*3.2. Eating Behaviors and Dietary Preferences in People Experiencing Chronic Pain*

Optimal dietary and nutrient intake are essential elements of musculoskeletal health. In addition to weight changes, a suboptimal nutrient intake and poor eating behaviors can cause altered serum nutrient levels, which can be observed among the patients with chronic pain. For instance, high levels of serum glutamate and aspartate were reported in patients with chronic migraine, orofacial pain, fibromyalgia, and complex regional pain syndrome [75–78]. Low levels of nutrients are also commonly recognized, such as vitamin D, omega-3 polyunsaturated fatty acid, vitamin B12, magnesium, zinc, ferritin, selenium, and folic acid [56,79]. Although, these studies do not draw conclusive and direct links with the aetiology of chronic pain, it is anticipated that chronic pain patients may have altered eating behaviors, either before the onset of pain or during the development of pain.

There is also an association between a suboptimal dietary intake and some pain conditions, such as irritable bowel syndrome (IBS) and pelvic pain syndromes [80,81]. Some special but diverse dietary triggers have been reported by headache patients (particularly migraines) [60]. It is also suggested that people experiencing pain generally consume more calories, added sugars, saturated fatty acids, sodium, and caffeine. This association has been demonstrated in a cross-sectional study that found one third of males and approximately half of female participants were consuming more than the recommended daily caloric intake, moderate fat intake, and a high saturated fat intake [82]. This study also showed that the intake of vitamin D, vitamin E, and magnesium, in people experiencing chronic pain, was lower than the recommended daily intake. Data from the British Birth Cohort Study has been analyzed and showed that women with chronic pain were more likely to decrease their intake of fruit and vegetables, and increase their high fatty foods consumption over time, compared to women without chronic pain [83]. The low intake of micronutrients has also been reported in another patient population with rheumatoid arthritis [84]. Another study observed that obese osteoarthritis patients had an increased calorie, fat, and sugar intake and this impacted on their pain severity [85]. Additionally, for patients with undernutrition, pain experiences could be accompanied by a loss of appetite and a decreased food intake [24,25,86,87]. This could lead to a poor dietary intake or absorption of nutrients (i.e., medications that affect gastrointestinal functions [87]) and subsequently a decreased fat free mass and impaired physical and mental functions (i.e., daily functioning and cognitive functions [86]).
