A search for “Anti-Inflammatory Diet” brings up more than 1000 books. A broader search across the Internet brings up more than 7 million hits on the subject. Amidst all the noise, where is today’s research about the link between chronic inflammation and diseases like cancer, heart disease and type 2 diabetes? And is there really research behind an anti-inflammatory diet?
Here, in Part 1 of a series, Susan Steck, PhD, MPH, RD, provides background for discussing inflammation and shares insights on weeding through today’s abundance of “anti-inflammatory diets”. Dr. Steck is a registered dietitian and Associate Professor of Epidemiology and Biostatistics in the Arnold School of Public Health at the University of South Carolina in Columbia. She is researching diet’s role in inflammation and the chronic diseases to which it is linked.
Following the video, read on for more on the story.
Inflammation: Real Concern or Hype?
Short-term inflammation is part of the body’s natural defense against injury and infection. Chronic, low-grade inflammation, however, seems to damage body tissues in ways that accelerate development of chronic health problems.
Scientists now consider atherosclerosis (“hardening of the arteries”) an inflammatory process, and inflammatory cells have been found in the fatty plaque that builds up in blood vessels. Inflammation may also promote cancer development at several stages, by damaging DNA, increasing cell turnover and increasing development of blood vessels that allow cancer cells to grow and spread.
Scientists have identified several different markers of inflammation that can indicate how changes in medication, diet or other aspects of lifestyle affect inflammation. There is much more to learn on this, since it’s possible that different markers tell us different aspects of the story. For example, perhaps some give a longer-term view than others do; some markers may best identify inflammation within blood vessels as others show inflammation more generally throughout the body.
Can Diet Be Anti-Inflammatory?
The key seems to be in how we define “healthy eating”. For example, one study compared scores from five different systems for evaluating healthfulness of eating habits with markers of inflammation in 660 women from the Nurses’ Health Study.
♦ Three of these healthy eating indices showed no relation to CRP or IL-6 markers of inflammation. Although these scores may indicate other aspects of how eating habits help or hurt health, a diet could be considered “healthy” and yet not show any association with inflammation. One of these scores focused more on whether the diet provided enough of nutrients like iron and calcium that may be low in some people’s diets. The other two gave points for more vegetables and fruits, but focused more on low-fat eating than on quality of fat and carbohydrate choices.
♦ Higher scores on the Alternate Healthy Eating Index were associated with less inflammation: 30% lower levels of CRP and 31% lower levels of IL-6. This score includes vegetable and fruit consumption, as well as fiber from whole grains, poultry and fish compared to meat intake, and fat consumption that is more polyunsaturated than saturated.
♦ Higher scores on the Alternate Mediterranean Diet Score were also linked with lower levels of inflammation: 24% lower CRP and 16% lower IL-6. (Statistically, there was no difference between the reduction in inflammation linked to this score and the index above.) This score represents an Americanized version of the Mediterranean diet, with higher scores indicating more vegetables and fruits, whole grains, nuts, fish and monounsaturated fat (as found in olive oil).
Can Diet Actually Change Inflammation?
Studies like the one above are “observational” studies. These studies show association –a link between different types of eating habits and higher or lower levels of inflammation. However, they don’t show cause-and-effect. The million-dollar question: Can a change in diet reduce inflammation?
We already see from multiple studies that inflammation is a two-way street. Even when markers indicate presence of chronic, low-grade inflammation, intervention trials show it can subside. Dr. Steck noted in our interview that regular physical activity is one way to decrease chronic inflammation. Eating habits also make a difference.
♦ The HEALS intervention trial showed decreased CRP in women who attended at least 60% of sessions in an intensive 12-week healthy diet and physical activity program combined with stress reduction. This group, who were all overweight or obese, had a decrease in inflammation without any change in weight, although waist:hip ratio decreased. Unfortunately, the drop in CRP did not hold up at one year, when the intensity of the intervention program had markedly decreased. A subgroup of men in the study’s intervention group showed lower CRP after both 12 weeks and 1 year.
♦ Men with metabolic syndrome given a Mediterranean diet for five weeks showed lower levels of CRP than those given a control diet. Even when deliberately avoiding weight loss, inflammation was reduced. However, in the next phase of the study that decreased calories to achieve about a 10% weight loss, the decrease in inflammation was even greater.
♦ It’s not necessarily as simple as adding more vegetables and fruits, however. In the FLAVURS trial, which added more total vegetables and fruits in one group, and more vegetables and fruits high in protective compounds called flavonoids in another group, improvements in inflammation were not consistent and show a picture that is hard to interpret.
Bottom Line: Lifestyle Makes a Difference
Inflammation now seems to be part of the development of multiple chronic diseases, and one of the common factors connecting heart disease, type 2 diabetes and cancer. We need further research to better understand inflammation and how to measure its effects. We already have enough evidence to support a healthy lifestyle as a way to reduce inflammation along with other factors that influence health. Now the work involves fine-tuning to identify which components of healthy eating are most important, and helping people become comfortable and confident implementing those steps.
In the next portion of my interview with Dr. Steck, we’ll hear more about specific eating choices that current research supports as part of an anti-inflammatory diet. Sign up to receive Smart Bytes by email so you don’t miss any of our upcoming discussion! (see right sidebar).
CardioSmart, from the American College of Cardiology, explains CRP, one of the most common markers of inflammation used in clinical practice and in many studies. This site also provides information on how markers of inflammation may help identify which people with high BMI are at greatest heart-related risk.
Check the American Heart Association (AHA) website for an explanation of inflammation’s link to heart disease. A recent AHA article explains that inflammation may be one of the factors that explains why good blood sugar control alone is not enough to escape the diabetes-heart disease connection.
If you want to learn more about the lab test for hs-CRP, Lab Tests Online offers peer-reviewed information you may find helpful.
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