Separating the Chaff from Grain, Fruit and Vegetables on Inflammation and Health
Inflammation is considered to be a key factor initiating many chronic non-communicable diseases. Some nutrients are known to influence inflammation. In a Belgian cross-sectional study of 2,524 generally healthy subjects (35-55y), Shivappa and colleagues measured associations between dietary recall data (Food Frequency Questionnaires of 25 foods items) and inflammatory markers (IL-6, homocysteine, C-reactive protein and fibrogen).
The study population was grouped into 3 tertiles. Age, BMI, C-reactive protein and fibrinogen were not different among groups with respect to the dietary inflammatory index but all food groups were (vegetables, fish, fruit, sugared drinks and meat). This is not too surprising given that ‘inflammatory effect scores’ for each food parameter derived from literature review. The value of this study is diminished because the methodology to define inflammatory effect scores is not described nor is a citation provided. Thus, researchers cannot replicate the findings. In addition, the application of an index to only 25 food items measured by food frequency is a terribly imprecise estimate of nutrient intake.
The study should not distract from the literature linking nutrition with inflammation.
Vitamin E, the α-tocopherol form, has been shown to affect lung function and seems to protect against lung inflammation. Asthma, an inflammatory reaction caused by a combination of genetic and environmental factors, is more prevalent among the poor and some ethnic groups (more common in African Americans, Hispanics and Puerto Ricans than Caucasians).
Increasing omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), levels relative to omega-6 levels leads to messenger molecules (resolvins) which are less inflammatory. Rheumatoid arthritis, an inflammatory disease, help patients reduce their use of painkillers and the failure rates of disease-modifying anti-rheumatic drugs.
Vitamin D supplementation has been shown to reduce C-reactive protein concentrations in pregnant women. Maternal inflammation during pregnancy may increase the risk of autism in children. There are many reasons to consume foods rich in antioxidant nutrients. In fact, a primary reason for recommendations to increase the consumption of fruit, vegetables and whole grains is the antioxidant nutrient content.
Rather than using poorly defined inflammatory food index scores and 25 items for food frequency questionnaires, more researchers should adopt the more rigorous approach of Hozawa and colleagues.
Shivappa N, Hebert JR, Rietzschel ER, De Buyzere ML, Langlois M, Debruyne E, Marcos A, Huybrechts I. Associations between dietary inflammatory index and inflammatory markers in the Asklepios Study. 2015. Br J Nutr doi: 10.1017/S0007114500395X
Abdala-Valencia H, Berdnikovs S, Cook-Mills JM. Vitamin E isoforms as modulators of lung inflammation. 2013 Nutrients doi:10.3390/nu5114347
Denman M. In patients with early rheumatoid arthritis, fish oil reduced failure of treatment with DMARDs. Annals of Internal Medicine. 2014 Annal Intern Med doi: 10.7326/0003-4819-16—4-2-1402180-02011
Hozawa A, Jacobs DR, Steffes MW, Gross MD, Steffen LM, Duk-Hee L. Relationships of circulating carotenoid concentrations with several markers of inflammation, oxidative stress, and endothelial dysfunction: The Coronary Artery Risk Development in Young Adults (CARDIA)/Young Adult Longitudinal Trends in Antioxidants (YALTA) Study. 2007 Clin Chem 53:447