In June 2012, around 200 scientists published the results of the Human Microbiome Project (HMP), a landmark genetic survey of the trillions of microbes composing the human microbiome. The $150 million initiative, begun in 2007 by the NIH, has followed hundreds of healthy people and sequenced genetic material from their bodily bacteria -- a harvest of more than 5 million genes [sources: HMP; Zimmer; Zimmer].
The HMP currently funds 15 projects with potential to show correlations between the microbiome and human health and diseases such as psoriasis, Crohn's disease, ulcerative colitis and esophageal cancer, among others [sources: Borody; HMP; Stein].
One Man's Trash ...
We stand on the threshold of a microbiotic renaissance, according to some physicians and microbiologists. As our understanding of this long-neglected field expands, so too will our treatment options.
As we mentioned, the place to start -- at least where fecal transplantation is concerned -- remains Clostridium difficile. According to the CDC, C. difficile infections kill 14,000 people in the United States annually, and its occurrence among hospitalized patients more than doubled from 2000 to 2009 [sources: Hudson; Zimmer]. One long-term follow-up study of 77 fecal transplant patients reported a 91 percent cure rate after just one fecal transplant, and a 98 percent cure rate with additional probiotics, antibiotics or fecal transplants [source: Brandt et al.].
Fecal microbiota might also hold answers for people with metabolic syndrome -- a collection of co-occurring risk factors, such as insulin resistance and extra weight around the middle, that increases the chance of coronary artery disease, stroke and type 2 diabetes [source: A.D.A.M.]. In some studies, fecal transplantation in metabolic syndrome patients reduced triglyceride levels and improved insulin sensitivity [source: Allen; Gewirtz].
Scientists have also tied obesity in rats to changes to the gut's microbiome. The intestines of obese persons contain a different set of microbes than those of non-obese persons, and clinical trial results suggest lean donors might help obese recipients lose weight by changing how they metabolize sugars [source: Zimmer].
"The composition and activity of gut microbiota is different in lean and obese individuals," says Dr. Alexander Khoruts, associate professor of medicine at University of Minnesota. "We know that animal energy metabolism can be changed by fecal microbiota transplantation. It is possible there will be something along these lines in humans."
"However, it is also clear that diet and lifestyle choices influence the composition of gut microbiota."
Indeed, we're only beginning to grasp the possibilities for fecal transplants and macrobiotics in general [source: Khoruts]. Don't confuse the two, however. Gut flora, though numerous, represent only a portion of total body microbes. Moreover, we do not yet fully understand the relationships between microbiota, health and disease, whether in the intestines or outside of them.
For example, a number of medical conditions may be linked to the intestine, including liver disease, migraines, chronic fatigue, rheumatoid arthritis, multiple sclerosis, Alzheimer's disease and Parkinson's disease, but how (or if) they relate to microbial therapy or fecal transplants remains unclear and will require substantial studies to answer [sources: Allen; Borody; Borody; Khoruts].
In the meantime, don't be too quick to "poo-poo" the idea of fecal transplantation. It's effective, fast and seems to have no side effects. But, as with any new therapy, we'll have to wait and see how it comes all out in the end.