The 'feeling good' hormone

Oct 9, 2007 09:53 GMT  ·  By

Healthy and cheap milk could come as the result of a new discovery: both in women and cows, the secretion of the milk is stopped by serotonin ("the feeling good" hormone).

"Knowing the chemical responsible for inhibiting milk production could help us to improve milk yields in other mammals," said lead researcher Dr. Nelson Horseman, University of Cincinnati professor of molecular and cellular physiology.

In lactating mammal females, milk production gradually slows down to ceasing when mammary glands are filled; once emptied, milk synthesis starts again.

It was not known what causes the inhibition of milk synthesis but a 2004 study made on mice pointed towards serotonin. Serotonin is a neurotransmitter secreted by the brain and the gut. Serotonin secreted by the gut is deposited in blood platelets and freed at wound sites, where it boosts clotting and healing. In the brain, low serotonin levels induce depression and various mood disorders.

Horseman's team has now found that serotonin is also involved in the synthesis of human milk.

"If we can understand how to stop or reduce serotonin production in the mammary gland, we can reverse its actions," said Horseman.

Specific drugs could decrease the body's serotonin synthesis.

"Inhibiting this chemical in the mammary gland has been shown to increase milk yields by up to 15 %. Improved milk yields could help ease milk shortages in some parts of the world caused by drought and increased demand. Demand for milk has increased in Asia and prices for milk have gone up across the world," said Horseman.

A US, in 2001-2005, price on milk grew up by 11 %.

"Farmers currently use a growth hormone to improve milk yields. Use of that hormone has declined in recent years at the request of consumers, but milk shortages are getting worse. Finding ways to increase yield in a way that's acceptable to consumers is important." said Horseman.

The rodent and human milk producing cells appeared to be very similar, having just one receptor for serotonin, but when it comes to cows, there are at least three receptors.

"We hope that by gaining a better understanding of how serotonin works in cows, we can find ways to inhibit its synthesis without the use of drugs or growth hormones. Our ultimate goal would be to increase milk yield in a way that's effective without side effects." said Horseman.