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Diet and Inflammation: Is There A Connection?

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DHA Molecule

DHA Molecule (Photo credit: Wikipedia)

Chronic inflammation has been implicated in the major diseases of our modern society including heart disease, some cancers, type 2 diabetes, arthritis, and Alzheimer’s disease.  Most human studies use a food frequency questionnaire and attempt to correlate the intake of certain foods with markers of inflammation in the blood.  These markers often include high-sensitive C reactive protein (HS-CRP), interleukin-6 (IL-6), and tumor necrosis factor (TNF-∂).

Is there a link between diet and inflammation?  What have we found out so far?  A great majority of the research has centered on omega-3 fatty acids. In a study called the Multi-Ethnic Study of Atherosclerosis (MESA),  omega-3 intake as unfried fish was inversely related with concentrations of IL-6 and another inflammatory marker in the blood called matrix metalloproteinase 3 (MMP-3).  For fried fish lovers, so such luck.

A study in Norway fed salmon that contained different amounts of omega-3 fatty acids to heart disease patients.  The results were that the people who ate the largest amount of omega-3 containing salmon had a significant reduction of IL-6.

A recent study used fish oil supplements given to 138 healthy, overweight, middle-aged, older adults. Inflammation is thought to accompany excess body fat.  Volunteers were given one of two different doses of omega-3 fatty acids (2.5 grams or 1.25 grams) or a placebo.  The supplemental doses contained a ratio of 7 to 1 of two fish oil fatty acids, EPA and DHA.  The placebo consisted of less than 2 teaspoons per day of mixed oils that came close to representing a typical American’s oil intake for a day.

In four months, the group taking either dose of the omega-3 supplements had significantly lower blood levels of inflammatory markers.  The low-dose group showed an average 10% decrease in  IL-6 and high dose group showed an average of 12% decrease.  Surprisingly, the placebo group saw an overall 36% increase in IL-6.

Tumor necrosis factor-alpha also dropped by only 0.2% in the low dose group and 2.3% in the higher dose group.  Again, the placebo group’s marker increased by an average of 12%.

The lead author, Jan Kiecolt-Glaser, professor of psychiatry and psychology at Ohio State University said: “Omega-3 fatty acids may be both protective so that inflammation doesn’t go up, as well as therapeutic by helping inflammation go down”.  The co-author of the study, Martha Belury, professor of human nutrition at Ohio State said: “These data support the idea that a higher dose of omega-3 is not necessarily better than a lower dose in terms of prevention of inflammation.

A healthy diet should include a proper ratio of omega-6 to omega-3 fatty acids to be most effective in providing healthy benefits.  Studies on omega-6 fats have shown mixed results on inflammation.  Some of the compounds produced by omega-6 fats have anti-inflammatory properties while a few others tend to promote inflammation.  However, they have not yet been shown to cause inflammation to any great degree.  The problem is that the American diet tends to contain 14-25 times more omega-6 fats than omega-3 fats.   The recommended ratio of omega-6/omega-3 fats is closer to 4:1 or ideally closer at 1:1.

Other foods and nutrients may have an effect on chronic inflammation in the body.  A comprehensive review examined the role of diet based on current research.  After reviewing the literature, they found that consumption of magnesium, fiber, monounsaturated fatty acids, flavonoids and carotenoids as well as omega-3 fats were associated with decreased levels of inflammatory markers.  On the other hand, saturated fats, trans fatty acids, high glycemic carbohydrates and a high omega-6/omega-3 ratio are associated with increased levels of inflammation.

Dietary Sources of Omega-6 and Omega-3 Fatty Acids

Omega-6

Linoleic acid – vegetable oils (corn, safflower, sunflower, soybean, animal meats)

Arachidonic acid – animal sources only (meat, eggs)

Omega-3

Alpha-linolenic acid – flaxseed, canola oil, walnuts, fortified foods

EPA and DHA – fish, fish oils, marine sources

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