Association). Regardless of a patient's needs, whether it be advice on general healthy eating, basic or complex nutrition recommendations, or personalized medical nutrition therapy, a dietitian can provide valuable input at all stages.

#### 5.3.1. General Healthy Eating

Each country has dietary guidelines for healthy eating. Dietary guidelines promote healthy eating and lifestyle behaviors, rather than treating nutrition-related diseases. They convey the big picture and encourage the consumption of a variety of nutrient-dense foods. While this is not specific to chronic pain, many people do not meet the recommendations in these guidelines, which will impact on their overall health and wellbeing. For example, in Australia, only 6% of adults met the recommended daily amount of fruit and vegetables in 2020–2021 [179]. This highlights that health professionals still need to support people to improve their dietary intake to align with the recommendations.

#### 5.3.2. Basic Nutrition Recommendations for Chronic Pain

Basic recommendations for chronic pain, such as those provided in Table 2, are simple recommendations that all health professionals can support and help their clients to achieve. These are more specific to chronic pain as they address the underlying mechanisms, such as inflammation and oxidative stress.

#### 5.3.3. Complex Recommendations for Chronic Pain

Some people have a more complicated relationship with nutrition and pain, this is often due to the multiple barriers and/or underlying mechanisms and/or comorbidities, such as FGIDs. As previously mentioned, FGIDs are often associated with chronic pain and nutrition-related strategies should be provided by a dietitian.

#### 5.3.4. Personalized Medical Nutrition Therapy

Dietitians are trained to provide personalized medical nutrition therapy which acknowledges that a one-size fits all approach is not appropriate as individuals have different circumstances. Using the Nutrition Care Process [180], dietitians translate evidence-based nutrition information into tailored and practical dietary advice. Dietitians also participate in ongoing professional development to keep apprised of new or updated information. Patients who want to trial an elimination diet must do so with the support of a dietitian to ensure they maintain an adequate nutrition. Patients who have multiple comorbidities requiring multiple nutrition strategies should see a dietitian who can work with them to facilitate the appropriate dietary changes.

#### **6. Future Perspectives**

Nutrition interventions deserve to be an essential part of pain management [4,14]. Diet is a modifiable lifestyle factor that can be improved through nutrition interventions. At present, although nutrition is gaining more attention in pain management, current evidence mostly comes from preclinical studies, observational trials, or experimental studies that lack control groups or long-term follow up periods. Most of the available human trials are observational studies and explore the association between nutrition and pain, but do not clarify the causality behind the interactions between nutritional factors and pain. Future trials should consist of high-quality randomized controlled trials in more specific populations and on various chronic pain conditions. Studies in clinical settings need to be carefully designed to match patient characteristics due to the complexity of chronic pain. Clinical trials may explore both pain and nutritional-related comorbidities, such as patients with excess weight and vulnerable groups with somatic (i.e., frail elderly with multimorbidity) or psychiatric diseases (i.e., eating disorders). Additionally, it is of interest to explore more specific dietary patterns and dietary quality in the clinical populations so that real-world data may support the evidence of the appropriate dietary therapies in target patient populations. The latest research, however, is usually based on the general populations [57,181].

Current dietary guidelines provide advice for the general population to ensure people consume adequate nutrition and prevent chronic diseases [8]. However, as suggested in the observational studies, the needs of people experiencing pain differ from those who do not experience chronic pain. Thus, specific dietary guidelines need to be developed for chronic pain. These guidelines need to take into consideration the specific needs of people experiencing pain. They also need to be incorporated into the assessment and diagnosis procedures for chronic pain. Nutritional screening and assessments should be specific for people experiencing pain and be adapted, based on the evidence related to the pathophysiology and underlying mechanisms of chronic pain. The lack of clinical guidelines for nutrition and chronic pain indicates that the evidence needs to be synthesized into a clinical guideline for nutrition and chronic pain.

Investigating the relationship between nutritional factors and the physiological processes of the body are highly complex due to the difficulty of isolating the impacts of nutritional factors from the high number of confounding factors among individuals. As a starting point, developing general dietary guidelines for specific populations and subgroups constitutes an important place in pain medicine. However, based on novel and innovative technology and science, there will most likely be a shift from a "one size fits all" approach to personalized nutritional (pain) medicine. Improving technological development will allow researchers and clinicians to deal with large and more complex amounts of data which can be adapted to pain and nutrition. To exemplify, artificial intelligence and machine learning based software and applications have a great potential to collect real life and complex data from individuals and to capture meaningful insights for research and clinical purposes.

It is also important to explore the barriers people with chronic pain experience when adopting healthier eating patterns, to ensure successful and meaningful change. One perspective is to address other lifestyle factors in parallel to nutritional intervention. Strong associations were found between dietary habits, sedentary behaviors, and physical activity, especially among younger people [182,183]. Diet and sleep also have a bidirectional relationship [184]. Since sedentary behavior and sleep disturbances are extremely common among patients with chronic pain, future nutrition-based studies may consider the evaluation and combined effects of lifestyle interventions (physical activity, sedentary behavior, sleep, and dietary therapy).
