Tuesday, February 16, 2010

Designing an Anti-Inflammatory Diet

Help your patients prevent chronic disease by reducing inflammation risk factors.

By James Gerber, MS, DC.
Reproduced from the February 2010 issue of ACA News, a publication of the American Chiropractic Association.

The pathological process of inflammation has been understood for decades, but only recently health conditions not previously associated with inflammation, such as heart disease, cancer and degenerative brain disease, have been linked with this process. As a result, there has been an expansion of interest in discovering how anti-inflammatory interventions might help in the prevention or management of many diseases.

Natural approaches to achieving anti-inflammatory effects through the diet typically include: 1) an attempt to shift dietary fatty acid intake to reduce pro-inflammatory products of fatty acid metabolism, 2) an increased intake of plant-based foods that are naturally high in antioxidants and other anti-inflammatory phytonutrients and 3) a search for potentially allergenic foods, which, when eliminated, may lower systemic immune responses that promote inflammation. Let’s consider each of these strategies, the evidence supporting their rationale and the steps needed to implement them.

The Complexity of Fatty Acids
Fatty acids, specifically certain members of the omega-6 and omega-3 polyunsaturated families, are precursors of eicosanoids such as prostaglandins that have many influences on local tissues, including the mediation of inflammatory mechanisms. One of the omega-6 family, arachidonic acid, can be converted to a variety of powerful promoters of inflammation, while conversion of gamma-linolenic acid (GLA, another omega-6 fatty acid) and eicosapentaenoic acid (EPA, a long-chain omega-3 fatty acid) does not help promote inflammation to any considerable degree.

Since these precursors compete with each other for conversion to their respective eicosanoid products, a relative anti-inflammatory balance would be achieved by minimizing arachidonic acid and/or maximizing GLA and EPA in the diet. This is the rationale for modifying fatty acid intake in the anti-inflammatory diet, as well as for the use of anti-inflammatory fatty acids, such as fish oils, as supplements.

Popular anti-inflammatory diets often oversimplify the relative contribution of different omega-6 and omega-3 fatty acids to the inflammatory response. Since arachidonic acid can be produced in the body from other omega-6 precursors, a broad recommendation is typically made to limit omega-6 intake from all sources, even though some omega-6 precursors, such as GLA, are anti-inflammatory. Similarly, since EPA can be produced from other omega-3 precursors, a broad recommendation to increase intake in general from all omega-3 sources is common, even though short-chain omega-3s are converted to EPA to a limited degree only.

Clinical studies have shown the most promise for increasing food and supplemental sources of EPA and other long-chain omega-3s, beginning at about 500 mg/day for heart disease prevention and up to 3,000 mg/day for clinical anti-inflammatory effects. Reducing dietary sources of arachidonic acid by minimizing animal fats and flesh has some support, as well. GLA has shown promise as a supplement in amounts beginning at about 1,000 mg/day, but it is not present in edible foods. Flaxseed and its oil are rich in short-chain omega-3 and have some
healthful properties, but flaxseed oil was ineffective in the only clinical trial to date that investigated effects on a chronic inflammatory disease.

Clearly, the best evidence for designing the fatty acid contribution of an anti-inflammatory diet is to increase EPA intake from marine sources such as oily fish (salmon, sardines, herring, trout, black cod) and oysters, aiming for consuming these foods several times a week, and to reduce dietary sources of arachidonic acid (meat, high-fat milk and cheese products, eggs) as much as possible. This was demonstrated well in a randomized controlled trial in rheumatoid arthritis patients that found benefits from either a diet low in arachidonic acid or supplementation with fish oils—but an even larger clinical effect when both strategies were combined.

Switching to Plants
Plant-based foods are the richest dietary sources of substances known to affect the biology of inflammation, such as antioxidants and phenolics, which include the flavonoid family. The Mediterranean diet, with its emphasis on unprocessed plant-based foods and phenolic-rich olive oil, as well as recommending seafood as a preferred source of animal protein and fat, has emerged as a healthful anti-inflammatory diet. (To view Mediterranean Diet Food Pyramid, go to www.mediterraneandiet.com/tag/new-mediterranean-pyramid/.)

This diet has not only been found helpful for the prevention of heart disease through anti-inflammatory and other mechanisms, but has even helped reduce symptoms and disease activity in patients with rheumatoid arthritis. The Mediterranean diet and probably other, similar plant-based diets are certainly legitimate models for an anti-inflammatory diet.

Reducing Allergic Response
The role of food allergy in inflammatory disease has primarily focused on disorders of joints, such as rheumatoid arthritis; of the intestine, such as Crohn’s disease; and of the skin, as in atopic dermatitis. While benefits from food allergy identification and avoidance have been frequently demonstrated in individual cases and some clinical trials, controversy persists due to lack of double-blind challenges to confirm true sensitivities in most research. Of course, most dietary interventions cannot easily be concealed from subjects in a clinical trial, so placebo effects could explain the positive results on symptoms reported in these studies. Nonetheless, at least one rheumatoid arthritis trial has demonstrated persistent benefits of a low-allergen diet for up to one year.

A Combined Approach
Clinical benefits of anti-inflammatory diets may be due to a combination of the above mechanisms. Researchers in Sweden and other countries have shown that a “vegan diet free of gluten” has positive effects on symptoms and clinical signs of inflammatory diseases in trials lasting as long as one year. Such a diet would be void of arachidonic acid; free of potentially allergenic wheat, dairy and egg products; and high in plant-based antioxidants and other potentially anti-inflammatory phytonutrients. Similarly, the Mediterranean diet will typically have a more favorable omega-3/omega-6 fatty acid balance and might significantly limit potential allergens from animal-based foods. Clearly, there is more than one way to design an anti-inflammatory diet or to explain the benefits of such an approach.

Dr. Gerber is associate professor of clinical sciences at Western States Chiropractic College (WSCC) and is the lead instructor for WSCC nutrition courses. He has authored conservative care pathway protocols for treating dyslipidemia and obesity, as well as for using specialized supplements for treating joint disorders and musculoskeletal trauma. Dr. Gerber can be reached at jgerber@wschiro.edu.

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