Table 3. Summary of studies investigating association between lettuce and spinach intake and BC risk.
| Food item | Author, year | Design | Cohort/Location | Menopausal status | Adjusted intake (g/d) | Estimated flavonoid contribution (mg/d) | Outcome | OR/HR/RR (95%CI) |
| Lettucea | ||||||||
| Farvid, 2016 [134] | Cohort | NHS | Pre | 9.6 | Apigenin, 0 – 0.012 | Adolescent intake; No association | OR= 0.99 (0.95-1.04) | |
| Luteolin, 0 – 0.091 | ||||||||
| Kaempferol, 0.001 – 0.014 | ||||||||
| Myricetin, 0 – 0.006 | Early adult intake; No association | OR= 1.00 (0.98-1.01) | ||||||
| Quercetin, 0.14 – 0.73 | ||||||||
| Jung, 2013 [135] | Pooled cohort | Pooled analysis of 20 cohort studies | All | 56 | Apigenin, 0 – 0.073 | ER-; Decreased risk | RR= 0.91 (0.84-0.98) | |
| Luteolin, 0 – 0.532 | ||||||||
| Kaempferol, 0.006 – 0.084 | ER+; No association | RR= 1.01 (0.97-1.05) | ||||||
| Myricetin, 0 – 0.039 | ||||||||
| Quercetin, 0.80 – 4.26 | ||||||||
| Katsouyanni, 1986 [142] | Case-control | Athens, Greece | All | 12 | Apigenin, 0 – 0.016 | Decreased risk | OR= 0.75 (0.59-0.95) | |
| Luteolin, 0 – 0.114 | ||||||||
| Kaempferol, 0.001 – 0.018 | ||||||||
| Myricetin, 0 – 0.008 | ||||||||
| Quercetin, 0.17 – 0.91 | ||||||||
| Huang, 2004 [143] | Case-control | Nagoya, Japan | All | ≥14.4 | Apigenin, 0 – 0.018 | Fam Hx-; No Association | OR= 0.98 (0.88-1.09) | |
| Luteolin, 0 – 0.137 | ||||||||
| Kaempferol, 0.001 – 0.022 | ||||||||
| Myricetin, 0 – 0.01 | Fam Hx+; No association | OR= 0.98 (0.62-1.53) | ||||||
| Quercetin, 0.20 – 1.10 | ||||||||
| Spinach | ||||||||
| Boggs, 2010 [133] | Cohort | Black Women’s Health Study | All | 12 | Luteolin, 0.089 | No association | RR= 0.79 90.62-1.00) | |
| Pre | Kaempferol, 0.766 | No association | RR= 0.73 (0.51-1.05) | |||||
| Post | Myricetin, 0.042 | No association | RR= 0.84 (0.59-1.19) | |||||
| Quercetin, 0.476 | ||||||||
| Farvid, 2016 [134] | Cohort | NHS | Pre | 8 | Luteolin, 0.059 | Adolescent intake; No association | HR= 1.09 (0.98-1.21) | |
| Kaempferol, 0.51 | ||||||||
| Myricetin, 0.028 | ||||||||
| Quercetin, 0.318 | Early adult intake; No association | HR= 0.99 (0.92-1.06) | ||||||
| Jung, 2013 [135] | Pooled cohort | Pooled analysis of 20 cohort studies | All | 15 | Luteolin, 0.111 | ER-; No association | RR= 0.91 (0.80-1.04) | |
| Kaempferol, 0.957 | ||||||||
| Myricetin, 0.052 | ||||||||
| Quercetin, 0.596 | ER+; No association | RR= 1.00 (0.90-1.11) | ||||||
| Longnecker, 1997 [144] | Case-control | North East U.S.A. | All | ≥8.75 | Luteolin, ≥0.065 | Decreased risk | RR= 0.64 (0.43-0.94) | |
| Kaempferol, ≥0.56 | ||||||||
| Myricetin, ≥0.031 | ||||||||
| Quercetin, ≥0.347 |
aRanges for lettuce flavonoid load due to differences in content between butterhead, romaine, green leaf, red leaf, and iceberg varieties.