Chronic, low-grade inflammation can become a bridge to development of high blood pressure, heart disease, type 2 diabetes and cancer.
Is this just hype, or could one factor really pose risk to so much of what threatens health as we get older? If the risk it poses is real, how can you choose among all the anti-inflammatory diet and anti-inflammatory foods and supplements that appear in headlines everywhere?
These are the questions for today’s Smart Bytes®….
Measuring Inflammation: What is a CRP test?
Inflammation can occur in the body in several forms, and a blood test known as CRP (C-reactive protein) is a common way to measure it.
Acute inflammation occurs quickly following an injury such as a splinter in your finger or an infection. In a masterfully orchestrated defense, increased blood flow to the area brings white blood cells and body proteins that attack the intruder and heal injured tissue. As the threat is resolved, inflammation ends.
Chronic inflammation involves an ongoing body defense response when harmful forces continue that can end up damaging blood vessels and other body tissues, accelerating development of long-term health problems.
Scientists measure a wide range of cell signaling proteins secreted by immune and other body cells as part of inflammation as they study how inflammation affects health and how it can be managed.
CRP is a marker protein produced in the liver that is used not only in research, but also in clinical care. “Regular” CRP tests (usually reported as milligrams per deciliter – mg/dl) can identify very high levels of inflammation like those seen in major infections or inflammatory diseases like rheumatoid arthritis and lupus. Regular CRP is not sensitive enough to pick up low-grade inflammation, however .
High-sensitivity CRP – hsCRP – detects low-grade inflammation that as a chronic condition is a marker of disease risk. For hsCRP, levels are reported as milligrams per liter (mg/L):
- Less than 1 mg/L is healthiest.
- Between 1 and 3 mg/L indicates intermediate risk.
- Above 3 mg/L indicates high risk.
- Values of hsCRP above 10 mg/L may signal an infection or other short-term cause of inflammation, so recommendations call for a test to be repeated in 2 to 3 weeks (with the lower value, not the average of the two tests, used to assess risk).
- Using hsCRP is most helpful for evaluating cardiovascular risk in people who have borderline results for other major risk factors, or in people with an LDL-cholesterol <130 mg/dl, according to the latest guidelines from the American Association of Clinical Endocrinologists (AACE) and American College of Endocrinology (ACE).
To understand overall health risk, hsCRP needs to be interpreted in the context of other risk factors.
The midpoint (median) of hsCRP levels in the United States is close to 2 mg/L. About 1 in 4 people has levels exceeding 3 mg/L, according to a Journal of the American College of Cardiology review.
[clickToTweet tweet=”1 in 4 Americans may have inflammation biomarker levels signaling high risk. Update via @KarenCollinsRD” quote=”1 in 4 Americans may have inflammation biomarker levels signaling high risk. “]
What’s the Risk of Chronic Inflammation?
Heart disease is more than the traditional image of “clogged pipes”.
- Inflammation plays a role in development and destabilization of atherosclerotic plaque in blood vessels.
- Inflammation in blood vessels promotes “vascular remodeling” that leads to a stiffness in arteries. This can raise blood pressure and make high blood pressure less responsive to medications aimed at controlling it .
Cancer risk is also linked in multiple studies to elevated hsCRP. There’s solid evidence of reasons for such a link. But it’s important to check how studies adjust for other influences on cancer risk, since factors like smoking and obesity can also raise cancer risk outside of effects on inflammation.
- Over time, inflammation can damage DNA, beginning the process of cancer development.
- Inflammatory proteins also seem to promote cancer progression through several metabolic pathways.
Type 2 diabetes risk may also increase with elevated hsCRP. Chronic low-grade inflammation is considered a key factor leading to insulin resistance. And frequent high blood sugars can in turn contribute to oxidative stress that promotes more inflammation.
What are Anti-Inflammatory Foods?
Evidence is good that how you eat can help fight inflammation. But how to make sense of all the headlines announcing the “ultimate” or “best ever” anti-inflammatory food?
Don’t Confuse Lab vs. Human Studies
Human studies are expensive and complicated to conduct. So many of the studies that make headlines about anti-inflammatory choices are actually laboratory studies in which individual nutrients or compounds found in food are provided to animals or even added to isolated cells. This provides a good starting point for identifying potential ways to create an anti-inflammatory diet, but don’t make these studies the basis for your decisions about healthy eating.
- Many potentially anti-inflammatory compounds – like a wide range of different polyphenols in tea, berries, onions, soy, grapes and spices like turmeric and ginger – are broken down to smaller, more easily absorbed compounds before they leave the digestive tract and circulate in the blood. So testing the large compound is not testing what is actually reaching body cells.
- Whether nutrient or medicine, dose matters. Even when the “right” substance is tested and shows anti-inflammatory effects, that doesn’t tell us what amounts we’d need in our diets to get a benefit.
- When nutrients or compounds show anti-inflammatory effects in these studies, headlines — or our interpretation of them — can lead us to assume that “more is better”. Not true.
Even though excess amounts of highly reactive particles known as “free radicals” lead to oxidative stress that can increase inflammation, the goal for health is not to remove these particles completely. Research now shows that low levels of these particles triggers action from the body’s natural antioxidant defense system (consisting of a variety of binding compounds and enzymes that convert free radicals to less reactive forms).
We see an example of how we got ahead of ourselves by assuming more is better in considering the SELECT trial, a major national study aimed at reducing risk of prostate cancer. Not only were supplements of selenium and vitamin E in amounts well beyond dietary recommendations, but considered safe, found ineffective in reducing risk of prostate cancer. Risk of prostate cancer increased in men taking vitamin E alone, and development of high-grade prostate cancer (the most dangerous form) increased when men who started off with adequate levels of selenium added more of this antioxidant mineral.
[clickToTweet tweet=”Lab studies can show potential, but don’t make them the basis for planning an anti-inflammatory diet. @KarenCollinsRD” quote=”Lab studies can show potential, but don’t make them the basis for planning an anti-inflammatory diet.”]
An Arsenal of Anti-Inflammatory Foods
A variety of health conditions and diet and lifestyle choices can lead to chronic low-grade inflammation. So rather than seeking one single step to avoid it, evidence supports creating a personalized strategy based on selecting a group of protective choices that can fit individual preferences.
Here are some components for creating an anti-inflammatory diet:
- Foods rich in antioxidants and compounds that support the body’s antioxidant defenses
- Foods that support health-protective gut bacteria
- Foods supplying omega-3 fatty acids needed to produce anti-inflammatory compounds
In the next edition of Smart Bytes®, we’ll look at specific examples of these foods.
What Makes an Anti-Inflammatory Diet ?
Foods like those above offer a variety of nutrients and compounds that can help minimize the chronic, low-grade inflammation that threatens health. However, this doesn’t mean that adding a few All-Star foods to overall unhealthy eating habits will protect health.
Every healthy choice helps, but get a big picture view of your eating habits by considering the proportion of foods like those above that may decrease inflammation in comparison to foods and lifestyle habits that promote inflammation.
Overall Day-to-Day Eating Habits as Key
In previous Smart Bytes® we’ve discussed the evidence on eating habits influencing chronic inflammation by looking through the lens of the Dietary Inflammatory Index (DII). The DII is a single score based on 45 different nutrients and compounds that research has individually suggested as potential influences (for good or for bad) on inflammation.
- Increase in DII score (meaning more inflammatory) is associated with increased risk of a CRP level in the high-risk category of over 3.0 mg/L. More inflammation-promoting diets as identified by DII scores have also been linked with greater risk of colorectal cancer, insulin resistance (the first step on the road to type 2 diabetes), and greater cancer and cardiovascular disease mortality.
More recently, eating habits that create an anti-inflammatory diet has been studied with the EDIP (Empirical Dietary Inflammatory Pattern) score. Researchers at Harvard developed the EDIP, based on 18 different food groups, half expected to be inflammatory foods and half to be anti-inflammatory foods.
- Highest scores on the food-based EDIP (more inflammatory) were associated with about 40 to 60 percent higher levels of hsCRP compared to lowest scores, even after adjusting for non-dietary factors known to affect inflammation. And highest scores on an index that combined the nutrient-focused DII and food-focused EDIP showed even greater elevations in hsCRP.
The crucial question: If you make shifts to improve the healthfulness of your eating habits, can levels of inflammation change?
- A study using another scoring system, which focuses on foods and nutrients supported by research as part of a diet to lower risk of chronic diseases, shows hopeful results. Highest diet quality scores among women in the Nurses’ Health Study II linked to lower levels of hsCRP. And women whose diet quality improved the most over 13 years showed an 11 percent drop in hsCRP, whereas women whose diets improved least showed a 16 percent increase in the inflammatory marker.
- These links of diet quality and inflammation became smaller when researchers adjusted for weight (as body mass index, BMI). This makes sense, given the large influence excess body fat has in promoting inflammation. What this means is that it’s important to consider how eating habits help support a healthy weight as part of how we consider what makes a healthy, anti-inflammatory diet.
[clickToTweet tweet=”Tools that score eating habits show healthier choices can reduce inflammation. Update via @KarenCollinsRD” quote=”Scores capture different aspects of healthy eating, yet are similar in showing that changing habits can reduce inflammation.”]
Bottom Line on Chronic Inflammation:
Chronic low-grade inflammation promotes development of heart disease, type 2 diabetes and at least some forms of cancer. Medications can tackle individual problems, like high blood pressure and cholesterol, and a growing number are able to affect background pathways like insulin resistance and inflammation. But with all that success, to promote health in an even broader context, experts are consistent in emphasizing the need to start with healthy eating and lifestyle habits to address inflammation. Evidence shows that changing habits can change inflammation.
Come back for the next Smart Bytes®, when we’ll look inside the scoring systems and the research behind them in search of specific doable strategies for an anti-inflammatory diet.
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Huang T, Tobias DK, Hruby A, Rifai N, Tworoger SS, Hu FB. An Increase in Dietary Quality Is Associated with Favorable Plasma Biomarkers of the Brain-Adipose Axis in Apparently Healthy US Women. J Nutr. 2016 May;146(5):1101-8.
Jellinger PS et al. American Association of Clinical Endocrinologists and American College of Endocrinology Guidelines for Management of Dyslipidemia and Prevention of Cardiovascular Disease – Executive Summary. Endocr Pract. 2017 Apr 2;23(4):479-497.
Li Y et al. Hs-CRP and all-cause, cardiovascular, and cancer mortality risk: A meta-analysis. Atherosclerosis. 2017; 259: 75-82.
Liu C et al. Adiponectin, TNF-α and inflammatory cytokines and risk of type 2 diabetes: A systematic review and meta-analysis. Cytokine. 2016; 86:100-109.
Lopez-Candales A, Hernández Burgos PM, Hernandez-Suarez DF, Harris D. Linking Chronic Inflammation with Cardiovascular Disease: From Normal Aging to the Metabolic Syndrome. J Nat Sci. 2017 Apr;3(4): e341.
Meeuwsen JAL et al. Prognostic Value of Circulating Inflammatory Cells in Patients with Stable and Acute Coronary Artery Disease. Front Cardiovasc Med. 2017; 4:44.
Ridker PM. A Test in Context. High-Sensitivity C-Reactive Protein. Journal of the American College of Cardiology. 2016 Feb; 67(6): 712-723.
Tabung FK et al. An Empirical Dietary Inflammatory Pattern Score Enhances Prediction of Circulating Inflammatory Biomarkers in Adults. J. Nutr. 2017; 147(8):1567-1577.
Credit: Blood test photo used with permission and purchased from 123rf.com, Image #39620579 by angellodeco