The link between nutrition and chronic low back pain

This dissertation consisted of four main parts that overall contributed to the understanding of the role of nutrition in non-specific chronic low back pain (nCLBP) by unraveling the link between nutrition and chronic pain.
Part I consisted of two narrative reviews and aimed to provide an overview of the existing knowledge on the interaction between nutrition and chronic non-cancer, non-neuropathic pain; and to highlight the need for more experimental human studies in the nutrition and chronic pain field. Overall, available evidence showed a bi-directional relationship between nutrition and chronic pain. Oxidative stress and inflammation were suggested as the dominant underlying mechanisms of this interaction alongside other potential main action mechanisms including gut-brain axis, disturbed glucose and lipid metabolism, and obesity and overweight. The findings also highlighted that the main evidence regarding the link between nutrition and pain comes from preclinical animal studies or observational human trials, which indicates a lack of high-quality evidence like randomized controlled trials, systematic reviews, and meta-analyses.
Part II compromised two systematic reviews and aimed to systematically review the literature in both chapters to provide insights into the pronociceptive and analgesic effects of diets on non-neuropathic, non-visceral, and non-cancer acute and chronic pain in preclinical animal studies; and to investigate the link between diet and chronic musculoskeletal pain in observational and experimental human studies. In the first systematic review, we aimed to review the preclinical animal literature, to further guide us in our human research focus and aims. Results of this review showed that a high-palatable diet, and excessive intake of saturated, monounsaturated, and omega-6 polyunsaturated fatty acids decrease pain sensitivity in acute pain whilst the same nutritional factors have nociceptive impacts in chronic pain models. Additionally, findings from preclinical animal studies pointed antinociceptive effect of calorie restriction and anti-inflammatory nutrient intake. In the second systematic review, we aimed to identify the effects of dietary patterns on pain sensitivity and additionally to explore the link between nutritional intake and pain sensitivity by reviewing experimental and observational human studies. Overall findings highlighted the nociceptive effect of plant-based dietary patterns on chronic musculoskeletal pain which also were known with anti-inflammatory effects. There was no study identified that investigated the effects of dietary patterns on nCLBP population.
Part III consisted of a case-control study and aimed to investigate the association between diet quality, dietary intakes, and pain in patients suffering from nCLBP compared to pain-free healthy controls (HCs). The findings of our study showed that patients with nCLBP have a lower diet quality, eat more pro-inflammatory, have less intake of nutrients known for their anti-inflammatory and anti-oxidative properties, and drink less water compared to HCs. Accordingly, pain sensitivity mainly showed a negative correlation with the pro-inflammatory diet and nutritional intakes known for anti-inflammatory properties (i.e., vitamins E, D, A, B6, B12, and zinc).
Part IV consisted of a randomized cross-over trial and aimed to contribute to the understanding of the association between nutritional factors and nCLBP by investigating the differences in glucose metabolism between patients with nCLBP and HCs; and by exploring the association between pain and glucose metabolism responses in nCLBP. In this study we primarily investigated differences in post-prandial glycaemic responses (PPGR) to high (sucrose) and low glycaemic indexed (GI) (isomaltulose) beverages in women with nCLBP and HCs and explored whether any group that showed greater PPGR to high GI beverage would benefit when high GI beverage was replaced with low GI beverage. Secondly, this study explored the association between PPGR and pain in patients with CLBP. Results of this study showed us normoglycaemic nCLBP patients might have a higher risk of developing impaired glucose tolerance compared to pain-free individuals and might benefit more when high GI carbohydrates are replaced with low GI ones. Because, compared to HCs, nCLBP patients had higher PPGR to high GI beverage intake while there was no difference in PPGR between the two groups when they ingest low GI beverages. In terms of pain sensitivity, our findings did not identify any association between pain sensitivity and glucose metabolism.