What is inflammation?
Inflammation refers to the body’s physiological response to damage and threats including injuries, infections, and irritants such as pollen and chemicals. A cut on your finger turns red signifying acute inflammation. It is one of our body’s defense mechanisms and is essential to our daily survival. Chronic (systemic) inflammation, during which the body produces anti-inflammatory compounds long after the threat has subsided, harms multiple aspects of health and well-being as noted below.
Measures of chronic inflammation and metabolic health
Cardiovascular disease causes more deaths globally and in the US than any other cause. Levels of three factors, high-sensitivity C-reactive protein (a marker of chronic inflammation), low-density cholesterol, and lipoprotein(a), all significantly predict risk of cardiovascular disease over 5 and 10-year periods. Researchers at Harvard extended the prediction period to 30 years using data for 27,939 female health professionals with an average age of 55 years at baseline. After adjusting for confounding factors, all three markers individually and collectively significantly predicted risk of a major cardiovascular event (heart attack, cardiac revascularization, stroke, death) during follow-up. Compared to participants in the bottom quintile (healthiest) of each marker level, participants in the highest quintile (least healthy) of high-sensitivity C-reactive protein, low-density cholesterol, and lipoprotein(a) had 70, 36, and 33 percent higher risks of a major cardiovascular event. Compared to participants with no marker in the highest (least healthy) quintile, participants in the highest quintile for all three markers had 271 percent higher risk of a major cardiovascular event. You can ask your medical provider to test for high-sensitivity C-reactive protein to reveal your inflammatory status.
Pro-inflammatory diet and cardiovascular disease
Chronic, low-grade systemic inflammation increases risks of cardiometabolic diseases and dementia. An international team of researchers used data from 84,342 participants with an average of 64 years at baseline in the UK Biobank to see if cardiometabolic disease and an inflammatory diet increased the risk of developing dementia. Examples of anti-inflammatory dietary items include turmeric, fiber (fruits, vegetables, beans), flavones, isoflavones, and beta-carotene (orange vegetables like carrots and winter squash). Inflammatory diet was evaluated using the Dietary Inflammatory Index, which combines the inflammatory potential of 31 dietary compounds or foods and the amounts eaten. Higher scores reflect higher inflammatory potential of a particular diet.
Participants with at least one cardiometabolic disease (such as type 2 diabetes) had a significant 81 percent higher risk of developing dementia during an average follow-up of 12 years compared to those without cardiometabolic disease. Participants with cardiometabolic disease and a pro-inflammatory diet had a significant 138 percent higher risk of developing dementia compared to those without cardiometabolic disease and with an anti-inflammatory diet. In addition, brain imaging studies showed that participants with an anti-inflammatory diet had high gray-matter volume (indicating less neurodegeneration) and lower white matter hyperintensity volume (indication less vascular injury). If there’s anything you really don’t want in your later years, it’s dementia. Eating better food can provide you with a host of benefits. Based on this study, how about eating an anti-inflammatory diet by boosting the amount of fruits and vegetables like Swiss chard that you eat every day?
Pro-inflammatory diet
Systemic inflammation may be an underlying cause of dementia. The level of systemic inflammation present in an individual’s diet may reflect, at least in part, the overall pro-inflammatory nature of that person’s physiology. Researchers in China used data from 166,377 participants with an average baseline age of 56 years in the UK Biobank to test this idea. The inflammatory status of participants’ diets was quantified using the Dietary Inflammatory Index (DII), in which negative values are anti-inflammatory and positive values are pro-inflammatory.
After a median follow-up of 9.5 years, compared to participants in the lowest quartile of DII values, those in the highest quartile had a significant 25 percent higher risk of developing all-cause dementia. No significant relationships appeared for Alzheimer’s disease or vascular dementia. The risk of dementia increased sharply when the DII value exceeded 1.30. Above that value, each 1.0 increase in DII value predicted a significant 39 percent increase in risk of developing Alzheimer’s disease. In addition, the risk of developing dementia increased disproportionately for participants with body-mass index values greater than 25 (the low end of the overweight range). Finally, magnetic resonance data showed that the total volume of white matter hyperintensities increased (reflecting more vascular injury) and the volume of gray matter in the hippocampus decreased (reflecting more neurodegeneration) as DII values increased. This study add supports the idea that chronic inflammation may contribute to dementia.
Dietary fiber
Higher intake of dietary fiber predicts lower inflammation and lower risk of cardiovascular disease. Researchers used data from 4,125 participants with an average of 73 years in the Cardiovascular Health Study cohort to see if different types of dietary fiber affected inflammation and cardiovascular risk in older Americans. After adjusting for a limited set of confounding factors, each 5-gram increase in total or cereal fiber predicted significant 5 and 14 percent decreases in cardiovascular disease risk, respectively. However, these significant associations disappeared after additional adjustment. Analysis of eight different markers of inflammation showed that each 5-gram increase in total or cereal fiber predicted significantly lower levels of C-reactive protein, which is the most commonly used marker of inflammation. The eight inflammation markers collectively accounted for only 16 percent of the reduction in cardiovascular disease risk. Thus, the beneficial effect of dietary fiber (in particular cereal fiber) on cardiovascular health apparently arises mostly thorough pathways other than inflammation.
Social isolation
Social isolation, the subjective feeling of insufficient social contacts, may lead to psychological, biological, and behavioral responses that may promote inflammatory processes, which predict increased rate of aging. Researchers at Johns Hopkins University tested this idea using cross-sectional data from 4,648 participants with an average of 76 years in the National Health and Aging Trends Study. Social isolation was evaluated with four criteria: 1) living with at least one other person, 2) talking to two or more persons about important matters in the past year, 3) attending religious services in the past month, and 4) participation in clubs or groups or doing volunteer work in the past month. Participants received one point for each criterion that they met. Markers of inflammation included C-reactive protein and interlukin-6 measured on dried blood samples. Participants were as socially isolated or severely socially isolated if they received scores of zero or one, respectively.
Social isolation and severe social isolation were more common in participants who were older, had lower incomes, ever smoked, had three or more chronic conditions, and who were frail. After full multivariable adjustment, participants who were socially isolated or severely socially isolated had significantly higher levels of C-reactive protein than participants were not socially isolated. Similarly, participants who were socially isolated had significantly higher levels of interlukin-6 compared to participants who were not socially isolated. This study provides evidence that adverse health effects of social isolation might operate in part via increased inflammation.
Self-perceptions of aging
Positive self-perceptions of aging predict longer survival. A more positive view of aging might reduce inflammation and reduce the risk of cardiovascular disease, the leading cause of death in the US. Researchers at Yale used data from 4,149 participants with an average age of 68 years in the Health and Retirement Study to see if participants with lower levels of C-reactive protein would predict survival during follow-up. C-reactive protein levels were measured from dried blood spots. In fact, participants with higher self-perceptions of aging at baseline had longer survival over two years following measurement of C-reactive protein. In addition, higher baseline positive self-perceptions of aging predicted lower C-reactive protein levels four years later. Finally, the indirect effect of inflammation partially mediated the effect of positive self-perceptions of aging on survival. Thus, higher self-perceptions of aging appear to directly and indirectly (through less inflammation) increase survival.
What to do
You don’t want chronic inflammation, because it predicts increased risks of bad health outcomes, such as cardiovascular disease and dementia. One way to reduce your risk of inflammation is eat a better diet that features lots of fruits, vegetables, and legumes.
