Objective To perform construct validation of the population-based Dietary Inflammatory Index (DII) using dietary data from two different dietary assessments and serum high-sensitivity C-reactive protein (hs-CRP) as the construct validator. Design Using data derived from (i) three 24 h dietary recalls (24HR) at baseline and at the end of each subsequent quarter (i.e. up to fifteen over a year) and (ii) a 7 d dietary recall (7DDR) measured at baseline and then quarterly, regression analyses were conducted to test the effect of the DII score on serum hs-CRP as dichotomous (≤3mg/l, >3mg/l), while controlling for important potential confounders. Setting Existing data from the Seasonal Variation of Blood Cholesterol Study (SEASONS), a longitudinal observational study of healthy participants recruited in Worcester, MA, USA and participants were followed for 1 year. Subjects Participants who had at least one hs-CRP measurement over her/his 1-year participation (n 495 for 24HR, n 559 for 7DDR). Results Higher DII scores were associated with values of hs-CRP >3 mg/l (OR = 1·08; 95% CI 1·01, 1·16, P = 0·035 for the 24HR; and OR = 1·10; 95% CI 1·02, 1·19, P = 0·015 for the 7DDR). Conclusions The population-based DII was associated with interval changes in hs-CRP using both the 24HR and 7DDR. The success of this first-of-a-kind attempt at relating individuals’ intakes of inflammation-modulating foods using this refined DII, and the finding that there is virtually no drop-off in predictive capability using a structured questionnaire in comparison to the 24HR standard, sets the stage for use of the DII in a wide variety of other epidemiological and clinical studies.

Some studies have suggested that eating patterns, which describe eating frequency, the temporal distribution of eating events across the day, breakfast skipping, and the frequency of eating meals away from home, may be related to obesity. Data from the Seasonal Variation of Blood Cholesterol Study (1994-1998) were used to evaluate the relation between eating patterns and obesity. Three 24-hour dietary recalls and a body weight measurement were collected at five equally spaced time points over a 1-year period from 499 participants. Data were averaged for five time periods, and a cross-sectional analysis was conducted. Odds ratios were adjusted for other obesity risk factors including age, sex, physical activity, and total energy intake. Results indicate that a greater number of eating episodes each day was associated with a lower risk of obesity (odds ratio for four or more eating episodes vs. three or fewer = 0.55, 95% confidence interval: 0.33, 0.91). In contrast, skipping breakfast was associated with increased prevalence of obesity (odds ratio = 4.5, 95% confidence interval: 1.57, 12.90), as was greater frequency of eating breakfast or dinner away from home. Further investigation of these associations in prospective studies is warranted.

Inflammation is associated with a number of chronic conditions, such as cancer and cardiovascular disease. Reducing inflammation may help prevent or treat these conditions. Diet has consistently been shown to modulate inflammation. To facilitate research into the inflammatory effect of diet on health in humans, we sought to develop and validate an Inflammatory Index designed to assess the inflammatory potential of individuals' diets. An Inflammatory Index was developed based on the results of an extensive literature search. Using data from a longitudinal observational study that carefully measured diet and the inflammatory marker, serum high-sensitivity (hs) C-reactive protein (CRP), in approximately 600 adults for 1 y, we conducted analyses to test the effect of Inflammatory Index score on hs-CRP as a continuous and dichotomous (3 mg/L) indicator of inflammatory response, while controlling for important potential confounders. Results based on continuous measures of hs-CRP suggested that an increasing Inflammatory Index score (representing movement toward an antiinflammatory diet) was associated with a decrease in hs-CRP. Analyses using hs-CRP as a dichotomous variable showed that an antiinflammatory diet was associated with a decrease in the odds of an elevated hs-CRP (P = 0.049). The results are consistent with the ability of the Inflammatory Index to predict hs-CRP and provide additional evidence that diet plays a role in the regulation of inflammation, even after careful control of a wide variety of potential confounders.

Purpose Many dietary factors have either pro- or anti-inflammatory properties. We previously developed a dietary inflammatory index (DII) to assess the inflammatory potential of diet. In this study we conducted a construct validation of the DII based on data from a food frequency questionnaire and three inflammatory biomarkers in a subsample of 2,567 postmenopausal women in the Women’s Health Initiative Observational Study. Methods We used multiple linear and logistic regression models, controlling for potential confounders, to test whether baseline DII predicted concentrations of interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor alpha receptor 2 (TNFα-R2), or an overall biomarker score combining all three inflammatory biomarkers. Results The DII was associated with the four biomarkers with beta estimates (95%CI) comparing the highest with lowest DII quintiles as follows: IL-6: 1.26 (1.15, 1.38), Ptrend<0.0001; TNFα-R2: 81.43 (19.15, 143.71), Ptrend=0.004; dichotomized hs-CRP (odds ratio for higher versus lower hs-CRP): 1.30 (0.97, 1.67), Ptrend=0.34); and the combined inflammatory biomarker score: 0.26 (0.12, 0.40), Ptrend=0.0001. Conclusion The DII was significantly associated with inflammatory biomarkers. Construct validity of the DII indicates its utility for assessing the inflammatory potential of diet and for expanding its use to include associations with common chronic diseases in future studies.

Objective-To describe seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population. Design-A longitudinal observational study.Setting-Most of the study participants were recruited from a health maintenance organization (HMO) in central Massachusetts, USA. Additional individuals of Hispanic descent were recruited from outside of the HMO population to increase the ethnic diversity of this sample.Subjects-Data from 593 participants, aged 20-70, were used for this investigation. Each participant was followed quarterly (five sampling points: baseline and four consecutive quarters) for 1-year period. Body weight measurements and three 24-h dietary and physical activity recalls were obtained on randomly selected days (including 2 weekdays and 1 weekend day) per quarter. Sinusoidal regression models were used to estimate peak-to-trough amplitude and phase of the peaks.Results-Daily caloric intake was higher by 86 kcal/day during the fall compared to the spring. Percentage of calories from carbohydrate, fat and saturated fat showed slight seasonal variation, with a peak in the spring for carbohydrate and in the fall for total fat and saturated fat intake. The lowest physical activity level was observed in the winter and the highest in the spring. Body weight varied by about 1/2 kg throughout the year, with a peak in the winter (P<0.001 winter versus summer). Greater seasonal variation was observed in subjects who were male, middle aged, nonwhite, and less educated.Conclusions-Although there is seasonal variation in diet, physical activity and body weight, the magnitude of the change is generally small in this population.