Historically, nutrition’s relationship to health and disease was studied by ancient Greek, Egyptian, Chinese and Indian physicians. The ancient Hebrew dietary laws were for the prevention of disease, and special diets were provided for various painful conditions. Hippocrates said "your medicine shall be your food and your food shall be your medicine." The Corpus Hippocraticum contains specific diets for particular diseases including some where pain was an important symptom. Diet for disease continued as an important part of treatment during the middle ages and into the renaissance. In the early nineteenth century physiology became an experimental science and study of the physiology of digestion (absorption, assimilation, and metabolism) of food was extensively studied and the study of nutrition progressed.

Malnutrition may result if any of the component processes; intake, absorption, assimilation, metabolism, or excretion becomes disrupted to the extent that physical and/or emotional well-being is changed and illness develops. Of equal importance is the fact that malnutrition can result from diseases that interfere with these processes. Pain associated with disease, can interfere with nutrition by physical changes and changes in mood, with a decrease in appetite and metabolic changes in the other processes. When this situation transpires, effective pain relief contributes to the care of the patient and helps to produce a state of well-being.

Obesity may result if any of the component processes dietary intake, absorption, assimilation metabolism or excretion is disrupted. In general obesity occurs when the body takes in more calories than are utilized by the total metabolic process. Body mass index (BMI) is now a standard measurement of obesity, in which the height in meters is divided by the square of the weight in kilograms. A BMI of 25 is considered the threshold for defining obesity. It is known that many chronic illnesses are higher in the very obese (BMI at or above 30), when compared to those with a BMI less than 25. The risks of cardiovascular disease, diabetes and other life-threatening illnesses are increased, together with reduced daily function and lower quality of life in those with BMI’s over 30. In addition obesity contributes to many painful conditions, causing excessive strain on joints ligaments and muscle.

Physical activity is very important in health as well as in weight control, pain relief and can help prevent disease. The type of physical activity is not as important as the regularity of activity. Such activity as housework, yard work, sports, and planned exercise are all beneficial, if done on a regular basis for 30 minutes 5 to 7 days per week. Physical exercise helps to control weight by burning the excess calories that otherwise would be stored as fat, because body weight is determined by the calories you eat and use every day. Exercise, can also reduce the chances of heart disease, stroke and help to regulate blood pressure, and is also helpful in the control of diabetes, back pain and osteoporosis.

Nutrition and Acute Pain
Patients who suffer acute pain (trauma induced or surgical) can now be safely and effectively fed in the following ways: (a) hypertonic nutrient solutions infused through central venous catheters into the superior vena cava; (b) the intravenous administration of safe fat emulsions; (c) enteric formula diets administered by gastric feeding tubes. These thing together with improvement in anesthesia and ventilatory support, new antibiotics, and intensive care units have greatly reduced surgical and trauma mortality. Concern exists about the increased demand on various organs by the detrimental effects of anesthesia and surgery such as pulmonary complication, myocardial infarction, thromboembolism and other complications. Many now believe that the neuroendocrine response to surgery can be reduced by preemptive use of neural blockade with local anesthesia. This can be accomplished by prior infiltration of the surgical incision with local anesthesia, spinal (SAB) using local anesthesia with or without opioids or epidural block especially continuous epidural block with opioids. The reduction of pain reduces the stress and improves ventilation, cardiac function, and gastro intestinal activity and improves general well being as well as nutritional status.

Nutritional support must meet the metabolic needs of the individual whether enteral or parenteral. Nutrients need to include, protein, carbohydrate and fat in varying amounts depending on their breakdown and synthesis, as well as electrolytes Normally, 85% of daily energy use is from fat and carbohydrates and 15% from protein. No strict indications are available in selecting the patient in need of special nutritional support, however, the majority of patients undergoing elective procedure will tolerate starvation for short periods of time, and attention to nutrition can minimize morbidity. Some of the factors to be considered in determining the need for enteral or parenteral support include patient age, previous state of health, degree of metabolic insult (burn patients or those who are septic), and those who are severely stressed. There may be other factors that indicate inadequate nutritional status, such as significant weight loss over the previous several months or a body weight of less the 85% of ideal body weight. Laboratory tests may help in identifying those patients at risk, together with the overall impression of the physician.

There are several factors that need to be considered in deciding on the need for enteral or parenteral nutrition supplementation in individual patients. In previously healthy patients the need for nutritional support increases with the age of the patient and the duration of starvation and in those with chronic medical diseases (chronic obstructive pulmonary disease, hepatic insufficiency, diabetes, congestive heart disease etc). Other factors such as the metabolic insult in burned and septic and severely stressed patients need to be given nutritional supplementation early.

If the need for nutritional support is decided the best route must be determined. In our opinion the enteral route should be chosen whenever possible, as its benefits appear to surpass the simple nutritional value of the feeding given. Studies seem to indicate that critically ill patients have decreased rates of morbidity and mortality when enteral fed as compared to those parenterally fed. Benefits are; decreased atrophy of the gut, maintains of gut lymphoid tissue and decreased cost. Parenteral nutrition is required in some situations such as gastrointestinal-cutaneous fistula, short bowel syndrome, acute renal failure, hepatic insufficiency, inflammatory bowel disease and anorexia nervosa. It also may have a supporting role in radiation enteritis or chemotherapy toxicity, Hyperemesis gravidarum and prolonged ileus. The components of parenteral solutions include 25% dextrose, 5% amino acids, vitamins, trace elements and varying amounts of electrolytes.

Nutrition plays a very important part in various causes of pain (cancer and non-cancer pain, headache, arthritis, rheumatic disease, osteoarthritis and obesity, gout, Paget’s disease, myofascial pain syndrome, neuropathic and various painful neuropathies, painful chronic visceral disease and many others) all can benefit from various, alteration in diet or nutrition. For most painful condition I recommend  vitamin C and E as well as high B complex together with a good multivitamin with minerals formula.

Reference:
Bonica’s The Management of Pain, Second Edition