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United States Department of Agriculture

Agricultural Research Service

Inflammation - Bad or Good
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By Forrest H. Nielsen

Recently, the word inflammation has gotten a sinister reputation in nutrition.  The reason is that inflammation is thought to be a major risk factor for some ailments that prevent everyday well-being and often are life-threatening.    These ailments are called chronic diseases because they take time to develop.  They include heart and blood vessel disease, diabetes, osteoporosis, arthritis, and Alzheimer's disease.  

Human survival, however, depends upon inflammation.  Inflammation is the body's immediate response to infection or injury.   It results in redness, swelling, heat and pain.  This response happens because blood flow increases and blood vessels change to allow infection fighting blood cells and large molecules to move from the blood stream into tissue that needs healing.   The cells and molecules kill bacteria and remove damaged tissue through inducing the formation of a reactive form of oxygen.  The cellular and molecular response also signals for biochemical changes that cause unwanted cells to destruct. 

Inflammation and reactive oxygen are designed to work best under certain conditions.   These conditions are a well-nourished person with a mild to moderate injury or infection over a short period of time. 
The inflammatory response shows its bad side when it is roused in the body without the need to fight an acute injury or infection.  This results in inflammation that usually is prolonged and does not develop typically, and thus is called low-grade or chronic inflammation. 

Chronic inflammation can induce the excessive formation of reactive oxygen that attacks healthy tissue, which is called oxidative stress.   Chronic inflammation is mainly triggered by improper nutrition, particularly deficient intakes of nutrients regulating the inflammatory response and excessive calorie intake leading to obesity.  Because excessive reactive oxygen damages tissue, chronic inflammation also can be triggered by dietary practices that cause oxidative stress.  These practices include, for example, high intakes of simple sugars such as fructose and sucrose and low intakes of anti-oxidant nutrients such as vitamin C and zinc. 

Both animal and human studies have shown that obesity is associated with chronic inflammation.   Compared to fat tissue from lean people, fat from obese people contains more cells that produce activators of the inflammatory response.   In addition, the blood of obese people usually contains more of the different molecules involved in the inflammatory response than blood in lean people.  As a result, chronic inflammation is considered a reason that obesity, which affects over 35% of the population, is a major risk factor for chronic diseases such as heart disease and diabetes.

An example of a nutrient deficiency that may be responsible for some low-grade inflammation is magnesium deficiency.  Animal-model  experiments show that magnesium has a regulatory role in inflammation and magnesium deficiency results in inflammation and oxidative stress.   Both decreased magnesium intakes and blood magnesium levels have been associated with an increased marker of chronic inflammation in people of all ages.   Numerous studies have shown that a low magnesium status occurs often in people with diseases that have a chronic inflammation component, including  heart disease, diabetes, high blood pressure, and osteoporosis. 

The idea that a low magnesium status has a role in low-grade inflammation and chronic disease may not be unusual because a recent nutrition survey indicated that about 60% of adults in the United States do not consume the estimated average requirement for magnesium.  Even less adults meet the recommended dietary allowance or RDA for magnesium of 310-320 milligrams per day for women and 400-420 milligrams per day for men.

Not all people who are obese or magnesium deficient exhibit low-grade inflammation and oxidative stress.   Animal experiments suggest that this happens because other nutritional factors can prevent or lessen the inflammation or oxidative stress.  Among the food components with anti-inflammatory or anti-oxidant action are omega-3 fatty acids, coenzyme Q10, vitamin C, vitamin E, and plant chemicals in foods such as blueberries, cherries, grape seed, and green tea.  Low intakes of omega-3 fatty acids, vitamin C and vitamin E may make inflammation or oxidative stress worse. 

This also means that a combination of a low magnesium status and obesity would be more likely to result in chronic inflammation and oxidative stress and increasing the risk of chronic disease than either one alone.

All chronic diseases apparently have two components:   chronic inflammation and oxidative stress.  They occur together because one induces the other.   However, taking a specific anti-inflammatory agent may not prevent all the changes induced by oxidative stress that lead to increased risk for chronic disease.  Likewise, taking a specific anti-oxidant supplement may not prevent all changes caused by chronic inflammation.  Examples of this are studies showing that estrogen therapy, which is anti-inflammatory, did not prevent heart disease; neither did supplemental vitamin E, which is an anti-oxidant.    This indicates that the best way to prevent chronic inflammation and oxidative stress that increases the risk for heart disease is to maintain a proper body weight and eat a diet that provides essential nutrients in adequate amounts and rich in foods that have anti-inflammatory and anti-oxidant actions.      


Last Modified: 3/15/2010
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