In a trial of ipriflavone for osteoporosis, 29 of the 132 women in the ipriflavone group completing the three-year trial developed a clinically significant drop in lymphocytes.¹⁴ These cells, which make up approximately 22 to 28% of the white blood cells in the normal adult, are critical components of the immune system and its ability to respond to viral infections. In some of these women, a return to normal levels took almost two years after they had stopped the ipriflavone. Since this finding has been reported in one other smaller clinical trial,¹⁵ it suggests that women choosing to take ipriflavone should have their lymphocytes measured regularly by their doctor.

In double-blind studies, the frequency of perceived side effects in ipriflavone-treated people (14.5%) was actually less than that observed in people receiving the placebo (16.1%).¹⁵ Side effects were mainly mild stomach upset. Researchers recommend that patients with severe kidney disease take a lower amount of ipriflavone (200 to 400 mg daily).¹⁷