TABLE 2.
Subgroup analysis of studies investigated the association of various food groups with risk of breast cancer
| Subgroup factors | n of studies | RR (95% CI) | I², % |
|---|---|---|---|
| Red meat, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 9 | 1.02 (0.94–1.12) | 17.1 |
| Postmenopause | 11 | 1.09 (0.99–1.20) | 63.0 |
| P between-group heterogeneity | 0.34 | ||
| Estrogen-progesterone receptor | |||
| Er+Pr+ | 4 | 1.21 (0.93–1.58) | 75.6 |
| Er+Pr− | 2 | 0.97 (0.81–1.15) | 0.0 |
| Er−Pr− | 3 | 1.22 (0.91–1.64) | 30.3 |
| P between-group heterogeneity | 0.17 | ||
| Follow-up | |||
| <10 y | 8 | 1.22 (1.09–1.37) | 44.1 |
| ≥10 y | 12 | 1.03 (0.96–1.11) | 47.4 |
| P between-group heterogeneity | <0.001 | ||
| Geographic location | |||
| Europe | 12 | 1.12 (1.02–1.22) | 51 |
| North America | 7 | 1.09 (0.98–1.21) | 71.6 |
| P between-group heterogeneity | 0.12 | ||
| Number of cases | |||
| <1000 | 6 | 1.14 (0.95–1.36) | 44.4 |
| ≥1000 | 14 | 1.09 (1.02–1.17) | 63.1 |
| P between-group heterogeneity | 0.06 | ||
| Poultry, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 5 | 1.01 (0.98–1.05) | 27.6 |
| Postmenopause | 8 | 0.99 (0.96–1.02) | 59.3 |
| P between-group heterogeneity | 0.27 | ||
| Follow-up | |||
| <10 y | 8 | 0.97 (0.87–1.07) | 38.1 |
| ≥10 y | 5 | 0.96 (0.88–1.06) | 5.8 |
| P between-group heterogeneity | 0.94 | ||
| Geographic location | |||
| Europe | 5 | 1.07 (0.96–1.20) | 0.0 |
| USA | 7 | 0.93 (0.86–1.01) | 38.0 |
| P between-group heterogeneity | 0.12 | ||
| Number of cases | |||
| <1000 | 6 | 1.08 (0.97–1.19) | 40 |
| ≥1000 | 7 | 0.99 (0.98–1.0) | 35.9 |
| P between-group heterogeneity | 0.04 | ||
| Fish, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 6 | 1.02 (0.92–1.14) | 0.0 |
| Postmenopause | 9 | 0.99 (0.93–1.04) | 0.0 |
| P between-group heterogeneity | 0.52 | ||
| Follow-up | |||
| <10 y | 5 | 1.05 (0.87–1.26) | 64.7 |
| ≥10 y | 12 | 0.98 (0.91–1.07) | 0.0 |
| P between-group heterogeneity | 0.87 | ||
| Geographic location | |||
| Europe | 9 | 0.99 (0.88–1.12) | 20.6 |
| USA | 6 | 1.01 (0.87–1.16) | 52.2 |
| Asia | 3 | 1.12 (0.85–1.47) | 0.0 |
| P between-group heterogeneity | 0.63 | ||
| Number of cases | |||
| <1000 | 9 | 1.15 (0.82–1.60) | 49.1 |
| ≥1000 | 8 | 0.98 (0.93–1.03) | 0.0 |
| P between-group heterogeneity | 0.24 | ||
| Egg, 50 grams/day | |||
| Menopause status | |||
| Premenopause | 4 | 1.06 (0.91–1.23) | 39.5 |
| Postmenopause | 4 | 1.01 (0.94–1.09) | 0.0 |
| P between-group heterogeneity | 0.71 | ||
| Follow-up | |||
| <10 y | 3 | 1.0 (0.95–1.06) | 0.0 |
| ≥10 y | 8 | 1.04 (0.93–1.16) | 61.7 |
| P between-group heterogeneity | 0.32 | ||
| Geographic location | |||
| Europe | 5 | 1.03 (0.98–1.08) | 68.5 |
| USA | 3 | 1.02 (0.93–1.12) | 0.0 |
| Asia | 2 | 0.87 (0.70–1.08) | 75 |
| P between-group heterogeneity | 0.34 | ||
| Number of cases | |||
| <1000 | 6 | 1.11 (0.82–1.50) | 70.3 |
| ≥1000 | 5 | 1.01 (0.97–1.06) | 0.0 |
| P between-group heterogeneity | 0.34 | ||
| Total meat, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 4 | 1.04 (0.93–1.16) | 48.3 |
| Postmenopause | 7 | 1.04 (0.98–1.10) | 83.9 |
| P between-group heterogeneity | 0.66 | ||
| Follow-up | |||
| <10 y | 7 | 1.13 (1.03–1.23) | 73.1 |
| ≥10 y | 7 | 1.02 (0.96–1.08) | 55.2 |
| P between-group heterogeneity | <0.001 | ||
| Geographic location | |||
| Europe | 7 | 1.06 (1.02–1.10) | 73.4 |
| USA | 6 | 1.0 (0.98–1.02) | 78.9 |
| P between-group heterogeneity | 0.03 | ||
| Number of cases | |||
| <1000 | 8 | 1.29 (1.10–1.51) | 59.7 |
| ≥1000 | 6 | 1.01 (0.97–1.06) | 72.7 |
| P between-group heterogeneity | <0.001 | ||
| Processed meat, 50 grams/day | |||
| Menopause status | |||
| Premenopause | 6 | 1.03 (0.92–1.16) | 0.0 |
| Postmenopause | 11 | 1.11 (1.01–1.22) | 32.2 |
| P between-group heterogeneity | 0.49 | ||
| Follow-up | |||
| <10 y | 8 | 1.19 (1.03–1.38) | 35.6 |
| ≥10 y | 7 | 1.17 (0.94–1.46) | 76.9 |
| P between-group heterogeneity | 0.29 | ||
| Geographic location | |||
| Europe | 10 | 1.37 (1.16–1.62) | 46.1 |
| USA | 6 | 1.005 (0.93–1.08) | 0.0 |
| P between-group heterogeneity | 0.001 | ||
| Number of cases | |||
| <1000 | 9 | 1.29 (1.01–1.64) | 60.0 |
| ≥1000 | 8 | 1.07 (0.96–1.20) | 45.8 |
| P between-group heterogeneity | 0.001 | ||
| Dairy, 200 grams/day | |||
| Menopause status | |||
| Premenopause | 7 | 0.96 (0.90–1.02) | 54.8 |
| Postmenopause | 7 | 0.99 (0.96–1.02) | 27.1 |
| P between-group heterogeneity | 0.39 | ||
| Follow-up | |||
| <10 y | 4 | 0.96 (0.95–0.97) | 0.0 |
| ≥10 y | 6 | 0.99 (0.97–1.01) | 50.3 |
| P between-group heterogeneity | 0.004 | ||
| Geographic location | |||
| Europe | 4 | 0.96 (0.85–1.09) | 42.5 |
| USA | 5 | 0.97 (0.94–0.997) | 58.3 |
| P between-group heterogeneity | 0.02 | ||
| Number of cases | |||
| <1000 | 4 | 0.91 (0.82–1.02) | 0.0 |
| ≥1000 | 6 | 0.97 (0.96–0.98) | 72.4 |
| P between-group heterogeneity | 0.34 | ||
| Milk, 200 grams/day | |||
| Menopause status | |||
| Premenopause | 4 | 1.0 (0.92–1.09) | 0.0 |
| Postmenopause | 8 | 1.0 (0.96–1.03) | 33.0 |
| P between-group heterogeneity | 0.89 | ||
| Type of milk | |||
| Low fat | 5 | 1.01 (0.97–1.06) | 57.3 |
| Whole milk | 6 | 1.03 (0.99–1.08) | 0.0 |
| P between-group heterogeneity | 0.35 | ||
| Follow-up | |||
| <10 y | 6 | 0.98 (0.92–1.05) | 49.8 |
| ≥10 y | 7 | 0.99 (0.96–1.03) | 60.5 |
| P between-group heterogeneity | 0.97 | ||
| Geographic location | |||
| Europe | 8 | 0.99 (0.95–1.03) | 63.1 |
| USA | 4 | 0.98 (0.95–1.01) | 0.0 |
| P between-group heterogeneity | 0.10 | ||
| Number of cases | |||
| <1000 | 8 | 0.95 (0.88–1.03) | 67.1 |
| ≥1000 | 5 | 1.0 (0.98–1.01) | 0.0 |
| P between-group heterogeneity | 0.37 | ||
| Cheese, 30 grams/day | |||
| Menopause status | |||
| Premenopause | 4 | 0.93 (0.70–1.25) | 53.7 |
| Postmenopause | 7 | 0.90 (0.82–0.99) | 76.3 |
| P between-group heterogeneity | 0.29 | ||
| Follow-up | |||
| <10 y | 5 | 0.96 (0.87–1.06) | 60.4 |
| ≥10 y | 5 | 0.94 (0.87–1.01) | 75.1 |
| P between-group heterogeneity | 0.37 | ||
| Geographic location | |||
| Europe | 8 | 0.95 (0.91–0.99) | 77.9 |
| USA | 2 | 1.04 (0.49–2.19) | 76.1 |
| P between-group heterogeneity | 0.63 | ||
| Number of cases | |||
| <1000 | 5 | 0.95 (0.81–1.12) | 81 |
| ≥1000 | 5 | 0.98 (0.95–1.01) | 60.1 |
| P between-group heterogeneity | 0.025 | ||
| Fruit, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 3 | 0.97 (0.93–1.0) | 0.0 |
| Postmenopause | 10 | 0.98 (0.96–1.0) | 62 |
| P between-group heterogeneity | 0.50 | ||
| Estrogen-progesterone receptor | |||
| Er+Pr+ | 4 | 0.97 (0.96–0.99) | 0.0 |
| Er−Pr− | 4 | 0.98 (0.94–1.02) | 0.0 |
| Er+Pr− | 5 | 0.99 (0.94–1.04) | 43.6 |
| P between-group heterogeneity | 0.65 | ||
| Geographic location | |||
| Europe | 6 | 0.967 (0.94–0.99) | 68.6 |
| North America | 5 | 0.98 (0.97–0.99) | 0.0 |
| Asia | 4 | 0.87 (0.73–1.05) | 86.1 |
| P between-group heterogeneity | 0.70 | ||
| Number of cases | |||
| <1000 | 9 | 0.96 (0.92–0.998) | 70.8 |
| ≥1000 | 6 | 0.97 (0.95–0.99) | 64.1 |
| P between-group heterogeneity | 0.51 | ||
| Vegetable, 100 grams/day | |||
| Menopause status | |||
| Premenopause | 4 | 1.01 (0.96–1.06) | 0.0 |
| Postmenopause | 10 | 1.01 (0.995–1.022) | 0.0 |
| P between-group heterogeneity | 0.98 | ||
| Estrogen receptor | |||
| Er+ | 4 | 0.99 (0.96–1.01) | 1.1 |
| Er− | 4 | 0.94 (0.90–0.997) | 52.7 |
| P between-group heterogeneity | 0.11 | ||
| Geographic location | |||
| Europe | 6 | 0.97 (0.95–0.99) | 0.0 |
| USA | 5 | 0.99 (0.95–1.02) | 63.3 |
| Asia | 3 | 0.92 (0.84–1.01) | 45.4 |
| P between-group heterogeneity | 0.004 | ||
| Number of cases | |||
| <1000 | 10 | 0.97 (0.94–1.001) | 62.4 |
| ≥1000 | 4 | 0.97 (0.95–1.0) | 0.0 |
| P between-group heterogeneity | 0.10 | ||
| Fruit and vegetable, 100 grams/day | |||
| Geographic location | |||
| Europe | 3 | 0.99 (0.98–1.0) | 0.0 |
| USA | 3 | 0.98 (0.97–0.99) | 0.0 |
| Asia | 2 | 0.94 (0.78–1.12) | 90.2 |
| P between-group heterogeneity | 0.22 | ||
| Number of cases | |||
| <1000 | 3 | 0.95 (0.89–1.01) | 67.8 |
| ≥1000 | 5 | 0.99 (0.97–1.0) | 46.9 |
| P between-group heterogeneity | 0.19 | ||
| Total cereals, 20 grams/day | |||
| Menopause status | |||
| Premenopause | 5 | 1.0 (0.99–1.01) | 0.0 |
| Postmenopause | 7 | 1.0 (0.99–1.01) | 22.3 |
| P between-group heterogeneity | 0.40 | ||
| Grain, 20 grams/day | |||
| Whole/refined | |||
| Whole grain | 5 | 1.0 (0.99–1.01) | 30.8 |
| Refined grain | 7 | 1.0 (0.99–1.01) | 0.0 |
| P between-group heterogeneity | 0.025 | ||
| Follow-up | |||
| <10 y | 6 | 1.0 (0.99–1.01) | 31.7 |
| ≥10 y | 8 | 0.99 (0.98–1.01) | 0.0 |
| P between-group heterogeneity | 0.15 | ||
| Geographic location | |||
| Europe | 6 | 1.0 (0.99–1.01) | 0.0 |
| North America | 4 | 0.99 (0.95–1.02) | 75.7 |
| Asia | 3 | 1.0 (0.98–1.02) | 0.0 |
| P between-group heterogeneity | 0.76 | ||
| Number of cases | |||
| <1000 | 9 | 1.0 (0.99–1.01) | 15.4 |
| ≥1000 | 5 | 1.0 (0.99–1.01) | 32.7 |
| P between-group heterogeneity | 0.83 | ||
+, positive/present; −, negative/not present; Er, estrogen receptor; Pr, progesterone receptor; RR, risk ratio.