New York, June 6 (IANS): US researchers have found no evidence to support the popular claims that eating the placenta after childbirth may protect new mothers against depression or boost their energy.

They have warned that eating the placenta - either raw, cooked or encapsulated - may be an unknown risk for the women who eat it and for their infants, if they are breastfeeding.

In recent times, celebrities such as Kourtney Kardashian blogged and raved about the benefits of their personal placenta "vitamins and spiked women's interest in the practice of consuming their placentas after childbirth.

For the study, the researchers from Northwestern University Feinberg School of Medicine in the US reviewed 10 published research studies on placentophagy.

"There are a lot of subjective reports from women who perceived benefits, but there has not been any systematic research investigating the benefits or the risk of placenta ingestion," said corresponding study author Crystal Clark, assistant professor of psychiatry and behavioural sciences.

The researchers noted the increasing popularity of the the common belief that eating the placenta offers protection against postpartum depression, reduces post-delivery pain, boosts energy, helps with lactation, promotes skin elasticity, enhances maternal bonding or replenishes iron in the body.

"Our sense is that women choosing placentophagy, who may otherwise be very careful about what they are putting into their bodies during pregnancy and nursing, are willing to ingest something without evidence of its benefits and, more importantly, of its potential risks to themselves and their nursing infants," lead author Cynthia Coyle noted.

"More concerning, there are no studies examining the risk of ingesting the placenta, called placentophagy, which acts as a filter to absorb and protect the developing fetus from toxins and pollutants," scientists said.

"There are no regulations as to how the placenta is stored and prepared, and the dosing is inconsistent, women really don't know what they are ingesting," Coyle said.

Although, almost all non-human placental mammals ingest their placenta after giving birth, the first documented accounts of postpartum women practicing placentophagy were in North America in the 1970's, the study reports.

In recent years, advocates and the media have popularised health benefits of the practice, and more women are considering it as an option for postpartum recovery.

"The popularity has spiked in the last few years," Clark said.

"Our sense is that people aren't making this decision based on science or talking with physicians. Some women are making this based on media reports, blogs and websites," Clark added.

The study was published in the journal Archives of Women's Mental Health.