Diet Quality Is Inversely Associated with C-Reactive Protein Levels in Urban, Low-Income African-American and White Adults

Background C-reactive protein (CRP), an inflammatory biomarker, is influenced by many factors, including socioeconomic position, genetics, and diet. The inverse association between diet and CRP is biologically feasible because micronutrients with antioxidative properties may enable the body to manage the balance between production and accumulation of reactive species that cause oxidative stress. Objective To determine the quality of the diet consumed by urban, low-income African-American and white adults aged 30 to 64 years, and association of diet quality with CRP. Design Data from a cross-sectional study were used to evaluate diet quality assessed by mean adequacy ratio (MAR). Two 24-hour recalls were collected by trained interviewers using the US Department of Agriculture automated multiple pass method. Participants The sample consisted of Healthy Aging in Neighborhoods of Diversity across the Life Span baseline study participants, 2004-2009, who completed both recalls (n=2,017). Main outcome measures MAR equaled the average of the ratio of intakes to Recommended Dietary Allowance for 15 vitamins and minerals. CRP levels were assessed by the nephelometric method utilizing latex particles coated with CRP monoclonal antibodies. Statistical analysis Linear ordinary least square regression and generalized linear models were performed to determine the association of MAR (independent variable) with CRP (dependent variable) while adjusting for potential confounders. Results MAR scores ranged from 74.3 to 82.2. Intakes of magnesium and vitamins A, C, and E were the most inadequate compared with Estimated Average Requirements. CRP levels were significantly associated with MAR, dual-energy x-ray absorptiometry-measured body fat, and hypertension. A 10% increase in MAR was associated with a 4% decrease in CRP. Conclusions The MAR was independently and significantly inversely associated with CRP, suggesting diet is associated with the regulation of inflammation. Interventions to assist people make better food choices may not only improve diet quality but also their health, thereby possibly reducing risk for cardiovascular disease.