Last fall, the Centers for Disease Control and Prevention (CDC) released a report that a newborn developed life-threatening blood poisoning passed on from its mother when she took bacteria-contaminated pills.
Weeks later, researchers at the University of Nevada, Las Vegas, published research showing it had absolutely no impact on a mother's mental health.
Supporters of the practice often claim the organ contains valuable vitamins and hormones that could prevent postpartum depression.
Researchers from the University of Nevada, Las Vegas, analyzed 12 women who took placenta capsules and 15 who had placebo pills after giving birth.
They investigated the placenta capsules' health effects, including their ability to prevent postpartum depression.
The findings were published in the journal Women and Birth.
Results reveal placenta capsules do not decrease a new mother's risk of postpartum depression.
Study author Professor Daniel Benyshek, said: "Our results might be seen as proof that placentophagy doesn't 'really work' because we did not find the type of clear, robust differences in maternal hormone levels or postpartum mood between the placenta group and placebo group that these types of studies are designed to detect."
Yet the findings did show consuming the placenta influences women's hormones, which could potentially have some benefits.
Lead author Dr Sharon Young said: "While the study doesn't provide firm support for or against the claims about the benefits of placentophagy, it does shed light on this much debated topic by providing the first results from a clinical trial specifically testing the impact of placenta supplements on postpartum hormones, mood, and energy.
"What we have uncovered are interesting areas for future exploration, such as small impacts on hormone levels for women taking placenta capsules, and small improvements in mood and fatigue in the placenta group."
Earlier in 2017, the Medical University of Vienna published research showing the placenta contains insufficient levels of nutrients, such as zinc, iron and selenium, to benefit women's health.
It may also accumulate heavy metals, which could cause seizures and life-threatening complications if ingested, according to the researchers.
Study author Dr Alex Farr said: "Medically speaking, the placenta is a waste product.
"Most mammals eat the placenta after birth, but we can only guess why they do so.
"After the placenta is genetically part of the newborn, eating the placenta borders on cannibalism."
The placenta is most commonly consumed in capsule form, but can be eaten raw, cooked, dehydrated or in smoothies.
