Lactoferrin not only inhibits bone breakdown but also boosts bone growth four times faster than normal when injected directly into bone, the scientists reported yesterday.
Further research is needed before the protein can be developed as a bone health supplement, cautioned the University of Auckland's Osteoporosis Research Group. But their findings could have a major impact on both industry and healthcare.
Osteoporosis is second only to cardiovascular disease in terms of global health care problems, according to the World Health Organisation, and currently affects some 200 million people. The number of sufferers is however set to increase steadily with growing numbers of elderly living longer, and obesity adding extra strain on bones.
In the UK, health and social care for osteoporosis patients already costs the taxpayer around £1.7 billion per year, according to the Department of Health.
The New Zealand team, who reported their findings at the Global Dairy Summit conference in Melbourne, is the first to reveal the bone-building properties of lactoferrin, demonstrated on cell cultures and in mice.
Project leader, associate professor Jill Cornish, pointed out that local injection of lactoferrin resulted in such "phenomenal bone growth" that it could be applied directly to a fracture site to promote faster healing than growth factor treatments currently available.
A lot of research has been done on the development of treatments to inhibit bone resorption, but little is known about how to build bone, she added.
"This is what differentiates lactoferrin and makes it so exciting - it's a double whammy if you like, inhibiting the formation of cells that resorb bone and stimulating the cells that form bone."
Healthy bone depends on continual regeneration, carried out by the two main types of bone cell - osteoclasts that break down old bone, and osteoblasts, which form new bone. Osteoporosis occurs when there is an imbalance in this process and the old bone develops fine fractures.
Lactoferrin is found in both cows' and human milk and is particularly concentrated in colostrum, the substance newborns receive at birth before breast milk is fully established.
Dr Cornish says it is not surprising that milk contains a number of growth factors but this is the first time that lactoferrin has received this attention.
Lactoferrin is already sold as a nutritional supplement and ingredient in functional foods and along with other value added whey fractions, like lactoperoxidase, colostrum/IgG, a-lactalbumin, b-lactoglobulin and glycomacropeptides, is currently enjoying strong growth, hitting 20 per cent per year in some geographical areas, according to research from 3A Business Consulting.
The Auckland team is now looking at how lactoferrin works.
"We have discovered two new receptors on the bone-forming cells and lactoferrin is working through at least one of these to promote bone growth. So we think we have discovered a new anabolic (cell growth and differentiation) pathway in bone," she said.
"This is significant because other molecules may be working through these receptors leading to new treatment options."
LactoPharma, a joint venture between the dairy ingredients group Fonterra and Auckland UniServices, the university's commercial arm, to discover and commercialise novel bioactive components from milk and colostrums, has filed patent applications for the protein as a bone growth factor as well as the two new receptors on the osteoblasts.
The research findings were published in September issues of Endocrinology (vol 145, no 9, pp4366-4374) and Molecular Endocrinology.