The dietary inflammatory index or DII helps link diet, inflammation and disease development. Now in its second iteration, the index brings together forty-five different parameters to assess the inflammatory potential of your diet.[1]
Over the last fifteen years, researchers have been collating studies highlighting different foods and their contributions to chronic inflammation. The aim is to try and create a quantitative measure of how diet causes or cures inflammation over time.
Using food and dietary measures to reduce inflammation has been the cornerstone of natural medicine’s success. Recently, this index has moved us closer to a level of clarity around what we might expect regarding diet and inflammation.
Why is inflammation significant when it comes to your health?
Well, chances are that you know someone affected by inflammation. Globally, three out of five people die due to chronic inflammatory diseases like, for example, stroke, chronic respiratory illnesses, heart or cardiovascular disease, cancer, obesity, and diabetes.[2]
This statistic isn’t considering the mental and digestive health conditions now connected to inflammation, such as depression for example.
My patients, myself included, have been helped by an anti-inflammatory diet. Up until the dawn of the DII, it’s been hard to articulate how to structure these diets properly, aside from classic paleo-leaning diet structures. This, it seems is going to change.
Before we delve into this a little further, defining a few terms is essential.
The best way to understand inflammation is to see it as the beacon the brain uses to send the immune system somewhere in the body that needs attention. It often occurs as a reaction or response to something, such as an injury or infection.[3]
Inflammation is chronic when it lasts for over six months to years.[4]
An important note with chronic inflammation is that you might not get the localised pain, swelling and heat seen with acute infection, such as when you cut yourself. It can take longer to develop, be more subtle, and take longer to resolve.
There are different immune reactions you can experience from food that involve inflammation.
And it’s important to differentiate between them so we can better understand the DII and the type of inflammation it’s causing in the body.
The most severe and visible food intolerance is anaphylaxis. Most people can understand this. Maybe you know someone whose got peanut, shellfish or bee-sting allergies? If they encounter what they’re allergic to, it can be life-threatening if not dealt with quickly. This reaction would be considered an allergy and meditated by an immune cell called IgE.
Another form of intolerance is non-IgE-mediated. Within these groups of reactions, we see gluten and dairy sensitivity and autoimmune conditions such as Celiac disease.[5]
These sensitivities can come from digestive and absorption-based issues and various other elements. The critical thing to understand when it comes to the dietary inflammatory index is that the inflammation caused by the foods in the index can sometimes overlap with these sensitivities or at least appear that way.
To make it easier, though, I want you to consider the foods in the DII as being more pro-inflammatory in a subtle, chronic way.
The cool thing is that one of the elements that make the dietary inflammatory index is that we can use markers in the blood to track levels of inflammation connected to food. These markers, in general, are called interleukins.
Any easy way to think of how interleukins work is as intermediaries between immune and inflammatory cells.[6] Therefore, if there a higher levels of particular types of these interleukins in the blood, then we know that there are higher levels of inflammation present.
Initially, the first DII was conceived with only C-reactive protein in mind, another marker of inflammation in the blood. C-reactive protein is often present in higher levels of inflammation too.
Now in the second iteration, the new DII has both the interleukins and C-reactive protein included to assess how inflammatory or anti-inflammatory a food is.
From here, we can now use the DII to measure people’s diets and specific disease frequency.
Let’s look at some of the research up to now, starting with depression. One study on older people particularly caught my eye on this one. Estimates suggest that one in five older people meet the criteria for the diagnosis of depression.[7] This prevalence isn’t just for Chinese people but is a ubiquitous problem worldwide.
A study released this year suggested that diets that scored highly on the DII, representative of a more-pro-inflammatory diet, were associated with higher levels of depression and suicidal ideation.[8]
Another study released this year confirmed this, citing that a diet higher on the DII is associated with an increased risk of depression in people with chronic illnesses such as hypertension, diabetes or cardiovascular disease.[9]
Another study released in March this year expanded the effects of a diet higher on the DII. Findings showed diets were higher on the DII increased overall stress and anxiety in two hundred and sixty university students.[10]
Research also points to a link between a pro-inflammatory diet measured via the DII and irritable bowel syndrome (IBS).
A case-control study found that the DII score was significantly higher in people with IBS compared to their healthy counterparts.[11] A second Persian study found the same result when looking at over three thousand people, showing those with a diet scoring higher on the DII had an increased risk of developing IBS, especially women.[12]
I think this might be a more chicken-and-egg scenario for IBS. With IBS and the immune system closely related in the first place, it’s possible that the pro-inflammatory diets may have exacerbated an existing problem. This ambiguity is why in the IBS and DII studies, we’ll need to keep an eye out for better, more conclusive research.
How do I know if my diet scores high on the DII?
For a start, it may not be as complicated as you think. For instance, you may already know which foods are pro-inflammatory.
A western diet is pro-inflammatory mainly due to the sugar, red meat, dairy products, refined carbohydrates and fried foods.[13] Alcohol and tobacco are also significant contributors.[14]
In contrast, a diet that scores lower on the DII would be similar to the classic Mediterranean diet. Rich in vegetables, olive oil and nuts, with lower amounts of red meat, beef and lamb, replaced with poultry and fish, the Mediterranean diet structure has good evidence of reducing the DII score in patients with coronary heart disease.[15]
Whilst this study is positive, it only had fifty-six participants. One of the interesting notes was that whilst the DII was reduced, the participants didn’t see significant improvements in their inflammatory markers as a translation.[16]
This part of the study is interesting because reducing the dietary inflammatory index or DII might just be one part of the picture.
For example, was the Mediterranean diet structure enough to bring down the inflammatory markers? Or was the presence of poultry and other saturated fat still sufficient to keep the markers elevated?
These questions show the benefits of having an index where differing diet structures can be compared over time and used in the context of what they are trying to treat. I call this diet as a prescription, and its utility is one of the reasons why diet is so effective in a natural medicine treatment. It has to be applied correctly, though. Although associated with reduced all-cause and cause-specific mortality,[17] the Mediterranean diet may not be enough as a therapeutic intervention to change the game once a disease has developed.
Something else to consider about a pro-inflammatory diet and your health.
We discussed how a pro-inflammatory diet could increase markers in the blood, like C-reactive protein, which predicts your chronic disease risk.[18] When you take the time to see all the independent studies that score highly in the DII and their associations with different illnesses, from chronic kidney disease[19] to obesity,[20]it’s easy to think that having a pro-inflammatory diet is just not good all-around.
Just like exercise seems to be suitable for everything (hint – it is[21]), the DII research has shown us that being mindful of our diets and their potential to cause inflammation is a move that won’t just help specific illnesses. It may also as help your healthspan in the long term.
Hope this helps.
References
[1] Shivappa N, Steck SE, Hurley TG, Hussey JR, Hébert JR. Designing and developing a literature-derived, population-based dietary inflammatory index. Public Health Nutr. 2014;17(8):1689-1696. doi:10.1017/S1368980013002115
[2] Pahwa R, Goyal A, Jialal I. Chronic Inflammation. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493173/
[3] Chen L, Deng H, Cui H, et al. Inflammatory responses and inflammation-associated diseases in organs. Oncotarget. 2017;9(6):7204-7218. Published 2017 Dec 14. doi:10.18632/oncotarget.23208
[4] Pahwa R, Goyal A, Jialal I. Chronic Inflammation. In: StatPearls. Treasure Island (FL): StatPearls Publishing; August 8, 2022.
[5] Guandalini S, Newland C. Differentiating food allergies from food intolerances. Curr Gastroenterol Rep. 2011;13(5):426-434. doi:10.1007/s11894-011-0215-7
[6] Justiz Vaillant AA, Qurie A. Interleukin. [Updated 2022 Aug 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499840/
[7] Zhong BL, Ruan YF, Xu YM, Chen WC, Liu LF. Prevalence and recognition of depressive disorders among Chinese older adults receiving primary care: A multi-center cross-sectional study. J Affect Disord. 2020;260:26-31. doi:10.1016/j.jad.2019.09.011
[8] Xiao Y, Huang W. Association of Dietary Inflammatory Index With Depression and Suicidal Ideation in Older Adult: Results From the National Health and Nutrition Examination Surveys 2005-2018. Front Psychiatry. 2022;13:944154. Published 2022 Jul 5. doi:10.3389/fpsyt.2022.944154
[9] Jiang C, Yin H, Liu A, Liu Q, Ma H, Geng Q. Dietary inflammatory index and depression risk in patients with chronic diseases and comorbidity. J Affect Disord. 2022;301:307-314. doi:10.1016/j.jad.2022.01.008
[10] Attlee A, Saravanan C, Shivappa N, et al. Higher Dietary Inflammatory Index Scores Are Associated With Stress and Anxiety in Dormitory-Residing Female University Students in the United Arab Emirates. Front Nutr. 2022;9:814409. Published 2022 Mar 10. doi:10.3389/fnut.2022.814409
[11] Eslampour E, Ghanadi K, Aghamohammadi V, et al. “Association between dietary inflammatory index (DII) and risk of irritable bowel syndrome: a case-control study”. Nutr J. 2021;20(1):60. Published 2021 Jun 28. doi:10.1186/s12937-021-00721-5
More references!
[12] Salari-Moghaddam A, Keshteli AH, Esmaillzadeh A, Adibi P. Adherence to the pro-inflammatory diet in relation to prevalence of irritable bowel syndrome. Nutr J. 2019;18(1):72. Published 2019 Nov 11. doi:10.1186/s12937-019-0487-6
[13] Tan QQ, Du XY, Gao CL, Xu Y. Higher Dietary Inflammatory Index Scores Increase the Risk of Diabetes Mellitus: A Meta-Analysis and Systematic Review. Front Endocrinol (Lausanne). 2021;12:693144. Published 2021 Aug 11. doi:10.3389/fendo.2021.693144
[14] Shivappa, Nitin & Hebert, James & Rosato, Valentina & Serraino, Diego & Vecchia, Carlo. (2016). Inflammatory potential of diet and risk of laryngeal cancer in a case–control study from Italy. Cancer Causes & Control. 27. 10.1007/s10552-016-0781-y.
[15] Mayr HL, Thomas CJ, Tierney AC, et al. Randomization to 6-month Mediterranean diet compared with a low-fat diet leads to improvement in Dietary Inflammatory Index scores in patients with coronary heart disease: the AUSMED Heart Trial. Nutr Res. 2018;55:94-107. doi:10.1016/j.nutres.2018.04.006
[16] Mayr HL, Thomas CJ, Tierney AC, et al. Randomization to 6-month Mediterranean diet compared with a low-fat diet leads to improvement in Dietary Inflammatory Index scores in patients with coronary heart disease: the AUSMED Heart Trial. Nutr Res. 2018;55:94-107. doi:10.1016/j.nutres.2018.04.006
Wait? More references?!
[17] Mitrou PN, Kipnis V, Thiébaut AC, et al. Mediterranean dietary pattern and prediction of all-cause mortality in a US population: results from the NIH-AARP Diet and Health Study. Arch Intern Med. 2007;167(22):2461-2468. doi:10.1001/archinte.167.22.2461
[18] Na W, Kim M, Sohn C. Dietary inflammatory index and its relationship with high-sensitivity C-reactive protein in Korean: data from the health examinee cohort. J Clin Biochem Nutr. 2018;62(1):83-88. doi:10.3164/jcbn.17-22
[19] Yan LJ, Zhang FR, Ma CS, Zheng Y. Higher dietary inflammatory index is associated with increased all-cause mortality in adults with chronic kidney disease. Front Nutr. 2022;9:883838. Published 2022 Jul 22. doi:10.3389/fnut.2022.883838
[20] Tavakoli A, Mirzababaei A, Moosavi H, Mehranfar S, Keshavarz SA, Mirzaei K. Dietary inflammatory index (DII) may be associated with hypertriglyceridemia waist circumference phenotype in overweight and obese Iranian women: a cross sectional study. BMC Res Notes. 2021;14(1):312. Published 2021 Aug 16. doi:10.1186/s13104-021-05712-7
[21] Nocon M, Hiemann T, Müller-Riemenschneider F, Thalau F, Roll S, Willich SN. Association of physical activity with all-cause and cardiovascular mortality: a systematic review and meta-analysis. Eur J Cardiovasc Prev Rehabil. 2008;15(3):239-246. doi:10.1097/HJR.0b013e3282f55e09
