Table 3.
Seasonality of the diet quality score and of each contributing food group, n = 12,589 observations
| Outcome | Model | Seasonal variation* | 95% Confidence interval | Mean daily score/intake | Seasonal variation in percentagesa | Peak | Nadir |
|---|---|---|---|---|---|---|---|
| Diet quality score (0–14) | Model 1 | 0.12 | 0.03–0.21 | ||||
| Model 2 | 0.10 | 0.01–0.18 | 6.72 | 1.49 | 19-Dec | 19-Jun | |
| Kilocalories/day | Model 1 | 45.93 | 17.92–73.95 | ||||
| Model 2 | 46.03 | 18.27–73.80 | 2067.43 | 2.23 | 29-Nov | 30-May | |
| Food groups | |||||||
| Vegetables (g/day) | Model 1 | 4.67 | − 2.19–11.54 | ||||
| Model 2 | 4.81 | − 1.96–11.58 | 210.09 | 2.29 | 1-Sep | 2-Mar | |
| Fruits (g/day) | Model 1 | 6.57 | − 5.360–18.50 | ||||
| Model 2 | 3.18 | − 8.63–14.99 | 284.84 | 1.12 | 3-Dec | 4-Jun | |
| Whole grain (g/day) | Model 1 | 2.95 | − 0.37–6.27 | ||||
| Model 2 | 2.95 | − 0.37–6.27 | 125.36 | 2.35 | 12-Feb | 12-Aug | |
| Legumes (g/day) | Model 1 | 3.52 | 2.62–4.42 | ||||
| Model 2 | 3.51 | 2.61–4.41 | 9.09 | 38.61 | 30-Dec | 30-Jun | |
| Nuts (g/day) | Model 1 | 0.82 | 0.20–1.45 | ||||
| Model 2 | 0.78 | 0.16–1.41 | 8.25 | 9.45 | 25-Jan | 26-Jul | |
| Dairy (g/day) | Model 1 | 16.95 | 5.03–28.87 | ||||
| Model 2 | 17.52 | 5.60–29.44 | 365.65 | 4.79 | 17-Jun | 16-Dec | |
| Fish (g/day) | Model 1 | 1.45 | 0.57–2.33 | ||||
| Model 2 | 1.52 | 0.64–2.40 | 14.82 | 10.26 | 1-Jun | 30-Nov | |
| Tea (mL/day) | Model 1 | 21.48 | 9.21–33.76 | ||||
| Model 2 | 19.82 | 7.65–32.00 | 288.42 | 6.87 | 9-Feb | 9-Aug | |
| Whole grain ratio | Model 1 | 0.59 | − 0.66–1.83 | ||||
| Model 2 | 0.50 | − 0.75–1.75 | 68.54 | 0.73 | 10-Oct | 10-Apr | |
| Unsaturated fat and oil ratio | Model 1 | 0.45 | − 1.00–1.91 | ||||
| Model 2 | 0.32 | − 1.16–1.79 | 52.41 | 0.61 | 19-Feb | 19-Aug | |
| Red and processed meat (g/day) | Model 1 | 2.11 | − 0.26–4.47 | ||||
| Model 2 | 2.43 | 0.11–4.75 | 89.70 | 2.71 | 4-Nov | 6-May | |
| Sugar-containing beverages (mL/day) | Model 1 | 13.01 | 7.22–18.80 | ||||
| Model 2 | 12.96 | 7.16–18.77 | 75.52 | 17.16 | 1-Jun | 1-Dec | |
| Alcohol (g/day) | Model 1 | 0.41 | − 0.25–1.07 | ||||
| Model 2 | 0.34 | − 0.31–0.99 | 11.47 | 2.96 | 16-Jun | 16-Dec | |
| Salt (mg/day) | Model 1 | 84.87 | 18.37–151.38 | ||||
| Model 2 | 80.70 | 14.50–146.90 | 5658.87 | 1.43 | 5-Feb | 5-Aug | |
Bold coefficients are statistically significant at 95% confidence level
Model 1 includes cosinor terms, sex, age, cohort and energy intake
Model 2 additionally adjusted for physical activity, smoking behavior, body mass index, prevalent diseases (stroke, myocardial infarction, diabetes mellitus type 2, and cancer), and education
*Seasonal variation = maximum difference between the highest annual average (peak) and lowest annual average (nadir)
aSeasonal variation in percentages (seasonal variation/mean daily score or intake × 100%)