Soy looked the same for women on tamoxifen and women not on it
Pooling 32 observational studies of breast cancer survivors, higher soy isoflavone intake went with 26 percent lower recurrence, and the two groups came out almost identical.
What the study found
Tamoxifen users and non-users showed the same soy association
Pooling 32 observational studies of breast cancer survivors, higher soy isoflavone intake went with 26 percent lower recurrence, and the estimates for women taking tamoxifen and women not taking it came out almost identical. The worry that soy blunts the drug does not show up here.
The caveat · On tamoxifen, it could be no effect
The tamoxifen-user estimate, unlike the non-user one, still includes no effect within its range of uncertainty, so the near-identity is between point estimates rather than between two equally firm results. Every study pooled is observational, with self-reported diet.