1. 2021;24;335-344Nutrition/Dietary Supplements and Chronic Pain in Patients with Cancer and Survivors of Cancer: A Systematic Review and Research Agenda
   Systematic Review
   Jo Nijs, PhD, Anneleen Malfliet, PhD, Peter Clarys, PhD, Iris Coppieters, PhD, Sevilay Tumkaya Yilmaz, MSc, Tom Deliens, PhD, and Ömer Elma, MSc.

BACKGROUND: Chronic pain is one of the most often seen, but often undertreated, sequelae in survivors of cancer. Also, this population often shows significant nutritional deficiencies, which can affect quality of life, general health status, and even risk of relapse. Given the influence of nutrition on brain plasticity and function, which in turn is associated with chronic pain in the population with cancer, it becomes relevant to focus on the association between pain and nutritional aspects in this population.

OBJECTIVE: To identify relevant evidence regarding nutrition and chronic pain in patients with cancer/survivors of cancer.

STUDY DESIGN: Systematic review.

METHODS: PubMed, Embase, and Web of Science were systematically searched for interventional and experimental studies that included patients with cancer /survivors of cancer with chronic pain, a nutrition-related observation/examination, and a pain-related outcome. Studies that complied with the inclusion and exclusion criteria were screened for methodological quality and risk of bias by using the Qualsyst (standard quality assessment criteria for evaluating primary research) tool.

RESULTS: The 2 included studies entailed uncontrolled trials which examined different nutritional supplements usage in various patients with cancer (breast, gastrointestinal and gynecological  cancers). One study evaluated the effects of vitamin C, but did not report a change in pain outcomes. The other study, looking at the nutritional supplements glucosamine and chondroitin, found an improvement in pain after 12- and 24 weeks.

LIMITATIONS: The limitations to the generalization of these results include the insufficient amount of eligible studies and diversity in therapeutic interventions and participant groups.

CONCLUSION: The association between nutrition and chronic pain in patients with cancer /survivors of cancer is not well documented. The available studies are uncontrolled, and are therefore limited to draw firm conclusions. Additional research is highly needed, and a research agenda is proposed within this paper.

KEY WORDS: Survivors of cancer, chronic pain, nutrition, diet