Nutritional approaches to pain management can involve both changes in diet and the use of dietary supplements, including vitamins, minerals, enzymes and other substances. These strategies can be used to prevent pain, such as migraine headache, or promote the relief of pain and inflammation as part of a comprehensive pain management strategy. Like the herbal remedies, research in nutritional approaches is in an early phase. Although nutritional therapies are often perceived to have fewer side effects than pharmaceuticals, this may or may not be true and some nutrients are known to be unsafe in certain circumstances or at certain doses. The use of these therapies should be discussed with a health professional.
Dietary manipulation may influence pain perception or inflammation, and there have been numerous studies to evaluate the outcomes associated with different quantities of food or specific dietary factors. Although the data are limited, studies have begun to assess the effects of fasting (Hafstrom, 1988), food allergies (Panush, 1990), and various dietary constituents, such as a glycemic diet (Liu, 2002), lectins (Cordain, 2000), dietary blue green algae (Merchant, 2001), and green tea polyphenols (Yang, 1998). Recently, animal studies have measured the effect of phytoestrogens (plant estrogens) in soy-containing diets on pain physiology (Shir, 2002). Green tea polyphenols are flavonoids, and like other food substances (e.g., grape seed proanthocyanidins and citrus flavonoids) may have anti-oxidant effects (Chan, 1997; Sen, 2001; Manthey, 2001). These anti-oxidant effects could potentially have a variety of health benefits, including a treatment effect in painful inflammatory disorders (Manthey, 2000; Meydani, 2001).
Vegetarian diets have been advocated for fibromyalgia (Kaartinen, 2000) and rheumatoid arthritis (Kjeldsen-Kragh, 1994, 1999). There is a suggestion that fasting followed by a vegetarian diet can be useful to treat the symptoms of rheumatoid arthritis, including pain, morning stiffness, and tender and swollen joints (Muller, 2001). A low-fat vegetarian diet may reduce the duration and intensity of the premenstrual syndrome and pain during menstruation (Barnard, 2000).
Essential fatty acids (omega-3 and omega-6) perform a variety of functions in the body, including the regulation of immune and inflammatory responses. Recent research suggests that the levels of these chemicals, and the balance between them, could be involved in human disease, such as arthritis and other inflammatory conditions (Simopoulos, 1997; Sinclair, 2000; Kelly, 2001)
The standard American diet is already heavily weighted towards omega-6 fatty acids and some scientists recommend an increase in omega-3 fatty acid intake and a decrease in omega-6 fatty acid intake. The typical American diet provides more than 10 times the needed amount of omega-6, with estimates of the ratio between omega-6 and omega-3 ranging from 14:1 to 20:1. The optimal ratio is thought to be approximately 4:1. Common sources of omega-3 fatty acids are coldwater fish such as salmon, herring, sardines and halibut, and nonhydrogenated oils such as canola, grape seed, walnut, hemp and flaxseed oils. Common sources of omega-6 fatty acids include cottonseed, corn and other types of vegetable oils that are used in most processed foods.
Studies have suggested that the use of a dietary supplement containing specific essential fatty acids could have favorable effects on pain in patients with osteoarthritis or inflammatory disorders. They may enable patients with osteoarthritis to reduce their use of nonsteroidal anti-inflammatory drugs (Belch, 1998) and allow those with rheumatoid arthritis to reduce the use of other medications (Guesens, 1994). Studies also have shown that higher intake of omega-3 correlates with reduced menstrual pain (Deutch, 1995; Harel, 1996). Therapeutic use of fish oils to supplement omega-3 fatty acids should be supervised by a knowledgeable health care practitioner. These supplements can cause changes in blood lipids, increase the potential for bleeding and vitamin E deficiency, and with some preparations, carry the risk of vitamin A and D toxicities (Yeti, 1988).
Gamma-linolenic acid (GLA) is an unsaturated fatty acid derived from plant seed oils, such as evening primrose and borage seed oils. A number of studies have suggested that it reduces inflammation and produces improvement in patients with rheumatoid arthritis. Improvements include decreases in the duration of morning stiffness, joint pain and swelling, and the ability to reduce other medication usage (Rothman, 1995; Zurier, 1996; Leventhal, 1993). In addition GLA's may be useful in the preventive approach to migraine headaches by reducing the severity, frequency and duration of migraine attacks (Wagner, 1997). Since GLA is an omega-6 fatty acid, it is optimally taken with a balance of omega-3s.
5-hydroxytrytophan is the precursor to tryptophan, which is converted to serotonin, a neurotransmitter that plays a role in pain and inflammation. Increasing tyrptophan levels in the body may help to reduce chronic pain and reduce episodes of migraine headaches in those who are predisposed to migraines (Nicolodi, 1999). Tryptophan is no longer available as a dietary supplement due to a history of contamination. However, foods that contain high levels of tryptophan include salmon, tuna, garbanzo beans, cashew nuts, sunflower seeds, turkey, yogurt, bananas and dairy products.
Vitamin deficiencies are associated with a variety of diseases, some of which (like neuropathy) may be painful. The recommended daily allowances of vitamins are calculated to prevent deficiency, and a vitamin supplement should be taken if the ability of the diet to provide these substances is in question.
There is limited evidence that the additional use of specific vitamins may be therapeutic in some disorders. Vitamins B6 and B2 may play a role in reducing muscle spasms and cramps, preventing migraine (Schoenen, 1998), and reducing the symptoms of carpal tunnel syndrome (Folkers, 1990). Vitamin B12, which helps to maintain the sheath that surrounds and protects nerve fibers, may help pain from peripheral neuropathies and low back pain with sciatica (Mauro, 2000). The use of vitamin E, an anti-oxidant, may be effective in relieving pain and improving mobility in those osteoarthritis (Packer 1992) and a mixed anti-oxidant supplement containing vitamin C, vitamin E, selenium and L-methionine has shown promise in patients with pancreatic inflammatory pain (De las Heras Costa, 2000). In Germany, alpha-lipoic acid, another anti-oxidant found mostly in red meat, is an approved treatment for peripheral neuropathy. Administered intravenously, this substance appears to decrease the pain, burning, and numbness associated with neuropathy (Ziegler, 1997).
Minerals also may have therapeutic uses. Zinc and copper may help in wound healing and reduce pain and inflammation (Honkanen, 1991, Lansdown, 1996). Magnesium is analgesic for neuropathic pain in animal studies (Begon, 2002) and has shown clinical benefit in the treatment of migraine, cluster and tension headaches (Peikert, 1996; Mauskop, 1996; Demirkaya, 2001). It is unclear whether magnesium can reduce pain related to surgery (Hoinig, 1998; Ko, 2001). Magnesium's mechanism of action in pain management may be partly due to NMDA blockade (Begon, 2002).
Enzymes are substances that influence chemical reactions. Bromelain, a complex enzyme of pineapple, is commonly used in Europe as an anti-inflammatory compound for many forms of musculoskeletal injury, arthritis, cramps, post-surgery and post-traumatic swelling. It has been shown to be beneficial in reducing swelling, inflammation and pain by blocking the creation of proinflammatory compounds like prostaglandins, decreasing the production of kinins, and inhibiting fibrin production (Tasman, 1964). Although it is generally well tolerated, it can aggravate ulcers or esophagitis, and can interact with blood thinners (Meletis, 2000).
Glucosamine sulfate and chondroitin sulfate may favorably influence cartilage and have been studied as treatments for arthritis. Although some studies have had negative results, others suggest significant benefit from both these agents (McAlindon, 2000). Glucosamine sulfate has been shown to reduce symptoms of osteoarthritis (Reginster, 2001; Muller-Fassbender, 1994) and temporomandibular joint pain (Thie, 2001). The onset of improvement may take from one to three months; side effects are mild (Fillmore, 1999). Chondroitin sulfate was shown to be significantly superior to placebo in reducing pain in osteoarthritic joints, producing at least 50% improvement compared to placebo (Leeb, 2000). Further studies are needed to clarify its role in the treatment of arthritis and other pain conditions.