Table 3

Phytoestrogen consumption and thyroid cancer risk among women participating in the Bay Area Thyroid Cancer Study

Phytoestrogen (μg/day)CasesControlsORa95% CIORb95% CI
Isoflavones
 Genistein
  <5251061081.01.0
  525–8871451091.30.89–1.91.30.88–2.0
  888–14711351091.10.77–1.71.30.86–2.0
  1472–36801211090.970.65–1.41.10.72–1.7
  ≥3681831090.650.42–1.00.700.44–1.1
  Trend across quintilesP = 0.02P = 0.14
  Per 500 μg/day0.980.97–0.990.980.96–0.99
 Daidzein
  <4691121081.01.0
  470–7491281091.10.77–1.61.00.70–1.6
  750–12351401091.10.78–1.71.30.85–1.9
  1236–35961311090.920.62–1.41.00.67–1.6
  ≥3597791090.600.39–0.920.650.40–1.0
  Trend across quintilesP = 0.02P = 0.15
  Per 500 μg/day0.970.96–0.990.970.96–0.99
 Biochanin A
  <111101081.01.0
  12–201151091.00.69–1.51.00.69–1.6
  21–331211091.00.69–1.50.970.64–1.5
  34–511001090.820.55–1.20.790.52–1.2
  ≥521441091.20.78–1.71.10.72–1.7
  Trend across quintilesP = 0.78P = 0.95
  Per 10 μg/day1.020.98–1.051.010.98–1.05
 Formononetin
  <91381081.01.0
  10–181241090.850.59–1.20.950.64–1.4
  19–281111090.760.53–1.10.840.57–1.3
  29–511151090.770.53–1.10.850.57–1.3
  ≥521021090.650.44–0.960.780.51–1.2
  Trend across quintilesP = 0.03P = 0.21
  Per 10 μg/day0.970.94–0.990.980.95–1.01
 Total isoflavones
  <10461031081.01.0
  1047–16781341091.10.79–1.71.10.72–1.6
  1679–27391431091.20.79–1.71.30.88–2.0
  2740–72851271090.920.61–1.41.00.66–1.6
  ≥7286831090.610.40–0.940.650.41–1.0
  Trend across quintilesP = 0.02P = 0.13
  Per 1000 μg/day0.980.96–0.990.980.96–0.99
Coumestans
 Coumestrol
  <81.31181081.01.0
  81.4–123.11111090.870.60–1.30.950.63–1.4
  123.2–167.71011090.760.52–1.10.710.46–1.1
  167.8–270.41541091.10.78–1.71.10.71–1.6
  ≥270.51061090.730.48–1.10.780.49–1.2
  Trend across quintilesP = 0.56P = 0.55
  Per 50 μg/day0.970.94–1.010.980.94–1.2
Lignans
 Matairesinol
  <181201081.01.0
  19–281101090.870.60–1.30.790.52–1.2
  29–381051090.790.54–1.20.780.51–1.2
  39–561401091.00.70–1.51.00.67–1.5
  ≥571151090.790.52–1.20.720.46–1.1
  Trend across quintilesP = 0.56P = 0.49
  Per 10 μg/day1.000.96–1.041.000.96–1.04
 Secoisolariciresinol
  <421431081.01.0
  43–581141090.730.50–1.10.750.50–1.1
  59–801391090.840.58–1.20.820.55–1.2
  81–1061011090.570.38–0.850.580.38–0.89
  ≥107931090.470.31–0.730.560.35–0.89
  Trend across quintilesP = 0.0005P = 0.009
  Per 25 μg/day0.870.80–0.940.890.82–0.96
 Total Lignans
  <64.61241081.01.0
  64.7–90.71261090.950.66–1.40.980.66–1.5
  90.8–120.91221090.850.58–1.20.730.49–1.1
  121.0–160.91131090.770.52–1.10.800.52–1.2
  ≥161.01051090.630.41–0.970.680.43–1.1
  Trend across quintilesP = 0.02P = 0.07
  Per 25 μg/day0.940.89–0.990.950.90–1.00
Total Phytoestrogens
 <12521141081.01.0
 1252–18781211090.970.67–1.40.890.59–1.3
 1879–30281521091.20.81–1.71.20.84–1.9
 3028–75371191090.870.58–1.30.940.61–1.4
 ≥7538841090.600.39–0.930.620.39–0.99
 Trend across quintilesP = 0.03P = 0.14
 Per 1000 μg/day0.980.96–0.990.980.96–0.99
  • a Adjusted for age, race/ethnicity, and daily caloric intake.

  • b Adjusted for age, race/ethnicity, daily caloric intake, goiter or thyroid nodules, radiation to the head or neck, family history of proliferative thyroid disease, age at menarche, use of oral contraceptives, age at first full-term pregnancy/nulliparity (allowing for separate effects for women <45 and ≥45 years of age), and a composite variable including menopausal status and number of pregnancies in the last 5 years among premenopausal women.