The development of chronic pain is one of the most seen sequelae in the cancer survivor population. Literature reports the presence of pain in approximately 40% of 5-year survivors. Specifically, in breast cancer survivors, chronic pain is estimated to be present in at least 50% of this population. On the other hand, chronic low back pain is one of the leading causes of disability and decrease in quality of life. It has huge economical, psychological and social impacts on individuals, society and health institutions.

Unhealthy dietary behavior is associated with the occurrence, maintenance and management of chronic pain. Also, excessive calorie intake and diets rich in sugar, fat, sodium and caffeine were observed in patients having chronic pain. However, although nutritional factors are suggested as an associated lifestyle factor of chronic pain, limited attention is given to dietary and nutritional factors in relation to chronic pain.

One particular mechanism drawing attention in the link between nutrition and pain are blood glucose levels and the glycemic response. Animal research shows the potential for reduced blood glucose to influence several pathways involved in chronic pain, including decreased oxidative stress, and reduced neuronal excitability. Given the link between blood glucose levels, as well as the evidence for the importance of interpersonal variability in the glycemic response, this glycemic response can also be of interest for chronic pain research. Finding a possible link between both the glycemic response and pain-related outcomes, could give direction to further research focussing on implementing (personalized) nutritional/dietary advise to maintain healthy blood glucose levels in people suffering from chronic pain.

Therefore, this study will provide the first step in this promising line of research, by being the first to look for differences in glycemic response between breast cancer survivors having chronic pain and healthy pain-free controls, and between chronic low back pain patients and healthy pain-free controls.

Secondly, this study will also investigate possible associations between glycemic response, pain-related outcomes, nutrition related outcomes, physical activity, and body composition for breast cancer survivors and chronic low back pain patients separately in comparison with healthy pain-free controls.

Study Design:

This study will be carried out as an experimental, cross-over study, including two pain populations, one control group and two assessment sessions.

At the first session, firstly, all participants will undergo an assessment including pain-related outcomes, nutrition-related outcomes, and measures of physical activity, quality of life, body composition, and fasting blood glucose. Secondly, participants will be given a test beverage (with a high or low glycemic index, randomly decided), after which blood glucose levels will be assessed several times during the next 120 minutes.

At the second session, two days later (washout period), only fasting blood glucose levels will be tested again, after which the study participants will be given the other test beverage, after which blood glucose levels will be monitored once more for 120 minutes. Other outcome measures will not be re-assessed after exposure to the beverages, as we do not expect a direct influence of these test beverages on the outcome variables.

Results will be analysed and published separately for chronic low back pain patients and breast cancer survivors.

Recruitment of participants:

Participants will be recruited via posters and flyers. These posters and flyers will also be distributed to general practitioners, pharmacists, physiotherapists, health insurance companies, etc., who will be asked to alert potential participants to the possibility of study participation. Information and recruitment messages will also be placed on the website and social media platforms of the Pain in Motion research group.

Informed consent:

Prior to participating in the studies, each participant will be asked to read and sign a participant information sheet and a consent form

GROUP 1=Chronic Low Back Pain

Inclusion Criteria

• Women between 18 and 65 years old;
• Native Dutch speaker;
• Experiencing chronic nonspecific low back pain (i.e. pain present for at least 3 months, at least 3 days per week);
• No new medication or new treatments started in the 6 weeks prior to or during study participation;
• Non-specific failed back surgery can be included if the operation was anatomically successful and happened at least 3 years ago;
• No physical exertions over 3 Metabolic Equivalent of Task (MET) in the 3 days before the assessments;
• No analgesics/ caffeine/ alcohol/ nicotine 48 hours prior to the assessments

Exclusion Criteria

• People who have any other diagnosed systemic diseases e.g. diabetes mellitus, hypertension, cardiovascular diseases etc;
• Participants who have neuropathic pain according to "Douleur Neuropathique 4 Questionnaire" and the S-LANSS Neuropathic Pain Score;
• Chronic widespread pain diagnosis (like fibromyalgia, chronic fatigue syndrome, whiplash);
• Current pregnancy or pregnant in the past year;
• Specific spinal pathology (e.g., hernia, spinal stenosis, spondylolisthesis, infection, spinal fracture or malignancy)

GROUP 2= Breast Cancer Survivors

Inclusion Criteria

• Female breast cancer survivors with chronic pain (lasting at least 3 months, at least 3 days per week);
• Participants between 18 and 65 years old;
• Native Dutch speaker;
• Active treatment ended at least 3 months ago (i.e. surgery, radiotherapy and chemotherapy; hormone and immune therapy can be going on);
• No analgesics/ caffeine/ alcohol/ nicotine 48 hours prior to the assessments

Exclusion Criteria

• People who have any other systemic disease like hypertension, Type II Diabetes etc;
• Current pregnancy or pregnant in the past year;
• Current active cancer process;
• Tube feeding

GROUP 3= Healthy, Pain-Free Controls

Inclusion Criteria

• Female, healthy and pain-free participants between 18 and 65 years old;
• Native Dutch speaker;
• No analgesics/ caffeine/ alcohol/ nicotine 48 hours prior to the assessments

Exclusion Criteria

• Current pregnancy or pregnant in the past year;
• People who have any other diagnosed systemic diseases e.g. diabetes mellitus, hypertension, cardiovascular diseases;
• Participants who have neuropathic pain according to "Douleur Neuropathique 4 Questionnaire" and the S-LANSS Neuropathic Pain Score;
• Chronic widespread pain diagnosis (like fibromyalgia, chronic fatigue syndrome, whiplash);
• Specific spinal pathology (e.g., hernia, spinal stenosis, spondylolisthesis, infection, spinal fracture or malignancy)

The Investigator and the Participating Site shall treat all information and data relating to the Study disclosed to Participating Site and/or Investigator in this Study as confidential and shall not disclose such information to any third parties or use such information for any purpose other than the performance of the Study. The collection, processing and disclosure of personal data, such as patient health and medical information is subject to compliance with applicable personal data protection and the processing of personal data (Directive 95/46/EC and Belgian law of December 8, 1992 on the Protection of the Privacy in relation to the Processing of Personal Data).

Data are anonymous if no one, not even the researcher, can connect the data to the individual who provided it. No identifying information is collected from the individual.