Ouch! You just stubbed your toe. It quickly swells, gets hot, turns red and it hurts. You may curse, but you are actually experiencing the beginning of the healing process. “Inflammation” is the body’s attempt to right the wrongs caused by physical injury, infection or exposure to toxins. Thanks to “acute” inflammation, you will soon be back to kicking without pain. Long term or “chronic” inflammation, however, is a different story. That may have you kicking the bucket.
Way back in the 1st century AD, Roman encyclopaedist Aulus Cornelius Celsus produced a comprehensive medical work, De Medicina, in which he described the use of opiates to counter pain, explained that fever was the body’s attempt to restore health and introduced the tetrad of “rubor (redness),” “calor (heat),” “tumor (swelling)” and “dolor (pain)” as the cardinal signs of a condition we now refer to as inflammation. Of course, knowledge of physiology at the time was too rudimentary to offer an explanation for what was going on, but it was clear that inflammation was a prelude to healing.
Today, we know that redness is caused by dilation of blood vessels in the area of injury as a result of an increased blood flow that can also be sensed as heat because blood is warm. The blood delivers white blood cells (neutrophils) to clean up the cellular debris caused by injury, antibodies to destroy bacteria and viruses and clotting factors that prevent the spread of infectious agents through the body. Chemical mediators of inflammation, such as histamine and cytokines change the permeability of blood vessel walls to allow white blood cells to diffuse from the bloodstream into injured tissues. Prostaglandins rush to the scene to elevate temperature and impair microbial activity. As fluid carrying white blood cells enters injured tissue from the blood stream, it causes swelling ,which in turn causes pain.
Finally, after the white blood cells have managed to gobble up the remains of injured tissues, and antibodies have neutralized microbes, healthy cells begin to multiply. Pain resolves, swelling subsides and memory of the acute inflammation fades.
Now for a more worrisome scenario. Inflammation is an essential response for dealing with various forms of assault on the body, but it is not always perfectly controlled. Cholesterol deposits in arteries, foreign substances such as silica dust as well as some infectious organisms may resist the body’s attempts to eliminate them and precipitate a continuous attack by white blood cells. The immune system can also make a mistake and launch an inflammatory strike against a normal body component resulting in an “autoimmune disease” such as rheumatoid arthritis, multiple sclerosis, celiac disease or Type 1 diabetes. Even some foods or specific components can be seen as an enemy to be neutralized. The result is a chronic, low grade inflammation that is associated with cardiovascular disease, diabetes and some cancers.
Obviously, chronic inflammation is undesirable, but how do we know when it is present and what can we do about it? The inflammatory activity of white blood cells is associated with the release of chemicals into the bloodstream that can serve as markers of inflammation, with the major ones being interleukin 6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), fibrinogen, homocysteine and tumour necrosis factor alpha (TNF-alpha). These markers rise with obesity, smoking, inactivity, sleep deprivation and poor diet.
The diet connection has received much attention because it is a readily modifiable lifestyle factor. Based on an extensive literature search of cell culture studies, animal experiments with specific nutrients, and human epidemiological studies in which the relationship between inflammation markers and diet was determined, researchers have developed a “dietary inflammatory index (DII).” Through a complex formula, various foods and 45 specific nutrients are assigned numerical values based on how they affect inflammatory markers. Sugar, trans fats, refined carbohydrates, omega-6 fats, red and processed meat are classified as inflammatory, while fibre, vitamin E, vitamin C, beta-carotene, magnesium and moderate alcohol intake are anti-inflammatory. A food frequency questionnaire can then be used to calculate the anti-inflammatory effect of a specific diet.
It comes as no great surprise that the typical “Western” diet with its high red meat, full-fat dairy, refined grain and low fruit and vegetable consumption is associated with higher levels of CRP, IL-6 and fibrinogen. By contrast, the “Mediterranean diet,” which features whole grains, fruits, vegetables, fish, olive oil, moderate alcohol consumption and little butter or red meat, is associated with lower levels of inflammation.
When DII scores were calculated in a study of some 5,000 adults, those who ranked in the top quarter, meaning they consumed the most inflammatory foods, had much higher CRP levels than those in the bottom quartile. This indicates that a DII score can indeed predict whether a specific diet is linked with inflammation. Even more significantly, meta analyses, essentially the pooling of relevant studies, found an association between a low DII score and protection against cancer as well as cardiovascular disease.
Does this mean that we should all be testing for inflammatory markers in our blood to know whether we are at risk of chronic low-grade inflammation? Not unless a physician suspects, based on symptoms, that there may be some disease process. Otherwise, what you would do in response to elevated markers is what we should all be doing anyway. Exercise, watch our weight, minimize highly processed foods and emphasize whole grains, fruits, vegetables, beans, lentils, nuts, fish and olive oil. As far as the plethora of dietary supplements flooding the market with claims of “reducing inflammation” go, the only documented reduction will be to your bank account.
Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.