Anti-inflammatory diets and ingredients claim to reduce incidence of some diseases, but do the claims hold up?
Inflammation is beneficial as it helps the body recover from infection and injuries. However, chronic inflammation leads to excessive formation of free radicals that damage body tissues and contribute to the development of all chronic diseases. And, inflammation is the “underlying cause of autoimmune diseases and a contributing factor in the development of neurodegenerative diseases and some forms of cancer," says Prakash Nagarkatti, Ph.D., vice president for research, University of South Carolina, Center for Dietary Supplements and Inflammation, Columbia, SC.
Inflammation fighters
Fatty acids. Omega-6 fatty acids influence inflammation, though their effects may vary between obese and lean individuals, depend on other dietary factors and vary considerably between each different fatty acid (International Journal of Obesity, 2012; 36: 797-804). A review of 15 randomized controlled trials for 2 to 9 weeks found the addition of linoleic acid to diets did not increase markers of inflammation, but large intakes of linoleic acid alone or in combination with diets low in alpha linolenic acid (ALA) could influence inflammatory markers (Journal of the Academy of Nutrition and Dietetics, 2012; 112:1,029-1,041).
“There is a lot of evidence the omega-3 fatty acids DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) can inhibit a range of factors involved in the inflammatory process. However, the implications of this for human health have been more difficult to establish, although there is evidence for a benefit for patients with rheumatoid arthritis. Beneficial effects seen in animal models of inflammatory bowel diseases and asthma have not been confirmed in humans," notes Ian Rowland, director of research, head of the Hugh Sinclair Unit of Human Nutrition, Berkshire, United Kingdom. A systematic review of 23 randomized, controlled trials found EPA and DHA supplementation improved several symptoms of rheumatoid arthritis, including joint swelling and pain, duration of morning stiffness, global assessments of pain and disease activity, and use of nonsteroidal anti-inflammatory drugs (British Journal of Nutrition, 2012; 107:S171-S184). And, a meta-analysis of 17 randomized, controlled trials found 1.7 to 9.6 grams omega-3s per day for 3 to 4 months reduced patient-reported joint pain intensity, minutes of morning stiffness and number of painful and/or tender joints in those with inflammatory joint pain from rheumatoid arthritis, inflammatory bowel disease or dysmenorrheal (Pain, 2007; 129:210-223). A dose of over 2 grams of EPA plus DHA per day may be necessary for attenuating inflammation (British Journal of Clinical Pharmacology, 2012, Jul 6).
Vitamins and minerals. Vitamin D reduces inflammation in the body, but more studies need to elucidate which disease states it may influence. In one study, supplementation with 2,000 IU vitamin D daily for 9 months decreased inflammatory cytokine levels in patients with congestive heart failure (American Journal of Clinical Nutrition, 2006; 83:754-759; Institute of Medicine, Food and Nutrition Board. National Academy Press, 2010).
Several animal studies show zinc reduces markers of inflammation. However, its effects may depend on the site of inflammation. In a randomized, double-blind trial, 45 mg zinc daily for 6 months significantly decreased several markers of inflammation in plasma compared to placebo in elderly adults (American Journal of Clinical Nutrition, 2010; 91:1,634-1,641). However, a 60-day, 45-gram dose of zinc had no effect on inflammation in 18 patients with chronic inflammatory rheumatic diseases (American Journal of Clinical Nutrition, 1993; 57:690-694).
Plant-based compounds. Animal studies show ginger has anti-inflammatory actions, and randomized controlled trials show 30 to 500 mg ginger taken daily for 3 to 6 weeks reduced osteoarthritis pain in adults (Arthritis and Rheumatism, 2001;44:2,531-2,538; Osteoarthritis and Cartilage, 2000; 8:9-12). Also, 2 grams of heat-treated or raw ginger consumed before a bout of exercise-induced muscle injury reduced pain 24 hours after the exercise session in college-aged students (The Journal of Pain, 2010; 11:894-903).
Resveratrol acts on several molecular targets associated with inflammation (International Reviews of Immunology, 2012; 31:202-222). A randomized, triple-blind, placebo-controlled study found a grape supplement containing 8 mg resveratrol consumed daily for 6 months, with a double dose consumed daily for the remaining 6 months of the study, improved inflammatory status in patients on statins compared to a conventional grape supplement or placebo (American Journal of Cardiology, 2012; 110:356-363).
Studies suggest curcumin may also exert its anti-inflammatory activity through several different pathways, including COX-2. It is poorly absorbed, though a 3.6 gram dose was detectable in tissue, and curcumin has been shown safe in doses up to 8 grams for 3 months (Clinical Cancer Research, 2004;10: 6,847-6,854; Journal of Alternative and Complementary Medicine, 2003; 8:161-168). Combining curcumin with piperine increases its bioavailability in both rats and humans (Planta Medica, 1998; 64:353-356).
The research on probiotics and inflammation is mixed due to differences in study design (Current Pharmaceutical Design, 2009;15:1428-1518). However, as Rowland notes : “In the case of probiotics, the evidence overall seems to be that they 'normalize' the immune status. If inflammation is low, they may stimulate pro inflammatory pathways, if inflammation is present, they can reduce it. The effects are species- and strain-specific, however. There is some evidence they have beneficial effects in adults with ulcerative colitis and both adults and children with irritable bowel syndrome."
Other promising compounds include bovine colostrum, indole-3-carbinol, which reduces several inflammatory compounds, coenzyme Q10, vitamins C and E, and natural chemicals in foods, including blueberries, cherries, grape seed and green tea (Nutrition Research, 2009; 29:275-280; International Journal of Obesity, 2011; 35:1,530-1,538; Mediators of Inflammation, 2010;2010; USDA ARS). In addition, low levels of magnesium, a mineral that is largely inadequate in the Western diet, contributes to chronic systemic inflammation in animal studies (American Journal of Medical Science, 2011; 342:125-128).
Compounds that promote inflammation
Diets high in glucose, saturated fat and advanced glycation end products (AGE) contribute to inflammation (British Journal of Nutrition, 2011; 106:S5-S78). Dietary AGEs are produced during cooking, particularly dry heat. Animal foods high in fat and protein are typically high in AGE, whereas carbohydrate-rich foods, including fruits, vegetables, milk and whole grains contain fewer AGEs, even after cooking. Lower cooking times and temperatures, moist heat and using acidic ingredients such as lemon juice or vinegar attenuate AGE formation during cooking (Journal of the American Dietetic Association, 2010; 110:911-916).
A balanced diet is one of the best defenses against disease. “No one dietary supplement or ingredient can cure disease or decrease one’s risk of developing a disease," notes Nagarkatti. "However, it is possible that a combination of ingredients may decrease some of the symptoms of various diseases. But, if you take too much of one anti-inflammatory ingredient, you may upset another pathway in the body.".
