What is the Anti-Inflammatory Diet and How Can it Treat Diabetes, Relieve Arthritis and Prevent Cancer?
The Anti-Inflammatory (AI) diet is designed to reduce systemic inflammation by eliminating inflammatory and allergenic foods such as wheat, corn, soy, dairy, beef, pork peppers, tomatoes, eggplant, potatoes, citrus fruits, processed oils, alcohol, caffeine and peanuts, and promoting anti-inflammatory foods such as fruits, vegetables, fish, whole grains and nuts (Zwickey et al., 2007).
Uncontrolled, systemic inflammation may play a role in diseases such as arthritis, obesity, diabetes and cancer (Weatherby, 2004; Nature Reviews Cancer, 2006). The AI diet may reduce the amount of inflammatory cytokines released in response to ingested antigens and reduce the risk of developing these diseases.
The proposed mechanism of the anti-inflammatory diet relies on a basic understanding of inflammation. The inflammatory process protects the body through its immune function and is required for health (Fox, 2008). However, these processes can also damage the body. Even when inflammation is triggered by pathogens, the inflammatory response can become exaggerated and inflict more harm than the actual pathogen. It has been established that inflammation plays a pathogenic role in Alzheimer’s disease, multiple sclerosis, atherosclerosis, asthma, rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes mellitus. Inflammation begins when bacteria break through the skin, or other external structures such as the digestive tract, respiratory tract, or genitourinary tract, and nonspecific mechanisms of phagocytosis and complement activation react to the pathogen. Neutrophils, which are a class of white blood cells, arrive early to a site of injury and infection and release chemical signals that recruit monocytes, lymphocytes, and other immune cells to the site. The bacterium also signals macrophages to secrete cytokines, which are regulatory molecules that recruit other cells of the immune system and promote aspects of the innate immune response such as phagocytosis or fever. Cytokines also activate B and T lymphocytes. B lymphocytes contain antibodies that coat the bacterium. The coated bacterium enters the neutrophil and is ingested by this phagocytic cell. Bacterium contents are retained in the neutrophil vacuole and lysosomal enzymes are released into the extra cellular matrix. Mast cells are initiated to release histamine, which causes the characteristics of local inflammation: redness, warmth, swelling, pus, and pain. Histamine binds to histamine receptors in the smooth muscle of bronchioles to stimulate bronchiolar constriction and relaxation of smooth muscle in blood vessels. The presence of histamine also increases capillary permeability, allowing more leukocytes to migrate to the infected area (Fox, 2008)
This process is similar in the digestive tract, but the mechanism for how food particles can incite an immune response is unclear. Claims regarding the anti-inflammatory response also suggest that systemic (throughout the body) inflammation could occur, but the mechanism for how cytokines enter the blood is also unclear. The excluded foods in the AI diet are thought to stimulate an inflammatory response in the gastrointestinal tract and potentially act as allergens in certain individuals (Zwickey et al., 2007). One possible mechanism for this reaction may be that certain food constituents may pass through the enterocytes of the small intestine but then become recognized as a foreign agent, or antigen. Gut associated lymphoid tissue, which has the ability to elicit specific immune responses at a local and systemic level, may react to the presence of the antigen (Isolauri et al. 2001). Gut associated lymphoid tissue stores immune cells, such as T cells and B cells. Upon presentation with an antigen, these lymphocytes release cytokines into the blood such as interleukin-6, which cause inflammation, according to a non peer-reviewed source (Dalhousie University, 2007). Continual stimulation of immune cells causes chronic inflammation which can manifest in flu-like symptoms such as fever, chills, fatigue, headaches and muscle stiffness (Jenschke et al., 2002). It has also been hypothesized that systemic inflammation may also lead to protein degradation, catabolism and hypermetabolism but this topic is relatively unresearched (Jenschke et al. 2002).
The anti-inflammatory properties of AI diet foods might be derived from their omega-3 and antioxidant content, found in foods such as salmon and various vegetables (Weatherby, 2004). However, this data is not supported in the academic community and requires further research. Extra-virgin olive oil, a food listed in the AI diet, has anti-inflammatory effects similar to those of ibuprofen (Brownlee, 2005). The active component in the oil, oleocanthal, inhibits two inflammation-inducing enzymes: cyclooxygenase 1 (Cox-1) and cyclooxygenase 2 (Cox-2). Ibuprofen also acts to relieve inflammation by inhibiting these same enzymes. However, this data is from a non peer-reviewed journal and requires further research.
Inflammation and Diabetes
Research examining inflammation and diabetes has relied on the analysis of blood samples for inflammation compounds such as IL-6 and tumor necrosis factor alpha (TNF-α), in addition to insulin and glucose levels (Christensen, 2002). Results have demonstrated a positive correlation between high cytokine levels and increased risk of developing diabetes. High blood concentrations of IL-6 tripled a person’s chance of developing type II diabetes (Christensen 2002). This information is not consistent with physiology text that links inflammation with type 1 diabetes.
Systemic, uncontrolled inflammation caused by high cytokine concentrations may also cause insulin resistance according to a non peer-reviewed article (Christensen, 2002). Recent, unconfirmed evidence shows that TNF-α blocks insulin from getting into cells. IL-6 has also been implicated in blocking insulin action by blocking the biological effects of the insulin receptor in liver cells. Insulin resistance caused by inflammatory agents could be a strong indicator for the development of diabetes later in life. In support of this, increased insulin resistance has also been observed in animals with infections and those with naturally high concentrations of cytokines. Inflammation is the process through which obesity can cause diabetes. Without fat cells, cytokines will not be at higher-than-normal concentrations.
Diet-driven Treatment for Arthritis
Antioxidant qualities of certain foods may relieve persistent inflammation throughout the body (Raloff, 1999). Antioxidants in green tea and tart cherries may potentially inhibit the Cox-2 enzyme, which incites an inflammatory response. Polyphenols were isolated from green tea and added them to the drinking water of an experimental group of mice. The mice were then injected with a substance that triggers immune reactions mimicking rheumatoid arthritis. Probes of the affected joints showed virtually no cartilage damage in the polyphenol-consuming mice. The control group showed significant cartilage damage as well as far higher concentrations of immune system cells, Cox-2 and TNF-α (Raloff, 1999). Antioxidant pigments of tart cherries also show anti-inflammatory activity in one study. One would need to consume 20 tart cherries per day as a natural alternative to aspirin (Raloff, 1999). Not only are cherry compounds 10 times as potent as aspirin in inhibiting Cox-1 and Cox-2, but they also remain active longer. The results of these studies should be repeated with large samples and specifics of the methods and materials need to be explicitly stated.
The Anti-Inflammatory Diet and Cancer Prevention
Specific antioxidants and other constituents of fruits and vegetables may also serve as a protective feature against cancer (Ames et al., 1995). Oxidative damage to DNA can cause lesions which can then lead to mutations when the cell divides. Mutations in several critical genes can lead to tumor formation. Chronic inflammation may increase cell division and the risk for cancer, but this mechanism is not clearly explained. There are natural defenses against mutations present in the body, including the glutathione transferases, though the defenses can be partially disabled by the lack of particular dietary nutrients, such as antioxidants (Ames et al., 1995).
When leukocytes combat bacteria, they release oxidizing agents that protect humans from immediate death from infection (Ames et al., 1995). These oxidants also cause oxidative damage to DNA including mutation and chronic cell killing with compensatory cell division. Consuming foods that are high in antioxidants appear to inhibit some of the pathology of chronic inflammation and may be especially important during times of pathogen infection. Hepatitis B and C, which are chronic infections, cause chronic inflammation and may lead to liver cancer. Due to leukocytes continual production of oxidants, chronic infections contribute to approximately one-third of the world’s cancer (Ames et al. 1995).
Hypotheses made about food, inflammation, and disease are worthy of in-depth scientific research. While present research on anti-inflammatory foods is inconclusive, continual study of this area may reveal benefits of adhering to the anti-inflammatory diet. The mechanism for food inciting an immune response must be investigated further to support the argument for the anti-inflammatory diet.
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Brownlee, Christen. “Olives Alive.” Science News 168, no. 10 (Sep. 3, 2005): 147-148.
Christensen, Damaris. “Inflammatory Ideas: New thoughts about causes of diabetes.” Science News 162, no. 9 (August 31, 2002): 136-138.
Dalhousie University: Faculty of Medicine, Immunology Bookcase. May 15, 2007. Accessed November 12, 2007. http://pim.medicine.dal.ca/cytok.htm
Isolauri, E., et al. “Probiotics: Effects on Immunity.” American Journal of Clinical Nutrition 73 (2001):50S-444S.
Jenschke, et al. “Insulin Attenuates the Systemic Inflammatory Response to Thermal Trauma.” Molecular Medicine 8, no. 8 (2002):443-450.
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